WTNT42 KNHC 031458
TCDAT2
TROPICAL STORM BERTHA DISCUSSION NUMBER   2
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
1100 AM EDT THU JUL 03 2008
 
THIS MORNINGS VISIBLE SATELLITE IMAGERY SHOW THAT THE CLOUD PATTERN
HAS BECOME BETTER ORGANIZED WITH TWO DISTINCT SPIRALING BANDS
OF DEEP CONVECTION.  DVORAK INTENSITY ESTIMATES FROM TAFB AND SAB
ARE 35 KT....THEREFORE THE SYSTEM HAS BEEN UPGRADED TO A TROPICAL
STORM...THE SECOND OF THE 2008 ATLANTIC SEASON. 

RECENT MICROWAVE AND VISIBLE SATELLITE IMAGERY SUGGEST THAT THE
CENTER IS A LITTLE FARTHER NORTH AND WEST OF THE PREVIOUS
ESTIMATES.  BECAUSE OF THE RELOCATION OF THE CENTER...THE INITIAL
MOTION IS A SOMEWHAT UNCERTAIN 285/12...A LITTLE FASTER THAN
BEFORE.  BERTHA IS LOCATED TO THE SOUTH OF A MID-LEVEL RIDGE OVER
THE EASTERN ATLANTIC AND MODEL GUIDANCE IS IN FAIRLY GOOD AGREEMENT
ON A CONTINUED WEST-NORTHWESTWARD TRACK DURING THE NEXT 2-3 DAYS. 
THEREAFTER...THE MODELS SUGGEST THAT BERTHA WILL APPROACH A
WEAKNESS IN THE SUBTROPICAL RIDGE OVER THE CENTRAL ATLANTIC.  THE
GFS...HWRF...AND GFDL MODELS THEREFORE SHOW A NORTHWESTWARD TURN
LATE IN THE FORECAST PERIOD.  THE NEW OFFICIAL FORECAST IS A LITTLE
FASTER AND NORTH OF THE PREVIOUS TRACK AND IS CLOSE TO A CONSENSUS
OF THE GFDL...GFS...HWRF...AND ECMWF MODELS. 
 
VERTICAL WIND SHEAR IS FORECAST TO REMAIN LIGHT DURING THE NEXT FEW
DAYS...HOWEVER...COOLER WATERS ALONG THE FORECAST TRACK SHOULD
LIMIT INTENSIFICATION.  SSTS ALONG THE TRACK ARE EXPECTED TO
INCREASE AFTER 48 HOURS WHICH WOULD FAVOR SOME STRENGTHENING. 
HOWEVER...LATE IN THE FORECAST PERIOD SOUTHWESTERLY SHEAR IS
EXPECTED TO INCREASE WHICH AGAIN SHOULD HALT STRENGTHENING.  THE
SHIPS AND LGEM MODELS PREDICT BERTHA TO BECOME A HURRICANE IN 72 TO
96 HOURS.  HOWEVER...THE NEW INTENSITY FORECAST WILL REMAIN A
LITTLE MORE CONSERVATIVE WHICH IS CLOSER TO THE GFDL AND HWRF
SOLUTIONS.
 
OUTER RAINBANDS ASSOCIATED WITH BERTHA ARE EXPECTED TO BRING GUSTY
WINDS AND LOCALLY HEAVY RAINFALL TO PORTIONS OF THE SOUTHERN CAPE
VERDE ISLANDS DURING THE NEXT 24 HOURS. 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      03/1500Z 13.3N  24.7W    35 KT
 12HR VT     04/0000Z 13.8N  26.7W    40 KT
 24HR VT     04/1200Z 14.7N  29.4W    45 KT
 36HR VT     05/0000Z 15.6N  32.5W    45 KT
 48HR VT     05/1200Z 16.6N  35.8W    50 KT
 72HR VT     06/1200Z 18.5N  42.5W    55 KT
 96HR VT     07/1200Z 21.5N  48.5W    55 KT
120HR VT     08/1200Z 25.0N  52.0W    55 KT
 
$$
FORECASTER BROWN
 

WTNT42 KNHC 032039
TCDAT2
TROPICAL STORM BERTHA DISCUSSION NUMBER   3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
500 PM EDT THU JUL 03 2008
 
THE CLOUD TOPS ASSOCIATED WITH BERTHA HAVE WARMED THIS
AFTERNOON...HOWEVER...BANDING FEATURES REMAIN WELL-DEFINED IN
VISIBLE IMAGERY AND A RECENT SSMIS MICROWAVE OVERPASS.   A SHIP
LOCATED ABOUT 45 NM NORTHEAST OF THE CENTER AT 1700 UTC REPORTED
SUSTAINED WINDS OF 29 KT.  THE LATEST DVORAK ESTIMATES FROM TAFB
AND SAB ARE 35 KT...WHICH REMAINS THE INITIAL ADVISORY INTENSITY. 

THE FORECAST SCENARIO REMAINS UNCHANGED AS BERTHA IS EXPECTED TO
CONTINUE MOVING WEST-NORTHWESTWARD SOUTH OF A MID-LEVEL RIDGE OVER
THE EASTERN ATLANTIC DURING THE NEXT FEW DAYS.  THEREAFTER...A
WEAKNESS IN THE RIDGE BETWEEN ABOUT 50W-60W WILL PLAY A ROLE IN THE
FUTURE TRACK OF BERTHA.  THE UKMET...ECMWF...AND HWRF MODELS DEPICT
A WEAKER AND SHALLOWER BERTHA...KEEPING THE CYCLONE ON A GENERAL
WEST-NORTHWESTWARD TRACK.  THE GFS AND GFDL MAINTAIN A STRONGER
TROPICAL CYCLONE THAT TURNS NORTHWESTWARD INTO THE WEAKNESS. THE
OFFICIAL FORECAST ASSUMES THAT BERTHA WILL BE STRONG AND DEEP
ENOUGH TO BE STEERED BY THE MID-LEVEL FLOW...FOLLOWING CLOSELY THE
GFDL AND THE GFS. 

SHEAR IS EXPECTED TO REMAIN LIGHT...BUT BERTHA IS FORECAST TO TRACK
OVER SSTS OF 25 DEGREES C....WHICH IS THE MAIN LIMITING FACTOR FOR
THE NEXT COUPLE OF DAYS.  THEREAFTER...THE SSTS ALONG THE TRACK ARE
EXPECTED TO INCREASE BUT SHEAR IS FORECAST TO BE STRONGER LATER IN
THE PERIOD.  THE SHIPS... LGEM...AND GFDL MODELS PREDICT BERTHA TO
REACH HURRICANE STRENGTH IN 3-5 DAYS.  THE NEW INTENSITY FORECAST
IS UNCHANGED AND CONSERVATIVE DUE TO THE AFOREMENTIONED LIMITING
FACTORS. 
 
THE CENTER OF BERTHA SHOULD MOVE AWAY FROM THE SOUTHERN CAPE VERDE
ISLANDS TONIGHT...HOWEVER OUTER RAINBANDS WILL CONTINUE TO BRING
GUSTY WINDS AND LOCALLY HEAVY RAINFALL TO PORTIONS OF THE SOUTHERN
CAPE VERDE ISLANDS DURING THE NEXT 24 HOURS.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      03/2100Z 13.6N  25.6W    35 KT
 12HR VT     04/0600Z 14.1N  27.6W    40 KT
 24HR VT     04/1800Z 15.0N  30.8W    45 KT
 36HR VT     05/0600Z 16.0N  34.2W    45 KT
 48HR VT     05/1800Z 16.9N  37.7W    50 KT
 72HR VT     06/1800Z 18.8N  44.5W    55 KT
 96HR VT     07/1800Z 21.5N  49.5W    55 KT
120HR VT     08/1800Z 25.0N  52.5W    55 KT
 
$$
FORECASTER BROWN
 

WTNT42 KNHC 040231
TCDAT2
TROPICAL STORM BERTHA DISCUSSION NUMBER   4
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
1100 PM EDT THU JUL 03 2008
 
BERTHA'S SATELLITE PRESENTATION HAS IMPROVED DURING THE LAST 6 HOURS
COURTESY OF A NEW BURST OF DEEP CONVECTION THAT BEGAN AROUND 1900
UTC.  BANDING FEATURES ARE ALSO BECOMING MORE PROMINENT IN BOTH
CONVENTIONAL AND MICROWAVE SATELLITE IMAGERY.  BASED ON THIS
TREND...THE INITIAL INTENSITY IS RAISED TO 40 KT WHICH IS A
COMPROMISE BETWEEN DVORAK INTENSITY ESTIMATES OF 45 KT AND 35 KT
FROM TAFB AND SAB...RESPECTIVELY.  DURING THE NEXT COUPLE OF
DAYS...BERTHA IS FORECAST TO BE LOCATED WITHIN A FAVORABLE
ATMOSPHERIC ENVIRONMENT BUT OVER MARGINALLY WARM SSTS.  SUCH
CONDITIONS SHOULD ALLOW FOR SLOW STRENGTHENING IN THE SHORT-TERM. 
THE OFFICIAL INTENSITY FORECAST IS ESSENTIALLY AN UPDATE OF THE
PREVIOUS ONE AND KEEPS BERTHA JUST BELOW HURRICANE STRENGTH OUT OF
RESPECT OF THE HWRF MODEL.  BEYOND 72 HOURS...VERTICAL SHEAR IS
FORECAST TO INCREASE AND THIS IS REFLECTED IN THE OFFICIAL FORECAST
WITH ARRESTED DEVELOPMENT.

A SERIES OF VERY USEFUL MICROWAVE PASSES INDICATES THAT BERTHA IS A
LITTLE FARTHER SOUTH THAN PREVIOUSLY THOUGHT WITH AN INITIAL MOTION
MORE TOWARDS THE WEST...280/12.  IT WOULD APPEAR THAT THE RECENT
BURST OF CONVECTION IS CAUSING THE CYCLONE TO RESPOND TO THE LARGE
MIDDLE TO UPPER-LEVEL RIDGE TO ITS NORTH.  THIS RIDGE SHOULD KEEP
BERTHA ON A GENERAL WEST-NORTHWESTWARD HEADING OVER THE NEXT 2-3
DAYS.  THEREAFTER...MOST OF THE DYNAMICAL MODELS INDICATE A TURN
TOWARDS THE NORTHWEST AS BERTHA REACHES A BREAK IN THE RIDGE.  EVEN
THOUGH BOTH THE UKMET AND ECMWF SHOW A SIMILAR EVOLUTION IN THE
LARGE-SCALE PATTERN...THESE MODELS KEEP A WEAKER AND SHALLOWER
CYCLONE ON A WEST-NORTHWESTWARD MOTION THROUGH THE ENTIRE FORECAST. 
SINCE THE OFFICIAL FORECAST ASSUMES BERTHA WILL REMAIN A DEEP
SYSTEM...A TURN TOWARDS THE NORTHWEST IS INDICATED BEYOND 72 HOURS. 
THIS IS SIMILAR TO THE PREVIOUS FORECAST...ALBEIT A BIT FARTHER
SOUTH TO ACCOUNT FOR THE INITIAL POSITION RELOCATION. 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      04/0300Z 13.4N  27.0W    40 KT
 12HR VT     04/1200Z 13.8N  29.2W    45 KT
 24HR VT     05/0000Z 14.6N  32.5W    45 KT
 36HR VT     05/1200Z 15.5N  35.9W    50 KT
 48HR VT     06/0000Z 16.6N  39.4W    55 KT
 72HR VT     07/0000Z 18.5N  45.5W    60 KT
 96HR VT     08/0000Z 21.5N  51.0W    60 KT
120HR VT     09/0000Z 25.5N  54.0W    60 KT
 
$$
FORECASTER RHOME
 

WTNT42 KNHC 040859
TCDAT2
TROPICAL STORM BERTHA DISCUSSION NUMBER   5
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
500 AM EDT FRI JUL 04 2008
 
A STRONG BURST OF DEEP CONVECTION BEGAN AT ABOUT 05Z...RESULTING IN
SUBJECTIVE DVORAK INTENSITY ESTIMATES AT 06Z OF 45-55 KT.  THESE
ESTIMATES...HOWEVER...WERE CONTINGENT UPON THE LOW-LEVEL
CIRCULATION CENTER BEING LOCATED MUCH FARTHER NORTH THAN PREVIOUSLY
THOUGHT...AND RIGHT IN THE MIDDLE OF THE CONVECTION.  PASSIVE
MICROWAVE IMAGES FROM TRMM AT 0146Z AND AMSR-E AT 0326Z SUGGEST THE
LOW-LEVEL CENTER HAS BEEN MOVING NORTH OF THE PREVIOUS MOTION
ESTIMATE...BUT BENEATH THE SOUTHERN PORTION OF THE COLD CLOUD TOP
CANOPY.  SINCE 06Z...THE CLOUD TOPS HAVE WARMED A BIT...SO I DO
NOT THINK THE DVORAK ESTIMATES WOULD BE AS HIGH NOW.  BEST I CAN
TELL FROM FIRST LIGHT VISIBLE IMAGES...THE LOW-LEVEL CENTER SEEMS TO
BE MOVING ALONG THE HEADING SUGGESTED BY THE MICROWAVE IMAGERY...OR
290/12... BENEATH THE SOUTHERN PORTION OF THE DEEP CONVECTION.  THE
INITIAL INTENSITY WILL BE HELD AT 40 KT FOR NOW...TO SEE IF THE
DEEP CONVECTION PERSISTS AS BERTHA HEADS TOWARD SLIGHTLY COOLER
WATERS TODAY.

THE FORECAST REASONING HAS NOT CHANGED TOO MUCH.  THE FIRST TWO DAYS
OF THE TRACK FORECAST HAVE BEEN ADJUSTED SLIGHTLY NORTHWARD...
MAINLY TO ACCOUNT FOR THE CHANGE IN THE INITIAL MOTION. 
THEREAFTER...ONCE BERTHA FINDS ITSELF DUE SOUTH OF THE MID-LEVEL
RIDGE TO ITS NORTH...THE TRACK HAS BEEN SPED UP AND EDGED A LITTLE
TO THE LEFT OR WEST...IN ACCORDANCE WITH A WESTWARD SHIFT IN MOST
OF THE MODELS.  ALL OF THE MODELS STILL FORECAST A WEAKNESS IN THE
RIDGE TO ALLOW BERTHA TO TURN TO THE RIGHT LATE IN THE FORECAST
PERIOD...BUT RECENT RUNS HAVE BEEN TRENDING TOWARD DELAYING THIS
TURN.  THE NEW OFFICIAL TRACK FORECAST IS KEPT CLOSE TO THE MODEL
CONSENSUS...BUT THE MODEL SPREAD IS SUBSTANTIAL AT DAYS 4-5.  THE
MODELS THAT FORECAST A STRONGER BERTHA...SUCH AS THE
GFDL...FORECAST MORE OF A NORTHWESTWARD MOTION BY DAY 5...WHILE
MODELS SUCH AS THE ECMWF AND UKMET INSIST ON A WEAKER CYCLONE
CONTINUING WEST-NORTHWESTWARD.  THE OFFICIAL INTENSITY
FORECAST...LIKE THE TRACK FORECAST...IS CLOSE TO THE
CONSENSUS...TAKING A STRONG TROPICAL STORM DOWN THE MIDDLE OF THE
GUIDANCE ENVELOPE...IN CLOSEST AGREEMENT WITH THE LGEM GUIDANCE. 
STRENGTHENING SHOULD BE LIMITED BY COOL WATERS DURING THE NEXT TWO
DAYS...AND BY INCREASING SHEAR ON DAYS 4 AND 5.  IT IS NOTABLE THAT
THE GFDL AND HWRF INTENSITY FORECASTS ARE VERY MUCH IN
DISAGREEMENT...INDICATIVE OF GREAT UNCERTAINTY IN THE INTENSITY
FORECAST AS WELL.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      04/0900Z 14.2N  28.3W    40 KT
 12HR VT     04/1800Z 15.0N  30.6W    45 KT
 24HR VT     05/0600Z 15.9N  34.0W    45 KT
 36HR VT     05/1800Z 16.6N  37.7W    50 KT
 48HR VT     06/0600Z 17.3N  41.4W    55 KT
 72HR VT     07/0600Z 19.0N  48.0W    60 KT
 96HR VT     08/0600Z 21.5N  53.0W    60 KT
120HR VT     09/0600Z 25.0N  56.5W    60 KT
 
$$
FORECASTER KNABB
 

WTNT42 KNHC 041449
TCDAT2
TROPICAL STORM BERTHA DISCUSSION NUMBER   6
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
1100 AM EDT FRI JUL 04 2008
 
THE CLOUD PATTERN OF BERTHA CONSISTS OF A COUPLE OF CLUSTERS OF
CONVECTION TO THE NORTH AND SOUTH OF THE CENTER EMBEDDED WITHIN A
LARGE CYCLONIC CIRCULATION IN THE LOW CLOUDS.  A QUIKSCAT OVERPASS
THAT WAS RECEIVED JUST AFTER THE ISSUANCE OF THE PREVIOUS
ADVISORY...SUGGEST THAT THE MAXIMUM WINDS WERE AROUND 45 KT.  THE
STRUCTURE OF THE CYCLONE HAS CHANGE LITTLE SINCE THAT TIME AND THE
LATEST DVORAK DATA T NUMBERS FROM SAB AND TAFB SUPPORT A 45 KT
INITIAL INTENSITY.

BERTHA WILL BE PASSING OVER SLIGHTLY COOLER WATERS DURING THE NEXT
24 HOURS...SO NO CHANGE IN INTENSITY IS EXPECTED IN THE NEAR TERM.
BETWEEN 24 AND 72 HOURS...CONDITIONS ARE EXPECTED TO BECOME
CONDUCIVE FOR GRADUAL STRENGTHENING AS SSTS INCREASE AND THE SHEAR 
REMAINS LOW.  MODELS SUGGEST THAT THE SHEAR COULD INCREASE
THEREAFTER...SO THE NEW FORECAST KEEPS THE INTENSITY JUST SHY OF
HURRICANE STRENGTH.  HOWEVER....IT IS WORTH MENTIONING THAT THE
SHIPS...LGEM...AND GFDL MODELS FORECAST BERTHA TO BECOME A
HURRICANE IN 3-4 DAYS.

BERTHA IS MOVING WEST-NORTHWESTWARD AT A LITTLE FASTER
PACE...290/14.  THE STORM SHOULD REMAIN ON THIS GENERAL HEADING
DURING THE NEXT 2-3 DAYS AS IT IS LOCATED SOUTH OF A MID-LEVEL
RIDGE OVER THE EASTERN ATLANTIC.  THE GUIDANCE HAS CONTINUED TO
SHIFT WESTWARD...BUT THERE REMAINS TWO DISTINCT ENVELOPES...ONE
THAT CONSISTS OF THE HWRF AND GFDL THAT TURN THE CYCLONE
NORTHWESTWARD BEYOND DAY 3....AND THE OTHER WHICH KEEPS BERTHA
ON A MORE WEST-NORTHWEST TRACK.  THE OFFICIAL FORECAST TRACK HAS
BEEN ADJUSTED WESTWARD TO REFLECT THE SHIFT IN THE GUIDANCE.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      04/1500Z 14.9N  29.7W    45 KT
 12HR VT     05/0000Z 15.7N  32.1W    45 KT
 24HR VT     05/1200Z 16.5N  35.6W    45 KT
 36HR VT     06/0000Z 17.2N  39.2W    50 KT
 48HR VT     06/1200Z 17.9N  42.9W    55 KT
 72HR VT     07/1200Z 19.5N  49.5W    60 KT
 96HR VT     08/1200Z 21.5N  54.5W    60 KT
120HR VT     09/1200Z 24.0N  59.0W    60 KT
 
$$
FORECASTER BROWN
 

WTNT42 KNHC 042030
TCDAT2
TROPICAL STORM BERTHA DISCUSSION NUMBER   7
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
500 PM EDT FRI JUL 04 2008
 
BERTHA HAD A RATHER RAGGED APPEARANCE IN SATELLITE IMAGERY AROUND
MID-DAY...HOWEVER...SINCE THEN A NEW BURST OF CONVECTION WITH VERY
COLD CLOUD TOPS HAS DEVELOPED NEAR AND NORTH OF THE CENTER.  DVORAK
INTENSITY ESTIMATES FROM TAFB AND SAB STILL SUPPORT AN INITIAL
INTENSITY OF 45 KT.  LITTLE CHANGE IN INTENSITY IS EXPECTED DURING
THE NEXT 24 HOURS AS BERTHA TRAVERSES OVER COOLER WATERS. 
THEREAFTER...THE SSTS WILL INCREASE ALONG THE PROJECTED
TRACK...HOWEVER...VERTICAL SHEAR IS FORECAST TO INCREASE IN THE 3-5
DAY TIME PERIOD.  THE NEW INTENSITY FORECAST IS UNCHANGED FROM THE
PREVIOUS ADVISORY AND KEEPS BERTHA'S INTENSITY BELOW HURRICANE
STRENGTH.  THE GFDL CONTINUES TO SHOW BERTHA REACHING HURRICANE
STATUS...BUT THE SHIPS MODEL HAS BACKED OFF A LITTLE...AND IS IN
LINE WITH THE OFFICIAL FORECAST.
 
BERTHA CONTINUES TO ACCELERATE AND IS NOW MOVING WEST-NORTHWESTWARD
OR 290/16.  LITTLE CHANGE IN HEADING IS EXPECTED DURING THE NEXT
2-3 DAYS AS THE STORM REMAINS SOUTH OF A MID-TROPOSPHERIC RIDGE.
THE GFDL TRACK HAS NOW SHIFTED WESTWARD AND HAS JOINED THE REMAINDER
OF THE MODEL GUIDANCE...EXCEPT FOR THE HWRF WHICH STILL INSISTS ON A
NORTHWESTWARD TURN.  THE NEW TRACK FORECAST REMAINS VERY SIMILAR TO
THE PREVIOUS ADVISORY THROUGH 48 HOURS BUT HAS SHIFTED FARTHER
SOUTHWESTWARD AT DAYS 3-5... IN GOOD AGREEMENT WITH THE LATEST
MODEL CONSENSUS AND THE ECMWF.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      04/2100Z 15.5N  31.6W    45 KT
 12HR VT     05/0600Z 16.2N  34.2W    45 KT
 24HR VT     05/1800Z 16.8N  37.8W    45 KT
 36HR VT     06/0600Z 17.4N  41.5W    50 KT
 48HR VT     06/1800Z 17.9N  45.2W    55 KT
 72HR VT     07/1800Z 19.2N  51.5W    60 KT
 96HR VT     08/1800Z 21.5N  56.0W    60 KT
120HR VT     09/1800Z 23.5N  60.5W    60 KT
 
$$
FORECASTER BROWN
 

WTNT42 KNHC 050234
TCDAT2
TROPICAL STORM BERTHA DISCUSSION NUMBER   8
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
1100 PM EDT FRI JUL 04 2008

MICROWAVE IMAGERY OVER THE LAST 12-24 HOURS INDICATES THAT BERTHA
HAS BEEN STAIR-STEPPING ITS WAY ACROSS THE ATLANTIC OSCILLATING
BETWEEN A WESTWARD AND NORTHWESTWARD HEADING WITH EACH NEW
CONVECTIVE BURST.  IRONING ALL THIS OUT YIELDS AN INITIAL MOTION
ESTIMATE OF 280/18...A LITTLE FASTER THAN BEFORE.  THERE HAS BEEN
LITTLE OVERALL CHANGE IN THE FORECAST PHILOSOPHY.  A STRONG RIDGE
TO THE NORTH SHOULD KEEP THE CYCLONE ON A GENERAL WESTWARD TO WEST-
NORTHWESTWARD MOTION DURING THE NEXT 2-3 DAYS.  WHILE MOST OF THE
DYNAMICAL MODELS STILL SHOW A WEAKNESS DEVELOPING IN THE RIDGE
NORTH OF BERTHA IN ABOUT THREE DAYS...THEY HAVE BEEN TRENDING
TOWARDS A MORE WESTWARD MOTION OF BERTHA DUE TO A WEAKER AND
SHALLOWER DEPICTION OF THE CYCLONE.  THE EXCEPTION IS THE HWRF
WHICH FORECASTS A STRONGER AND DEEPER BERTHA TURNING NORTHWESTWARD
BEYOND 72 HOURS DUE TO THE WEAKNESS.  THE OFFICIAL FORECAST IS
NUDGED A LITTLE WESTWARD BUT IS STILL NORTH OF MOST OF THE GUIDANCE
SINCE ONLY A MODEST INCREASE IN STRENGTH WOULD ALLOW BERTHA TO
RESPOND TO THE DEEPER AND MORE NORTHWARD STEERING.    
 
BERTHA CONTINUES TO EXHIBIT A CONVECTIVE BURSTING PATTERN WITH THE
LATEST BURST BEGINNING AROUND 2300 UTC.  AVAILABLE SATELLITE
INTENSITY ESTIMATES SUGGEST THAT THE SYSTEM HAS CHANGED LITTLE IN
STRENGTH WITH THE INITIAL INTENSITY HELD AT 45 KT. BERTHA IS
FORECAST TO MOVE OVER MARGINALLY WARM SSTS DURING THE NEXT 24 HOURS
WHICH IS EXPECTED TO LIMIT INTENSIFICATION.  THEREAFTER...SSTS
GRADUALLY INCREASE ALONG THE PROJECTED TRACK AND BERTHA IS EXPECTED
TO SLOWLY STRENGTHEN.  VERTICAL SHEAR IS FORECAST TO INCREASE
TOWARDS THE END OF THE FORECAST SO ARRESTED DEVELOPMENT IS SHOWN
BEYOND 72 HOURS.  THIS FORECAST IS SIMILAR TO THE PREVIOUS ONE AND
IS IN CLOSEST AGREEMENT WITH THE HWRF MODEL. 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      05/0300Z 16.0N  33.5W    45 KT
 12HR VT     05/1200Z 16.4N  36.2W    45 KT
 24HR VT     06/0000Z 17.0N  39.8W    45 KT
 36HR VT     06/1200Z 17.6N  43.6W    50 KT
 48HR VT     07/0000Z 18.1N  47.3W    55 KT
 72HR VT     08/0000Z 20.0N  53.5W    60 KT
 96HR VT     09/0000Z 22.0N  58.5W    60 KT
120HR VT     10/0000Z 24.0N  63.0W    60 KT
 
$$
FORECASTER RHOME
 

WTNT42 KNHC 050900
TCDAT2
TROPICAL STORM BERTHA DISCUSSION NUMBER   9
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
500 AM EDT SAT JUL 05 2008
 
BERTHA IS PASSING OVER SEA-SURFACE TEMPERATURES OF ROUGHLY 25
DEGREES CELSIUS...ABOUT THE COOLEST THE CYCLONE HAS ENCOUNTERED YET
DURING THE USUAL DIURNAL CONVECTIVE MAXIMUM...AND IT HAS BEEN
STRUGGLING TO PRODUCE VERY MUCH DEEP CONVECTION OVERNIGHT.  DVORAK
INTENSITY ESTIMATES AT 06Z WERE 35-45 KT...AND WHILE IT IS POSSIBLE
THE WINDS HAVE WEAKENED...THE ADVISORY INTENSITY WILL REMAIN 45 KT
FOR NOW.  DURING THE NEXT THREE DAYS...BERTHA HAS AN OPPORTUNITY TO
STRENGTHEN AS THE UNDERLYING WATER TEMPERATURES STEADILY WARM BY
ABOUT A DEGREE CELSIUS PER DAY ALONG THE FORECAST TRACK.  ALL OF
THE OBJECTIVE INTENSITY MODELS FORECAST INTENSIFICATION THROUGH 72
HOURS...WITH THE SHIPS AND LGEM REACHING 65 KT BY THEN...WHILE HWRF
AND GFDL ARE MORE CONSERVATIVE.  THE OFFICIAL INTENSITY FORECAST IS
A BLEND OF THESE SOLUTIONS AND IS THE SAME AS THE PREVIOUS ADVISORY
IN PEAKING AT 60 KT.  ONE SHOULD NOT PAY TOO MUCH ATTENTION TO THE
EXACT INTENSITY FORECAST...HOWEVER.  THE MAXIMUM WIND SPEED
PROBABILITY TABLE INCLUDED IN THIS FORECAST PACKAGE INDICATES
ROUGHLY EQUAL CHANCES OF BERTHA BEING A TROPICAL STORM OR A
HURRICANE AT 3 TO 5 DAYS.  WHETHER OR NOT BERTHA BECOMES A
HURRICANE WOULD SEEM TO DEPEND ON HOW WELL IT SURVIVES ITS STAY
OVER COOLER WATERS...AND JUST HOW MUCH WIND SHEAR IMPACTS THE
CYCLONE ONCE IT REACHES THE WARMER WATERS...AND BOTH OF THOSE
FACTORS ARE SOMEWHAT UNCERTAIN RIGHT NOW.

A COUPLE OF RECENT MICROWAVE OVERPASSES FROM AMSU AND AMSR-E PROVIDE
THE BASIS FOR THE INITIAL MOTION ESTIMATE OF 285/18.  OVERALL THE
DYNAMICAL MODEL GUIDANCE PROVIDES NO STRONG INDICATION THAT BERTHA
WILL DEVIATE MUCH FROM THE CURRENT WEST-NORTHWESTWARD HEADING
DURING THE NEXT SEVERAL DAYS.  THE WEAKNESS IN THE SUBTROPICAL
RIDGE CURRENTLY ALONG ABOUT 55W IS FORECAST BY THE MODELS TO BECOME
LESS PRONOUNCED AND TO PROPAGATE EASTWARD DURING THE NEXT COUPLE OF
DAYS...AND MOST OF THE GUIDANCE TRACKS SHOW BERTHA BYPASSING THIS
FEATURE WITH JUST A SLIGHT BEND TO THE RIGHT ON DAYS 3 THROUGH 5. 
THE HWRF IS THE ONLY DYNAMICAL MODEL CURRENTLY CALLING FOR BERTHA
TO TURN NORTHWARD BEFORE REACHING 60W.  THE MODEL CONSENSUS HAS
HARDLY BUDGED ON THIS CYCLE...AND THE NEW OFFICIAL TRACK FORECAST
IS ADJUSTED ONLY SLIGHTLY FASTER AND TO THE LEFT AT DAYS 3 THROUGH
5.  THIS NEW TRACK IS MOST SIMILAR TO THE GFDL...GFS...AND
ECMWF...BUT THE TRACK FORECAST UNCERTAINTY REMAINS SIGNIFICANT AS
REFLECTED BY THE CONTINUING LARGE SPREAD IN THE LONG-RANGE MODEL
GUIDANCE.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      05/0900Z 16.5N  35.3W    45 KT
 12HR VT     05/1800Z 17.0N  38.0W    45 KT
 24HR VT     06/0600Z 17.6N  41.8W    50 KT
 36HR VT     06/1800Z 18.2N  45.6W    55 KT
 48HR VT     07/0600Z 19.0N  49.3W    60 KT
 72HR VT     08/0600Z 20.5N  56.0W    60 KT
 96HR VT     09/0600Z 22.5N  61.0W    60 KT
120HR VT     10/0600Z 24.5N  66.0W    60 KT
 
$$
FORECASTER KNABB
 

WTNT42 KNHC 051452
TCDAT2
TROPICAL STORM BERTHA DISCUSSION NUMBER  10
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
1100 AM EDT SAT JUL 05 2008
 
WHILE MOVING OVER COOLER WATERS DURING THE PAST 24 HOURS BERTHA
STRUGGLED A LITTLE BIT...HOWEVER NOW THAT IT IS HEADING FOR
SLIGHTLY WARMER WATERS BERTHA APPEARS TO BE A LITTLE BETTER
ORGANIZED.  THE CYCLONE HAS MAINTAINED A CLUSTER OF DEEP CONVECTION
JUST NORTH AND WEST OF THE CENTER DURING THE PAST SEVERAL HOURS. 
DVORAK INTENSITY ESTIMATES REMAIN BETWEEN 35-45 KT AND THE INITIAL
INTENSITY IS UNCHANGED.   CONDITIONS SHOULD BECOME MORE CONDUCIVE
FOR STRENGTHENING AS SSTS ALONG THE PROJECTED PATH GRADUALLY
INCREASE AND THE SHEAR REMAINS LOW DURING THE NEXT 3 DAYS.  THE NEW
NHC INTENSITY FORECAST IS UNCHANGED THROUGH 48 HOURS BUT NOW
PREDICTS BERTHA TO REACH HURRICANE STRENGTH IN 72 HOURS. 
THEREAFTER...DUE TO UNCERTAINTIES IN THE AMOUNT OF PREDICTED
SHEAR...THE INTENSITY IS HELD A LITTLE BELOW THE LGEM...SHIPS...AND
GFDL MODELS WHICH SHOW ADDITIONAL INTENSIFICATION.
 
BERTHA HAS BEEN MOVING A LITTLE MORE WESTWARD DURING THE PAST 6-12
HOURS AND THE INITIAL MOTION ESTIMATE IS 280/18.  A WEAKNESS IN THE
RIDGE BETWEEN 50W-60W IS FORECAST TO LIFT NORTHWARD AND THE
SUBTROPICAL RIDGE WILL REMAIN THE PREDOMINANT STEERING MECHANISM
FOR THE NEXT SEVERAL DAYS.  THIS SHOULD KEEP BERTHA ON A GENERAL
WEST TO WEST-NORTHWEST HEADING AT A RATHER BRISK PACE.  THERE
REMAINS A LARGE AMOUNT OF MODEL SPREADS AT DAYS 4 AND 5. 
HOWEVER...MOST OF THE MODEL TRACKS HAVE SHIFTED A LITTLE
NORTHWARD...EXCEPT FOR THE UKMET WHICH KEEPS A WEAKER TROPICAL
CYCLONE MOVING WESTWARD.  THE MODEL CONSENSUS SHIFTED VERY CLOSE TO
THE NHC TRACK...SO LITTLE CHANGE WAS NEEDED FROM THE PREVIOUS
OFFICIAL FORECAST. 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      05/1500Z 16.6N  37.3W    45 KT
 12HR VT     06/0000Z 17.0N  40.1W    45 KT
 24HR VT     06/1200Z 17.6N  43.9W    50 KT
 36HR VT     07/0000Z 18.4N  47.6W    55 KT
 48HR VT     07/1200Z 19.1N  51.2W    60 KT
 72HR VT     08/1200Z 20.8N  57.5W    65 KT
 96HR VT     09/1200Z 23.0N  62.5W    65 KT
120HR VT     10/1200Z 25.0N  67.0W    65 KT
 
$$
FORECASTER BROWN
 

WTNT42 KNHC 052040
TCDAT2
TROPICAL STORM BERTHA DISCUSSION NUMBER  11
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
500 PM EDT SAT JUL 05 2008
 
BERTHA HAS CHANGED LITTLE IN ORGANIZATION SINCE THIS MORNING. THE
CYCLONE CONTINUES TO MAINTAIN AN AREA OF CONVECTION NEAR AND TO THE
NORTH OF THE CENTER.  DVORAK INTENSITY ESTIMATES ARE A UNANIMOUS 45
KT...WHICH REMAINS THE INITIAL INTENSITY.  ENVIRONMENTAL CONDITIONS
ARE FORECAST TO BECOME MORE CONDUCIVE FOR STRENGTHENING ALONG THE
PROJECTED PATH.  BERTHA IS CURRENTLY OVER SSTS OF ABOUT 25 DEGREES
CELSIUS...BUT THE SSTS WILL BE INCREASING BY ABOUT ONE DEGREE PER
DAY DURING THE NEXT 3 DAYS.  SHEAR IS EXPECTED TO REMAIN LOW AT
LEAST DURING THE NEXT 72 HOURS...BUT PROJECTED TO INCREASE A LITTLE
THEREAFTER.  THE NEW INTENSITY FORECAST IS UNCHANGED FROM THE
PREVIOUS ADVISORY WHICH SHOWED BERTHA BECOMING A HURRICANE IN ABOUT
3 DAYS...FOLLOWED BY LITTLE CHANGE IN STRENGTH AT DAYS 4 AND 5.  THE
INTENSITY FORECAST IS SIMILAR TO THE CONSENSUS OF THE HWRF...
GFDL...LGEM AND SHIPS MODELS.

BERTHA CONTINUES RACING WESTWARD WITH AN INITIAL MOTION OF 275/18. 
A GENERAL WEST TO WEST-NORTHWESTWARD MOTION SHOULD CONTINUE FOR THE
NEXT COUPLE OF DAYS.  THEREAFTER...THERE IS A VERY LARGE SPREAD IN
THE MODEL GUIDANCE.  THE MODELS WHICH MAINTAIN A DEEPER AND STRONGER
BERTHA TURN THE CYCLONE MORE NORTHWESTWARD IN RESPONSE TO A
WEAKNESS IN THE RIDGE CURRENTLY OVER THE CENTRAL ATLANTIC. 
MEANWHILE...THE MODELS THAT DEPICT A WEAKER AND SHALLOWER CYCLONE
CONTINUE TO TRACK IT WESTWARD SOUTH OF THE LOW-LEVEL RIDGE OVER THE
ATLANTIC.  THE NHC FORECAST TRACK ASSUMES THAT BERTHA WILL REMAIN
DEEP ENOUGH TO DECELERATE DUE TO THE WEAKER RIDGE.  THE NEW
FORECAST TRACK IS JUST A LITTLE SOUTH OF THE PREVIOUS ADVISORY
THROUGH 72 HOURS...BUT SIMILAR THEREAFTER...AND IN BEST AGREEMENT
WITH THE ECMWF...NOGAPS...AND THE GUNA MODEL CONSENSUS. 

IT IS TOO EARLY TO DETERMINE IF BERTHA WILL EVER POSE A THREAT
TO ANY LAND AREAS.
  
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      05/2100Z 16.7N  39.3W    45 KT
 12HR VT     06/0600Z 17.1N  42.1W    45 KT
 24HR VT     06/1800Z 17.8N  45.9W    50 KT
 36HR VT     07/0600Z 18.5N  49.5W    55 KT
 48HR VT     07/1800Z 19.3N  52.8W    60 KT
 72HR VT     08/1800Z 20.8N  58.1W    65 KT
 96HR VT     09/1800Z 22.5N  63.0W    65 KT
120HR VT     10/1800Z 25.0N  67.0W    65 KT
 
$$
FORECASTER BROWN
 

WTNT42 KNHC 060234
TCDAT2
TROPICAL STORM BERTHA DISCUSSION NUMBER  12
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
1100 PM EDT SAT JUL 05 2008
 
LATEST SATELLITE IMAGERY INDICATES THAT BERTHA CONTINUES TO EXHIBIT
A CONVECTIVE BURSTING PATTERN WITH THE CENTER CURRENTLY LOCATED
NEAR THE SOUTH SIDE OF THE COLDEST CLOUD TOPS. DVORAK INTENSITY
ESTIMATES ARE UNCHANGED AND SO IS THE INITIAL INTENSITY...45 KT.
BERTHA IS BEGINNING TO ENCOUNTER WARMER WATERS AND THE CYCLONE IS
EXPECTED TO REACH THE 27 DEGREE CELSIUS ISOTHERM IN 36-48 HOURS.
SINCE THE SHEAR IS EXPECTED TO BE LIGHT DURING THIS PERIOD...SLOW
STRENGTHENING IS EXPECTED. THE FORECAST BECOMES MORE UNCERTAIN
BEYOND 48 HOURS DUE TO SPREAD IN THE TRACK MODELS AND THE RESULTING
DIFFERENCES IN THE ATMOSPHERIC CONDITIONS BERTHA MIGHT EXPERIENCE.
A TRACK MORE TOWARDS THE NORTH WOULD ALLOW MORE STRENGTHENING WHILE
A TRACK MORE TOWARDS THE WEST WOULD RESULT IN INCREASING VERTICAL
SHEAR. SINCE THE OFFICIAL TRACK FORECAST TAKES BERTHA INTO AN AREA
WITH MODERATE VERTICAL SHEAR...ARRESTED DEVELOPMENT IS FORECAST
BEYOND 72 HOURS. THIS NEW OFFICIAL FORECAST IS CONSISTENT WITH THE
PREVIOUS FORECAST BUT SLIGHTLY LOWER THAN THE CONSENSUS OF THE
AVAILABLE INTENSITY MODELS. 
 
BERTHA CONTINUES TO MOVE RAPIDLY WESTWARD WITH AN INITIAL MOTION OF
280/18. THIS GENERAL MOTION IS EXPECTED TO CONTINUE FOR THE NEXT
36-48 HOURS COURTESY OF A STRONG RIDGE TO THE NORTH.  THEREAFTER...
THE CYCLONE BEGINS TO ENCOUNTER A WEAKNESS IN THE SUBTROPICAL RIDGE
AND TRACK MODELS DIVERGE SIGNIFICANTLY.  IN FACT...THE SPREAD IN
THE TRACK MODELS SPAN NEARLY 1300 MILES AT DAY 5 WITH THE UKMET
MODEL KEEPING BERTHA HEADED WESTWARD AND THE HWRF TURNING THE
CYCLONE NORTHWARD.  GIVEN THE UNCERTAINTY...THE OFFICIAL FORECAST
IS SIMILAR TO THE PREVIOUS FORECAST AND LIES IN THE MIDDLE OF THE
TRACK MODEL ENVELOPE.   
 
IT SHOULD BE NOTED THAT THERE IS LARGER THAN NORMAL UNCERTAINTY IN
BOTH THE TRACK AND INTENSITY FORECASTS OF BERTHA.  ACCORDINGLY...IT
IS MUCH TOO EARLY TO DETERMINE IF BERTHA WILL OR WILL NOT POSE A
THREAT TO ANY LAND AREAS.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      06/0300Z 17.0N  41.2W    45 KT
 12HR VT     06/1200Z 17.4N  44.0W    45 KT
 24HR VT     07/0000Z 18.1N  47.6W    50 KT
 36HR VT     07/1200Z 18.9N  51.0W    55 KT
 48HR VT     08/0000Z 19.6N  53.7W    60 KT
 72HR VT     09/0000Z 21.5N  59.0W    65 KT
 96HR VT     10/0000Z 23.5N  63.5W    65 KT
120HR VT     11/0000Z 26.0N  67.5W    65 KT
 
$$
FORECASTER RHOME
 

WTNT42 KNHC 060851
TCDAT2
TROPICAL STORM BERTHA DISCUSSION NUMBER  13
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
500 AM EDT SUN JUL 06 2008

NOT MANY CHANGES TO REPORT WITH BERTHA THIS MORNING. THE CYCLONE
CONTINUES TO MOVE QUICKLY WESTWARD ALONG A HEADING OF ABOUT 280/19
TO THE SOUTH OF THE SUBTROPICAL RIDGE. THE OBJECTIVE GUIDANCE IS IN
VERY GOOD AGREEMENT THROUGH ABOUT 48 HOURS ON A GENERAL
WEST-NORTHWESTWARD MOTION...AND A GRADUAL SLOWING OF THE FORWARD
SPEED AS HEIGHTS BUILD TO THE NORTHWEST OF BERTHA OVER THE
SUBTROPICAL WESTERN ATLANTIC. THE MODELS STILL DIVERGE
SIGNIFICANTLY AT DAYS 3 THROUGH 5...BUT THEY HAVE GENERALLY COME
INTO A LITTLE BETTER AGREEMENT ON A TURN TOWARD THE NORTHWEST BY
THEN...ALTHOUGH AT A FORWARD SPEED OF ABOUT HALF OF BERTHA'S
CURRENT MOTION. THE OUTLIER IS THE HWRF THAT FORECASTS A MUCH
SOONER TURN TOWARD THE NORTH ALONG ABOUT 58W. NONE OF THE
MODELS...HOWEVER...FORECAST BERTHA TO REACH 30 DEGREES NORTH
LATITUDE WITHIN FIVE DAYS. WHILE THE RIDGE OVER THE WESTERN
ATLANTIC IS FORECAST TO BE MUCH WEAKER BY THE END OF THE FIVE-DAY
FORECAST PERIOD...THE MODELS DO NOT DEPICT A HIGH-AMPLITUDE TROUGH
THAT WOULD ACCELERATE BERTHA INTO THE MIDDLE LATITUDES. SO IT IS
FAR TOO EARLY TO DETERMINE IF OR WHEN BERTHA WILL RECURVE. THE NEW
OFFICIAL TRACK FORECAST IS ADJUSTED SLIGHTLY TO THE RIGHT...TOWARD
BUT NOT AS FAR EAST AS THE CONSENSUS.

THE WATERS BENEATH BERTHA ARE CURRENTLY ABOUT 26 CELSIUS AND
CONTINUE TO GET WARMER AS THE CYCLONE PROCEEDS WESTWARD...AND BY 48
HOURS FROM NOW THEY SHOULD BE APPROACHING 28 CELSIUS.  VERTICAL
WIND SHEAR SHOULD NOT STRENGTHEN DURING THIS PERIOD...SO GRADUAL
STRENGTHENING IS FORECAST IN LINE WITH NEARLY ALL OF THE OBJECTIVE
INTENSITY GUIDANCE...AND BERTHA COULD BE A HURRICANE IN A COUPLE OF
DAYS.  BEYOND THAT TIME...THE WATERS WILL BE PLENTY WARM...SO THE
DETERMINING FACTOR ON THE INTENSITY OF BERTHA WILL PROBABLY BE WIND
SHEAR.  THE UPPER-LEVEL PATTERN FORECAST BY THE MODELS AT DAYS 3
THROUGH 5 IS COMPLEX...AND IT IS HARD TO DETERMINE JUST HOW MUCH
SHEAR WILL BE AFFECTING BERTHA DURING THAT PERIOD.  DESPITE TAKING
INTO ACCOUNT A MODEST INCREASE IN SHEAR BASED ON THE GFS MODEL WIND
FIELDS...THE SHIPS AND LGEM FORECAST 70-75 KT AT 72-120 HOURS...SO
THE NEW OFFICIAL INTENSITY FORECAST PEAKS AT 70 KT...A LITTLE
HIGHER THAN THE PREVIOUS ADVISORY.  GIVEN THE UNCERTAINTIES IN THE
ATMOSPHERIC PATTERN AT THOSE LONG RANGES...HOWEVER...THIS IS NOT A
HIGH CONFIDENCE INTENSITY FORECAST.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      06/0900Z 17.3N  43.2W    45 KT
 12HR VT     06/1800Z 17.9N  46.1W    50 KT
 24HR VT     07/0600Z 18.7N  49.5W    55 KT
 36HR VT     07/1800Z 19.6N  52.5W    60 KT
 48HR VT     08/0600Z 20.4N  55.1W    65 KT
 72HR VT     09/0600Z 22.5N  60.0W    70 KT
 96HR VT     10/0600Z 24.5N  64.0W    70 KT
120HR VT     11/0600Z 27.0N  67.5W    70 KT
 
$$
FORECASTER KNABB
 

WTNT42 KNHC 061446
TCDAT2
TROPICAL STORM BERTHA DISCUSSION NUMBER  14
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
1100 AM EDT SUN JUL 06 2008
 
A SERIES OF MICROWAVE OVERPASSES THIS MORNING SHOW THAT BERTHA HAS
CHANGED LITTLE IN ORGANIZATION DURING THE PAST 24 HOURS. QUIKSCAT
DATA FROM 0852 UTC INDICATE THAT THE MAXIMUM WINDS REMAIN ABOUT 45
KT...WHICH AGREES WITH THE LATEST DVORAK INTENSITY ESTIMATES.
HOWEVER...RECENT VISIBLE SATELLITE IMAGES REVEAL AN INCREASE IN
CONVECTION WHICH MAY FORETELL AN INCREASE IN STRENGTH. SSTS UNDER
BERTHA HAVE INCREASED TO AROUND 26 CELSIUS AND ARE EXPECTED TO WARM
A COUPLE OF DEGREES DURING THE NEXT 2 DAYS. SHEAR IS FORECAST TO
REMAIN LOW...SO GRADUAL STRENGTHENING IS EXPECTED DURING THE NEXT
48 HOURS AND BERTHA COULD BECOME A HURRICANE DURING THAT TIME.
LATER IN THE FORECAST PERIOD...IT IS DIFFICULT TO DETERMINE EXACTLY
WHAT EFFECT AN UPPER-LEVEL TROUGH OVER THE WESTERN ATLANTIC WILL
HAVE ON THE CYCLONE. IF IT REMAINS IN PLACE...THE TROUGH WOULD
PRODUCE AN INCREASE IN SOUTHWESTERLY SHEAR. SOME OF THE GLOBAL
MODELS SUGGEST A WEAKENING OF THE TROUGH HOWEVER...WHICH WOULD KEEP
BERTHA IN A MORE FAVORABLE ENVIRONMENT. DUE TO THESE UNCERTAINTIES
THE INTENSITY FORECAST BEYOND 3 DAYS KEEPS BERTHA AT THE SAME
STRENGTH.

BERTHA CONTINUES MOVING RAPIDLY WESTWARD OR 280/18 KT. A
WEST-NORTHWESTWARD TRACK WITH A REDUCTION IS FORWARD SPEED IS
EXPECTED DURING THE NEXT DAY OR TWO. THERE IS A LITTLE LESS SPREAD
IN THE MODELS THIS MORNING...WITH THE MAJORITY OF THE GUIDANCE
SHOWING A MORE NORTHWESTWARD TURN IN 2-3 DAYS AS THE RIDGE OVER THE
WESTERN ATLANTIC BEGIN TO WEAKEN. THE HWRF CONTINUES TO INSIST ON
THE TURN OCCURRING MUCH SOONER...WHILE THE UKMET REMAINS THE
WESTERNMOST MODEL BUT WITH A WEAKENED TROPICAL CYCLONE OR EVEN AN
OPEN WAVE. THE OFFICIAL TRACK HAS BEEN ADJUSTED EASTWARD...BUT IT
REMAINS LEFT OF MOST OF THE GUIDANCE AND ALSO LEFT OF THE MODEL
CONSENSUS.

FORECAST POSITIONS AND MAX WINDS
 
INITIAL      06/1500Z 17.4N  45.1W    45 KT
 12HR VT     07/0000Z 18.0N  47.8W    50 KT
 24HR VT     07/1200Z 18.9N  50.9W    55 KT
 36HR VT     08/0000Z 19.7N  53.5W    60 KT
 48HR VT     08/1200Z 20.5N  56.0W    65 KT
 72HR VT     09/1200Z 22.5N  60.5W    70 KT
 96HR VT     10/1200Z 25.0N  64.0W    70 KT
120HR VT     11/1200Z 27.0N  66.5W    70 KT
 
$$
FORECASTER BROWN
 

WTNT42 KNHC 062057
TCDAT2
TROPICAL STORM BERTHA DISCUSSION NUMBER  15
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
500 PM EDT SUN JUL 06 2008
 
A COUPLE OF MICROWAVE IMAGES JUST RECEIVED SUGGEST THAT BERTHA'S
VORTEX IS TILTED A LITTLE.  THE IMAGES INDICATE THAT THE
LOW-LEVEL CENTER IS LOCATED JUST SOUTHWEST OF THE MID-LEVEL CENTER.
HOWEVER...THESE IMAGES ALSO SUGGEST THAT THE OVERALL STRUCTURE HAS
IMPROVED WITH THE APPEARANCE OF AN EYE FEATURE...SUGGESTING THAT
BERTHA IS STRENGTHENING.  DVORAK INTENSITY ESTIMATES WERE 45 KT AT
18Z...BUT WITH THE IMPROVING STRUCTURE THE INITIAL INTENSITY IS
INCREASED TO 50 KT. CONDITIONS APPEAR CONDUCIVE FOR STRENGTHENING
DURING THE NEXT COUPLE OF DAYS AND BERTHA COULD BECOME A HURRICANE. 
HOWEVER...INDICATIONS ARE THAT BEYOND 48 HOURS...WESTERLY SHEAR
COULD HALT ANY ADDITIONAL STRENGTHENING AS SUGGESTED BY THE SHIPS
MODELS.
 
BERTHA IS MOVING WEST-NORTHWESTWARD OR 285/17 KT.  ALL OF THE
AVAILABLE GUIDANCE SHOWS A NORTHWEST TURN AS THE RIDGE OVER THE
WESTERN ATLANTIC WEAKENS IN A FEW DAYS. HOWEVER...THERE REMAINS
SOME SPREAD IN THE GUIDANCE AS TO WHEN THE TURN OCCURS.  THE HWRF
AND GFDL...WHICH DEPICT A STRONG TROPICAL CYCLONE REMAINS ALONG
THE EASTERN EDGE OF THE MODEL ENVELOPE.  THE UKMET WHICH KEEPS
BERTHA WEAKER IS ALONG THE WESTERN EDGE. THE NEW TRACK
FORECAST IS ADJUSTED SLIGHTLY EASTWARD...BUT STILL REMAINS
WEST OF THE MODEL CONSENSUS.
  
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      06/2100Z 18.1N  47.0W    50 KT
 12HR VT     07/0600Z 18.7N  49.6W    55 KT
 24HR VT     07/1800Z 19.5N  52.3W    60 KT
 36HR VT     08/0600Z 20.2N  54.6W    65 KT
 48HR VT     08/1800Z 20.9N  56.7W    70 KT
 72HR VT     09/1800Z 23.0N  60.5W    70 KT
 96HR VT     10/1800Z 26.0N  64.0W    70 KT
120HR VT     11/1800Z 29.0N  65.5W    70 KT
 
$$
FORECASTER BROWN
 

WTNT42 KNHC 070234
TCDAT2
TROPICAL STORM BERTHA DISCUSSION NUMBER  16
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
1100 PM EDT SUN JUL 06 2008
 
THE SATELLITE PRESENTATION HAS GRADUALLY IMPROVED DURING THE PAST
SEVERAL HOURS. THE CONVECTION IS SYMMETRIC ABOUT THE CENTER WHILE
THE OUTFLOW HAS BEEN EXPANDING WESTWARD...TYPICAL OF AN
INTENSIFYING CYCLONE. FURTHERMORE...CONSECUTIVE MICROWAVE DATA SHOW
A WELL DEFINED RING OF DEEP CONVECTION...OR EYE-LIKE FEATURE...
WHICH IS GRADUALLY BECOMING ALIGNED VERTICALLY.  THIS COULD
EVENTUALLY BE THE PRECURSOR OF AN EYE FORMATION.  DVORAK T-NUMBERS
HAVE INCREASED AND NOW SUPPORT AN INITIAL INTENSITY OF 55 KNOTS. 
THE OCEAN IS PLENTY WARM AHEAD OF BERTHA SO THE SHEAR WILL BE THE
MAIN PRIMARY LARGE SCALE FACTOR CONTROLLING THE FUTURE INTENSITY.
WE ARE NOT CONSIDERING EYEWALL CYCLES AT THIS TIME...IN CASE AN EYE
FORMS.  BECAUSE THE SHEAR IS EXPECTED TO BE WEAK FOR THE NEXT DAY
OR TWO... STRENGTHENING IS INDICATED AND BERTHA COULD BECOME A
HURRICANE ON MONDAY. THEREAFTER...THE SHEAR IS EXPECTED TO
FLUCTUATE SO NO IMPORTANT CHANGES IN INTENSITY ARE FORECAST. 

THE CENTER IS A LITTLE FARTHER NORTH AS IT APPEARS TO BE REALIGNING
WITH THE MID-LEVEL VORTEX. THIS IS NOT A CHANGE IN TRACK SINCE 
BERTHA IS STILL MOVING TOWARD THE WEST-NORTHWEST OR 285 DEGREES AT
17 KNOTS.  A WEAKNESS OF THE SUBTROPICAL RIDGE ALONG 50 TO 55
DEGREES WEST WILL PROBABLY CAUSE BERTHA TO BEGIN TO SLOW DOWN SOON. 
THE SUBTROPICAL RIDGE IS EXPECTED TO REBUILD SOME IN A DAY OR TWO
CAUSING BERTHA TO CONTINUE ON A WEST-NORTHWEST TO NORTHWEST TRACK.
BY THE END OF THE FORECAST PERIOD...THE STEERING CURRENTS ARE
FORECAST TO WEAKEN AGAIN AND BERTHA SHOULD SLOW DOWN CONSIDERABLY
AS INDICATED BY SOME GLOBAL MODELS. THE OFFICIAL FORECAST IS
CONSISTENT WITH MOST OF THE TRACK GUIDANCE WHICH IS IN MUCH BETTER
AGREEMENT TONIGHT. NO NEED TO DISCUSS EVERY MODEL. 

FORECAST POSITIONS AND MAX WINDS
 
INITIAL      07/0300Z 18.6N  48.9W    55 KT
 12HR VT     07/1200Z 19.3N  51.5W    60 KT
 24HR VT     08/0000Z 20.0N  54.5W    70 KT
 36HR VT     08/1200Z 21.0N  57.0W    70 KT
 48HR VT     09/0000Z 22.0N  59.5W    70 KT
 72HR VT     10/0000Z 24.0N  62.0W    70 KT
 96HR VT     11/0000Z 27.0N  64.5W    70 KT
120HR VT     12/0000Z 30.0N  65.5W    70 KT
 
$$
FORECASTER AVILA
 

WTNT42 KNHC 070900
TCDAT2
HURRICANE BERTHA DISCUSSION NUMBER  17
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
500 AM EDT MON JUL 07 2008
 
IN THE HOURS LEADING UP TO 00Z...SEVERAL CONSECUTIVE MICROWAVE
OVERPASSES OCCURRED ON ROUGHLY AN HOURLY BASIS...AND ALMOST MADE IT
SEEM LIKE WE WERE RECEIVING RADAR FIXES. THOSE IMAGES REVEALED A
WELL-DEFINED AND VERTICALLY-ALIGNED EYE FEATURE...AND MORE RECENTLY
AN IMAGE FROM AMSU TAKEN AT 0517Z ALSO DEPICTED AN EYE. THE
MICROWAVE EYE DIAMETER APPEARS TO BE ABOUT 15-20 N MI. GOES
INFRARED IMAGERY HAS INTERMITTENTLY EXHIBITED HINTS OF AN
EYE...ESPECIALLY AROUND 06Z WHEN SUBJECTIVE DVORAK INTENSITY
ESTIMATES FROM TAFB AND SAB WERE BOTH 65 KT. OBJECTIVE DVORAK
ESTIMATES REMAIN SLIGHTLY BELOW THE HURRICANE THRESHOLD...BUT GIVEN
THE MICROWAVE SIGNATURES THE SYSTEM IS UPGRADED TO A HURRICANE...
THE FIRST OF THE 2008 ATLANTIC SEASON...WITH AN INTENSITY OF 65 KT.
WHILE A HURRICANE DOES NOT FORM EVERY YEAR IN JULY IN THE ATLANTIC
BASIN...IT HAS CERTAINLY HAPPENED BEFORE...INCLUDING IN 1996 WHEN
ANOTHER HURRICANE BERTHA FORMED...COINCIDENTALLY ALSO ON JULY 7.

EXTRAPOLATION OF THE EARLIER SERIES OF MICROWAVE IMAGES MATCHES UP
QUITE WELL WITH MORE RECENT GEOSTATIONARY FIXES TO YIELD AN INITIAL
MOTION ESTIMATE OF 285/17. THE SUBTROPICAL RIDGE TO THE NORTH OF
BERTHA IS PROVIDING THE STEERING...BUT THAT FEATURE IS FORECAST BY
THE DYNAMICAL MODELS TO GRADUALLY WEAKEN OVER THE WESTERN ATLANTIC
DURING THE NEXT FEW DAYS...ALLOWING BERTHA'S TRACK TO STEADILY BEND
TO THE RIGHT...BUT ALSO SLOW DOWN SUBSTANTIALLY. ALL OF THE MODELS
GENERALLY AGREE ON THIS SCENARIO...BUT THERE REMAINS A HEALTHY
AMOUNT OF SPREAD REGARDING AT WHAT LONGITUDE BERTHA WILL TURN. THE
NEW OFFICIAL TRACK FORECAST IS EDGED SLIGHTLY TO THE RIGHT TOWARD
THE CONSENSUS AND IS A TAD SLOWER AT THE END. GIVEN THE WEAK
STEERING CURRENTS AND LACK OF A HIGH-AMPLITUDE TROUGH OVER THE
WESTERN ATLANTIC DURING THE NEXT SEVERAL DAYS...IT IS STILL NOT
GUARANTEED THAT BERTHA WILL RECURVE.

THE UPPER-LEVEL WINDS NEAR BERTHA ARE NOT FORECAST TO CHANGE
APPRECIABLY DURING THE NEXT COUPLE OF DAYS...WHILE UNDERLYING
SEA-SURFACE TEMPERATURES WARM A LITTLE MORE...SO SOME ADDITIONAL
STRENGTHENING IS FORECAST ALONG THE LINES OF THE SHIPS AND LGEM
GUIDANCE.  AT 3 TO 5 DAYS...THE GLOBAL MODELS DISAGREE ON THE
EVOLUTION OF AN UPPER-LEVEL TROUGH IN THE VICINITY OF THE TROPICAL
CYCLONE...AND SO IT REMAINS UNCLEAR HOW MUCH WIND SHEAR WILL AFFECT
BERTHA THEN.  THE NEW OFFICIAL INTENSITY FORECAST PEAKS AT 80 KT
WITHIN THE NEXT COUPLE OF DAYS...BUT THEN SHOWS GRADUAL WEAKENING
DUE TO THE POTENTIAL FOR INCREASING SHEAR...AND DUE TO COOLER
WATERS AS BERTHA PROGRESSES NORTHWARD ALONG THE FORECAST TRACK.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      07/0900Z 19.3N  50.2W    65 KT
 12HR VT     07/1800Z 19.9N  52.5W    70 KT
 24HR VT     08/0600Z 20.8N  55.0W    75 KT
 36HR VT     08/1800Z 21.7N  57.1W    80 KT
 48HR VT     09/0600Z 22.7N  59.0W    80 KT
 72HR VT     10/0600Z 25.0N  62.0W    75 KT
 96HR VT     11/0600Z 28.0N  64.0W    70 KT
120HR VT     12/0600Z 30.5N  64.5W    70 KT
 
$$
FORECASTER KNABB
 

WTNT42 KNHC 071432
TCDAT2
HURRICANE BERTHA DISCUSSION NUMBER  18
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
1100 AM EDT MON JUL 07 2008
 
BERTHA'S SATELLITE PRESENTATION HAS BECOME MORE IMPRESSIVE DURING
THE LAST 6 HOURS WITH A DISTINCT EYE NOW APPARENT.  THE INITIAL
INTENSITY IS INCREASED TO 80 KT IN LINE WITH THE CONSENSUS OF THE
VARIOUS SATELLITE ESTIMATES.  IN THE SHORT-TERM...THERE ARE NO
APPARENT ENVIRONMENTAL FACTORS WHICH WOULD INHIBIT FURTHER
INTENSIFICATION TODAY AND THE OFFICIAL FORECAST NOW CALLS FOR
BERTHA TO BECOME A CATEGORY TWO HURRICANE.  HOWEVER...THE INTENSITY
FORECAST BECOMES MORE UNCERTAIN BEYOND 36 HOURS AS THE GLOBAL
MODELS DISAGREE ON THE DETAILS OF THE DEVELOPMENT OF AN UPPER-LEVEL
TROUGH OVER THE WESTERN ATLANTIC.  THE GFS FORECAST THE MOST
UNFAVORABLE ENVIRONMENT WITH BERTHA ESSENTIALLY RUNNING INTO THE
TROUGH.  NOT SURPRISINGLY...THE SHIPS AND LGEM STATISTICAL
MODELS...WHICH INCLUDE ATMOSPHERIC INFORMATION FROM THE GFS...SHOW
CONSIDERABLE WEAKENING.  MEANWHILE...THE UKMET...GFDL...AND HWRF
MODELS SHOWS A MUCH MORE FAVORABLE ENVIRONMENT AND DELAY WEAKENING
UNTIL THE VERY END OF THE FORECAST PERIOD.  THE OFFICIAL INTENSITY
FORECAST LEANS MORE TOWARDS THE HIGHER SHEAR SCENARIO INDICATED BY
THE GFS BUT DOES NOT WEAKEN BERTHA AS FAST AS THE SHIPS AND LGEM
MODELS. 
 
THERE HAS BEEN LITTLE CHANGE IN THE HURRICANE'S HEADING DURING THE
LAST 6 HOURS WITH THE INITIAL MOTION ESTIMATE ESSENTIALLY
UNCHANGED... 285/13.  HOWEVER...BERTHA IS BEGINNING TO ENCOUNTER A
WEAKNESS IN THE SUBTROPICAL RIDGE WHICH SHOULD RESULT IN A GRADUAL
TURN TOWARDS THE NORTH AND A REDUCTION IN FORWARD SPEED.  THE
MODELS GENERALLY AGREE ON THIS EVOLUTION...BUT THERE REMAINS SOME
SPREAD AMONGST THE MODELS ON WHAT LONGITUDE BERTHA WILL TURN NORTH.
WHILE THE DEGREE OF THE TURN HAS IMPORTANT IMPLICATIONS REGARDING
POTENTIAL IMPACTS TO BERMUDA...IT IS MUCH TO EARLY TO DETERMINE IF
BERTHA WILL ACTUALLY THREATEN THAT ISLAND.  HOWEVER...INTERESTS IN
BERMUDA SHOULD MONITOR THE PROGRESS OF THIS SYSTEM.  THE NEW
OFFICIAL FORECAST IS NUDGED SLIGHTLY EASTWARD TOWARD THE TRACK
MODEL CONSENSUS. 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      07/1500Z 19.6N  51.3W    80 KT
 12HR VT     08/0000Z 20.3N  53.3W    90 KT
 24HR VT     08/1200Z 21.2N  55.5W    90 KT
 36HR VT     09/0000Z 22.1N  57.5W    85 KT
 48HR VT     09/1200Z 23.2N  59.2W    80 KT
 72HR VT     10/1200Z 25.5N  62.0W    75 KT
 96HR VT     11/1200Z 28.5N  63.5W    70 KT
120HR VT     12/1200Z 31.0N  63.5W    70 KT
 
$$
FORECASTER RHOME
 

WTNT42 KNHC 072035
TCDAT2
HURRICANE BERTHA DISCUSSION NUMBER  19
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
500 PM EDT MON JUL 07 2008
 
BERTHA'S SATELLITE PRESENTATION HAS CONTINUED TO IMPROVE THIS
AFTERNOON WITH A VERY DISTINCT EYE NOW SURROUNDED BY A RING OF COLD
CLOUD TOPS. SUBJECTIVE DVORAK T NUMBERS WERE UNANIMOUSLY 5.0 BUT
OBJECTIVE NUMBERS HAVE INCREASED TO 6.0 FOR THE PAST 3 HOURS. THIS
SUPPORTS AN INITIAL INTENSITY OF 100 KT MAKING BERTHA A MAJOR
CATEGORY THREE HURRICANE ON THE SAFFIR-SIMPSON HURRICANE SCALE.
BERTHA'S INTENSIFICATION TO MAJOR HURRICANE TODAY HIGHLIGHTS THE
DIFFICULTIES OF FORECASTING RAPID INTENSITY CHANGES. IN THE
SHORT-TERM...SHEAR IS EXPECTED TO BE LOW AND THE INTENSITY WILL BE
PRIMARILY CONTROLLED BY EYEWALL CYCLES. AS A RESULT...SOME
FLUCTUATIONS IN INTENSITY ARE LIKELY. IN A DAY OR TWO...THE GFS
MODEL STILL INDICATES INCREASING SHEAR. THE SHIPS AND LGEM
STATISTICAL MODELS...WHICH BASE THEIR SHEAR ESTIMATES FROM THE
GFS...SHOW WEAKENING BEYOND 24 HOURS AND SO DOES THE OFFICIAL
FORECAST.
 
BERTHA HAS BEEN MOVING MORE TOWARDS THE NORTHWEST DURING THE LAST
COUPLE OF HOURS WITH A REDUCTION IN FORWARD SPEED...BOTH INDICATIONS
THAT THE HURRICANE HAS REACHED THE MUCH-ANTICIPATED WEAKNESS IN THE
RIDGE.  SINCE BERTHA COULD BE WOBBLING...THE INITIAL MOTION
ESTIMATE BASED ON A 12 HOUR AVERAGE IS 300/10.  TRACK GUIDANCE
REMAINS IN GOOD AGREEMENT ON A GRADUAL NORTHWARD TURN DURING THE
NEXT 2-3 DAYS.  THEREAFTER...GLOBAL MODELS SUGGEST THAT THE
STEERING CURRENTS COULD BECOME WEAK LEADING TO INCREASED UNCERTAINTY
IN THE TRACK FORECAST.  EVEN THOUGH THE OFFICIAL FORECAST IS
SHIFTED A LITTLE TO THE EAST...IT IS STILL WAY TOO SOON TO
DETERMINE WHETHER OR NOT BERTHA WILL AFFECT BERMUDA.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      07/2100Z 20.1N  52.1W   100 KT
 12HR VT     08/0600Z 20.8N  53.5W   100 KT
 24HR VT     08/1800Z 21.7N  55.4W    95 KT
 36HR VT     09/0600Z 22.9N  57.3W    90 KT
 48HR VT     09/1800Z 24.0N  59.0W    85 KT
 72HR VT     10/1800Z 26.5N  61.5W    80 KT
 96HR VT     11/1800Z 29.0N  62.5W    75 KT
120HR VT     12/1800Z 31.5N  62.5W    75 KT
 
$$
FORECASTER RHOME
 

WTNT42 KNHC 080236
TCDAT2
HURRICANE BERTHA DISCUSSION NUMBER  20
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
1100 PM EDT MON JUL 07 2008

DURING THE AFTERNOON HOURS BETWEEN 1900 AND 2300 UTC...BOTH NHC AND
CIMSS OBJECTIVE T-NUMBERS WERE OSCILLATING AROUND 6.0 ON THE DVORAK
SCALE. NORMALLY THESE NUMBERS CORRESPOND TO AN INTENSITY OF 115
KNOTS.  DURING THAT TIME THE EYE BECAME VERY DISTINCT AND WAS
SURROUNDED BY VERY COLD TOPS.  BERTHA COULD HAVE REACHED A PEAK
INTENSITY A LITTLE BIT HIGHER THAN PREVIOUSLY ESTIMATED DURING THAT
PERIOD. SINCE THEN...OBJECTIVE T-NUMBERS HAVE COME DOWN A LITTLE
BIT AND NEW ESTIMATES SUPPORT AN INTENSITY OF 105 KNOTS.  MINIMUM
CENTRAL PRESSURE HAS ALSO BEEN ADJUSTED. THE INTENSITY IS EXPECTED
TO BE CONTROLLED BY EYEWALL REPLACEMENT CYCLES DURING THE NEXT 12
TO 24 HOURS WHEN BERTHA COULD FLUCTUATE IN INTENSITY. THEREAFTER...
THE OFFICIAL FORECAST CALLS FOR SLIGHT WEAKENING DUE TO INCREASING
SHEAR BUT NOT AS MUCH WEAKENING AS PREDICTED BY THE SHIPS MODEL. 
NEVERTHELESS...THE INTENSITY FORECAST CONTINUES TO BE HIGHLY
UNCERTAIN.

ON THE OTHER HAND...THE TRACK FORECAST HAS BECOME A LITTLE MORE
CERTAIN SINCE THE TRACK MODELS ARE IN BETTER AGREEMENT AND THE
GUIDANCE ENVELOPE IS SMALLER. BERTHA IS MOVING TOWARD THE
WEST-NORTHWEST OR 300 DEGREES AT 10 KNOTS WHILE APPROACHING A
WEAKNESS IN THE SUBTROPICAL RIDGE.  THE RIDGE IS EXPECTED TO
REBUILD SOME AND THIS PATTERN WOULD FAVOR A CONTINUATION OF THE
WEST-NORTHWEST TRACK FOR A DAY OR TWO....FOLLOWED BY A GRADUAL TURN
TO THE NORTHWEST AND NORTH.  BY DAYS 4 AND 5 THE STEERING CURRENTS
ARE FORECAST TO COLLAPSE AND BERTHA WILL PROBABLY MEANDER FOR A
LITTLE BIT.

BERTHA IS CERTAINLY NOT THE ONLY MAJOR HURRICANE THAT HAS FORMED IN
THE MONTH OF JULY. THE LAST OCCURRENCES WERE HURRICANES DENNIS AND
EMILY IN 2005.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      08/0300Z 20.8N  52.8W   105 KT
 12HR VT     08/1200Z 21.5N  54.2W   100 KT
 24HR VT     09/0000Z 22.5N  56.0W   100 KT
 36HR VT     09/1200Z 23.5N  58.0W    95 KT
 48HR VT     10/0000Z 25.0N  59.5W    85 KT
 72HR VT     11/0000Z 27.5N  61.5W    80 KT
 96HR VT     12/0000Z 30.0N  62.0W    75 KT
120HR VT     13/0000Z 32.0N  62.0W    75 KT
 
$$
FORECASTER AVILA
 

WTNT42 KNHC 080832
TCDAT2
HURRICANE BERTHA DISCUSSION NUMBER  21
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
500 AM EDT TUE JUL 08 2008

THE EYE OF THE HURRICANE HAS BECOME A LITTLE LESS DISTINCT OVER THE
PAST SEVERAL HOURS.  NONETHELESS...BERTHA HAS BEEN MAINTAINING A
FAIRLY SYMMETRICAL RING OF COLD CLOUD TOPS AROUND THE CENTER. 
SUBJECTIVE AND OBJECTIVE DVORAK T-NUMBERS HAVE COME DOWN SLIGHTLY
BUT CURRENT INTENSITY ESTIMATES...BOTH OBJECTIVE AND SUBJECTIVE...
REMAIN CLOSE TO 105 KT.  HENCE THE ADVISORY INTENSITY IS UNCHANGED. 
SOME FLUCTUATIONS IN STRENGTH ASSOCIATED WITH EYEWALL REPLACEMENTS
COULD OCCUR WITHIN THE NEXT 12 HOURS OR SO.  IN THE LONGER-TERM...
THE ENVIRONMENT IS EXPECTED TO GRADUALLY BECOME LESS CONDUCIVE FOR
STRENGTHENING AS BERTHA MOVES TOWARDS HIGHER LATITUDES.  THIS IS
REFLECTED IN THE SHIPS MODEL...WHICH WEAKENS BERTHA TO MINIMAL
HURRICANE STRENGTH BY 72 HOURS.  THE OFFICIAL INTENSITY FORECAST
CLOSELY FOLLOWS THE INTENSITY MODEL CONSENSUS ICON.

EYE FIXES GIVE A MOTION ESTIMATE OF 310/9 WHICH IS SLIGHTLY TO THE
RIGHT OF PREVIOUS ESTIMATES.  GLOBAL MODELS ARE NOW IN FAIRLY GOOD
AGREEMENT THAT BERTHA WILL HEAD FOR A WEAKNESS IN THE
MID-TROPOSPHERIC SUBTROPICAL RIDGE AND TURN NORTHWARD LATER IN THE
FORECAST PERIOD.  IT SHOULD BE NOTED THAT THE GFDL AND HWRF MODELS
HAVE BEEN CALLING FOR THIS SCENARIO MORE CONSISTENTLY THAN THE
OTHER GUIDANCE OVER THE PAST COUPLE OF DAYS.  THE OFFICIAL TRACK
FORECAST IS ADJUSTED EAST OF THE PREVIOUS ONE BUT IS STILL TO THE
WEST OF MOST OF THE DYNAMICAL MODEL TRACKS AS WELL AS THE MODEL
CONSENSUS.  BY DAY 5...STEERING CURRENTS COULD BECOME QUITE WEAK
AND BERTHA MAY MOVE SLOWLY AND ERRATICALLY AS IT WAITS TO BE
EVENTUALLY PICKED UP BY A TROUGH IN THE WESTERLIES.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      08/0900Z 21.4N  53.3W   105 KT
 12HR VT     08/1800Z 22.2N  54.4W   100 KT
 24HR VT     09/0600Z 23.4N  55.9W    95 KT
 36HR VT     09/1800Z 24.7N  57.4W    90 KT
 48HR VT     10/0600Z 26.0N  58.6W    85 KT
 72HR VT     11/0600Z 28.0N  59.5W    80 KT
 96HR VT     12/0600Z 30.0N  59.5W    75 KT
120HR VT     13/0600Z 32.0N  59.0W    70 KT
 
$$
FORECASTER PASCH
 

WTNT42 KNHC 081440
TCDAT2
HURRICANE BERTHA DISCUSSION NUMBER  22
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
1100 AM EDT TUE JUL 08 2008
 
CONVENTIONAL AND MICROWAVE IMAGERY SHOW A RAPID DEGRADATION OF
BERTHA'S STRUCTURE DURING THE LAST 6 HOURS.  THE EYE HAS
DISAPPEARED AND CLOUD TOPS HAVE WARMED CONSIDERABLY.  THERE IS ALSO
EVIDENCE IN MICROWAVE IMAGERY THAT THE WESTERN PORTION OF THE
EYEWALL HAS ERODED.  A BLEND OF THE FINAL T AND CI NUMBERS FROM THE
DVORAK TECHNIQUE SUPPORTS AN INITIAL INTENSITY OF 90 KT AND LATEST
OBJECTIVE T NUMBERS SUGGEST AN EVEN LOWER INTENSITY.  THE INITIAL
INTENSITY IS CONSERVATIVELY SET AT 90 KT.  IT WOULD APPEAR THAT
BERTHA HAS FINALLY ENCOUNTERED THE HIGHER SHEAR ENVIRONMENT WE'VE
BEEN FORECASTING.  ADDITIONALLY...THE CYCLONE IS MOVING OVER
SLIGHTLY COOLER WATERS AND THERE ARE SOME INDICATIONS IN SATELLITE
IMAGERY THAT IT COULD BE ENTRAINING DRY AIR.  BOTTOM LINE...THE
ENVIRONMENT LOOKS RATHER HOSTILE AND BERTHA SHOULD CONTINUE TO
WEAKEN IN THE SHORT-TERM.  TOWARDS THE END OF THE FORECAST
PERIOD...THE SHEAR COULD RELAX AND SSTS INCREASE SO THERE IS SOME
POTENTIAL FOR A LITTLE RE-INTENSIFICATION.  HOWEVER...GIVEN THE
UNCERTAINTY IN INTENSITY FORECASTING...THE OFFICIAL FORECAST MERELY
SHOWS SLOW WEAKENING THROUGH THE FORECAST PERIOD AND IS IN GOOD
AGREEMENT WITH A CONSENSUS OF THE VARIOUS INTENSITY MODELS. 
 
BERTHA HAS BEEN MOVING A LITTLE TO THE RIGHT OF THE PREVIOUS
ESTIMATE OR 315/9.  BERTHA SHOULD CONTINUE TO GRADUALLY TURN
NORTHWARD OVER THE NEXT COUPLE OF DAYS AS A MID-LEVEL RIDGE OVER
THE WESTERN ATLANTIC WEAKENS AND IS REPLACED BY A WEAK TROUGH. 
SINCE THE STEERING CURRENTS COULD BECOME RATHER WEAK AS A RESULT OF
THIS EVOLUTION...BERTHA COULD MOVE SLOWLY AND ERRATICALLY
TOWARDS THE END OF THE FORECAST.  IT IS FOR THIS REASON THAT
INTERESTS IN BERMUDA SHOULD CONTINUE TO MONITOR THE PROGRESS OF
THIS SYSTEM. TRACK MODELS HAVE NOT CHANGED SIGNIFICANTLY SINCE THE
LAST FORECAST SO ONLY COSMETIC CHANGES TO THE OFFICIAL TRACK
FORECAST ARE NEEDED AT THIS TIME.   
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      08/1500Z 22.1N  53.8W    90 KT
 12HR VT     09/0000Z 23.1N  54.9W    85 KT
 24HR VT     09/1200Z 24.3N  56.4W    80 KT
 36HR VT     10/0000Z 25.5N  57.8W    80 KT
 48HR VT     10/1200Z 26.6N  58.7W    75 KT
 72HR VT     11/1200Z 28.5N  59.5W    70 KT
 96HR VT     12/1200Z 30.5N  59.5W    65 KT
120HR VT     13/1200Z 32.5N  58.5W    65 KT
 
$$
FORECASTER RHOME
 

WTNT42 KNHC 082031
TCDAT2
HURRICANE BERTHA DISCUSSION NUMBER  23
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
500 PM EDT TUE JUL 08 2008
 
BERTHA'S SATELLITE PRESENTATION CONTINUES TO DEGRADE THIS AFTERNOON
AND DVORAK DATA T-NUMBERS HAVE FALLEN DURING THE LAST 6 HOURS. THE
INITIAL INTENSITY IS LOWERED TO 75 KT BASED ON AN AVERAGE OF THE
VARIOUS INTENSITY ESTIMATES. INDEED...BERTHA'S RAPID
INTENSIFICATION YESTERDAY HAS BEEN EQUALED BY ITS RAPID WEAKENING
TODAY. SUCH INTENSITY FLUCTUATIONS REMAIN A FORECASTING CHALLENGE
AND SERVE AS AN IMPORTANT REMINDER FOR THE UNCERTAINTIES ASSOCIATED
WITH INTENSITY FORECASTS. GIVEN THE CURRENT TREND IN SATELLITE
IMAGERY...CONTINUED WEAKENING IS POSSIBLE IN THE SHORT-TERM. MOST
OF THE INTENSITY MODELS SUGGEST THAT BERTHA MIGHT EVEN REGAIN SOME
STRENGTH LATER IN THE FORECAST AS THE SHEAR RELAXES AND THE SSTS
INCREASE. DUE TO THE UNCERTAINTY...THE OFFICIAL FORECAST SHOWS
SLIGHT WEAKENING IN THE SHORT-TERM WITH LITTLE CHANGE THEREAFTER.

BERTHA CONTINUES MOVING NORTHWESTWARD WITH AN INITIAL MOTION
ESTIMATE OF 310/10. BERTHA SHOULD CONTINUE TO GRADUALLY TURN
NORTHWARD OVER THE NEXT COUPLE OF DAYS AS A MID-LEVEL RIDGE OVER
THE WESTERN ATLANTIC WEAKENS AND IS REPLACED BY A WEAK TROUGH. THIS
EVOLUTION OF THE LARGE-SCALE PATTERN COULD RESULT IN THE STEERING
CURRENTS BECOMING RATHER WEAK BEYOND 72 HOURS...AND BERTHA COULD
MOVE SLOWLY AND ERRATICALLY TOWARDS THE END OF THE FORECAST. IT IS
FOR THIS REASON THAT INTERESTS IN BERMUDA SHOULD CONTINUE TO
MONITOR THE PROGRESS OF THIS SYSTEM. TRACK MODELS HAVE NOT CHANGED
SIGNIFICANTLY SINCE THE LAST ADVISORY AND NEITHER HAS THE OFFICIAL
FORECAST.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      08/2100Z 22.7N  54.8W    75 KT
 12HR VT     09/0600Z 23.6N  56.0W    70 KT
 24HR VT     09/1800Z 24.8N  57.4W    65 KT
 36HR VT     10/0600Z 26.0N  58.5W    65 KT
 48HR VT     10/1800Z 27.0N  59.2W    65 KT
 72HR VT     11/1800Z 29.0N  60.0W    60 KT
 96HR VT     12/1800Z 31.0N  59.5W    60 KT
120HR VT     13/1800Z 33.0N  58.5W    60 KT
 
$$
FORECASTER RHOME
 

WTNT42 KNHC 090231
TCDAT2
HURRICANE BERTHA DISCUSSION NUMBER  24
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
1100 PM EDT TUE JUL 08 2008

THERE HAS BEEN NO SIGNIFICANT CHANGE IN THE CLOUD PATTERN ASSOCIATED
WITH BERTHA. THERE IS A LITTLE BIT OF SOUTHEASTERLY SHEAR AND MOST
OF THE DEEP CONVECTION IS IN A WELL-DEFINED CYCLONICALLY CURVED
CONVECTIVE BAND TO THE WEST OF THE CENTER. BASED ON DVORAK
T-NUMBERS...THE BEST ESTIMATE OF THE INTENSITY IS 70 KNOTS. I AM
NOT QUITE SURE IF BERTHA HAS GIVEN UP AND WILL CONTINUE TO WEAKEN.
THE HURRICANE IS HEADING FOR WARMER WATERS AND LOWER SHEAR SO
REINTENSIFICATION IS NOT OUT OF THE QUESTION. BECAUSE OF THE MIXED
SIGNALS AMONG GUIDANCE...WITH THE SHIPS MODEL WEAKENING THE
HURRICANE AND BOTH GFDL AND HWRF SUGGESTING SLIGHT
STRENGTHENING...THE OFFICIAL FORECAST HAS OPTED TO KEEP BERTHA AS A
70 KT HURRICANE FOR THE NEXT 3 DAYS.  THEREAFTER...THE SHEAR IS
FORECAST TO INCREASE AND GRADUAL WEAKENING IS INDICATED.  

BERTHA HAS CONTINUED TO MOVE TOWARD THE NORTHWEST OR 310 DEGREES AT
10 KNOTS. A GRADUAL TURN TO THE NORTH IS EXPECTED BEYOND 48 HOURS
AS THE MID-LEVEL RIDGE CURRENTLY NORTH OF THE CYCLONE WEAKENS AND A
SHORT WAVE APPROACHES THE U.S. EAST COAST FROM THE WEST.
HOWEVER...THIS GENERAL NORTHWARD MOTION BETWEEN 48 AND 120 HOURS IS
EXPECTED TO BE PAINFULLY SLOW SINCE STEERING CURRENTS ARE FORECAST
TO BE VERY WEAK.  THERE WAS A SLIGHT CHANGE IN THE 00Z GUIDANCE.
UNANIMOUSLY...THEY ALL SHIFTED A DEGREE OR TWO WESTWARD...INCLUDING
THE HWRF WHICH WAS FARTHER EAST AND HAS NOW JOINED THE REST OF THE
MODEL SUITE. THE OFFICIAL TRACK FORECAST WAS SHIFTED A LITTLE BIT
TO THE WEST AND IS NOW ON THE RIGHT SIDE OF THE GUIDANCE
ENVELOPE...IN FACT...JUST EAST OF THE GFDL AND THE HWRF. I DO NOT
WANT TO CHANGE THE TRACK TOO MUCH SINCE I WOULD NOT BE SURPRISED IF
THE GUIDANCE SHIFTS BACK TO THE EAST IN THE NEXT RUN.   

 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      09/0300Z 23.1N  55.8W    70 KT
 12HR VT     09/1200Z 24.0N  57.0W    70 KT
 24HR VT     10/0000Z 25.5N  58.5W    70 KT
 36HR VT     10/1200Z 27.0N  60.0W    70 KT
 48HR VT     11/0000Z 28.0N  60.5W    70 KT
 72HR VT     12/0000Z 30.0N  61.0W    70 KT
 96HR VT     13/0000Z 31.5N  61.0W    65 KT
120HR VT     14/0000Z 33.5N  60.0W    60 KT
 
$$
FORECASTER AVILA
 

WTNT42 KNHC 090833
TCDAT2
HURRICANE BERTHA DISCUSSION NUMBER  25
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
500 AM EDT WED JUL 09 2008

THE CLOUD PATTERN ASSOCIATED WITH BERTHA APPEARS TO HAVE BECOME
SLIGHTLY MORE CIRCULAR AND ORGANIZED OVER THE PAST FEW HOURS.  A
SLIGHT EXPANSION OF THE CIRRUS CANOPY OVER THE SOUTHERN AND WESTERN
PORTIONS OF THE CIRCULATION SUGGESTS THAT VERTICAL SHEAR MAY BE
DECREASING.  THIS IS CONSISTENT WITH WATER VAPOR ANIMATIONS WHICH
SHOW AN UPPER-LEVEL CYCLONE NEAR 27N 68W MOVING WESTWARD AND
FARTHER AWAY FROM THE TROPICAL CYCLONE.  DVORAK SATELLITE CURRENT
INTENSITY ESTIMATES ARE ONLY 55 TO 65 KT AND THEREFORE THE CURRENT
WIND SPEED IS ADJUSTED TO 65 KT FOR THIS ADVISORY.  THE SHIPS MODEL
WHICH USES THE GFS UPPER-LEVEL WIND FORECAST DOES NOT SHOW A
DECREASE IN SHEAR OR ANY STRENGTHENING.  HOWEVER THE GFDL AND HWRF
MODELS...BOTH OF WHICH HAVE SOME LIMITED SKILL IN INTENSITY
PREDICTION...FORECAST A MODEST INCREASE IN STRENGTH OVER THE NEXT
48 HOURS OR SO.  MY WIND SPEED FORECAST ONLY HINTS AT THE
POSSIBILITY OF RE-INTENSIFICATION.  HOWEVER BERTHA WILL CONTINUE TO
TRAVERSE WARM WATERS FOR A COUPLE OF DAYS AND SINCE OTHER
ENVIRONMENTAL FACTORS DO NOT APPEAR INHIBITING...IT WOULD NOT BE
SURPRISING TO SEE IT BECOME STRONGER AGAIN.

ALTHOUGH THERE HAS BEEN A FAIR AMOUNT OF SCATTER IN THE CENTER FIXES
OVERNIGHT...MY ESTIMATE OF INITIAL MOTION IS STILL NORTHWESTWARD OR
305/9.  THERE HAS BEEN NO SIGNIFICANT CHANGE IN THE TRACK FORECAST
REASONING FROM THE PREVIOUS ADVISORY PACKAGE.   A MID-TROPOSPHERIC
ANTICYCLONE TO THE NORTH OF BERTHA IS LIKELY TO WEAKEN AS A 500 MB
SHORTWAVE TROUGH MOVES OFF OF THE U.S. EAST COAST IN 2-3 DAYS. 
THIS EVOLUTION SHOULD CAUSE THE MOTION OF THE HURRICANE TO SLOW
FURTHER AND TO TURN MORE NORTHWARD AROUND THAT TIME.  GLOBAL MODELS
INDICATE THAT THE TROUGH WILL MISS BERTHA AND LEAVE IT IN WEAK
STEERING CURRENTS UNTIL NEAR THE END OF THE FORECAST PERIOD WHEN A
NEW AND STRONGER TROUGH APPROACHES THE EAST COAST.  A VERY SLOW
MOTION IS INDICATED AROUND DAYS 3-4 DUE TO THE WEAK STEERING AND
BERTHA COULD ALSO MOVE ERRATICALLY AROUND THAT TIME.  BY DAY 5 THE
OFFICIAL FORECAST SHOWS A SLIGHT INCREASE IN NORTH-NORTHEASTWARD
MOTION IN RESPONSE TO THE SECOND TROUGH.  THE OFFICIAL TRACK
FORECAST IS QUITE CLOSE TO THE VARIABLE DYNAMICAL MODEL
CONSENSUS...TVCN.

IT IS STILL TOO EARLY TO KNOW WHETHER BERTHA WILL HAVE AN IMPACT ON
BERMUDA.  INTERESTS ON THAT ISLAND SHOULD CONTINUE TO MONITOR THE
PROGRESS OF THIS HURRICANE OVER THE NEXT COUPLE OF DAYS.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      09/0900Z 23.5N  56.5W    65 KT
 12HR VT     09/1800Z 24.2N  57.8W    65 KT
 24HR VT     10/0600Z 25.4N  59.2W    70 KT
 36HR VT     10/1800Z 26.8N  60.2W    70 KT
 48HR VT     11/0600Z 28.0N  61.0W    70 KT
 72HR VT     12/0600Z 30.0N  61.5W    70 KT
 96HR VT     13/0600Z 31.0N  61.5W    65 KT
120HR VT     14/0600Z 33.0N  61.0W    60 KT
 
$$
FORECASTER PASCH
 

WTNT42 KNHC 091440
TCDAT2
HURRICANE BERTHA DISCUSSION NUMBER  26
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
1100 AM EDT WED JUL 09 2008
 
BERTHA'S CLOUD PATTERN HAS IMPROVED THIS MORNING AND THE EYE APPEARS
TO BE REFORMING. THE INITIAL INTENSITY REMAINS 65 KT BASED ON 1200Z
DVORAK CLASSIFICATIONS BUT BERTHA LOOKS TO BE IN THE PROCESS OF
STRENGTHENING. THE INTENSITY FORECAST CONTINUES TO BE CHALLENGING.
IN THE SHORT-TERM...THE ATMOSPHERE APPEARS FAVORABLE FOR
STRENGTHENING AND THE OCEAN IS PLENTY WARM. HOWEVER...THE VARIOUS
INTENSITY MODELS ARE NOT IN GOOD AGREEMENT ON HOW MUCH OR EVEN WHEN
REINTENSIFICATION MIGHT OCCUR. GIVEN THE CURRENT TREND IN THE
SATELLITE PRESENTATION...THE OFFICIAL FORECAST ASSUMES SOONER
RATHER THAN LATER AND SHOWS BERTHA STRENGTHENING DURING THE FIRST
24 HOURS. THEREAFTER...BERTHA WILL BE MOVING OVER WARMER WATERS BUT
WITH INCREASING VERTICAL SHEAR MAKING IT UNCLEAR WHETHER
INTENSIFICATION WILL CONTINUE. GIVEN THE UNCERTAINTY...THE OFFICIAL
FORECAST CONTINUES THE PREVIOUSLY SHOWN TREND OF SLOW WEAKENING. AS
THE ABOVE SHOWS...THERE IS CONSIDERABLE UNCERTAINTY IN THE
INTENSITY FORECAST.
 
THE INITIAL MOTION IS ESSENTIALLY UNCHANGED FROM THE PREVIOUS
PACKAGE...300/10.  BERTHA SHOULD CONTINUE A SLOW TURN NORTHWARD
DURING THE NEXT 2-3 DAYS AS A MID-TROPOSPHERIC ANTICYCLONE
CURRENTLY NEAR BERMUDA IS FORECAST TO WEAKEN AND A 500 MB
SHORTWAVE TROUGH MOVES OFF OF THE U.S. EAST COAST.  BEYOND 72
HOURS...THE TRACK BECOMES A LITTLE LESS CERTAIN AS THE SHORTWAVE IS
NOT CURRENTLY FORECAST TO PICK UP THE CYCLONE.  RATHER...IT LEAVES
BERTHA BEHIND IN WEAK STEERING CURRENTS POSSIBLY RESULTING IN SLOW
AND ERRATIC MOTION AT THE END OF THE FORECAST.  TRACK MODELS HAVE
NOT DEMONSTRATED GOOD RUN TO RUN CONSISTENCY.  AS A RESULT...THE
NEW OFFICIAL TRACK FORECAST IS ESSENTIALLY UNCHANGED AND LIES WEST
OF THE DYNAMICAL MODEL CONSENSUS.
 
IT IS STILL TOO EARLY TO KNOW WHETHER BERTHA WILL HAVE AN IMPACT ON
BERMUDA.  INTERESTS ON THAT ISLAND SHOULD CONTINUE TO MONITOR THE
PROGRESS OF THIS HURRICANE OVER THE NEXT COUPLE OF DAYS.

 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      09/1500Z 24.2N  57.5W    65 KT
 12HR VT     10/0000Z 24.7N  58.5W    70 KT
 24HR VT     10/1200Z 25.9N  59.7W    75 KT
 36HR VT     11/0000Z 27.2N  60.6W    75 KT
 48HR VT     11/1200Z 28.3N  61.1W    70 KT
 72HR VT     12/1200Z 30.0N  61.5W    70 KT
 96HR VT     13/1200Z 31.5N  61.5W    65 KT
120HR VT     14/1200Z 33.5N  60.5W    60 KT
 
$$
FORECASTER RHOME
 

WTNT42 KNHC 092032
TCDAT2
HURRICANE BERTHA DISCUSSION NUMBER  27
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
500 PM EDT WED JUL 09 2008
 
BERTHA'S SATELLITE PRESENTATION HAS DRAMATICALLY IMPROVED DURING THE
LAST 6 HOURS.  THE CYCLONE NOW HAS A DISTINCTIVE EYE AND IS
SURROUNDED BY A SYMMETRIC RING OF COLD CLOUD TOPS.  THE INITIAL
INTENSITY IS RAISED TO 90 KT BASED ON A BLEND OF THE SATELLITE
CLASSIFICATIONS FROM SAB AND TAFB.  BERTHA IS FORECAST TO BE IN A
SEEMINGLY FAVORABLE ENVIRONMENT FOR THE NEXT DAY OR SO AND
CONTINUED STRENGTHENING IS EXPECTED IN THE SHORT-TERM.  BEYOND 36
HOURS...VERTICAL SHEAR IS STILL EXPECTED TO GRADUALLY INCREASE AND
SSTS SLOWLY FALL.  THIS ENVIRONMENT IS EXPECTED TO RESULT IN A SLOW
WEAKENING TREND THROUGH THE END OF THE FORECAST PERIOD.  IT SHOULD
BE NOTED THAT BERTHA COULD BECOME A LITTLE STRONGER THAN CURRENTLY
FORECAST IN THE FIRST 24 HOURS. 
 
BERTHA HAS RECENTLY WOBBLED A LITTLE RIGHT OF THE PREVIOUS MOTION
ESTIMATE BUT THE 12 HOUR AVERAGE MOTION IS ESSENTIALLY
UNCHANGED...305/10.  THE TRACK FORECAST PHILOSOPHY IS THE SAME AS
IN THE PREVIOUS ADVISORY.  A MID-TROPOSPHERIC ANTICYCLONE
CURRENTLY OVER THE WESTERN ATLANTIC IS FORECAST TO MOVE
NORTHEASTWARD WHILE A SHORTWAVE TROUGH MOVES OFF OF THE U.S. EAST
COAST.  THIS SHOULD RESULT IN BERTHA MAKING A GRADUAL TURN TOWARD
THE NORTH DURING THE NEXT 2-3 DAYS.  HOWEVER...THIS TROUGH IS
FORECAST TO BYPASS BERTHA TO THE NORTH AND LEAVE IT BEHIND IN
RELATIVELY WEAK STEERING CURRENTS.  ACCORDINGLY...THE OFFICIAL
FORECAST SHOWS A SLOW NORTHWARD MOTION AT DAYS 3 AND 4.  A SECOND
TROUGH MOVING OFF THE UNITED STATES EAST COAST ON DAY 5 COULD
RESULT IN SOME NORTHWARD ACCELERATION LATE IN THE FORECAST PERIOD. 
IN GENERAL...TRACK MODELS HAVE CHANGED LITTLE SINCE THE LAST
ADVISORY...AND THE NEW OFFICIAL TRACK FORECAST IS ESSENTIALLY AN
UPDATE OF THE PREVIOUS ONE.
 
IT IS STILL TOO EARLY TO KNOW WHETHER BERTHA WILL HAVE AN IMPACT ON
BERMUDA.  INTERESTS ON THAT ISLAND SHOULD CONTINUE TO MONITOR THE
PROGRESS OF THIS HURRICANE OVER THE NEXT COUPLE OF DAYS.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      09/2100Z 24.8N  58.1W    90 KT
 12HR VT     10/0600Z 25.6N  59.2W   100 KT
 24HR VT     10/1800Z 26.8N  60.2W   100 KT
 36HR VT     11/0600Z 28.0N  61.0W   100 KT
 48HR VT     11/1800Z 29.1N  61.3W    95 KT
 72HR VT     12/1800Z 31.0N  61.5W    85 KT
 96HR VT     13/1800Z 32.5N  61.0W    80 KT
120HR VT     14/1800Z 35.5N  60.0W    75 KT
 
$$
FORECASTER RHOME
 

WTNT42 KNHC 100300
TCDAT2
HURRICANE BERTHA DISCUSSION NUMBER  28
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
1100 PM EDT WED JUL 09 2008

THERE HAVE BEEN NO APPRECIABLE CHANGES IN THE SATELLITE APPEARANCE
OF THE HURRICANE DURING THE PAST FEW HOURS.  OBJECTIVE DVORAK
ESTIMATES APPROACHED 100 KT A FEW HOURS AGO BUT HAVE SINCE COME
BACK DOWN IN LINE WITH THE 00Z SUBJECTIVE ESTIMATES...WHICH SUPPORT
MAINTAINING THE ADVISORY INTENSITY AT 90 KT.  BERTHA CURRENTLY LIES
OVER SEA-SURFACE TEMPERATURES OF ALMOST 28 CELSIUS...AND THE WATERS
ALONG THE FORECAST TRACK WILL REMAIN ABOUT THE SAME FOR THE NEXT
COUPLE OF DAYS.  GLOBAL MODELS DO NOT APPEAR TO FORECAST AN
INCREASE IN VERTICAL WIND SHEAR IMPACTING THE TROPICAL CYCLONE
DURING THAT PERIOD...SO ALL OF THE OBJECTIVE INTENSITY MODELS
FORECAST AT LEAST A LITTLE STRENGTHENING.  THE OFFICIAL FORECAST
AGAIN CALLS FOR BERTHA TO REGAIN MAJOR HURRICANE STATUS...IN
AGREEMENT WITH THE HWRF MODEL.  GRADUAL WEAKENING IS FORECAST AT
DAYS 3 THROUGH 5 DUE TO COOLING SSTS AND THE POTENTIAL
FOR AN INCREASE IN SHEAR...IN LINE WITH THE INTENSITY MODEL
CONSENSUS.  THE SHIPS AND LGEM...HOWEVER...FORECAST MORE RAPID
WEAKENING THAN THE GFDL AND HWRF...SO HOW MUCH WEAKENING OCCURS
NEAR THE END OF THE FORECAST IS RATHER UNCERTAIN...AND DEPENDS IN
PART ON HOW FAST BERTHA MOVES TOWARD COOLER WATERS BY THAT TIME.

THE HURRICANE CONTINUES MOVING NORTHWESTWARD OR ALONG 315 DEGREES AT
ABOUT 10 KT...WITH STEERING PROVIDED BY A MID-LEVEL RIDGE TO ITS
NORTH.  AS THAT RIDGE SLIDES EASTWARD AND WEAKENS DURING THE NEXT
TWO TO THREE DAYS...BERTHA IS FORECAST TO GRADUALLY TURN TOWARD THE
NORTH AND SLOW DOWN.  THIS PORTION OF THE FORECAST IS AGREED UPON
WELL BY THE VARIOUS DYNAMICAL MODELS...BUT THEN THEY START TO
DIVERGE...ESPECIALLY IN TERMS OF FORWARD SPEED...DUE TO VARYING
DEPICTIONS OF WHEN A HIGH-AMPLITUDE TROUGH WILL EMERGE OFF THE EAST
COAST OF THE UNITED STATES.  THE UKMET...NOGAPS...AND GFDL FORECAST
BERTHA TO SPEED UP BEYOND 72 HOURS AHEAD OF A SLIGHTLY MORE
PROGRESSIVE TROUGH...WHILE THE 18Z GFS AND THE 12Z ECMWF FORECAST
BERTHA TO STALL AT 72-120 HOURS...WAITING FOR THAT TROUGH TO
PERHAPS PICK BERTHA UP LATER.  THE NEW OFFICIAL TRACK FORECAST IS
SLOWED DOWN A LITTLE AT THE END COMPARED TO THE PREVIOUS
ADVISORY...AS AN APPROXIMATE COMPROMISE BETWEEN THESE EXTREMES.  IT
IS IMPORTANT TO NOTE THAT ALL OF THE MODELS SHOW A RELATIVELY SLOW
MOTION AT AROUND 72 HOURS...NOT FAR EAST OF BERMUDA...AND BERTHA
COULD MOVE ERRATICALLY DURING THAT TIME FRAME.  THEREFORE...
INTERESTS ON THAT ISLAND SHOULD CLOSELY MONITOR THE PROGRESS OF
BERTHA FOR THE NEXT SEVERAL DAYS.

CONSIDERING THE COMBINED FORECAST UNCERTAINTIES IN THE
TRACK...INTENSITY...AND SIZE OF BERTHA...THERE IS ALREADY A 43%
CHANCE THAT BERMUDA WILL EXPERIENCE SUSTAINED WINDS OF TROPICAL
STORM FORCE DURING THE NEXT FIVE DAYS...AS CONVEYED IN THE WIND
SPEED PROBABILITY PRODUCT ACCOMPANYING THIS ADVISORY PACKAGE.

 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      10/0300Z 25.5N  58.9W    90 KT
 12HR VT     10/1200Z 26.4N  59.9W   100 KT
 24HR VT     11/0000Z 27.5N  60.8W   100 KT
 36HR VT     11/1200Z 28.7N  61.5W   100 KT
 48HR VT     12/0000Z 29.7N  61.8W    95 KT
 72HR VT     13/0000Z 31.0N  62.0W    85 KT
 96HR VT     14/0000Z 32.5N  61.5W    75 KT
120HR VT     15/0000Z 35.5N  60.5W    65 KT
 
$$
FORECASTER KNABB/BROWN
 

WTNT42 KNHC 100834
TCDAT2
HURRICANE BERTHA DISCUSSION NUMBER  29
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
500 AM EDT THU JUL 10 2008

DVORAK T-NUMBERS REMAIN AT 5.0 CORRESPONDING TO 90 KT...WHICH IS
USED FOR THE ADVISORY INTENSITY.  THERE HAS BEEN SOME EROSION OF
DEEP CONVECTION OVER THE SOUTHWEST QUADRANT OF THE
HURRICANE...PROBABLY DUE TO THE COMBINATION OF INCREASED
SOUTH-SOUTHWESTERLY SHEAR AND THE INTRUSION OF DRIER AIR.  GIVEN
THIS EVOLUTION...I HAVE ELECTED TO BACK OFF SLIGHTLY ON THE
INTENSITY PREDICTION.  THE CURRENT OFFICIAL WIND SPEED FORECAST IS
A BLEND OF THE STATISTICAL/DYNAMICAL GUIDANCE SHIPS AND LGEM ALONG
WITH THE PURELY DYNAMICAL MODELS GFDL AND HWRF.  SEA SURFACE
TEMPERATURES SHOULD REMAIN SUFFICIENTLY WARM FOR STRENGTHENING
THROUGH AT LEAST 3-4 DAYS...BUT THE SHIPS MODEL DIAGNOSES 27-31 KT
OF VERTICAL SHEAR IN 3-5 DAYS.  THEREFORE WEAKENING IS LIKELY TO
OCCUR IN THE LATTER PART OF THE FORECAST PERIOD.

BERTHA'S FORWARD MOTION HAS SLOWED A BIT AND IS NOW ABOUT 315/8.  AN
ANTICYCLONE TO THE NORTH OF THE HURRICANE WILL CONTINUE TO SLIDE
EASTWARD OVER THE NEXT DAY OR TWO...SO THE TRACK OF THE HURRICANE
IS LIKELY TO BEND TOWARD THE NORTH THROUGH 48 HOURS.  BEYOND THAT
TIME...THE TRACK FORECAST IS COMPLICATED BY THE FACT THAT THE
DYNAMICAL MODELS...IN PARTICULAR THE GFS...SHOW A MID-LEVEL
ANTICYCLONE DEVELOPING TO THE NORTH OF BERTHA IN AROUND 72 HOURS. 
THIS DEVELOPMENT WOULD AT LEAST RETARD THE NORTHWARD PROGRESS OF
THE HURRICANE AND...IF THE ANTICYCLONE TURNS OUT TO BE STRONG
ENOUGH...COULD EVEN FORCE A TURN TO THE LEFT AS INDICATED BY THE
GFS.  THE GFDL AND HWRF MODELS RESPOND TO THE INCREASED RIDGING
MAINLY BY SLOWING THE TROPICAL CYCLONE AS IT CROSSES 30N LATITUDE. 
IT IS CERTAINLY POSSIBLE FOR BERTHA TO MOVE ERRATICALLY IN ABOUT 3
DAYS...BUT THE DETAILS OF THAT MOTION ARE OF COURSE UNKNOWN.  BY
THE END OF THE FORECAST PERIOD...THE FLOW AHEAD OF A LARGE-
AMPLITUDE 500 MB TROUGH NEARING THE U.S EAST COAST IS EXPECTED TO
CAUSE BERTHA TO MOVE NORTH-NORTHEASTWARD WITH SOME INCREASE IN
FORWARD SPEED.

THE RADII OF 12-FT SEAS HAVE BEEN ADJUSTED BY THE TROPICAL ANALYSIS
AND FORECAST BRANCH BASED ON A JASON SATELLITE ALTIMETER PASS OVER
BERTHA...WHICH IS QUITE CONSISTENT WITH THE LATEST OUTPUT FROM THE
NORTH ATLANTIC HURRICANE WAVE MODEL. 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      10/0900Z 26.0N  59.4W    90 KT
 12HR VT     10/1800Z 27.0N  60.3W    95 KT
 24HR VT     11/0600Z 28.0N  61.1W    95 KT
 36HR VT     11/1800Z 29.1N  61.8W    95 KT
 48HR VT     12/0600Z 29.9N  62.0W    90 KT
 72HR VT     13/0600Z 31.0N  62.0W    80 KT
 96HR VT     14/0600Z 32.5N  62.0W    70 KT
120HR VT     15/0600Z 36.0N  61.0W    60 KT
 
$$
FORECASTER PASCH
 

WTNT42 KNHC 101451
TCDAT2
HURRICANE BERTHA DISCUSSION NUMBER  30
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
1100 AM EDT THU JUL 10 2008
 
SATELLITE IMAGERY INDICATES THAT THE EYE OF BERTHA HAS BECOME
SOMEWHAT RAGGED THIS MORNING...AND THE CONVECTIVE TOPS IN THE
EYEWALL HAVE WARMED.  THIS HAS RESULTED IN THE SATELLITE INTENSITY
ESTIMATES FROM TAFB AND SAB DECREASING TO 77 KT.  THE INITIAL
INTENSITY IS REDUCED TO 80 KT...AND THIS COULD BE A LITTLE
GENEROUS.  ALTHOUGH BERTHA HAS WEAKENED...THE OUTER BANDING HAS
INCREASED DURING THE NIGHT AND NOW SURROUNDS THE EYE AND CENTRAL
DENSE OVERCAST.  THE CIRRUS OUTFLOW IS FAIR TO GOOD IN ALL
DIRECTIONS EXCEPT THE SOUTHEAST...WHERE IT IS POOR TO NON-EXISTENT.
 
THE INITIAL MOTION REMAINS 315/8.  BERTHA IS ON THE SOUTH SIDE OF A
MID-LEVEL ANTICYCLONE SEEN IN WATER VAPOR IMAGERY NEAR 37N59W.  THE
ANTICYCLONE WILL WEAKEN AS A MID/UPPER-LEVEL SHORTWAVE TROUGH OVER
THE NORTHEASTERN UNITED STATES MOVES INTO THE ATLANTIC DURING THE
NEXT 24-36 HOURS.  THIS PATTERN EVOLUTION SHOULD CAUSE BERTHA TO
TURN NORTHWARD.  THE SHORTWAVE TROUGH IS FORECAST TO PASS NORTH OF
BERTHA...AND FROM 36-72 HR THE LARGE-SCALE MODELS FORECAST A
MID-LEVEL RIDGE TO BUILD NORTH OF THE HURRICANE IN THE WAKE OF THE
TROUGH.  THE TRACK MODELS RESPOND TO THIS BY FORECASTING ERRATIC
MOTION AS BERTHA APPROACHES BERMUDA.  THE NEW FORECAST TRACK WILL
CALL FOR A SLOW NORTHWARD MOTION DURING THIS TIME AS A COMPROMISE
BETWEEN THE VARIOUS TWISTS AND TURNS OF THE TRACK GUIDANCE. 
HOWEVER...THERE IS A POSSIBILITY THAT BERTHA COULD JOG LEFT OF THE
FORECAST TRACK CLOSER TO BERMUDA AS SHOWN BY THE GFS...UKMET...AND
CANADIAN MODELS.  AFTER 72 HR...A SECOND MID/UPPER-LEVEL TROUGH
MOVING INTO THE WESTERN ATLANTIC SHOULD WEAKEN THE RIDGE...WHICH
SHOULD CAUSE BERTHA TO MOVE SOMEWHAT FASTER TOWARD THE NORTH.

THE INTENSITY FORECAST IS A CONUNDRUM.  THE LARGE-SCALE MODELS
FORECAST A LARGE UPPER-LEVEL ANTICYCLONE TO DEVELOP OVER BERTHA
DURING THE NEXT 24-48 HR WHILE THE SYSTEM IS STILL OVER WARM WATER.
THIS ENVIRONMENT SHOULD BE FAVORABLE FOR STRENGTHENING...YET NONE
OF THE INTENSITY FORECAST GUIDANCE CALLS FOR SIGNIFICANT
STRENGTHENING DURING THIS TIME.  GIVEN THE ENVIRONMENT...THE
INTENSITY FORECAST WILL BUCK THE MODEL GUIDANCE AND CALL FOR SLIGHT
STRENGTHENING DURING THE FIRST 24-36 HR.  THEREAFTER...THE
LARGE-SCALE MODELS SUGGEST THE POSSIBILITY OF INCREASED VERTICAL
WIND SHEAR...ALTHOUGH THEY DIFFER ON THE DETAILS.  THIS...COMBINED
WITH COOLING SEA SURFACE TEMPERATURES...ARE EXPECTED TO CAUSE BERTA
TO SLOWLY WEAKEN.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      10/1500Z 26.5N  60.2W    80 KT
 12HR VT     11/0000Z 27.5N  61.0W    80 KT
 24HR VT     11/1200Z 28.5N  61.6W    85 KT
 36HR VT     12/0000Z 29.5N  62.0W    85 KT
 48HR VT     12/1200Z 30.1N  62.0W    80 KT
 72HR VT     13/1200Z 31.5N  62.0W    75 KT
 96HR VT     14/1200Z 33.5N  61.5W    65 KT
120HR VT     15/1200Z 37.0N  61.0W    55 KT
 
$$
FORECASTER BEVEN
 

WTNT42 KNHC 101527
TCDAT2
HURRICANE BERTHA DISCUSSION NUMBER  30...CORRECTED
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
1100 AM EDT THU JUL 10 2008

...CORRECTED TYPO IN LAST SENTENCE...
 
SATELLITE IMAGERY INDICATES THAT THE EYE OF BERTHA HAS BECOME
SOMEWHAT RAGGED THIS MORNING...AND THE CONVECTIVE TOPS IN THE
EYEWALL HAVE WARMED.  THIS HAS RESULTED IN THE SATELLITE INTENSITY
ESTIMATES FROM TAFB AND SAB DECREASING TO 77 KT.  THE INITIAL
INTENSITY IS REDUCED TO 80 KT...AND THIS COULD BE A LITTLE
GENEROUS.  ALTHOUGH BERTHA HAS WEAKENED...THE OUTER BANDING HAS
INCREASED DURING THE NIGHT AND NOW SURROUNDS THE EYE AND CENTRAL
DENSE OVERCAST.  THE CIRRUS OUTFLOW IS FAIR TO GOOD IN ALL
DIRECTIONS EXCEPT THE SOUTHEAST...WHERE IT IS POOR TO NON-EXISTENT.
 
THE INITIAL MOTION REMAINS 315/8.  BERTHA IS ON THE SOUTH SIDE OF A
MID-LEVEL ANTICYCLONE SEEN IN WATER VAPOR IMAGERY NEAR 37N59W.  THE
ANTICYCLONE WILL WEAKEN AS A MID/UPPER-LEVEL SHORTWAVE TROUGH OVER
THE NORTHEASTERN UNITED STATES MOVES INTO THE ATLANTIC DURING THE
NEXT 24-36 HOURS.  THIS PATTERN EVOLUTION SHOULD CAUSE BERTHA TO
TURN NORTHWARD.  THE SHORTWAVE TROUGH IS FORECAST TO PASS NORTH OF
BERTHA...AND FROM 36-72 HR THE LARGE-SCALE MODELS FORECAST A
MID-LEVEL RIDGE TO BUILD NORTH OF THE HURRICANE IN THE WAKE OF THE
TROUGH.  THE TRACK MODELS RESPOND TO THIS BY FORECASTING ERRATIC
MOTION AS BERTHA APPROACHES BERMUDA.  THE NEW FORECAST TRACK WILL
CALL FOR A SLOW NORTHWARD MOTION DURING THIS TIME AS A COMPROMISE
BETWEEN THE VARIOUS TWISTS AND TURNS OF THE TRACK GUIDANCE. 
HOWEVER...THERE IS A POSSIBILITY THAT BERTHA COULD JOG LEFT OF THE
FORECAST TRACK CLOSER TO BERMUDA AS SHOWN BY THE GFS...UKMET...AND
CANADIAN MODELS.  AFTER 72 HR...A SECOND MID/UPPER-LEVEL TROUGH
MOVING INTO THE WESTERN ATLANTIC SHOULD WEAKEN THE RIDGE...WHICH
SHOULD CAUSE BERTHA TO MOVE SOMEWHAT FASTER TOWARD THE NORTH.

THE INTENSITY FORECAST IS A CONUNDRUM.  THE LARGE-SCALE MODELS
FORECAST A LARGE UPPER-LEVEL ANTICYCLONE TO DEVELOP OVER BERTHA
DURING THE NEXT 24-48 HR WHILE THE SYSTEM IS STILL OVER WARM WATER.
THIS ENVIRONMENT SHOULD BE FAVORABLE FOR STRENGTHENING...YET NONE
OF THE INTENSITY FORECAST GUIDANCE CALLS FOR SIGNIFICANT
STRENGTHENING DURING THIS TIME.  GIVEN THE ENVIRONMENT...THE
INTENSITY FORECAST WILL BUCK THE MODEL GUIDANCE AND CALL FOR SLIGHT
STRENGTHENING DURING THE FIRST 24-36 HR.  THEREAFTER...THE
LARGE-SCALE MODELS SUGGEST THE POSSIBILITY OF INCREASED VERTICAL
WIND SHEAR...ALTHOUGH THEY DIFFER ON THE DETAILS.  THIS...COMBINED
WITH COOLING SEA SURFACE TEMPERATURES...ARE EXPECTED TO CAUSE BERTHA
TO SLOWLY WEAKEN.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      10/1500Z 26.5N  60.2W    80 KT
 12HR VT     11/0000Z 27.5N  61.0W    80 KT
 24HR VT     11/1200Z 28.5N  61.6W    85 KT
 36HR VT     12/0000Z 29.5N  62.0W    85 KT
 48HR VT     12/1200Z 30.1N  62.0W    80 KT
 72HR VT     13/1200Z 31.5N  62.0W    75 KT
 96HR VT     14/1200Z 33.5N  61.5W    65 KT
120HR VT     15/1200Z 37.0N  61.0W    55 KT
 
$$
FORECASTER BEVEN
 

WTNT42 KNHC 102043
TCDAT2
HURRICANE BERTHA DISCUSSION NUMBER  31
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
500 PM EDT THU JUL 10 2008
 
A RECENT TRMM OVERPASS AND GOES VISIBLE IMAGERY INDICATE THAT THE
OUTER CONVECTIVE BANDING NOTED EARLIER HAS WRAPPED UP INTO AN OUTER
EYEWALL WITH A DIAMETER OF ABOUT 75 N MI.  THIS FEATURE SURROUNDS
THE ORIGINAL INNER EYE WHICH IS ABOUT 10 N MI WIDE.  BASED ON
SATELLITE INTENSITY ESTIMATES AND WARMING OF THE CLOUD TOPS IN THE
INNER EYEWALL...THE INITIAL INTENSITY IS REDUCED TO 75 KT.  THE
CIRRUS OUTFLOW REMAINS GOOD IN THE NORTHWESTERN SEMICIRCLE...AND
HAS INCREASED SINCE THIS MORNING IN THE SOUTHEASTERN SEMICIRCLE.

THE INITIAL MOTION IS 315/9.  WATER VAPOR IMAGERY SHOWS A COMPLEX
STEERING PATTERN...CONSISTING OF A BROAD MID/UPPER-LEVEL TROUGH
OVER THE NORTHEASTERN UNITED STATES AND A MID-LEVEL RIDGE NORTH OF
BERTHA THAT ARE MOVING EASTWARD...AND AN UPPER-LEVEL LOW NEAR
28N69W THAT IS MOVING SLOWLY WESTWARD.  IN THE SHORT TERM...THIS
PATTERN SHOULD CAUSE BERTHA TO TURN NORTHWARD AS SHOWN IN THE NEW
FORECAST TRACK.  DURING THE 36-72 HR PERIOD...A MID-LEVEL RIDGE
DEVELOPING BEHIND THE SHORTWAVE TROUGH IS LIKELY TO BLOCK BERTHA'S
NORTHWARD MOTION...WITH THE POSSIBILITY OF ERRATIC MOTION NEAR OR
TO THE EAST OF BERMUDA.  THEREAFTER...THE LARGE-SCALE MODELS
CURRENTLY AGREE THAT A SECOND TROUGH MOVING THROUGH THE
NORTHWESTERN ATLANTIC WILL BYPASS BERTHA...LEAVING THE STORM
TRAPPED IN THE SUBTROPICAL RIDGE TO THE NORTH OR NORTHEAST OF
BERMUDA.  IN A MAJOR SHIFT FROM PREVIOUS RUNS...NONE OF THE
DYNAMICAL MODELS SHOW BERTHA REACHING 40N IN 5 DAYS.  BASED ON
THIS...THE FORECAST TRACK WILL CALL FOR A SLOWER NORTHWARD MOTION
THAN IN THE PREVIOUS PACKAGE... WITH THE TRACK SMOOTHING THROUGH
SOME OF THE ERRATIC MOTION FORECASTS IN THE MODELS.  THE NEW TRACK
IS CLOSER TO BERMUDA THAN THE PREVIOUS TRACK...AND BERTHA COULD COME
EVEN CLOSER TO BERMUDA IF THE JOGS TO THE LEFT IN THE UKMET AND
CANADIAN MODELS VERIFY.

AN UPPER-LEVEL ANTICYCLONE IS BUILDING OVER BERTHA...AND THE STORM
STILL HAS A DAY OR TWO MORE OVER WARM SEA SURFACE TEMPERATURES. 
THUS...EVEN THOUGH NONE OF THE FORECAST MODELS CALL FOR SIGNIFICANT
STRENGTHENING...THE HURRICANE COULD RE-INTENSIFY AT THE END OF THE
EYEWALL REPLACEMENT CYCLE.  BASED ON THIS...THE NEW INTENSITY
FORECAST CALLS FOR MODEST STRENGTHENING IN 24 HR.  LATER IN THE
FORECAST PERIOD...BERTHA IS EXPECTED TO MOVE OUT FROM UNDER THE
ANTICYCLONE AND ENCOUNTER VERTICAL WIND SHEAR.  THIS SHOULD OCCUR
AS BERTHA REACHES COOLER WATERS AND RESULT IN A WEAKENING TREND.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      10/2100Z 27.2N  60.8W    75 KT
 12HR VT     11/0600Z 28.0N  61.7W    75 KT
 24HR VT     11/1800Z 29.0N  62.2W    80 KT
 36HR VT     12/0600Z 29.8N  62.5W    80 KT
 48HR VT     12/1800Z 30.5N  62.5W    75 KT
 72HR VT     13/1800Z 31.5N  62.5W    70 KT
 96HR VT     14/1800Z 33.0N  62.5W    60 KT
120HR VT     15/1800Z 36.0N  62.0W    50 KT
 
$$
FORECASTER BEVEN
 

WTNT42 KNHC 110300
TCDAT2
HURRICANE BERTHA DISCUSSION NUMBER  32
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
1100 PM EDT THU JUL 10 2008
 
A SERIES OF MICROWAVE OVERPASSES THROUGHOUT THE DAY INDICATE THAT
THE INNER EYEWALL HAS BEEN SLOWLY DETERIORATING...WHILE A NEW OUTER
EYEWALL HAS BEEN TAKING SHAPE.  THE MOST RECENT IMAGE...FROM SSMIS
AT 2319Z...DEPICTS THE OUTER EYEWALL AS A COMPLETELY CLOSED RING AT
A RADIUS OF ABOUT 60 N MI...WITH BARELY HALF OF THE INNER EYEWALL
REMAINING.  TRENDS IN GEOSTATIONARY INFRARED IMAGERY REFLECT THE
EVOLVING STRUCTURE...AS THE EYE HAS JUST ABOUT DISAPPEARED WHILE
CLOUD TOPS HAVE BEEN COOLING ABOVE THE OUTER RING SEEN IN THE
MICROWAVE.  IN ADDITION...A QUIKSCAT PASS BACK AT 23Z DEPICTED A
SECONDARY WIND MAXIMUM IN THE OUTER EYEWALL.  DVORAK INTENSITY
ESTIMATES AT 00Z WERE ALL 75 KT...BUT IT IS HARD TO ESTIMATE EVEN
VERY SHORT-TERM INTENSITY CHANGES GIVEN THE ONGOING STRUCTURAL
CHANGES...EVEN THOUGH THE OCEAN AND ATMOSPHERIC ENVIRONMENTS ARE NOT
PROHIBITIVE FOR STRENGTHENING.  IT IS POSSIBLE THAT BERTHA WILL
WEAKEN SOME UPON THE FINAL DEMISE OF THE INNER EYEWALL...AND IT IS
ALSO POSSIBLE THAT THE NEW OUTER EYEWALL WILL EVENTUALLY CONTRACT
AND BE ACCOMPANIED BY SOME STRENGTHENING...BUT I AM NOT GOING TO
TRY TO EXPLICITLY FORECAST SUCH CHANGES.  THE MOST PRUDENT
APPROACH...WHICH IS ALSO SUPPORTED BY THE OBJECTIVE GUIDANCE...IS
TO KEEP THE INTENSITY LEVEL FOR THE NEXT COUPLE OF DAYS...FOLLOWED
BY GRADUAL WEAKENING AS THE WIND SHEAR POTENTIALLY INCREASES AND
BERTHA PASSES OVER GRADUALLY COOLER SEA-SURFACE TEMPERATURES.  THE
NEW INTENSITY FORECAST HAS JUST A SLIGHTLY LOWER PEAK INTENSITY
THAN THE PREVIOUS ADVISORY.

BERTHA APPEARS TO BE GRADUALLY SLOWING DOWN...AND THE INITIAL MOTION
ESTIMATE IS NOW 315/7.  THE FORECAST AND ITS SUPPORTING REASONING
HAVE NOT REALLY CHANGED FOR THE FIRST 48 HOURS OR SO...INCLUDING A
VERY SLOW FORWARD MOTION IN A COUPLE OF DAYS NEAR BERMUDA.  BEYOND
THAT TIME...ESSENTIALLY ALL OF THE MODELS HAVE SHIFTED TO THE EAST
AND FORECAST A FASTER MOTION AT 4-5 DAYS...THIS TIME FORECASTING
BERTHA TO BE PULLED NORTHWARD A LITTLE SOONER BY A TROUGH ALONG THE
U.S. EAST COAST BY THEN...WITH SLIGHTLY LESS RIDGING TO THE NORTH
TO BLOCK BERTHA'S POLEWARD PROGRESS.  THE NEW OFFICIAL TRACK
FORECAST DOES NOT COMPLETELY BUY INTO THIS MUCH OF A SHIFT IN THE
MODELS...BUT IT IS ADJUSTED EASTWARD AND MOST OF THE WAY TOWARD THE
CONSENSUS.  SINCE THIS NEW TRACK STILL DOES NOT FORECAST BERTHA TO
BE GOING ANY FASTER THAN ABOUT 5-7 KT AT THE END OF THE FIVE-DAY
PERIOD...THIS ADJUSTMENT DOES NOT REPRESENT A HUGE CHANGE IN WHERE
WE EXPECT BERTHA TO BE IN FIVE DAYS.

THE LATEST WIND SPEED PROBABILITY PRODUCT ACCOMPANYING THIS ADVISORY
PACKAGE INDICATES THAT...GIVEN UNCERTAINTIES IN THE FORECASTS OF
BERTHA'S TRACK...INTENSITY...AND SIZE...THERE ROUGHLY A 50% CHANCE
THAT WINDS OF TROPICAL STORM FORCE WILL AFFECT BERMUDA DURING THE
NEXT FIVE DAYS.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      11/0300Z 27.7N  61.2W    75 KT
 12HR VT     11/1200Z 28.4N  61.9W    75 KT
 24HR VT     12/0000Z 29.5N  62.6W    75 KT
 36HR VT     12/1200Z 30.4N  62.6W    75 KT
 48HR VT     13/0000Z 31.1N  62.3W    70 KT
 72HR VT     14/0000Z 32.5N  61.5W    65 KT
 96HR VT     15/0000Z 34.5N  60.5W    60 KT
120HR VT     16/0000Z 37.0N  59.0W    55 KT
 
$$
FORECASTER KNABB
 

WTNT42 KNHC 110849
TCDAT2
HURRICANE BERTHA DISCUSSION NUMBER  33
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
500 AM EDT FRI JUL 11 2008
 
THE LATEST SATELLITE MICROWAVE DATA AT 02Z INDICATED THAT BERTHA WAS
CONTINUING ITS EYEWALL REPLACEMENT CYCLE...WITH A FRAGMENT OF THE
OLD INNER EYEWALL REMAINING INSIDE THE 60 N MI WIDE OUTER EYEWALL. 
INFRARED IMAGERY SINCE THEN SUGGESTS LITTLE CHANGE IN THE STRUCTURE
OF THE HURRICANE.  SATELLITE INTENSITY ESTIMATES FROM TAFB AND SAB
REMAIN 77 KT...SO THE INITIAL INTENSITY REMAINS 75 KT.  THE CIRRUS
OUTFLOW IS NOW FAIR TO GOOD IN ALL DIRECTIONS.

THE INITIAL MOTION IS NOW 315/6.  TRACK GUIDANCE IS IN GOOD
AGREEMENT THAT BERTHA WILL TURN NORTHWARD DURING THE NEXT 36 HR AS
A MID-LEVEL RIDGE NORTH OF THE HURRICANE MOVES EASTWARD.  SERIOUS
GUIDANCE DIVERGENCE OCCURS BEYOND THAT TIME.  THE GFS IS NOW
CALLING FOR A SLOW EASTWARD MOTION FROM 48-120 HR...THE UKMET
CALLING FOR A SLOW NORTHWARD MOTION...AND THE ECMWF AND CANADIAN
MODELS TRAPPING BERTHA IN THE SUBTROPICAL RIDGE AND STALLING IT
NEAR 31N61W.  THE OTHER DYNAMICAL GUIDANCE FORECAST BERTHA TO MOVE
SLOWLY NORTH-NORTHEASTWARD IN RESPONSE TO WEAK RIDGING TO THE EAST
AND A SERIES OF MID/UPPER-LEVEL SHORTWAVE TROUGHS MOVING THROUGH
THE EASTERN UNITED STATES.  SINCE THE ECMWF AND GFS ARE NOT SHOWING
MUCH RUN-TO-RUN CONSISTENCY...THE ONLY CHANGE TO THE FORECAST TRACK
FROM THE PREVIOUS ADVISORY WILL BE TO CALL FOR A SLOWER NORTH-
NORTHEASTWARD MOTION AFTER 48 HR.  THE NEW TRACK LIES ON THE LEFT
SIDE OF THE MODEL CONSENSUS IN BEST AGREEMENT WITH THE FLORIDA
STATE SUPERENSEMBLE.

BERTHA IS CURRENTLY UNDER A LARGE UPPER-LEVEL ANTICYCLONE...WITH THE
LARGE-SCALE MODELS FORECASTING THIS TO CONTINUE FOR AT LEAST 36 HR. 
BASED ON A CONSENSUS OF THE INTENSITY GUIDANCE...THE INTENSITY
FORECAST WILL KEEP BERTHA AT 75 KT DURING THIS TIME.  HOWEVER...
THERE IS STILL A CHANCE OF SOME STRENGTHENING AT THE END OF THE
EYEWALL REPLACEMENT CYCLE.  STARTING IN 48-72 HR...IT IS EXPECTED
THAT BERTHA WILL SLOWLY MOVE OUT FROM UNDER THE ANTICYCLONE AND
ENCOUNTER VERTICAL WIND SHEAR.  THIS...COMBINED WITH DECREASING SEA
SURFACE TEMPERATURES ALONG THE FORECAST TRACK...SHOULD CAUSE BERTHA
TO WEAKEN.  OCEAN ANALYSES FROM THE ATLANTIC OCEANOGRAPHIC AND
MARINE LABORATORY SHOW THAT THE WARM WATER UNDER BERTHA IS
RELATIVELY SHALLOW...AND THERE IS A CHANCE THAT THIS SLOW-MOVING
SYSTEM COULD UPWELL COLDER WATER UNDERNEATH IT.  THIS COULD
PARTICULARLY BE A FACTOR IF BERTHA STALLS FOR 24 HR OR MORE.

THE LATEST WIND SPEED PROBABILITIES INDICATE THAT...GIVEN
UNCERTAINTIES IN THE FORECASTS OF BERTHA'S TRACK...INTENSITY...AND
SIZE...THERE REMAINS ROUGHLY A 50% CHANCE THAT WINDS OF TROPICAL
STORM FORCE WILL AFFECT BERMUDA DURING THE NEXT FIVE DAYS.  A
TROPICAL STORM WATCH MAY BE ISSUED FOR THE ISLAND LATER TODAY.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      11/0900Z 28.0N  61.7W    75 KT
 12HR VT     11/1800Z 28.8N  62.3W    75 KT
 24HR VT     12/0600Z 29.7N  62.6W    75 KT
 36HR VT     12/1800Z 30.4N  62.5W    75 KT
 48HR VT     13/0600Z 31.3N  62.0W    70 KT
 72HR VT     14/0600Z 32.5N  61.0W    65 KT
 96HR VT     15/0600Z 34.0N  60.5W    60 KT
120HR VT     16/0600Z 36.0N  59.0W    55 KT
 
$$
FORECASTER BEVEN
 

WTNT42 KNHC 111437
TCDAT2
HURRICANE BERTHA DISCUSSION NUMBER  34
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
1100 AM EDT FRI JUL 11 2008
 
MICROWAVE DATA CONTINUES TO SHOW A SMALL FRAGMENT OF THE INNER
EYEWALL WITHIN A BETTER DEFINED AND LARGER RING OF CONVECTION
ASSOCIATED WITH THE OUTER EYEWALL.  CONVENTIONAL VIS/IR IMAGES SHOW
THAT BERTHA'S CLOUD PATTERN HAS CHANGED LITTLE WITH GOOD OUTFLOW IN
ALL QUADRANTS. DVORAK T-NUMBERS STILL SUGGEST AN INITIAL INTENSITY
OF 75 KNOTS. THE FIRST RECONNAISSANCE MISSION INTO BERTHA WILL BE
LATER TODAY...SO I WILL BE MORE CONFIDENT WITH THE INITIAL
INTENSITY WHEN THE PLANE GETS THERE. THE CURRENT CLOUD PATTERN
CONFIGURATION...ANNULAR TYPE...AND LOW SHEAR SUGGEST THAT THE
INTENSITY WILL NOT CHANGE IN THE NEXT DAY OR SO. THEREFORE...BERTHA
IS KEPT AT 75 KNOTS UNTIL SHEAR INCREASES AND MOVES OVER A COOLER
OCEAN. THEN...A GRADUAL WEAKENING IS INDICATED. ALTHOUGH IT APPEARS
THAT THE OUTER EYEWALL COULD SHRINK RESULTING IN INTENSIFICATION...
I AM NOT CONSIDERING IT IN THIS FORECAST BECAUSE I HAVE NO IDEA
WHEN OR IF THIS CYCLE WILL OCCUR.
 
BERTHA IS MOVING VERY SLOWLY...AS ANTICIPATED...TOWARD THE NORTHWEST
OR 320 DEGREES AT 5 KNOTS IN BETWEEN A SMALL SUBTROPICAL RIDGE AND
AN APPROACHING SHORTWAVE TROUGH. THIS PATTERN SHOULD KEEP BERTHA
WITHIN VERY WEAK STEERING CURRENTS FOR THE NEXT 2 OR 3 DAYS.
BERTHA IS EXPECTED TO TURN MORE TO THE NORTH AND EVENTUALLY MORE TO
THE NORTH-NORTHEAST. THIS WILL BE VERY SLOW AND BERTHA IS NOT
EXPECTED TO MOVE MORE THAN 300 N MI IN THREE DAYS. THIS IS
CONSISTENT WITH LATEST GUIDANCE WHICH SHOWS THE CORE OF BERTHA
MOVING WELL EAST OF BERMUDA BUT TROPICAL STORM FORCE WINDS EXTEND
FARTHER OUT AND COULD REACH THE ISLAND AND ADJACENT WATERS.
THEREFORE...GIVEN UNCERTAINTIES IN THE FORECASTS OF
BERTHA'S...TRACK... INTENSITY...AND SIZE...THE WEATHER SERVICE OF
BERMUDA HAS ISSUED A TROPICAL STORM WATCH FOR BERMUDA.
 
  
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      11/1500Z 28.5N  62.0W    75 KT
 12HR VT     12/0000Z 29.2N  62.5W    75 KT
 24HR VT     12/1200Z 30.2N  62.6W    75 KT
 36HR VT     13/0000Z 30.8N  62.2W    75 KT
 48HR VT     13/1200Z 31.5N  61.5W    70 KT
 72HR VT     14/1200Z 32.5N  60.5W    65 KT
 96HR VT     15/1200Z 34.5N  59.5W    60 KT
120HR VT     16/1200Z 37.0N  58.5W    55 KT
 
$$
FORECASTER AVILA
 

WTNT42 KNHC 112041
TCDAT2
HURRICANE BERTHA DISCUSSION NUMBER  35
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
500 PM EDT FRI JUL 11 2008
 
AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT HAS BEEN
INVESTIGATING BERTHA AND FOUND A 976 MB MINIMUM CENTRAL PRESSURE.
THE MAXIMUM REPORTED WINDS AT FLIGHT LEVEL...700 MB...HAVE BEEN OF
THE ORDER OF 90 TO 99 KNOTS IN NORTHEAST AND SOUTHEAST QUADRANTS
RESPECTIVELY. MAXIMUM SFMR WINDS WERE 72 KNOTS BUT THE DATA WAS
RAIN CONTAMINATED. A GOOD COMPROMISE BETWEEN THE TWO MEASUREMENTS
FOR THE INITIAL INTENSITY IS 80 KNOTS. LATEST AMSU DATA SHOW THAT
THE INNER WALL HAS BECOME A LITTLE BETTER DEFINED AND IS ALMOST
CLOSED AGAIN...SO THE CHANGE FOR REINTENSIFICATION EXISTS. AT THIS
TIME...THE INTENSITY FORECAST CALLS FOR NO SIGNIFICANT CHANGE IN
STRENGTH IN THE NEXT DAY OR SO. THEREAFTER...BERTHA SHOULD BEGIN TO
WEAKEN WHEN IT REACHES COOLER WATER AND HIGHER SHEAR.
 
BERTHA HAS SLOWLY BEGAN TO MOVE TOWARD THE NORTH-NORTHWEST AT 4
KNOTS AROUND THE EDGE OF THE SUBTROPICAL RIDGE. THE SHORTWAVE
CURRENTLY OVER THE EASTERN UNITED STATES COAST IS GOING TO BYPASS
BERTHA AND WILL LEAVE THE HURRICANE EMBEDDED WITHIN VERY WEAK
STEERING CURRENTS FOR A FEW DAYS. THE OFFICIAL FORECAST CALLS FOR A
SLOW MOTION TO THE NORTH-NORTHWEST TONIGHT WITH A GRADUAL TURN TO
THE NORTH AND THEN TO THE NORTH-NORTHEAST. LONG RANGE GLOBAL MODELS
ARE SUGGESTING THAT BERTHA WILL CONTINUE WITHIN VERY WEAK STEERING
CURRENTS AND I WILL NOT BE SURPRISED IF BERTHA KEEPS MEANDERING A
LITTLE LONGER. IN FACT...SOME MODELS KEEP BERTHA LOOPING FOR
SEVERAL DAYS.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      11/2100Z 29.1N  62.2W    80 KT
 12HR VT     12/0600Z 29.5N  62.7W    80 KT
 24HR VT     12/1800Z 30.2N  62.7W    80 KT
 36HR VT     13/0600Z 30.6N  62.5W    75 KT
 48HR VT     13/1800Z 31.5N  62.3W    70 KT
 72HR VT     14/1800Z 32.5N  62.0W    65 KT
 96HR VT     15/1800Z 34.0N  61.0W    60 KT
120HR VT     16/1800Z 35.0N  60.0W    55 KT
 
$$
FORECASTER AVILA
 

WTNT42 KNHC 120300
TCDAT2
HURRICANE BERTHA DISCUSSION NUMBER  36
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
1100 PM EDT FRI JUL 11 2008
 
THE GEOSTATIONARY SATELLITE APPEARANCE OF BERTHA HAS NOT CHANGED
THAT MUCH SINCE THE RECONNAISSANCE AIRCRAFT DEPARTED SEVERAL HOURS
AGO...AND THE SUBJECTIVE DVORAK ESTIMATES ARE ABOUT THE SAME...SO
THE ADVISORY INTENSITY REMAINS 80 KT.  BOTH INFRARED AND MICROWAVE
IMAGERY SUGGEST THERE IS STILL SOMETHING OF AN INNER EYEWALL THAT
REFUSES TO COMPLETELY GO AWAY...WHILE THE OUTER EYEWALL PERSISTS AS
A CLOSED RING AT A SLIGHTLY SMALLER RADIUS THAN 24 HOURS AGO.  ALL
OF THAT MEANS THAT THE WELL-ADVERTISED EYEWALL REPLACEMENT CYCLE IS
NOT EXACTLY PROCEEDING AT A BLISTERING PACE...AND I AM REALLY NOT
SURE HOW THE INNER CORE STRUCTURE WILL EVOLVE DURING THE NEXT 24
HOURS OR SO.  PERSISTENCE MIGHT BE A GOOD GUIDE...SO A VERY SLOW
CHANGE IN BERTHA'S STRUCTURE WILL BE THE ASSUMPTION DRIVING THE
FLAT INTENSITY FORECAST THROUGH 24 HOURS.  VERY GRADUAL WEAKENING
IS FORECAST THEREAFTER...IN ACCORDANCE WITH A CONSENSUS OF OUR
PRIMARY INTENSITY MODELS...AS BERTHA TAKES ITS TIME MOVING TOWARD
COOLER WATERS.  THE NEW OFFICIAL INTENSITY FORECAST IS ALMOST AN
EXACT COPY OF THE PREVIOUS ONE.

BERTHA IS CAUGHT IN A VERY WEAK STEERING REGIME AS IT CONTINUES
MOVING...BARELY...AT 335/4.  THE DYNAMICAL MODELS DO NOT OFFER MUCH
PROGNOSTIC EVIDENCE THAT A MID-LATITUDE TROUGH WITH SUFFICIENT
AMPLITUDE WILL BE ABLE TO GET BERTHA MOVING MUCH FASTER WITHIN THE
FIVE-DAY FORECAST PERIOD.  THE SHORTWAVE TROUGH CURRENTLY ALONG THE
U.S. NORTHEAST COAST WILL ALMOST CERTAINLY BYPASS BERTHA WELL TO
THE NORTH...AND NONE OF THE MODELS FORECAST BERTHA TO ACCELERATE
AHEAD OF THE NEXT TROUGH WITHIN FIVE DAYS...ALTHOUGH THAT TROUGH
LOOKS TO BE STRONGER AND MIGHT TRULY PICK UP BERTHA BEYOND THAT
TIME.  IN BETWEEN THOSE TWO TROUGHS...THE MODELS DISAGREE ON HOW
MUCH OF A RIDGE MIGHT FORM NORTH OF BERTHA...AND SOME OF THEM
FORECAST BERTHA TO STALL WITHIN THE NEXT DAY OR TWO.  IN
ADDITION...MOST OF THE MODELS SHOW AT LEAST SOME SOUTHWARD
COMPONENT OF MOTION ON DAY 5...IN RESPONSE TO A CUTOFF LOW FORECAST
TO BE NOT FAR NORTHEAST OF BERTHA BY THAT TIME.  THE RESULT OF THE
COMPLICATED SET OF INDIVIDUAL MODEL TRACKS IS A CONSENSUS THAT
LEADS ME TO SLOW DOWN THE OFFICIAL FORECAST JUST SLIGHTLY...ALSO
WITH A NUDGE TO THE WEST...ALONG A TRACK SIMILAR TO THE PREVIOUS
ADVISORY THAT SIMPLY BENDS BERTHA'S MOTION GRADUALLY TO THE
RIGHT... AT A SPEED OF ABOUT 3 KT THROUGHOUT THE FIVE-DAY FORECAST. 
SOME ERRATIC MOTION AT SOME POINT ALONG THE WAY WOULD NOT BE
SURPRISING.

THE PROBABILITY OF WINDS OF TROPICAL STORM FORCE OCCURRING IN
BERMUDA WITHIN THE NEXT FIVE DAYS...AS CONVEYED IN THE WIND SPEED
PROBABILITY PRODUCT INCLUDED IN EACH ADVISORY PACKAGE...HAS BEEN
GRADUALLY RISING DURING THE PAST COUPLE OF DAYS...AND HAS NOW
REACHED 58%.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      12/0300Z 29.4N  62.4W    80 KT
 12HR VT     12/1200Z 30.0N  62.6W    80 KT
 24HR VT     13/0000Z 30.6N  62.6W    80 KT
 36HR VT     13/1200Z 31.2N  62.5W    75 KT
 48HR VT     14/0000Z 31.7N  62.4W    70 KT
 72HR VT     15/0000Z 33.0N  62.0W    65 KT
 96HR VT     16/0000Z 34.0N  61.5W    60 KT
120HR VT     17/0000Z 35.0N  60.5W    60 KT
 
$$
FORECASTER KNABB
 

WTNT42 KNHC 120849
TCDAT2
HURRICANE BERTHA DISCUSSION NUMBER  37
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
500 AM EDT SAT JUL 12 2008
 
INFRARED SATELLITE IMAGERY SUGGESTS THAT THE INNER EYEWALL REMNANT
OF BERTHA IS FINALLY DISSIPATING...WITH THE CLOUD TOPS COOLING IN
THE LARGE OUTER EYEWALL.  SATELLITE INTENSITY ESTIMATES REMAIN
UNCHANGED FROM 6 HR AGO...AND BASED ON THIS AND PERSISTENCE FROM THE
PREVIOUS ADVISORY THE INITIAL INTENSITY REMAINS 80 KT.  THE CIRRUS
OUTFLOW REMAINS GOOD IN THE SOUTHERN SEMICIRCLE BUT HAS DECREASED
SOMEWHAT IN THE NORTHERN SEMICIRCLE.
 
THE INITIAL MOTION IS 340/4...AND THE 4 KT FORWARD SPEED COULD BE
GENEROUS.  BERTHA IS CURRENTLY EMBEDDED IN THE SUBTROPICAL RIDGE IN
AN AREA OF WEAK STEERING FLOW...WITH A MID/UPPER-LEVEL SHORTWAVE
TROUGH AND ASSOCIATED SURFACE COLD FRONT PASSING TO THE NORTH OF
THE HURRICANE.  THE LARGE-SCALE MODELS FORECAST THE TROUGH TO
BYPASS BERTHA WITH A MID-LEVEL SHORTWAVE RIDGE FORMING NORTH OF THE
HURRICANE.  THE ECMWF...NOGAPS...AND CANADIAN MODEL RESPOND TO THIS
BY JOGGING BERTHA TO THE WEST CLOSER TO BERMUDA....WHILE THE GFS...
HWRF..AND GFDL CALL FOR A NORTHWARD MOTION A LITTLE FARTHER TO THE
EAST.  THIS PORTION OF THE NEW FORECAST TRACK CALLS FOR A NORTHWARD
MOTION FOR ABOUT 72 HR...WITH THE 48-72 HR POSITION A LITTLE TO THE
WEST OF THE PREVIOUS TRACK IN DEFERENCE TO THE MODELS FORECASTING
A WESTWARD JOG.  AFTER 72 HR...THE LARGE-SCALE MODELS FORECAST THAT
A NEW TROUGH OVER THE EASTERN UNITED STATES WILL BE STRONG ENOUGH
TO LIFT BERTHA TO THE NORTHEAST OR EAST AT A FASTER FORWARD SPEED.
HOWEVER...THIS IS A SIGNIFICANT CHANGE FROM THE PREVIOUS MODELS
RUNS...AND THERE IS CONSIDERABLE SPREAD IN BOTH THE DIRECTION AND
SPEED OF MOTION.  THUS...THE NEW FORECAST FOR THOSE TIMES IS ONLY
SLIGHTLY FASTER THAN THE PREVIOUS FORECAST...AND CONSIDERABLY
SLOWER THAN THE CURRENT GUIDANCE.

THERE IS LITTLE CHANGE TO THE INTENSITY FORECAST PHILOSOPHY FROM THE
LAST SEVERAL ADVISORIES.  BERTHA SHOULD MAINTAIN ITS INTENSITY FOR
THE FIRST 24-36 HR WHILE UNDER AN UPPER-LEVEL ANTICYCLONE AND OVER
WARM SURFACE TEMPERATURES.  BY 36 HR...THE HURRICANE SHOULD BEGIN
TO WEAKEN AS IT REACHES COOLER WATERS.  THEN...BY 72 HR THE
VERTICAL WIND SHEAR IS FORECAST TO INCREASE...WHICH SHOULD INCREASE
THE WEAKENING RATE.  THE INTENSITY FORECAST IS IDENTICAL TO THE
LAST ADVISORY THROUGH 48 HR...THEN SHOWS MORE WEAKENING DUE TO THE
EXPECTED SHEAR.
 
A TROPICAL STORM WARNING WILL LIKELY BE ISSUED FOR BERMUDA LATER
THIS MORNING.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      12/0900Z 29.7N  62.5W    80 KT
 12HR VT     12/1800Z 30.1N  62.6W    80 KT
 24HR VT     13/0600Z 30.7N  62.6W    80 KT
 36HR VT     13/1800Z 31.3N  62.6W    75 KT
 48HR VT     14/0600Z 31.9N  62.6W    70 KT
 72HR VT     15/0600Z 33.5N  62.5W    60 KT
 96HR VT     16/0600Z 35.0N  61.5W    50 KT
120HR VT     17/0600Z 36.5N  59.5W    50 KT
 
$$
FORECASTER BEVEN
 

WTNT42 KNHC 121433
TCDAT2
HURRICANE BERTHA DISCUSSION NUMBER  38
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
1100 AM EDT SAT JUL 12 2008
 
AFTER A WEEK OR SO...I AM RUNNING OUT OF THINGS TO SAY ABOUT BERTHA.
THE CLOUD PATTERN HAS NOT CHANGED MUCH SINCE YESTERDAY AND CONSISTS
OF A LARGE DIFFUSE EYE SURROUNDED BY MODERATE CONVECTION. DVORAK
T-NUMBERS HAVE BEEN DECREASING AND GIVEN THE CURRENT SATELLITE
STRUCTURE THE INITIAL INTENSITY IS SET AT 75 KNOTS. AN AIR FORCE
RESERVE HURRICANE HUNTER WILL CHECK BERTHA LATER TODAY.  NO
SIGNIFICANT CHANGE IN STRENGTH IS EXPECTED DURING THE NEXT DAY OR
SO. DUE TO ITS SLOW MOTION...BERTHA IS PROBABLY CAUSING UPWELLING
AND THIS COULD RESULT IN A FASTER WEAKENING TREND.
 
BERTHA HAS BARELY MOVED DURING THE PAST FEW HOURS...PERHAPS TO THE
NORTH ABOUT 2 KNOTS. THE CURRENT PATTERN OF WEAK STEERING CURRENTS
WILL CONTINUE FOR THE NEXT SEVERAL DAYS...BUT STILL FAVORS A
GENERAL SLOW NORTHERLY TRACK DURING THE NEXT DAY OR TWO.
THEREAFTER...AS BERTHA GETS CLOSER TO THE MID-LATITUDE
WESTERLIES...THE CYCLONE IS EXPECTED TO BEGIN TO MOVE SLOWLY TOWARD
THE NORTH-NORTHEAST BUT MAINTAINING ITS SLOW PACE. DYNAMICAL TRACK
GUIDANCE SHOWS THIS SCENARIO AND HAS NOW BEGUN TO TURN BERTHA
TOWARD THE EAST BEYOND DAY FOUR.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      12/1500Z 29.9N  62.6W    75 KT
 12HR VT     13/0000Z 30.2N  62.7W    75 KT
 24HR VT     13/1200Z 30.7N  62.7W    75 KT
 36HR VT     14/0000Z 31.3N  62.7W    70 KT
 48HR VT     14/1200Z 32.0N  62.7W    65 KT
 72HR VT     15/1200Z 34.0N  62.0W    60 KT
 96HR VT     16/1200Z 35.5N  60.5W    50 KT
120HR VT     17/1200Z 36.0N  58.0W    50 KT
 
$$
FORECASTER AVILA
 

WTNT42 KNHC 122037
TCDAT2
HURRICANE BERTHA DISCUSSION NUMBER  39
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
500 PM EDT SAT JUL 12 2008
 
AN AIR FORCE PLANE HAS COMPLETED TWO PASSES THROUGH THE EYE OF
BERTHA AND THE MAXIMUM FLIGHT LEVEL WINDS WERE 79 AND 74 KT. THE
SFMR ON BOARD OF THE PLANE DID NOT REPORT ANY HURRICANE FORCE
WINDS...IN FACT...THE STRONGEST WINDS WERE 58 KNOTS IN THE
SOUTHEAST QUADRANT.  THE BEST ESTIMATE OF THE INITIAL INTENSITY IS
65 KNOTS...MAKING BERTHA BARELY A HURRICANE. ATMOSPHERIC CONDITIONS
ARE NOT HOSTILE FOR SOME STRENGTHENING BUT BERTHA HAS BEEN LOCATED 
TOO MANY HOURS IN THE SAME AREA PRODUCING UPWELLING. THE HURRICANE
HAS LOST A LOT OF THE DEEP CONVECTION BUT THE LOW-LEVEL CIRCULATION
IS LARGE AND VIGOROUS WHILE THE OUTFLOW IS WELL ESTABLISHED.
THEREFORE...BERTHA COULD GATHER SOME STRENGTH WHEN IT GETS OUT THAT
AREA OF COOL WATERS INDUCED BY THE HURRICANE ITSELF. FOR
NOW...BERTHA IS KEPT AS A 65 KNOT HURRICANE FOR A DAY OR TWO WITH A
GRADUAL WEAKENING THEREAFTER DUE TO INCREASING SHEAR. BERTHA IS
LIKELY TO BECOME LARGER AS IT GAINS LATITUDE AND BEGIN TO INTERACT
WITH THE MID-LATITUDE FLOW. 

BERTHA HAS BARELY MOVED DURING THE DAY. THE PATTERN OF WEAK STEERING
CURRENTS IS EXPECTED TO CONTINUE FOR THE NEXT DAY OR TWO....SO ONLY
A PAINFULLY SLOW NORTHWARD MOTION IS ANTICIPATED. BEYOND THREE
DAYS...BERTHA IS EXPECTED TO BE FULLY EMBEDDED WITHIN THE
MID-LATITUDE CIRCULATION AND LOCATED BETWEEN AN EASTWARD MOVING
TROUGH AND A LARGER CUT OFF LOW TO THE EAST. THIS PATTERN SHOULD
FORCE BERTHA ON A SLOW EASTWARD TRACK. THIS IS THE SOLUTION
PROVIDED MY MOST OF THE GLOBAL MODELS AS WELL AS THE DYNAMICAL TRACK
GUIDANCE.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      12/2100Z 29.9N  62.6W    65 KT
 12HR VT     13/0600Z 30.4N  62.7W    65 KT
 24HR VT     13/1800Z 31.0N  62.7W    65 KT
 36HR VT     14/0600Z 32.0N  62.8W    65 KT
 48HR VT     14/1800Z 33.0N  62.8W    60 KT
 72HR VT     15/1800Z 34.5N  61.5W    55 KT
 96HR VT     16/1800Z 35.5N  59.0W    50 KT
120HR VT     17/1800Z 35.5N  56.0W    50 KT
 
$$
FORECASTER AVILA
 

WTNT42 KNHC 130300
TCDAT2
HURRICANE BERTHA DISCUSSION NUMBER  40
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
1100 PM EDT SAT JUL 12 2008
 
BERTHA HAS SEEMINGLY DROPPED ANCHOR A COUPLE HUNDRED MILES SOUTHEAST
OF BERMUDA...AND IT HAS BEEN ABOUT 12 HOURS SINCE THE CENTER HAS
MOVED ENOUGH TO ASSIGN A MEANINGFUL FORWARD MOTION. THE TROPICAL
CYCLONE IS STUCK WITHIN A LARGE BREAK IN THE SUBTROPICAL RIDGE THAT
IT SHARES WITH TWO MID- TO UPPER-LEVEL LOWS...ONE NEAR THE BAHAMAS
AND THE OTHER ABOUT 1000 N MI TO ITS EAST. THE EASTERN LOW IS
FORECAST BY THE MODELS TO LIFT OUT AS A BIT OF RIDGING FORMS JUST
NORTHEAST OF BERTHA TOMORROW...AND ONCE THAT FEATURE
MATERIALIZES...BERTHA SHOULD BEGIN MOVING SLOWLY NORTHWARD AGAIN.
IN A COUPLE OF DAYS...THE NEXT MID-LATITUDE TROUGH SHOULD REACH THE
U.S. NORTHEAST COAST AND START PUSHING BERTHA EASTWARD. VERY LATE
IN THE FIVE-DAY FORECAST PERIOD...A NEW MID- TO UPPER-LEVEL LOW IS
FORECAST BY ALL MODELS TO DEVELOP CLOSE BY TO THE NORTHEAST OF
BERTHA...AND THE TROPICAL CYCLONE COULD HAVE A SOUTHWARD COMPONENT
OF MOTION BY THEN.  BASED ON THE MODEL GUIDANCE IN THIS
SCENARIO...THE NEW OFFICIAL TRACK FORECAST HAS BEEN ADJUSTED
SLIGHTLY WESTWARD FROM THE PREVIOUS ONE THROUGH ABOUT 72
HOURS...SINCE NEARLY ALL OF DYNAMICAL MODELS HAVE SHIFTED A BIT IN
THAT DIRECTION.  IT IS VERY IMPORTANT TO EMPHASIZE THAT EVEN
SLOW-MOVING TROPICAL CYCLONES SUCH AS THIS ONE CAN POSE CHALLENGING
TRACK FORECAST UNCERTAINTIES...AND THAT IT IS DIFFICULT TO
DETERMINE EXACTLY HOW CLOSE THE CENTER OF BERTHA WILL COME TO
BERMUDA. EVIDENCE OF THAT UNCERTAINTY LIES IN SOME OF THE LATEST
48-HOUR MODEL TRACKS...WITH THE GFDL AND HWRF JUST A HAIR EAST OF
THE OFFICIAL...BUT THE GFS IS FARTHER WEST.  THE SPREAD AT 4-5 DAYS
IS EVEN LARGER BUT THE SENSE IS FOR A GENERAL EASTWARD MOTION AT A
SLIGHTLY GREATER FORWARD SPEED.

THE INITIAL INTENSITY REMAINS 65 KT...SINCE THE CONVECTIVE PATTERN
HAS NOT CHANGED MUCH SINCE WE HAD AIRCRAFT DATA THIS
AFTERNOON...AND KEEPING BERTHA AS A HURRICANE IS SUPPORTED BY THE
LATEST SUBJECTIVE DVORAK CI NUMBERS.  FOLLOWING A BRIEF STRONG
BURST AROUND 00Z...THE COLD CLOUD TOPS HAVE BEEN GRADUALLY ON THE
DECLINE.  A SLOW WEAKENING TREND IS PROBABLY NOT TOO FAR IN THE
FUTURE...GIVEN THE EFFECTS OF OCEAN UPWELLING UNDER A STATIONARY
HURRICANE...AND SINCE WHEN BERTHA DOES GET MOVING IT SHOULD
ENCOUNTER STEADILY DECREASING SEA-SURFACE TEMPERATURES.  THE NEW
OFFICIAL INTENSITY FORECAST IS NOT MUCH OF A CHANGE FROM THE
PREVIOUS ADVISORY AND IS CONSISTENT WITH THE INTENSITY MODEL
CONSENSUS.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      13/0300Z 29.9N  62.4W    65 KT
 12HR VT     13/1200Z 30.2N  62.5W    65 KT
 24HR VT     14/0000Z 30.8N  62.8W    60 KT
 36HR VT     14/1200Z 32.0N  63.2W    60 KT
 48HR VT     15/0000Z 33.2N  63.2W    60 KT
 72HR VT     16/0000Z 35.5N  61.5W    55 KT
 96HR VT     17/0000Z 35.5N  58.0W    50 KT
120HR VT     18/0000Z 34.5N  55.0W    50 KT
 
$$
FORECASTER KNABB
 

WTNT42 KNHC 130854
TCDAT2
HURRICANE BERTHA DISCUSSION NUMBER  41
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
500 AM EDT SUN JUL 13 2008
 
THE CENTER OF BERTHA HAS BECOME MORE DIFFICULT TO LOCATE THIS
MORNING.  INFRARED IMAGERY SUGGESTS THE SYSTEM IS DRIFTING
SOUTHWARD.  HOWEVER...A COUPLE OF RECENT AMSU MICROWAVE OVERPASSES
SUGGEST THE LOW-LEVEL CENTER IS NORTH OF THE CENTER SEEN IN THE IR
IMAGERY...POSSIBLY DUE TO THE ONSET OF NORTHERLY VERTICAL WIND
SHEAR.  THE INITIAL POSITION IS AN AVERAGE OF LOCATIONS FROM THE IR
AND MICROWAVE DATA.  SATELLITE INTENSITY ESTIMATES ARE 65 KT FROM
TAFB AND 55 KT FROM SAB.  THE INITIAL INTENSITY REMAINS 65 KT...BUT
THIS COULD BE GENEROUS.

THE INITIAL MOTION IS STATIONARY.  LARGE-SCALE MODEL ANALYSES SHOW
THAT BERTHA IS EMBEDDED IN THE SUBTROPICAL RIDGE...WITH WATER VAPOR
IMAGERY SHOWING A MID-LEVEL SHORTWAVE RIDGE ABOUT TO PASS TO THE
NORTH OF THE CYCLONE.  THIS COMBINATION OF FEATURES SHOULD KEEP
BERTHA NEARLY STATIONARY DURING THE NEXT 12 HR OR SO...FOLLOWED BY
A SLOW MOTION TOWARD THE NORTHWEST AND NORTH AS THE MID-LEVEL RIDGE
AMPLIFIES THE SUBTROPICAL RIDGE EAST OF BERTHA AND A MID/UPPER-
LEVEL TROUGH MOVES INTO THE EASTERN UNITED STATES.  AFTER 72 HR...A
DEEP-LAYER LOW FORMING OVER THE NORTH CENTRAL ATLANTIC WILL LIKELY
STEER BERTHA EASTWARD OR EAST-SOUTHEASTWARD.  THE LARGE-SCALE
MODELS GENERALLY AGREE ON THIS SCENARIO...BUT THERE REMAINS SOME
SPREAD IN BOTH THE DIRECTION AND SPEED OF MOTION.  THE NEW FORECAST
TRACK IS SHIFTED TO THE LEFT OF THE PREVIOUS TRACK DURING THE FIRST
72 HR...AND EVENTUALLY WINDS UP AT THE 5 DAY POSITION FROM THE
PREVIOUS FORECAST.  THE NEW TRACK IS IN BEST AGREEMENT WITH THE
ECMWF.

BERTHA HAS ESSENTIALLY BEEN STATIONARY FOR 24 HR...AND IT IS LIKELY
UPWELLING COLDER WATER UNDERNEATH IT.  THIS SHOULD CAUSE A
WEAKENING TREND AS LONG AS THE CYCLONE REMAINS STATIONARY.  WHEN
BERTHA STARTS MOVING...THE FORECAST TRACK TAKES IT OVER COOLER
WATER AND INTO INCREASING VERTICAL WIND SHEAR.  DESPITE THESE
ISSUES...THE GFDL AND HWRF MAINTAIN BERTHA AS A HURRICANE FOR 5
DAYS...WHILE THE SHIPS MODEL FORECASTS WEAKENING TO 35 KT BY 5
DAYS.  THE NEW INTENSITY FORECAST COMPROMISES BETWEEN THESE
EXTREMES...CALLING FOR BERTHA TO WEAKEN TO 50 KT BY THE END OF THE
FORECAST PERIOD.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      13/0900Z 29.8N  62.5W    65 KT
 12HR VT     13/1800Z 30.1N  62.8W    60 KT
 24HR VT     14/0600Z 30.8N  63.2W    60 KT
 36HR VT     14/1800Z 32.0N  63.6W    60 KT
 48HR VT     15/0600Z 33.4N  63.5W    55 KT
 72HR VT     16/0600Z 35.5N  62.0W    50 KT
 96HR VT     17/0600Z 35.5N  59.0W    50 KT
120HR VT     18/0600Z 34.5N  55.0W    50 KT
 
$$
FORECASTER BEVEN
 

WTNT42 KNHC 131435
TCDAT2
TROPICAL STORM BERTHA DISCUSSION NUMBER  42
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
1100 AM EDT SUN JUL 13 2008
 
SATELLITE IMAGES INDICATE THAT MOST OF THE DEEP CONVECTION
ASSOCIATED WITH BERTHA HAS DECREASED EXCEPT WITHIN A BAND TO THE
NORTH OF THE CENTER. HOWEVER...BERTHA STILL HAS A LARGE AND
VIGOROUS LOW LEVEL CIRCULATION.  INITIAL INTENSITY IS SET AT 55
KNOTS AND A RECONNAISSANCE PLANE WILL GIVE US ADDITIONAL INTENSITY
AND WIND RADII INFORMATION LATER TODAY. SHEAR AND COOL WATER SHOULD
INDUCE WEAKENING...BUT MOST OF THE GLOBAL AND INTENSITY MODELS
EITHER STRENGTHEN OR KEEP BERTHA WITH THE SAME INTENSITY. THE
OFFICIAL FORECAST HAS OPTED FOR AN INITIAL WEAKENING AND THEN
FOLLOWS THE SHIPS MODELS CALLING FOR NO CHANGE IN INTENSITY.
 
BERTHA HAS BEEN MEANDERING FOR THE PAST 24 HOURS OR SO...BUT NOW
APPEARS TO BE MOVING TOWARD THE NORTHWEST OR 320 DEGREES AT ABOUT 2
TO 3 KNOTS. AS THE SUBTROPICAL RIDGE DEVELOPS AND A TROUGH
APPROACHES...THE CYCLONE SHOULD CONTINUE TO MOVE ON A SLOW
NORTHWESTERLY AND THEN NORTHERLY TRACK FOR A COUPLE OF DAYS. 
THEREAFTER...THE CYCLONE IS EXPECTED TO BE EMBEDDED WITHIN THE
MID-LATITUDE WESTERLIES AND BE STEERED SLOWLY EASTWARD.
HOWEVER...THIS PROCESS WILL SLOW AND TROPICAL CYCLONE BERTHA COULD
BE WITH US FOR SEVERAL MORE DAYS AS INDICATED BY GLOBAL MODELS.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      13/1500Z 30.2N  63.0W    55 KT
 12HR VT     14/0000Z 30.4N  63.0W    50 KT
 24HR VT     14/1200Z 31.5N  63.5W    50 KT
 36HR VT     15/0000Z 33.0N  63.6W    50 KT
 48HR VT     15/1200Z 34.5N  63.0W    50 KT
 72HR VT     16/1200Z 36.0N  61.0W    50 KT
 96HR VT     17/1200Z 36.0N  58.0W    50 KT
120HR VT     18/1200Z 35.0N  54.0W    50 KT
 
$$
FORECASTER AVILA
 

WTNT42 KNHC 132027
TCDAT2
TROPICAL STORM BERTHA DISCUSSION NUMBER  43
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
500 PM EDT SUN JUL 13 2008
 
AN AIR FORCE RESERVE RECONNAISSANCE PLANE JUST FINISHED TWO PASSES
ACROSS BERTHA. FLIGHT-LEVEL WINDS...SFMR AND DROPSONDES INDICATE
THAT BERTHA CONTINUES AS A 55 KT TROPICAL STORM. HIGH RESOLUTION
SATELLITE IMAGES SHOW A VIGOROUS LOW-LEVEL CIRCULATION ASSOCIATED
WITH THE CYCLONE BUT DEEP CONVECTION IS VERY LIMITED. SOME OF THE
DYNAMICAL MODELS INDICATE RESTRENGTHENING WHILE THE SHIPS GUIDANCE
MAINTAIN BERTHA WITH BASICALLY THE SAME INTENSITY.  THE OFFICIAL
FORECAST KEEPS BERTHA AS A 50 KT CYCLONE THROUGH FIVE DAYS....AS
INDICATED BY THE SHIPS MODEL. SOME INTENSIFICATION COULD OCCUR IF
BERTHA BEGINS TO ACQUIRE EXTRATROPICAL CHARACTERISTICS AS IT
INTERACTS WITH THE MID-LATITUDE WESTERLIES.  

BERTHA FOOLED ME ONCE AGAIN. IT APPEARS THAT BERTHA BEGAN A
NORTHWESTWARD DRIFT EARLIER TODAY BUT...IN FACT...IT WAS MOVING IN
CIRCLES AND IT COULD BE DOING ONE OF THESE LOOPS AGAIN. MODEL
GUIDANCE...WHICH IS NOW MORE IN GOOD AGREEMENT...INSISTS THAT
THE NORTHWARD MOTION SHOULD BEGIN TONIGHT AND SO DOES THE OFFICIAL
FORECAST. IN ABOUT 48 HOURS...BERTHA IS EXPECTED TO BE EMBEDDED
WITHIN THE MID-LATITUDE WESTERLIES AND BE STEERED SLOWLY EASTWARD.
THE CIRCULATION SHOULD THEN EXPAND WHILE GRADUALLY ACQUIRING
EXTRATROPICAL CHARACTERISTICS.  ONE WAY OR ANOTHER IT APPEARS THAT
BERTHA COULD BE WITH US FOR SEVERAL MORE DAYS.
  
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      13/2100Z 30.2N  63.1W    55 KT
 12HR VT     14/0600Z 30.5N  63.3W    50 KT
 24HR VT     14/1800Z 32.0N  63.8W    50 KT
 36HR VT     15/0600Z 33.5N  63.7W    50 KT
 48HR VT     15/1800Z 35.0N  62.5W    50 KT
 72HR VT     16/1800Z 35.5N  60.0W    50 KT
 96HR VT     17/1800Z 35.0N  57.0W    50 KT
120HR VT     18/1800Z 35.0N  54.0W    50 KT
 
$$
FORECASTER AVILA
 

WTNT42 KNHC 140258
TCDAT2
TROPICAL STORM BERTHA DISCUSSION NUMBER  44
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
1100 PM EDT SUN JUL 13 2008

IT APPEARS THAT BERTHA IS TAPPING LIGHTLY ON THE ACCELERATOR...WITH
AN INITIAL MOTION ESTIMATE OF 335/3.  MOST OF THE MODELS FORECAST A
GRADUAL INCREASE IN BERTHA'S FORWARD SPEED WITH A SUBTLE TURN TO
THE RIGHT DURING THE NEXT COUPLE OF DAYS...AROUND A WEAK MID-LEVEL
HIGH CURRENTLY JUST EAST OF THE STORM.  BY THAT TIME THE MODELS
FORECAST BERTHA TO BE NORTH OF THE RIDGE...AND IN BETWEEN A
MID-LATITUDE TROUGH NEAR THE NORTHEAST U.S. COAST AND A CUTOFF LOW
OVER THE CENTRAL NORTH ATLANTIC.  BERTHA AND THE CUTOFF LOW ARE
THEN FORECAST TO INTERACT WITH ONE ANOTHER IN A POTENTIALLY COMPLEX
MANNER ON DAYS 3 THROUGH 5...ALTHOUGH A GENERALLY EASTWARD MOTION
WITHIN THE MID-LATITUDE WESTERLIES IS IMPLIED BY THE MODEL
CONSENSUS.  THE UNUSUAL UNDULATIONS IN THE OFFICIAL TRACK BEYOND 48
HOURS ARE SUPPORTED BY ALL OF THE DYNAMICAL MODELS...BUT THE DIPS
AND TURNS IN THE MODEL TRACKS ARE A BIT MORE EXTREME THAN SHOWN IN
THE OFFICIAL FORECAST.  THERE IS ALSO GREAT DISAGREEMENT IN THE
GUIDANCE ON THE FORWARD SPEED OF BERTHA DURING THAT TIME
FRAME...BUT THE FIVE-DAY CONSENSUS POINT IS NOT FAR FROM THAT IN
THE PREVIOUS ADVISORY...SO ON BALANCE THE NEW TRACK IS NOT THAT
MUCH OF A CHANGE.

I HAVE NO SOLID REASON TO ALTER THE INITIAL INTENSITY OF 55 KT...AS
THE SUBJECTIVE DVORAK ESTIMATES HAVE NOT CHANGED MUCH...AND A
QUIKSCAT OVERPASS AROUND 23Z ONLY CAPTURED THE WESTERN HALF OF THE
CIRCULATION.  CLOUD TOPS OF THE OUTER BANDS HAVE WARMED DURING THE
PAST FEW HOURS...BUT IF ANYTHING THE CONVECTION NEAR THE CENTER HAS
INCREASED EVER SO SLIGHTLY.  A CONSENSUS OF THE VARIOUS INTENSITY
MODELS DOES NOT SUGGEST MUCH CHANGE IN BERTHA'S STRENGTH DURING THE
NEXT SEVERAL DAYS AS IT PASSES OVER GRADUALLY COOLER SEA-SURFACE
TEMPERATURES.  THE NEW OFFICIAL FORECAST HOLDS ON TO THE CURRENT
INTENSITY THROUGH 36 HOURS AND ONLY SHOWS A SLIGHTLY WEAKER SYSTEM
BEYOND THAT TIME.  THIS FORECAST IS VERY CLOSE TO THE SHIPS AND
LGEM...BUT STILL BELOW THE GFDL AND HWRF THAT FORECAST BERTHA TO
AGAIN BECOME A HURRICANE.  WHILE THAT POSSIBILITY CANNOT BE RULED
OUT...IT APPEARS TO BE THE LESS LIKELY OPTION...ESPECIALLY GIVEN
THE CONVOLUTED STATE OF BERTHA'S INNER CORE.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      14/0300Z 30.5N  63.1W    55 KT
 12HR VT     14/1200Z 31.5N  63.5W    55 KT
 24HR VT     15/0000Z 33.0N  63.6W    55 KT
 36HR VT     15/1200Z 34.6N  63.1W    55 KT
 48HR VT     16/0000Z 35.8N  62.0W    50 KT
 72HR VT     17/0000Z 35.5N  59.5W    50 KT
 96HR VT     18/0000Z 34.5N  56.5W    50 KT
120HR VT     19/0000Z 35.5N  53.0W    50 KT
 
$$
FORECASTER KNABB
 

WTNT42 KNHC 140900
TCDAT2
TROPICAL STORM BERTHA DISCUSSION NUMBER  45
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
500 AM EDT MON JUL 14 2008
 
BERTHA IS FINALLY...TRULY ON THE MOVE...AND THE INITIAL MOTION
ESTIMATE IS NOW 335/7.  THE CONVECTION HAS ALSO PERKED UP A BIT
WITHIN THE PAST FEW HOURS...EVEN IN THE SHORT TIME SINCE THE DVORAK
INTENSITY ESTIMATES WERE MADE AT 06Z...SO THE ADVISORY INTENSITY
REMAINS ON THE HIGH END OF THOSE ESTIMATES AT 55 KT.  RADAR IMAGERY
FROM BERMUDA SHOWS THAT OUTER BANDS OF BERTHA HAVE BEGUN PASSING
OVER THAT ISLAND...AND THE PRIMARY BAND OF CONVECTION THAT WRAPS
AROUND FROM THE EAST TO THE NORTHWEST OF THE CENTER IS NOT FAR
OFFSHORE.  IT APPEARS THAT THE CENTER OF BERTHA WILL PASS VERY
CLOSE TO THE EAST OF BERMUDA LATER TODAY...CLOSE ENOUGH TO BRING
TROPICAL STORM CONDITIONS TO THAT ISLAND.  GIVEN THE SPRAWLING
NATURE OF THE SYSTEM...SIGNIFICANT CHANGES IN STRENGTH DO NOT
APPEAR LIKELY TODAY.  THE INTENSITY MODEL CONSENSUS ALSO SUGGESTS
LITTLE CHANGE DURING THE NEXT SEVERAL DAYS...ALTHOUGH THE GFDL AND
HWRF STILL FORECAST BERTHA TO REGAIN HURRICANE STATUS.

BERTHA HAS MADE NORTHWARD PROGRESS FASTER THAN PREVIOUSLY
FORECAST...AND THE TRACK HAS BEEN SPED UP A LITTLE THROUGH 48
HOURS.  ONCE BERTHA ROUNDS THE RIDGE CURRENTLY TO ITS EAST AND
STARTS HEADING EASTWARD AHEAD OF THE NEXT MID-LATITUDE TROUGH...THE
STEERING MECHANISMS BECOME COMPLICATED DUE TO A CUTOFF LOW FORECAST
TO APPROACH BERTHA FROM THE EAST.  THE INTERACTION BETWEEN THE TWO
CYCLONIC CIRCULATIONS COULD RESULT IN AN UNDULATING BUT GENERALLY
EASTWARD TRACK OF BERTHA AS INDICATED BY ALL OF THE DYNAMICAL
MODELS.  AS IN THE PREVIOUS OFFICIAL FORECAST...THE NEW TRACK
INCLUDES THESE UNDULATIONS...BUT SMOOTHS THROUGH THEM JUST A
LITTLE.  THE NEW FIVE-DAY POINT HAS ALSO BEEN SPED UP TOWARD THE
MODEL CONSENSUS THAT SUGGESTS BERTHA WILL ACCELERATE OVER THE
NORTHERN ATLANTIC A LITTLE MORE THAN FORECAST IN PREVIOUS MODEL
RUNS.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      14/0900Z 31.5N  63.6W    55 KT
 12HR VT     14/1800Z 32.6N  63.9W    55 KT
 24HR VT     15/0600Z 34.2N  63.5W    60 KT
 36HR VT     15/1800Z 35.8N  62.6W    55 KT
 48HR VT     16/0600Z 36.4N  61.5W    55 KT
 72HR VT     17/0600Z 35.0N  59.5W    50 KT
 96HR VT     18/0600Z 34.5N  55.5W    50 KT
120HR VT     19/0600Z 37.5N  51.0W    50 KT
 
$$
FORECASTER KNABB
 

WTNT42 KNHC 141458
TCDAT2
TROPICAL STORM BERTHA DISCUSSION NUMBER  46
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
1100 AM EDT MON JUL 14 2008
 
THE INITIAL MOTION IS 350/6.  BERTHA IS EXPECTED TO CONTINUE ON A
NORTHWARD TRACK FOR THE NEXT DAY OR SO AS MID-LEVEL HIGH PRESSURE
TO THE NORTHEAST OF THE CYCLONE WEAKENS AND SLIDES EASTWARD.  WITH
THE STRONGEST WINDS LOCATED 50-60 NMI FROM THE CENTER...
HOWEVER...THE PRECISE TRACK OF THE CENTER IS RELATIVELY UNIMPORTANT
FOR CONDITIONS ON BERMUDA...WHERE TROPICAL STORM FORCE WINDS COULD
CONTINUE THROUGH TOMORROW MORNING. AFTER BERTHA PASSES BERMUDA...A
COMPLICATED STEERING PATTERNS AWAITS...WITH A STRONG UPPER-LEVEL
LOW CURRENTLY NEAR 40N/42W FORECAST TO DROP SOUTHWESTWARD.  MODEL
GUIDANCE IS NOT IN GOOD AGREEMENT ON THE INTERACTION BETWEEN BERTHA
AND THE UPPER LOW.  THE HWRF AND GFDL MAINTAIN A STRONG TROPICAL
CYCLONE AND SWING BERTHA RAPIDLY AROUND THE SOUTH SIDE OF THE UPPER
LOW...WHILE THE GFS LIFTS THE UPPER LOW NORTHEASTWARD AFTER ABOUT
72 HOURS...LEAVING BERTHA BEHIND.  AS THE UPPER-LOW AND BERTHA
APPROACH...NORTHWESTERLY WIND SHEAR SHOULD INCREASE MARKEDLY...AND
I SUSPECT THE HWRF/GFDL SOLUTIONS ARE KEEPING BERTHA TOO STRONG AND
MAY THEREFORE BE OVERDOING THE INTERACTION.  THE OFFICIAL FORECAST
IS CLOSE TO THE FSSE SUPERENSEMBLE AND THE PREVIOUS ADVISORY.

THERE IS NOT MUCH DEEP CONVECTION ASSOCIATED WITH BERTHA RIGHT
NOW...AND A QUIKSCAT PASS AT 1030Z SUGGESTS THAT THE WINDS MIGHT BE
A LITTLE BELOW THE ADVISORY INTENSITY OF 55 KT.  A RECONNAISSANCE
AIRCRAFT WILL BE IN THE CYCLONE IN ANOTHER COUPLE OF HOURS.  THE
QUIKSCAT DATA REVEALED A 50-60 NMI RMW.  GIVEN THIS STRUCTURE...NO
SIGNIFICANT CHANGES IN INTENSITY ARE EXPECTED WHILE THE STORM IS IN
THE VICINITY OF BERMUDA.  THE WILL BE SOME OPPORTUNITY FOR
STRENGTHENING OVER THE NEXT DAY OR SO BEFORE BERTHA ENCOUNTERS SOME
COOLER WATERS AND NORTHWESTERLY SHEAR.  THE OFFICIAL INTENSITY
FORECAST IS IN BEST AGREEMENT WITH THE SHIPS AND LGEM GUIDANCE.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      14/1500Z 32.0N  63.8W    55 KT
 12HR VT     15/0000Z 33.2N  63.9W    55 KT
 24HR VT     15/1200Z 34.8N  63.2W    60 KT
 36HR VT     16/0000Z 35.9N  62.0W    55 KT
 48HR VT     16/1200Z 36.0N  61.0W    55 KT
 72HR VT     17/1200Z 34.5N  58.5W    50 KT
 96HR VT     18/1200Z 35.0N  55.0W    50 KT
120HR VT     19/1200Z 38.0N  51.0W    50 KT
 
$$
FORECASTER FRANKLIN
 

WTNT42 KNHC 142044
TCDAT2
TROPICAL STORM BERTHA DISCUSSION NUMBER  47
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
500 PM EDT MON JUL 14 2008
 
THE AIR FORCE RESERVE UNIT RECONNAISSANCE AIRCRAFT INVESTIGATING
BERTHA FOUND SFMR SURFACE WINDS OF 60 KT IN THE SOUTHWEST
QUADRANT...WINDS THAT WERE WERE CONFIRMED BY A CO-LOCATED
DROPSONDE.  OVER THE PAST FEW HOURS...THERE HAS BEEN A RESURGENCE
IN DEEP CONVECTION...PERHAPS AS A RESULT OF BERTHA FINALLY MOVING
AWAY FROM WHERE IT HAD BEEN PARKED.   THIS STRENTHENING REQUIRED
THE ISSUANCE OF A HURRICANE WATCH FOR BERMUDA...AS THIS PORTION OF
THE CYCLONE HAS YET TO CLEAR THE ISLAND.  UPPER-LEVEL CIRRUS ARE
EXPANDING IN ALL QUADRANTS...AND IT IS NOW EXPECTED THAT BERTHA
WILL BECOME A HURRICANE BEFORE COOLER WATERS AND INCREASING
NORTHWESTERLY SHEAR AFFECT THE STORM IN 36-48 HOURS.  

THE INITIAL MOTION IS 350/6...WHICH REPRESENTS THE MOTION OF THE
OVERALL CYCLONE RATHER THAN THAT OF THE SMALL SWIRL THAT IS VISIBLE
ROTATING WITHIN THE CONVECTIVE RING.  THE SHORT TERM TRACK
PHILOSOPHY IS UNCHANGED...WITH BERTHA EXPECTED TO GRADUALLY TURN
NORTHEASTWARD OVER THE NEXT DAY OR TWO AROUND THE PERIPHERY OF A
MID-LEVEL ANTICYCLONE. AFTER THAT...BERTHA'S PATH WILL BE
DETERMINED BY ITS INTERACTION WITH A STRONG UPPER-LEVEL LOW
CURRENTLY NEAR 39N/43W BUT FORECAST TO DROP SOUTHWESTWARD TOWARD
THE TROPICAL CYCLONE. THE 12Z MODEL GUIDANCE AS A WHOLE IS SLOWER
THAN IT HAD BEEN...WITH THE BULK OF THE GUIDANCE INDICATING THAT
THE UPPER LOW WILL SHOVE BERTHA SOUTHEASTWARD...AWAY FROM THE
WESTERLIES. THE OFFICIAL FORECAST SHOWS LESS ACCELERATION ON DAYS
4-5 THAN THE PREVIOUS ADVISORY...BUT EVEN SO IS FASTER THAN JUST
ABOUT EVERYTHING EXCEPT THE HWRF AND GFDL. 
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      14/2100Z 33.0N  64.1W    60 KT
 12HR VT     15/0600Z 34.2N  63.7W    65 KT
 24HR VT     15/1800Z 35.3N  62.8W    65 KT
 36HR VT     16/0600Z 35.7N  61.8W    65 KT
 48HR VT     16/1800Z 35.2N  60.7W    60 KT
 72HR VT     17/1800Z 34.0N  57.5W    55 KT
 96HR VT     18/1800Z 35.5N  54.5W    50 KT
120HR VT     19/1800Z 38.0N  51.0W    50 KT
 
$$
FORECASTER FRANKLIN
 

WTNT42 KNHC 150259
TCDAT2
TROPICAL STORM BERTHA DISCUSSION NUMBER  48
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
1100 PM EDT MON JUL 14 2008
 
THE CENTER OF BERTHA IS STEADILY MOVING AWAY FROM BERMUDA.  THE
CYCLONE IS IN THE PROCESS OF MAKING A GRADUAL RIGHT TURN...SO THE
DIRECTION OF MOTION HAS BEEN FREQUENTLY CHANGING...BUT THE ESTIMATE
VALID AT ADVISORY TIME IS 015/8.  WATER VAPOR IMAGERY SHOWS THAT
THE CUTOFF LOW CURRENTLY ABOUT 1000 N MI EAST-NORTHEAST OF BERTHA
IS SLIDING SOUTHWESTWARD AND PUTTING THE SQUEEZE ON WHAT IS LEFT OF
THE NARROW MID-LEVEL RIDGE IN BETWEEN.  THAT RIDGE HAS BEEN
STEERING BERTHA NORTHWARD TODAY...SO AS IT ERODES...BERTHA IS
FORECAST BY ALL OF THE DYNAMICAL MODELS TO MAKE A SHARPER RIGHT
TURN IN ABOUT 24 HOURS...AND THEN HEAD SOUTHEASTWARD AS IT MORE
DIRECTLY INTERACTS WITH THE CUTOFF LOW.  ALL OF THE MODELS AGREE
THAT THE CUTOFF LOW WILL LIFT OUT IN ABOUT 72 HOURS...LEAVING
BERTHA TO BE STEERED GENERALLY NORTHEASTWARD BY THE MID-LATITUDE
WESTERLIES LATE IN THE FORECAST PERIOD.  THE NEW OFFICIAL FORECAST
TRACK CONTINUES TO DEPICT WHAT LOOKS LIKE A SINE WAVE...THIS TIME
WITH SLIGHTLY MORE AMPLITUDE...BUT WITH THE NET MOTION OVER FIVE
DAYS BEING EAST-NORTHEASTWARD.  THE FORWARD SPEED OF BERTHA BEYOND
72 HOURS IS RATHER UNCERTAIN...AS THE VARIOUS MODELS AGREE ON THE
PATH BUT NOT ON HOW FAST THE CYCLONE WILL GO.

THE DEEPEST CONVECTION HAS ROTATED AROUND THE CENTER FROM THE
SOUTHWESTERN QUADRANT...WHICH DIRECTLY AFFECTED BERMUDA EARLIER
TODAY...AND NOW IS FOCUSED SOUTHEAST AND EAST OF THE CENTER. 
OTHERWISE...THE OVERALL STRUCTURE OF THE CYCLONE IS ESSENTIALLY
UNCHANGED...AS ARE THE DVORAK ESTIMATES AT 55 KT.  USING CONTINUITY
FROM EARLIER AIRCRAFT OBSERVATIONS...THE ADVISORY INTENSITY REMAINS
60 KT.  THE INTENSITY FORECAST IS MOSTLY UNCHANGED...CALLING FOR
BERTHA TO BE AT HURRICANE STATUS DURING THE NEXT COUPLE OF DAYS. 
THIS FORECAST MIGHT NOT BE EXACTLY RIGHT...BUT THE INTENSITY
CONSENSUS SUGGESTS BERTHA WILL BE NEAR THE THRESHOLD BETWEEN
TROPICAL STORM AND HURRICANE INTENSITY FOR A FEW DAYS.  A WEAKENING
TREND IS INDICATED IN THE OFFICIAL FORECAST AT DAYS 4 AND 5 AS
BERTHA HEADS NORTHEASTWARD TOWARD NOTICEABLY COOLER WATERS...IN
BEST AGREEMENT WITH THE SHIPS AND LGEM STATISTICAL-DYNAMICAL
MODELS.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      15/0300Z 33.8N  63.7W    60 KT
 12HR VT     15/1200Z 34.9N  63.0W    65 KT
 24HR VT     16/0000Z 35.7N  61.9W    65 KT
 36HR VT     16/1200Z 35.4N  60.6W    65 KT
 48HR VT     17/0000Z 34.4N  59.2W    65 KT
 72HR VT     18/0000Z 33.5N  55.5W    60 KT
 96HR VT     19/0000Z 36.0N  52.0W    55 KT
120HR VT     20/0000Z 39.5N  49.0W    50 KT
 
$$
FORECASTER KNABB
 

WTNT42 KNHC 150859
TCDAT2
TROPICAL STORM BERTHA DISCUSSION NUMBER  49
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
500 AM EDT TUE JUL 15 2008
 
BERTHA HAS PUT A LITTLE MORE DISTANCE BETWEEN ITSELF AND
BERMUDA...AND THE PREVIOUSLY FORECAST TURN TOWARD THE RIGHT IS
MATERIALIZING. THE INITIAL MOTION ESTIMATE IS 030/8...BUT THE
HEADING WILL LIKELY CHANGE ALMOST CONTINUOUSLY DURING THE NEXT
COUPLE OF DAYS...DURING WHICH TIME BERTHA IS FORECAST BY NEARLY ALL
OF THE MODELS TO KEEP TURNING RIGHT. WATER VAPOR IMAGERY
SHOWS THAT A MID-LATITUDE TROUGH IS ABOUT TO EXIT THE U.S. EAST
COAST AND GIVE BERTHA A SHOVE TO THE EAST...BUT ALSO A LARGE CUTOFF
LOW CLOSING IN ON BERTHA FROM THE OTHER DIRECTION. ONCE BERTHA AND
THE CUTOFF LOW MEET UP DURING THE NEXT COUPLE OF DAYS...THE
GUIDANCE INDICATES BERTHA WILL THEN FOLLOW AN UNDULATING TRACK. THE
OFFICIAL FORECAST MOTION IS SHARPLY SOUTHEASTWARD ON DAY TWO...THEN
GENERALLY NORTHEASTWARD ON DAYS 3-5 AS THE CUTOFF LOW IS FORECAST
TO LIFT OUT AGAIN...ALL IN GENERAL AGREEMENT WITH MOST MODELS. THE
MODELS DO NOT AGREE...HOWEVER...ON THE FORWARD SPEED OF BERTHA ON
DAYS 3-5...IN PART DUE TO VARYING DEPICTIONS OF BERTHA'S DEPTH AND
STRENGTH. THE NEW OFFICIAL TRACK IS SIMILAR TO THE PREVIOUS ONE AND
PRESUMES THAT BERTHA WILL BE WEAKER BY THAT TIME AND NOT ACCELERATE
AS QUICKLY NORTHEASTWARD AS THE GFDL AND HWRF ARE SUGGESTING...AND
INSTEAD RELIES MAINLY ON A BLEND OF THE GFS AND ECMWF.

THE INITIAL AND FORECAST INTENSITIES ARE UNCHANGED.  THE SATELLITE
APPEARANCE OF BERTHA REMAINS MUCH AS IT WAS A FEW HOURS AGO...AND
DVORAK ESTIMATES GENERALLY SUPPORT KEEPING THE INITIAL INTENSITY AT
60 KT.  BERTHA HAS AN OPPORTUNITY TO STRENGTHEN DURING THE NEXT
COUPLE OF DAYS AS IT REMAINS OVER SEA-SURFACE TEMPERATURES BETWEEN
26 AND 27 CELSIUS...BUT SIGNIFICANT STRENGTHENING DOES NOT APPEAR
LIKELY GIVEN THE SPRAWLING NATURE OF THE SYSTEM.  BEYOND 48
HOURS...GRADUAL WEAKENING IS AGAIN FORECAST DUE TO COOLER WATERS
AND A STRONG POSSIBILITY OF INCREASING SHEAR.  THAT SCENARIO IS THE
ONE PAINTED BY THE SHIPS AND LGEM GUIDANCE...WHICH DIFFERS FROM THE
GFDL AND HWRF...BOTH OF WHICH FORECAST BERTHA TO REMAIN A HURRICANE
FOR MUCH OF THE NEXT FIVE DAYS.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      15/0900Z 34.7N  63.2W    60 KT
 12HR VT     15/1800Z 35.7N  62.3W    65 KT
 24HR VT     16/0600Z 35.9N  60.9W    65 KT
 36HR VT     16/1800Z 34.7N  59.8W    65 KT
 48HR VT     17/0600Z 33.7N  58.6W    65 KT
 72HR VT     18/0600Z 34.0N  55.0W    60 KT
 96HR VT     19/0600Z 37.0N  51.0W    55 KT
120HR VT     20/0600Z 41.0N  47.0W    50 KT
 
$$
FORECASTER KNABB
 

WTNT42 KNHC 151453
TCDAT2
TROPICAL STORM BERTHA DISCUSSION NUMBER  50
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
1100 AM EDT TUE JUL 15 2008

BERTHA IS MAINTAINING ITS STRUCTURE ON SATELLITE IMAGES THIS MORNING
WITH A NEW BURST OF CONVECTION ON THE NORTHEAST SIDE OF THE STORM...
AND APPARENT EYEWALL MESOVORTICES ROTATING QUICKLY AROUND THE
CENTER. HIGH-RESOLUTION QUIKSCAT SHOWS WINDS OF 55-60 KT...SO THE
INITIAL INTENSITY WILL REMAIN 60 KT FOR THIS ADVISORY.  THE STORM
STILL HAS A CHANCE TO BECOME A HURRICANE AGAIN DURING THE NEXT DAY
OR SO BEFORE VERTICAL WIND SHEAR INCREASES AS INDICATED BY ALL
MODELS.  THE STATISTICAL MODELS SUGGEST NO INTENSIFICATION BUT THE
DYNAMICAL MODELS SUCH AS THE GFDL/HWRF EMPHATICALLY SUGGEST BERTHA
WILL BECOME...AND MAINTAIN HURRICANE STRENGTH THROUGHOUT THE
FORECAST PERIOD.  THE INTENSITY FORECAST WILL BE CLOSER TO THE
STATISTICAL GUIDANCE AT THIS TIME AS THE UPPER ENVIRONMENT DOES NOT
SEEM TO BE TOO FAVORABLE FOR A HURRICANE BEYOND A COUPLE OF DAYS.  

THE STORM IS CURRENTLY MOVING 030/10...A LITTLE FASTER THAN BEFORE. 
A NARROW RIDGE TO THE EAST OF BERTHA IS STEERING THE CYCLONE
NORTHEASTWARD FOR THE TIME BEING.  THIS RIDGE IS FORECAST TO BE
ERODED BY ALL THE GLOBAL MODELS WITHIN 24 HOURS AS A LARGE
DEEP-LAYERED TROUGH APPROACHES FROM THE EAST.  THE BIGGEST
DISCREPANCY IS WHEN THE EXPECTED RIGHT TURN OF THE CYCLONE
EMERGES.   THE ECMWF/UKMET SHOW THAT THE TURN WILL BE DELAYED FOR
AN EXTRA 12 HOURS...ALLOWING THE STORM TO GAIN MORE LATITUDE AS
COMPARED TO THE GFS/GFDL/HWRF.  THE OFFICIAL FORECAST WILL SPLIT
THE DIFFERENCE BETWEEN THESE TWO MODEL CAMPS...AND SHIFTS THE TRACK
NORTHWARD IN THE SHORT-TERM.  UNCERTAINTY ALSO REMAINS HIGH IN THE
LONG-RANGE FORECAST AS THE GFDL/HWRF ARE STILL SHOWING BERTHA
SHOOTING OUT TO SEA WHILE THE GFS/ECMWF/UKMET ARE MUCH SLOWER. 
BECAUSE THE STORM IS NOT EXPECTED TO HAVE SUCH A WELL-DEVELOPED
STRUCTURE LIKE THE FORMER MODELS ARE INDICATING...THE OFFICIAL
FORECAST WILL LEAN MORE HEAVILY ON THE LARGE-SCALE MODELS THAT DELAY
THE TROPICAL CYCLONE'S EVENTUAL DEMISE.  AROUND 120 HOURS A
COMBINATION OF COOLER WATERS AND AN UPPER-LEVEL TROUGH INTERACTION
MAY...HOPEFULLY...START TO SIGNAL THE DEMISE OF BERTHA AS A
TROPICAL CYCLONE.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      15/1500Z 35.6N  62.7W    60 KT
 12HR VT     16/0000Z 36.4N  61.8W    65 KT
 24HR VT     16/1200Z 36.2N  60.7W    65 KT
 36HR VT     17/0000Z 35.1N  59.6W    65 KT
 48HR VT     17/1200Z 34.1N  58.2W    60 KT
 72HR VT     18/1200Z 34.5N  54.5W    55 KT
 96HR VT     19/1200Z 37.5N  50.0W    50 KT
120HR VT     20/1200Z 41.5N  46.0W    45 KT...BECOMING EXTRATROPICAL
 
$$
FORECASTER BLAKE
 

WTNT42 KNHC 152035
TCDAT2
TROPICAL STORM BERTHA DISCUSSION NUMBER  51
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
500 PM EDT TUE JUL 15 2008
 
THE SATELLITE PRESENTATION OF BERTHA HAS DEGRADED A BIT OVER THE
PAST FEW HOURS AS THE EYE HAS BECOME LESS DISTINCT.  HOWEVER...
THERE HAS BEEN NO CHANGE IN THE SATELLITE CLASSIFICATIONS...AND THE
CURRENT INTENSITY WILL BE KEPT AT 60 KT FOR THIS ADVISORY...WHICH
MIGHT BE A LITTLE GENEROUS.  IT APPEARS THAT THE STORM HAS ABOUT A
DAY LEFT TO POSSIBLY INTENSIFY BEFORE WIND SHEAR INCREASES...
ALTHOUGH SO FAR BERTHA SHOWS NO SIGNS OF BECOMING A HURRICANE. THE
INTENSITY FORECAST WILL REMAIN SIMILAR TO PREVIOUS... AND NOT TOO
FAR FROM THE FSU SUPERENSEMBLE.  THE GFS AND ECMWF ARE FORECASTING
THE SYSTEM TO INTERACT WITH AN UPPER-LEVEL TROUGH STARTING IN ABOUT
96 HR...WHICH SHOULD CAUSE AN EXTRATROPICAL TRANSITION OF BERTHA
AROUND DAY 5.
 
BERTHA HAS SHOWN NO INDICATION OF THE FORECAST RIGHT TURN AND
CONTINUES ON A TRACK OF ABOUT 030/8.  HOWEVER THIS CHANGE IN
DIRECTION SHOULD OCCUR SOON AS MIDDLE-LEVEL RIDGING IS BECOMING
WEAKER ON WATER VAPOR IMAGES.  AS THE RIDGE COLLAPSES...BERTHA
SHOULD BE STEERED MORE TO THE EAST...THEN SOUTHEAST AND NORTHEAST
IN AN ARCING SEMICIRCLE FASHION AROUND A LARGE DEEP-LAYERED LOW TO
THE EAST. MODEL GUIDANCE HAS COME INTO BETTER AGREEMENT IN TRACK
AND THE OFFICIAL FORECAST IS BASICALLY AN UPDATE OF THE PREVIOUS
ONE.  

BERTHA IS NOW THE LONGEST-LIVED JULY TROPICAL STORM IN ATLANTIC
HISTORY...WITH 12.5 DAYS AS A TROPICAL STORM OR GREATER.  THIS
ECLIPSES THE PREVIOUS RECORD OF 12.25 DAYS OCCURRING IN 1916 FROM
STORM #2.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      15/2100Z 36.4N  62.3W    60 KT
 12HR VT     16/0600Z 36.8N  61.5W    60 KT
 24HR VT     16/1800Z 36.3N  60.5W    65 KT
 36HR VT     17/0600Z 35.1N  59.5W    60 KT
 48HR VT     17/1800Z 34.2N  57.5W    55 KT
 72HR VT     18/1800Z 35.7N  53.5W    50 KT
 96HR VT     19/1800Z 39.5N  49.0W    45 KT
120HR VT     20/1800Z 43.5N  44.0W    45 KT...EXTRATROPICAL
 
$$
FORECASTER BLAKE
 

WTNT42 KNHC 160249
TCDAT2
TROPICAL STORM BERTHA DISCUSSION NUMBER  52
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
1100 PM EDT TUE JUL 15 2008
 
BERTHA'S SATELLITE PRESENTATION HAS CONTINUED TO SLOWLY DEGRADE THIS
EVENING AS THE CLOUD TOPS HAVE WARMED OVER THE SOUTHERN PORTION OF
THE STORM.  THE LATEST SUBJECTIVE DVORAK INTENSITY ESTIMATES FROM
TAFB AND SAB ARE 45 AND 55 KT...RESPECTIVELY.  A QUIKSCAT OVERPASS
FROM 2222 UTC SUGGEST THAT THE MAXIMUM WINDS WERE 50-55 KT...SO THE
INITIAL INTENSITY HAS BEEN LOWERED A LITTLE.  BERTHA STILL HAS A
LITTLE TIME TO RESTRENGTHEN...SINCE THE SHEAR IS EXPECTED TO REMAIN
LOW WHILE THE STORM MOVES SOUTHEASTWARD OVER SLIGHTLY WARMER WATERS
DURING THE NEXT DAY OR SO.  HOWEVER...THE NEW INTENSITY FORECAST
KEEPS BERTHA JUST SHY OF HURRICANE STRENGTH. AFTER 48 HOURS...
COOLER WATER AND INCREASING SOUTHWESTERLY SHEAR SHOULD BEGIN
BERTHA'S GRADUAL DEMISE AS A TROPICAL CYCLONE.  
 
BERTHA APPEARS TO BE PUTTING ON THE BRAKES ONCE AGAIN.  THERE ARE
INDICATIONS THAT THE ANTICIPATED EASTWARD TURN HAS COMMENCED AND
THE INITIAL MOTION ESTIMATE IS 055/5.  THE MODELS ARE IN GOOD
AGREEMENT SHOWING BERTHA TURNING SOUTHEASTWARD DURING THE NEXT
12-18 HOURS...FOLLOWED BY AN EASTWARD MOTION THEREAFTER...AROUND
THE LARGE DEEP-LAYER LOW TO THE EAST.  AS THE DEEP-LAYER LOW LIFTS
NORTHWARD IN ABOUT 72 HOURS...BERTHA SHOULD FINALLY FEEL THE
WESTERLIES AND STARTING HEADING NORTHEASTWARD.  THERE IS A LARGE
AMOUNT OF SPREAD ON BERTHA'S FORWARD SPEED AT DAYS 4 AND 5...WITH
THE UKMET AND GFS SHOWING LESS ACCELERATION...WHILE THE GFDL...
GFDN...AND NOGAPS RACE BERTHA NORTHEASTWARD.  FOR NOW...THE NEW
TRACK FORECAST IS BETWEEN THESE TWO SOLUTIONS...AND IS CLOSE THE
MODEL CONSENSUS AND THE 12Z ECMWF.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      16/0300Z 36.8N  61.6W    55 KT
 12HR VT     16/1200Z 36.9N  61.1W    55 KT
 24HR VT     17/0000Z 36.0N  60.2W    60 KT
 36HR VT     17/1200Z 34.7N  59.1W    60 KT
 48HR VT     18/0000Z 34.0N  57.5W    60 KT
 72HR VT     19/0000Z 36.5N  52.7W    50 KT
 96HR VT     20/0000Z 40.0N  48.0W    45 KT
120HR VT     21/0000Z 44.5N  42.5W    45 KT...EXTRATROPICAL
 
$$
FORECASTER BROWN
 

WTNT42 KNHC 160853
TCDAT2
TROPICAL STORM BERTHA DISCUSSION NUMBER  53
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
500 AM EDT WED JUL 16 2008
 
BERTHA IS CAUGHT BETWEEN MIDDLE TO UPPER-LEVEL SOUTHWESTERLY FLOW
AHEAD OF A TROUGH OVER THE EASTERN UNITED STATES AND NORTHERLY FLOW
ON THE WEST SIDE OF AN UPPER-LOW OVER THE CENTRAL ATLANTIC. THIS
HAS RESULTED IN BERTHA'S CLOUD PATTERN BECOMING INCREASINGLY
STRETCHED IN A SOUTHEAST TO NORTHWEST ORIENTATION. HOWEVER...THE
DVORAK INTENSITY ESTIMATES STILL SUPPORT 55 KT. BERTHA IS BEGINNING
AN ANTICIPATED TURN TOWARD THE SOUTH AND THIS TRACK IS EXPECTED TO
TAKE THE CYCLONE OVER PROGRESSIVELY WARMER WATERS DURING THE NEXT 2
DAYS. SINCE THE SHEAR IS EXPECTED TO REMAIN LOW DURING THIS
PERIOD...SOME RESTRENGTHENING IS POSSIBLE PRIOR TO THE CYCLONE
ENCOUNTERING COOLER WATER AND INCREASING VERTICAL SHEAR BEYOND 72
HOURS. THE NEW OFFICIAL INTENSITY FORECAST IS VERY SIMILAR TO THE
PREVIOUS ONE AND SHOWS BERTHA REMAINING JUST SHY OF HURRICANE
STRENGTH. 
 
BERTHA IS NOW MOVING TOWARD THE EAST-SOUTHEAST WITH AN INITIAL
MOTION ESTIMATE OF 100/05.  A SOUTHEAST TURN IS EXPECTED LATER
TODAY FOLLOWED BY A TURN EASTWARD AND NORTHEASTWARD IN 2-3 DAYS AS
THE CYCLONE CYCLONICALLY ROTATES AROUND A LARGE UPPER-LOW TO ITS
EAST. TRACK GUIDANCE IS IN GOOD AGREEMENT DURING THE FIRST 2 DAYS OF
THE FORECAST BUT THEN DIVERGES AT DAYS 3-5.  THE GUIDANCE ENVELOPE
SPANS NEARLY 1400 MILES AT DAY 5 AND IS BOUNDED BY THE NOGAPS
MODEL...WHICH RACES THE CYCLONE NORTHEASTWARD...AND THE GFS
MODEL...WHICH SHOWS A MUCH SLOWER EAST-NORTHEASTWARD MOTION.  THE
HWRF...GFDL...AND UKMET MODELS LIE IN BETWEEN THESE OUTLIER
SOLUTIONS AND ARE THE BASIS FOR THE SOUTHWARD SHIFT AND SLOWER
FORWARD SPEED SHOWN IN THE NEW OFFICIAL FORECAST. 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      16/0900Z 36.4N  61.0W    55 KT
 12HR VT     16/1800Z 36.1N  60.6W    55 KT
 24HR VT     17/0600Z 35.0N  60.0W    60 KT
 36HR VT     17/1800Z 34.1N  58.6W    60 KT
 48HR VT     18/0600Z 34.0N  56.5W    60 KT
 72HR VT     19/0600Z 36.5N  52.0W    50 KT
 96HR VT     20/0600Z 40.0N  47.0W    45 KT
120HR VT     21/0600Z 43.5N  41.0W    40 KT...EXTRATROPICAL
 
$$
FORECASTER RHOME
 

WTNT42 KNHC 161431
TCDAT2
TROPICAL STORM BERTHA DISCUSSION NUMBER  54
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
1100 AM EDT WED JUL 16 2008

THE SATELLITE PRESENTATION OF BERTHA HAS DEGRADED SINCE YESTERDAY
WITH AN ELONGATED APPEARANCE.  HOWEVER...A QUIKSCAT PASS AT 0938
UTC SHOWED MAXIMUM WINDS OF ABOUT 60 KT.  THIS ESTIMATE WILL BE
USED FOR THE INITIAL INTENSITY.  LITTLE CHANGE IN STRENGTH IS
FORECAST DURING THE NEXT COUPLE OF DAYS AS THE EFFECTS OF
INCREASING VERTICAL WIND SHEAR ON THE STORM MAY BE TEMPERED BY
INCREASING SSTS.  SHEAR IS FORECAST TO INCREASE BY ALL MODELS IN A
FEW DAYS...SO THE CYCLONE SHOULD WEAKEN MORE IN THE LONG-TERM. 
EXTRATROPICAL TRANSITION SHOULD OCCUR IN 4 OR 5 DAYS DUE TO THE
EFFECTS OF STRONG MID-LATITUDE WINDS AND RAPIDLY COOLING WATERS.

QUIKSCAT DATA HELPED PLACE THE CENTER A LITTLE FARTHER TO THE
NORTHWEST THIS MORNING...YIELDING AN UNCERTAIN MOTION ESTIMATE OF
100/3.  THE TROPICAL CYCLONE IS EXPECTED TO TURN TOWARD THE
SOUTHEAST TODAY AS IT PINWHEELS AROUND A LARGE MIDDLE- TO
UPPER-LEVEL LOW TO THE EAST.  MODEL GUIDANCE REMAINS IN GOOD
AGREEMENT ON AN ARCING PATH TAKING THE SYSTEM FARTHER AWAY FROM
NORTH AMERICA.  IN TWO TO THREE DAYS... A MID-LATITUDE TROUGH WILL
APPROACH BERTHA FROM THE WEST.  THERE IS SOME DISAGREEMENT ON HOW
QUICKLY THE STORM WILL MOVE OUT TO SEA...BUT MODELS ARE GENERALLY
FASTER WITH THE PROGRESSION OF THE STORM.  THE OFFICIAL FORECAST IS
FAIRLY SIMILAR TO THE PREVIOUS ONE AND IS A LITTLE FASTER.  


FORECAST POSITIONS AND MAX WINDS
 
INITIAL      16/1500Z 36.6N  60.7W    60 KT
 12HR VT     17/0000Z 36.0N  60.1W    60 KT
 24HR VT     17/1200Z 35.0N  58.7W    60 KT
 36HR VT     18/0000Z 34.7N  56.4W    60 KT
 48HR VT     18/1200Z 35.6N  54.0W    60 KT
 72HR VT     19/1200Z 40.0N  49.0W    50 KT
 96HR VT     20/1200Z 43.5N  44.5W    45 KT...BECOMING EXTRATROPICAL
120HR VT     21/1200Z 47.5N  39.0W    45 KT...EXTRATROPICAL
 
$$
FORECASTER BLAKE
 

WTNT42 KNHC 162043
TCDAT2
TROPICAL STORM BERTHA DISCUSSION NUMBER  55
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
500 PM EDT WED JUL 16 2008

BERTHA REMAINS A POWERFUL SYSTEM WITH A LARGE WIND FIELD AND A
RAGGED EYE. THERE HAS BEEN LITTLE CHANGE TO THE SATELLITE
PRESENTATION FROM THIS MORNING SO THE INITIAL INTENSITY WILL REMAIN
60 KT.  LARGE-SCALE GUIDANCE SUGGESTS THAT THE ENVIRONMENT AROUND
THE STORM SHOULD BE FAVORABLE ENOUGH TO MAINTAIN THE TROPICAL
CYCLONE'S INTENSITY FOR A DAY OR SO.  THEREAFTER...A SLOW DECREASE
IN STRENGTH IS FORECAST AS SSTS DIMINISH SLOWLY ALONG THE TRACK.
THE EXTRATROPICAL TRANSITION OF BERTHA SHOULD START IN ABOUT 3-4
DAYS DUE TO THE EFFECTS OF A MIDDLE-LATITUDE TROUGH AND EVEN COOLER
WATERS. THE OFFICIAL FORECAST IS SIMILAR TO THE PREVIOUS
ONE...SHOWING ONLY A SLOW DEMISE OF THE STORM.

THE STORM HAS MADE THE SOUTHEASTWARD TURN AND IS NOW MOVING 140/4. A
LARGE MIDDLE- TO UPPER-LEVEL LOW TO THE EAST IS NOW STEERING BERTHA
AROUND ITS PERIPHERY. MODEL GUIDANCE REMAINS IN GOOD AGREEMENT
DURING THE FIRST FEW DAYS OF THE FORECAST TAKING THE STORM TO THE
SOUTHEAST...EAST...THEN NORTHEAST. HOWEVER... THERE IS SOME
DISAGREEMENT AS TO WHETHER BERTHA WILL BE SENT OUT TO SEA BY THE
UPPER LOW OR WHETHER A SECOND TROUGH WILL FINISH OFF THE STORM.
MOST OF THE GUIDANCE IS GOING WITH A FASTER SOLUTION...AND THE
OFFICIAL FORECAST LEANS IN THAT DIRECTION.  
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      16/2100Z 36.1N  60.5W    60 KT
 12HR VT     17/0600Z 35.5N  59.9W    60 KT
 24HR VT     17/1800Z 34.7N  58.1W    60 KT
 36HR VT     18/0600Z 35.1N  55.6W    55 KT
 48HR VT     18/1800Z 36.9N  53.1W    55 KT
 72HR VT     19/1800Z 41.5N  47.5W    50 KT
 96HR VT     20/1800Z 46.5N  41.0W    45 KT...EXTRATROPICAL
120HR VT     21/1800Z 52.5N  32.5W    45 KT...EXTRATROPICAL
 
$$
FORECASTER BLAKE
 

WTNT42 KNHC 170244
TCDAT2
TROPICAL STORM BERTHA DISCUSSION NUMBER  56
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
1100 PM EDT WED JUL 16 2008
 
BERTHA'S SATELLITE APPEARANCE HAS CONTINUED TO GRADUALLY DEGRADE 
DURING THE PAST 24 HOURS.  THE CYCLONE IS PRODUCING VERY LITTLE 
DEEP CONVECTION AND THERE ARE VIRTUALLY NO CLOUD TOPS COLDER THAN
-50 DEGREES C.  DVORAK INTENSITY ESTIMATES HAVE DECREASED TO
45 KT...HOWEVER A QUIKSCAT OVERPASS AT 2156 UTC SUGGESTS THAT THE
WINDS REMAIN 55-60 KT...SO THE INITIAL INTENSITY IS UNCHANGED.
ALL OF THE INTENSITY GUIDANCE PREDICTS LITTLE CHANGE IN BERTHA'S
STRENGTH DURING THE NEXT DAY OR TWO...FOLLOWED BY GRADUAL WEAKENING
AS SSTS ALONG THE FORECAST TRACK COOL AND THE SHEAR INCREASES. 
BERTHA IS FORECAST TO BECOME EXTRATROPICAL IN ABOUT 4 DAYS. 
  
BERTHA IS MOVING A LITTLE FASTER TO THE SOUTHEAST...140/7.  LITTLE
CHANGE HAS BEEN MADE TO THE FORECAST TRACK THROUGH 36 HOURS AS
BERTHA IS PREDICTED TO MOVE SOUTHEASTWARD...THEN EASTWARD AROUND
THE SOUTHWESTERN PERIPHERY OF A LARGE MID- TO UPPER-LEVEL LOW. 
THEREAFTER...THE TRACK MODELS ARE IN GOOD AGREEMENT ON A
NORTHEASTWARD MOTION...BUT AT VARYING FORWARD SPEEDS. 
HOWEVER...THE MOST RECENT TRACK GUIDANCE IS IN A LITTLE BETTER
AGREEMENT THAN 6 HOURS AGO.  THE NEW NHC TRACK IS SIMILAR TO THE
PREVIOUS ADVISORY AND IS IN BEST AGREEMENT WITH THE FSU
SUPERENSEMBLE...12Z UKMET...AND GFDL...BUT IS SLOWER THAN THE MODEL
CONSENSUS.

THE 34 AND 50 KT WIND RADII OVER THE EASTERN SEMICIRCLE WERE
EXPANDED BASED ON THE SCATTEROMETER DATA. 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      17/0300Z 35.4N  59.8W    60 KT
 12HR VT     17/1200Z 34.6N  58.9W    60 KT
 24HR VT     18/0000Z 34.5N  56.8W    60 KT
 36HR VT     18/1200Z 35.5N  54.4W    55 KT
 48HR VT     19/0000Z 37.6N  51.7W    55 KT
 72HR VT     20/0000Z 42.5N  45.7W    50 KT
 96HR VT     21/0000Z 48.0N  39.0W    45 KT...EXTRATROPICAL
120HR VT     22/0000Z 54.5N  30.0W    45 KT...EXTRATROPICAL
 
$$
FORECASTER BROWN
 

WTNT42 KNHC 170837
TCDAT2
TROPICAL STORM BERTHA DISCUSSION NUMBER  57
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
500 AM EDT THU JUL 17 2008
 
NORTHWESTERLY SHEAR APPEARS TO BE TAKING ITS TOLL ON BERTHA AS THE
REMAINING THUNDERSTORM ACTIVITY IS LIMITED TO THE EAST AND
SOUTHEAST OF THE CENTER.  THE LATEST DVORAK INTENSITY ESTIMATES ARE
45 KT AND A RECENT ASCAT PASS SUGGESTS THAT BERTHA'S WINDS HAVE
INDEED DECREASED. THE INITIAL INTENSITY IS LOWERED TO PERHAPS A
GENEROUS 50 KT.  ALTHOUGH BERTHA IS FORECAST TO MOVE OVER SLIGHTLY
WARMER WATERS TODAY...CONTINUED SHEAR SHOULD MEAN LITTLE CHANGE IN
INTENSITY.  IN FACT...NO CHANGE IN INTENSITY IS PREDICTED
THROUGHOUT THE FORECAST PERIOD AND THIS IS IN LINE WITH 
THE LATEST SHIPS AND LGEM GUIDANCE.

BERTHA IS STILL MOVING SOUTHEASTWARD WITH AN INITIAL MOTION ESTIMATE
OF 140/9.  WATER VAPOR IMAGERY INDICATES THAT THE UPPER-LEVEL LOW
IS BEGINNING TO MOVE NORTHWARD AND BERTHA SHOULD TURN EASTWARD 
AROUND THE SOUTHWESTERN PERIPHERY OF THE LOW DURING THE NEXT 6-12
HOURS.  THEREAFTER....BERTHA SHOULD GRADUALLY ACCELERATE
NORTHEASTWARD.  THE NEW FORECAST IS ADJUSTED A LITTLE SOUTH OF THE
PREVIOUS TRACK DURING THE FIRST 24 HOURS...OTHERWISE IT IS VERY
SIMILAR TO THE PREVIOUS ADVISORY.  BERTHA SHOULD BECOME
EXTRATROPICAL IN 3-4 DAYS AND COULD GET ABSORBED BY A LARGER
EXTRATROPICAL LOW IN ABOUT 5 DAYS.  
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      17/0900Z 34.5N  59.2W    50 KT
 12HR VT     17/1800Z 34.0N  58.0W    45 KT
 24HR VT     18/0600Z 34.5N  55.7W    45 KT
 36HR VT     18/1800Z 36.3N  53.2W    45 KT
 48HR VT     19/0600Z 38.4N  50.2W    45 KT
 72HR VT     20/0600Z 43.1N  44.3W    45 KT...BECOMING EXTRATROPICAL
 96HR VT     21/0600Z 49.0N  37.0W    45 KT...EXTRATROPICAL
120HR VT     22/0600Z 56.0N  27.5W    45 KT...EXTRATROPICAL
 
$$
FORECASTER BROWN
 

WTNT42 KNHC 171442
TCDAT2
TROPICAL STORM BERTHA DISCUSSION NUMBER  58
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
1100 AM EDT THU JUL 17 2008
 
A QUIKSCAT PASS AT 0912 UTC SUGGESTED THAT THE MAXIMUM WINDS OF
BERTHA WERE ABOUT 50 KT AT THAT TIME. SINCE THEN...NEW
THUNDERSTORMS HAVE DEVELOPED IN THE EASTERN SEMICIRCLE OF THE
STORM. ALTHOUGH SATELLITE CLASSIFICATIONS ARE DECREASING...I'M
HESITANT TO LOWER THE WINDS TOO MUCH BASED ON THE QUIKSCAT DATA AND
THE RESILENCY OF THE SYSTEM. 50 KT WILL BE USED AS THE INITIAL
INTENSITY. LITTLE CHANGE IN STRENGTH IS FORECAST FOR THE NEXT DAY
OR SO IN AGREEMENT WITH MOST GUIDANCE. HOWEVER...IT IS TEMPTING TO
LOWER THE WINDS A LITTLE MORE BEFORE EXTRATROPICAL TRANSITION
OCCURS. THE OFFICIAL FORECAST IS VERY SIMILAR TO THE PREVIOUS
FORECAST AND IS BELOW MOST OF THE INTENSITY GUIDANCE. BERTHA MAY
BECOME A LARGE POWERFUL EXTRATROPICAL LOW IN THE HIGH LATITUDES OF
THE NORTH ATLANTIC BY DAY 5.
 
THE STORM APPEARS TO HAVE TURNED TOWARD THE EAST-SOUTHEAST AT ABOUT
8 KT.  THE CYCLONE SHOULD BEGIN ITS MOTION TOWARD THE NORTHEAST BY
TOMORROW AS IT IS STEERED AROUND A MIDDLE- TO UPPER-LEVEL LOW TO
THE NORTH.  MODEL GUIDANCE IS IN GOOD AGREEMENT ON THE TRACK AND
LITTLE CHANGE IS MADE TO THE OFFICIAL FORECAST.  THEREAFTER THE
BIGGEST QUESTION IS WHETHER A NEW MIDDLE-LATITUDE TROUGH WILL
CAPTURE BERTHA...LIKE THE UKMET/ECMWF SHOWS...OR THE STORM WILL
REMAIN A MORE SEPARATE ENTITY LIKE THE GFS/GFDL/HWRF SOLUTIONS. 
THE OFFICAL FORECAST LEANS ON THE WESTERN SIDE OF THE
GUIDANCE...SHOWING A LITTLE MORE TROUGH INTERACTION. 

BERTHA COULD BECOME ONE OF THE TOP 10 LONGEST-LIVED STORMS IN
HISTORY IF IT SURVIVES UNTIL THE WEEKEND.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      17/1500Z 34.2N  58.4W    50 KT
 12HR VT     18/0000Z 34.1N  56.9W    45 KT
 24HR VT     18/1200Z 35.2N  54.5W    45 KT
 36HR VT     19/0000Z 37.3N  51.8W    45 KT
 48HR VT     19/1200Z 39.3N  49.1W    45 KT
 72HR VT     20/1200Z 43.5N  43.0W    45 KT...BECOMING EXTRATROPICAL
 96HR VT     21/1200Z 51.0N  34.0W    50 KT...EXTRATROPICAL
120HR VT     22/1200Z 57.5N  22.0W    50 KT...EXTRATROPICAL
 
$$
FORECASTER BLAKE
 

WTNT42 KNHC 172041
TCDAT2
TROPICAL STORM BERTHA DISCUSSION NUMBER  59
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
500 PM EDT THU JUL 17 2008
 
SATELLITE IMAGES INDICATE THAT BERTHA IS MAINTAINING ITS STRUCTURE
AS A TROPICAL STORM WITH DEFINED BANDING FEATURES AND OUTFLOW
ALOFT.  CONVECTION HAS BEEN WELL-MAINTAINED...ESPECIALLY IN THE
NORTHEAST QUADRANT OF THE STORM.  THERE HAS BEEN NO CHANGE IN THE
SATELLITE CLASSIFICATIONS SO THE INITIAL INTENSITY WILL REMAIN 50
KT.  NO SIGNIFICANT INTENSITY FLUCTUATIONS ARE EXPECTED DURING THE
NEXT DAY OR SO AS THE STORM REMAINS UNDER THE INFLUENCE OF MODERATE
SHEAR AND WANING SSTS.  THE EXTRATROPICAL TRANSITION PROCESS SHOULD
START SHORTLY AFTER 48 HR DUE TO AN INCREASE IN SHEAR AND MORE
RAPIDLY DECREASING SSTS...AND BY 120 HR...THE REMNANTS OF BERTHA
WILL LIKELY BE ABSORBED INTO A LARGER EXTRATROPICAL LOW.

THE STORM HAS MADE AN EASTWARD TURN AND IS MOVING ABOUT 090/10.  A
BUILDING RIDGE TO THE EAST OF BERTHA SHOULD STEER THE STORM MORE TO
THE NORTHEAST TOMORROW...FOLLOWING CLOSE BEHIND A MIDDLE- TO
UPPER-LEVEL LOW TO ITS NORTH.  MODEL GUIDANCE IS TIGHTLY CLUSTERED
ON AN ACCELERATING PATH OUT TO SEA.  THE GFS HAS CHANGED FROM THE
SOUTH TO NORTH SIDE OF THE MODEL CONSENSUS...NOW SHOWING MORE
INTERACTION WITH A NEW MIDDLE-LATITUDE TROUGH IN A COUPLE OF DAYS. 
THE OFFICIAL FORECAST LIES ON THE LEFT SIDE OF THE CONSENSUS AND IS
PRETTY CLOSE TO THE PREVIOUS ONE.  
 
TO CLARIFY A PREVIOUS DISCUSSION COMMENT...BERTHA COULD BECOME ONE
OF THE TOP 10 LONGEST-LIVED ATLANTIC STORMS...IN TERMS OF DAYS AS A
TROPICAL STORM OR GREATER...IF IT SURVIVES UNTIL SUNDAY.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      17/2100Z 34.0N  57.2W    50 KT
 12HR VT     18/0600Z 34.4N  55.6W    45 KT
 24HR VT     18/1800Z 35.9N  53.3W    45 KT
 36HR VT     19/0600Z 37.8N  51.0W    45 KT
 48HR VT     19/1800Z 39.9N  48.3W    45 KT
 72HR VT     20/1800Z 45.0N  41.0W    50 KT...EXTRATROPICAL
 96HR VT     21/1800Z 53.5N  30.0W    50 KT...EXTRATROPICAL
120HR VT     22/1800Z...ABSORBED
 
$$
FORECASTER BLAKE
 

WTNT42 KNHC 180253
TCDAT2
TROPICAL STORM BERTHA DISCUSSION NUMBER  60
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
1100 PM EDT THU JUL 17 2008
 
BERTHA CONTINUES TO BE A RELENTLESS CYCLONE AS A NEW BURST OF DEEP
CONVECTION RECENTLY FORMED OVER THE SOUTHEASTERN SEMICIRCLE THUS
MAINTAINING THE OVERALL SATELLITE APPEARANCE.  BASED ON THIS...THE
INITIAL INTENSITY IS HELD AT 50 KT FOR THIS ADVISORY.  WHILE
VERTICAL SHEAR IS EXPECTED TO REMAIN RELATIVELY LOW FOR THE NEXT
DAY OR SO...BERTHA IS EXPECTED TO MOVE OVER INCREASINGLY COLDER
WATERS.  THIS SHOULD RESULT IN WEAKENING IN THE SHORT-TERM. BEYOND
48 HOURS...BAROCLINIC DYNAMICS AND POSSIBLE EXTRATROPICAL
TRANSITION COULD RESULT IN SOME RESTRENGTHENING.  HOWEVER...THERE
ARE DIFFERENCES AMONG THE VARIOUS DYNAMICAL MODELS WITH SOME MODELS
SHOWING BERTHA BECOMING A LARGE AND POWERFUL EXTRATROPICAL SYSTEM
WHILE OTHER MODELS SHOW A WEAKENING CYCLONE BEING ABSORBED INTO A
LARGER NON-TROPICAL LOW.  GIVEN THIS UNCERTAINTY...THE OFFICIAL
FORECAST SHOWS SLOW WEAKENING EARLY WITH A LITTLE RESTRENGTHENING
AT DAYS 4 AND 5. 

BERTHA CONTINUES TO ROTATE AROUND A MIDDLE TO UPPER LEVEL LOW
RESULTING IN A TURN TOWARDS THE EAST...AND THE INITIAL MOTION IS
NOW 100/15.  THE CYCLONE IS EXPECTED TO TURN NORTHEASTWARD AND
ACCELERATE DURING THE NEXT DAY OR SO AS IT COMPLETES ITS ROTATION
AROUND THE LOW AND THEN ENCOUNTERS STRONG SOUTHWESTERLY FLOW
AHEAD OF A MID-LATITUDE TROUGH MOVING OFF THE CANADIAN MARITIMES. 
AS WOULD BE EXPECTED WITH AN ACCELERATING CYCLONE...TRACK GUIDANCE 
DIVERGES QUITE A BIT DUE TO THEIR DIFFERENT FORWARD SPEEDS.  IN
GENERAL...TRACK GUIDANCE IS FASTER THAN BEFORE BUT THEY HAVE NOT
DEMONSTRATED GOOD RUN TO RUN CONSISTENCY.  THE OFFICIAL FORECAST IS
NUDGED TOWARDS THE CONSENSUS OF THE DYNAMICAL MODELS WHICH RESULTS
IN A SLIGHTLY FASTER TRACK FORECAST THAN BEFORE. 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      18/0300Z 33.9N  55.4W    50 KT
 12HR VT     18/1200Z 34.8N  53.7W    50 KT
 24HR VT     19/0000Z 36.7N  51.2W    45 KT
 36HR VT     19/1200Z 38.8N  48.6W    45 KT
 48HR VT     20/0000Z 41.2N  45.2W    40 KT
 72HR VT     21/0000Z 47.0N  36.5W    45 KT...EXTRATROPICAL
 96HR VT     22/0000Z 56.0N  24.0W    45 KT...EXTRATROPICAL
120HR VT     23/0000Z...ABSORBED
 
$$
FORECASTER RHOME
 

WTNT42 KNHC 180834
TCDAT2
TROPICAL STORM BERTHA DISCUSSION NUMBER  61
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
500 AM EDT FRI JUL 18 2008
 
TENACIOUS BERTHA CONTINUES TO HAVE A REMARKABLE WELL-DEFINED CLOUD
PATTERN WITH A CURVED CONVECTIVE BAND TO THE NORTH...AN EYE-LIKE
FEATURE AND LIMITED OUTFLOW. THE INITIAL INTENSITY IS KEPT AT 50
KNOTS...BUT IT COULD BE A LITTLE BIT STRONGER. AS BERTHA MOVES OVER
COOLER WATERS IT SHOULD WEAKEN AND BECOME EXTRATROPICAL IN ABOUT 48
HOURS. THEREAFTER...BERTHA SHOULD BE FULLY EMBEDDED IN THE HIGH
LATITUDE WESTERLIES AND BECOME ABSORBED BY A LARGER EXTRATROPICAL
CYCLONE. 

BERTHA IS MOVING TOWARD THE NORTHEAST OR 045 DEGREES AT 15 KNOTS. 
IT APPEARS THAT FINALLY BERTHA WILL ACCELERATE TO THE NORTHEAST
AHEAD OF A SHARP MID-LATITUDE TROUGH AS INDICATED BY GUIDANCE.  SOME
MODELS MAKE BERTHA EXTRATROPICAL SOONER THAN OTHERS BUT THEY ALL
LEAD TO THE SAME ENDING.

 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      18/0900Z 34.8N  53.7W    50 KT
 12HR VT     18/1800Z 36.6N  51.6W    50 KT
 24HR VT     19/0600Z 39.0N  48.8W    45 KT
 36HR VT     19/1800Z 42.5N  45.0W    45 KT
 48HR VT     20/0600Z 46.0N  41.0W    45 KT...EXTRATROPICAL
 72HR VT     21/0600Z 54.0N  31.0W    45 KT...EXTRATROPICAL
 96HR VT     22/0600Z...ABSORBED BY LARGE EXTRATROPICAL CYCLONE
 
$$

FORECASTER AVILA
 

WTNT42 KNHC 181436
TCDAT2
TROPICAL STORM BERTHA DISCUSSION NUMBER  62
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
1100 AM EDT FRI JUL 18 2008

BERTHA HAS A WELL-DEVELOPED CLOUD PATTERN...OCCASIONALLY SHOWING
SIGNS OF TRYING TO FORM AN EYE.  QUIKSCAT DATA FROM EARLIER SUGGEST
MAXIMUM WINDS OF 50-55 KT AND...SINCE SATELLITE CLASSIFICATIONS ALSO
SUPPORT 55 KT...THE INTENSITY IS RAISED TO 55 KT FOR THIS ADVISORY. 
KUDOS GO TO THE GFDL/HWRF MODELS WHICH CORRECTLY FORECAST THE
RE-INTENSIFICATION OF THE STORM.  HOWEVER...SSTS ARE NOW DECREASING
IN THE PATH OF THE STORM...WHICH COULD LIMIT ANY FUTURE GROWTH OF
THE SYSTEM.  IN ABOUT 24 HOURS...SSTS QUICKLY DROP AND VERTICAL
SHEAR IS FORECAST TO INCREASE...SO THIS COMBINATION SHOULD BEGIN A
WEAKENING OF THE STORM.  THE OFFICIAL FORECAST IS CLOSE TO THE
INTENSITY CONSENSUS.

THE INITIAL MOTION OF THE STORM IS 040/16.  THIS GENERAL MOTION WITH
AN INCREASE IN FORWARD SPEED IS EXPECTED AS THE STORM IS CAUGHT
BETWEEN A BUILDING HIGH TO THE SOUTHEAST AND THE MIDDLE-LATITUDE
WESTERLIES.  IN ABOUT 36 HOURS...COLD NORTH ATLANTIC WATERS AND
INTERACTIONS WITH A MIDDLE-LATITUDE TROUGH SHOULD START THE
EXTRATROPICAL TRANSITION PROCESS.  TRACK GUIDANCE IS ABOUT AS
TIGHTLY CLUSTERED AS IT CAN BE AND THE OFFICIAL FORECAST IS CLOSE
TO THE MIDDLE OF THE GUIDANCE.    

 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      18/1500Z 36.2N  52.3W    55 KT
 12HR VT     19/0000Z 38.1N  50.1W    55 KT
 24HR VT     19/1200Z 41.0N  46.8W    55 KT
 36HR VT     20/0000Z 44.2N  43.1W    50 KT...BECOMING EXTRATROPICAL
 48HR VT     20/1200Z 48.0N  38.5W    45 KT...EXTRATROPICAL
 72HR VT     21/1200Z 57.0N  25.5W    45 KT...EXTRATROPICAL
 96HR VT     22/1200Z...ABSORBED
 
$$
FORECASTER BLAKE
 

WTNT42 KNHC 182029
TCDAT2
HURRICANE BERTHA DISCUSSION NUMBER  63
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
500 PM EDT FRI JUL 18 2008

SATELLITE IMAGES INDICATE THAT BERTHA IS NOW A HURRICANE AGAIN.  THE
EYE HAS BECOME BETTER-DEFINED WITH DEEP CONVECTION INCREASING AROUND
A CONSOLIDATING EYEWALL.  THE INITIAL INTENSITY IS RAISED TO 65 KT
IN AGREEMENT WITH THE SATELLITE CLASSIFICATION FROM SAB.  BERTHA
SHOULDN'T BE A HURRICANE FOR TOO LONG AS IT IS FORECAST TO BE OVER
WATERS LESS THAN 70F BY THIS TIME TOMORROW.  A SLOW WEAKENING IS
INDICATED...WHICH IS IN GOOD AGREEMENT WITH MOST GUIDANCE.  PHASE
DIAGRAMS FROM FLORIDA STATE INDICATE THAT THE HURRICANE SHOULD
BEGIN ITS EXTRATROPICAL TRANSITION IN A DAY OR SO...WITH THE
PROCESS COMPLETE IN ABOUT 48 HR.  
 
BERTHA CONTINUES MOVING TO THE NORTHEAST...NOW AT ABOUT 19 KT. THERE
IS NO CHANGE TO THE SYNOPTIC REASONING. THE HURRICANE SHOULD
ACCELERATE OUT TO SEA IN A WELL-DEFINED STEERING CURRENT BETWEEN A
HIGH TO THE SOUTHEAST AND THE MIDDLE-LATITUDE WESTERLIES. MODEL
GUIDANCE IS GENERALLY SHOWING GREATER INTERACTION THAN EARLIER WITH
BERTHA AND AN APPROACHING TROUGH FROM NORTH AMERICA... RESULTING IN
A SLIGHTLY MORE POLEWARD TRACK OF THE CYCLONE. THE OFFICIAL
FORECAST IS SHIFTED WESTWARD TO ACCOUNT FOR THIS TREND AND LIES ON
THE EASTERN SIDE OF THE GUIDANCE ENVELOPE. 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      18/2100Z 37.6N  50.6W    65 KT
 12HR VT     19/0600Z 39.8N  48.2W    65 KT
 24HR VT     19/1800Z 42.9N  44.8W    60 KT
 36HR VT     20/0600Z 46.7N  40.6W    55 KT...BECOMING EXTRATROPICAL
 48HR VT     20/1800Z 51.5N  36.0W    50 KT...EXTRATROPICAL
 72HR VT     21/1800Z 61.0N  23.0W    50 KT...EXTRATROPICAL
 96HR VT     22/1800Z...ABSORBED
 
$$
FORECASTER BLAKE
 

WTNT42 KNHC 190243
TCDAT2
HURRICANE BERTHA DISCUSSION NUMBER  64
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
1100 PM EDT FRI JUL 18 2008
 
CONVECTION AROUND THE SOUTH SIDE OF BERTHA'S EYE HAS WEAKENED DURING
THE PAST SEVERAL HOURS.  HOWEVER...DVORAK INTENSITY ESTIMATES ARE
UNCHANGED...SO BERTHA REMAINS A 65 KT HURRICANE.  BERTHA IS NOT 
EXPECTED TO BE A HURRICANE MUCH LONGER AS IT WILL BE MOVING OVER
PROGRESSIVELY COOLER WATERS WITHIN THEN NEXT 12-24 HOURS.  THE
INTENSITY FORECAST CALLS FOR GRADUAL WEAKENING AS BERTHA 
BECOMES EXTRATROPICAL IN 24-36 HOURS. 

BERTHA CONTINUES TO ACCELERATE NORTHEASTWARD WITH A FORWARD SPEED
OF ABOUT 22 KT.  BERTHA IS FORECAST TO REMAIN ON A NORTHEAST
HEADING DURING THE NEXT 2-3 DAYS.  THE OFFICIAL FORECAST IS SIMILAR
TO THE PREVIOUS ADVISORY...BUT IS SLIGHTLY FASTER.  HOWEVER...THE
NEW TRACK FORECAST IS A LITTLE SLOWER THAN THE GFS...BUT IS AHEAD
OF THE MODEL CONSENSUS.  THE FORECAST 34 KT WIND RADII WERE
EXPANDED OUTWARD OVER THE EASTERN SEMICIRCLE IN GOOD AGREEMENT 
WITH A BLEND OF THE GLOBAL MODELS. 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      19/0300Z 39.5N  48.8W    65 KT
 12HR VT     19/1200Z 42.0N  46.0W    60 KT
 24HR VT     20/0000Z 45.4N  42.1W    55 KT...BECOMING EXTRATROPICAL
 36HR VT     20/1200Z 50.2N  37.5W    50 KT...EXTRATROPICAL
 48HR VT     21/0000Z 55.4N  32.1W    50 KT...EXTRATROPICAL
 72HR VT     22/0000Z 63.5N  20.0W    45 KT...EXTRATROPICAL
 96HR VT     23/0000Z...ABSORBED 
 
$$
FORECASTER BROWN
 

WTNT42 KNHC 190830
TCDAT2
HURRICANE BERTHA DISCUSSION NUMBER  65
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
500 AM EDT SAT JUL 19 2008
 
BERTHA HAS REMARKABLY MAINTAINED ITS TROPICAL STRUCTURE WITH AN EYE
SURROUNDED BY MODERATE CONVECTION. INITIAL INTENSITY IS KEPT AT 65
KNOTS BUT COULD BE A LITTLE BIT HIGHER...AS SUGGESTED BY DVORAK
ESTIMATES FROM TAFB.  I AM NOT GOING TO SPECULATE HOW MUCH LONGER
BERTHA WILL KEEP ITS STRUCTURE BUT THE CYCLONE IS MOVING OVER COOL
WATERS AND WITHIN THE MID-LATITUDE FLOW. CONSQUENTLY...BERTHA HAS
TO WEAKEN AND BEGIN TO BECOME EXTRATROPICAL...FAMOUS LAST WORDS.   

BERTHA IS MOVING TOWARD THE NORTHEAST OR 030 DEGREES AT 22 KNOTS.
THE HURRICANE SHOULD CONTINUE ON THIS GENERAL TRACK WITH A GRADUAL
INCREASE IN FORWARD SPEED UNTIL BECOME ABSORBED IN A COUPLE OF
DAYS.  TRACK GUIDANCE UNANIMOUSLY SHOWS THE HURRICANE ACCELERATING
TOWARD THE NORTHEAST.   
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      19/0900Z 41.2N  47.4W    65 KT
 12HR VT     19/1800Z 43.8N  44.8W    60 KT
 24HR VT     20/0600Z 48.0N  40.5W    50 KT...EXTRATROPICAL
 36HR VT     20/1800Z 53.0N  35.0W    50 KT...EXTRATROPICAL
 48HR VT     21/0600Z 58.0N  28.0W    50 KT...EXTRATROPICAL
 72HR VT     22/0600Z...EXTRATROPICAL
 
$$
FORECASTER AVILA
 

WTNT42 KNHC 191451
TCDAT2
HURRICANE BERTHA DISCUSSION NUMBER  66
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
1100 AM EDT SAT JUL 19 2008
 
BERTHA IS STILL A HURRICANE...EVEN THOUGH IT IS NOW WELL PAST 40
DEGREES NORTH LATITUDE AND OVER RATHER CHILLY SEA-SURFACE
TEMPERATURES.  A QUIKSCAT PASS AT AROUND 0820Z PRODUCED
25-KM-RESOLUTION RETRIEVED WIND SPEEDS AS STRONG AS ABOUT 60 KT IN
DEEP CONVECTION...AND THESE COULD CERTAINLY BE UNDERESTIMATES. 
DVORAK INTENSITY ESTIMATES AT 12Z REMAINED 65 KT...AND THAT IS THE
ADVISORY INTENSITY.  BERTHA'S LONG LIFE AS A TROPICAL CYCLONE IS
PROBABLY NEARING ITS END...HOWEVER...SINCE IT IS SO QUICKLY GAINING
LATITUDE.  THE OFFICIAL FORECAST CALLS FOR BERTHA TO BE AN
EXTRATROPICAL CYCLONE WITHIN ABOUT 24 HOURS AND THEN BE ABSORBED BY
A LARGER SYSTEM IN LESS THAN THREE DAYS.

THE HURRICANE IS RACING ALONG AT 035/22...AND THE FORWARD SPEED WILL
PROBABLY INCREASE DURING THE NEXT COUPLE OF DAYS AS THE CYCLONE
ENTERS THE FULL-BLOWN MID-LATITUDE WESTERLIES.  MODEL GUIDANCE IS
IN VERY GOOD AGREEMENT...WHICH IS NOT SURPRISING WHEN STEERING
CURRENTS ARE THIS WELL-DEFINED.  THE NEW OFFICIAL TRACK IS RIGHT ON
THE PREVIOUS ONE.
 
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      19/1500Z 43.1N  45.4W    65 KT
 12HR VT     20/0000Z 45.9N  42.6W    60 KT
 24HR VT     20/1200Z 50.5N  37.7W    55 KT...EXTRATROPICAL
 36HR VT     21/0000Z 55.7N  31.2W    50 KT...EXTRATROPICAL
 48HR VT     21/1200Z 60.8N  24.0W    50 KT...EXTRATROPICAL
 72HR VT     22/1200Z...ABSORBED
 
$$
FORECASTER KNABB
 

WTNT42 KNHC 192038
TCDAT2
HURRICANE BERTHA DISCUSSION NUMBER  67
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
500 PM EDT SAT JUL 19 2008
 
RELATIVELY DEEP CONVECTION PERSISTS ALL THE WAY AROUND THE
CIRCULATION CENTER...AND DVORAK ESTIMATES AT 18Z SUPPORT
MAINTAINING BERTHA AS A HURRICANE WITH MAXIMUM WINDS OF 65 KT. 
BERTHA IS CROSSING THE 20 DEGREE CELSIUS ISOTHERM...HOWEVER...AND
IT SEEMINGLY CANNOT HOLD ON TO TROPICAL CHARACTERISTICS MUCH
LONGER.  THE OFFICIAL FORECAST PRESUMES THAT EXTRATROPICAL
TRANSITION WILL BE WELL UNDERWAY...ALTHOUGH PERHAPS NOT
COMPLETE...BY 12 HOURS AS THE SYSTEM REACHES 17 CELSIUS
WATERS...BUT AFTER THAT THE SYSTEM SHOULD BE FULLY EXTRATROPICAL. 
THIS EVOLUTION IS CONSISTENT WITH THE FSU PHASE SPACE ANALYSIS BASED
ON THE GFS GLOBAL MODEL.  DESPITE THE TRANSITION...THE WINDS WILL
PROBABLY NOT FALL OFF VERY FAST...AND BERTHA WILL BE A LARGE AND
POWERFUL EXTRATROPICAL CYCLONE FOR TWO TO THREE DAYS UNTIL IT IS
ABSORBED BY OR MERGES WITH ANOTHER SYSTEM CROSSING CANADA.

THERE HAS BEEN NO DETECTABLE CHANGE TO THE INITIAL MOTION ESTIMATE
OF 035/22.  A GRADUAL INCREASE IN FORWARD SPEED IS FORECAST...ALONG
ABOUT THE SAME HEADING...IN CLOSE AGREEMENT WITH THE GFS MODEL. 
THE NEW OFFICIAL TRACK IS VERY SIMILAR TO THE PREVIOUS ADVISORY.

 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      19/2100Z 44.8N  43.3W    65 KT
 12HR VT     20/0600Z 47.9N  40.0W    60 KT
 24HR VT     20/1800Z 52.9N  34.3W    55 KT...EXTRATROPICAL
 36HR VT     21/0600Z 58.0N  27.2W    50 KT...EXTRATROPICAL
 48HR VT     21/1800Z 62.5N  20.0W    50 KT...EXTRATROPICAL
 72HR VT     22/1800Z...DISSIPATED
 
$$
FORECASTER KNABB
 

WTNT42 KNHC 200257
TCDAT2
TROPICAL STORM BERTHA DISCUSSION NUMBER  68
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
1100 PM EDT SAT JUL 19 2008
 
THE SATELLITE PRESENTATION OF BERTHA HAS DEGRADED OVER THE PAST FEW
HOURS...WITH THE CONVECTION BECOMING LESS SYMMETRIC AND BEGINNING
TO WARM. THE EYE THAT WAS VISIBLE SIX HOURS AGO IS GONE. DVORAK T
NUMBERS ARE DECREASING...AND THE INITIAL INTENSITY IS LOWERED TO 60
KT. FORECAST TO BE OVER 11C WATERS IN ABOUT 18 HOURS...BERTHA
SHOULD NOT BE ABLE TO MAINTAIN TROPICAL CHARACTERISTICS BEYOND
MIDDAY TOMORROW. DESPITE THE TRANSITION...THE WINDS WILL PROBABLY
NOT FALL OFF VERY FAST...AND BERTHA WILL BE A LARGE AND POWERFUL
EXTRATROPICAL CYCLONE FOR TWO TO THREE DAYS UNTIL IT IS ABSORBED BY
OR MERGES WITH ANOTHER SYSTEM CROSSING CANADA.
 
THE INITIAL MOTION IS 040/21...ABOUT THE SAME AS BEFORE.  AN
INCREASE IN FORWARD SPEED IS FORECAST...IN CLOSE AGREEMENT WITH A
TIGHTLY-PACKED MODEL CONSENSUS AND THE PREVIOUS ADVISORY. 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      20/0300Z 45.7N  41.8W    60 KT
 12HR VT     20/1200Z 49.8N  37.4W    55 KT
 24HR VT     21/0000Z 55.0N  31.4W    55 KT...EXTRATROPICAL
 36HR VT     21/1200Z 60.1N  24.8W    50 KT...EXTRATROPICAL
 48HR VT     22/0000Z 64.0N  18.0W    50 KT...EXTRATROPICAL
 72HR VT     23/0000Z...ABSORBED
 
$$
FORECASTER FRANKLIN
 

WTNT42 KNHC 200856
TCDAT2
TROPICAL STORM BERTHA DISCUSSION NUMBER  69
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
500 AM EDT SUN JUL 20 2008

ALTHOUGH THE CONVECTION IS NOT VERY DEEP...THE CLOUD PATTERN OF
BERTHA STILL LOOKS SOMEWHAT SYMMETRIC...I.E. TROPICAL...AND A SHIP
WITH CALL SIGN WDC6925 REPORTED 44 KT WINDS NOT FAR FROM THE
CENTER...WHICH IS ALSO INDICATIVE OF A TROPICAL STRUCTURE.  PHASE
SPACE ANALYSES FROM FLORIDA STATE UNIVERSITY USING THE GFS FORECAST
FIELDS INDICATE THAT BERTHA WILL BECOME AN EXTRATROPICAL CYCLONE
VERY SOON...PROBABLY NOT LONG AFTER 1200 UTC TODAY.  THE FORECAST
SHOWS BERTHA'S EXTRATROPICAL REMNANT BECOMING ABSORBED BY 72 HOURS
BUT GLOBAL MODELS FORECASTS SUGGEST THAT THIS EVENT COULD OCCUR
SOONER.  FOR NEXT DAY OR TWO...HOWEVER...THE POST-BERTHA CYCLONE
SHOULD REMAIN A FAIRLY POWERFUL EXTRATROPICAL STORM.

BERTHA IS ACCELERATING AND THE INITIAL MOTION IS NOW AROUND 035/26. 
AN ADDITIONAL INCREASE IN FORWARD SPEED IS EXPECTED AS THE CYCLONE
MOVES WITH THE FLOW ON THE SOUTHEAST SIDE OF A BROAD MID-LATITUDE
TROUGH...UNTIL THE SYSTEM MERGES WITH OR IS ABSORBED BY ANOTHER
LOW.  THE TRACK FORECAST IS IN GOOD AGREEMENT WITH THE MODEL
CONSENSUS AND SIMILAR TO THAT FROM THE PREVIOUS ADVISORY.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      20/0900Z 48.5N  38.9W    60 KT
 12HR VT     20/1800Z 52.5N  34.5W    55 KT...EXTRATROPICAL
 24HR VT     21/0600Z 58.0N  28.0W    55 KT...EXTRATROPICAL
 36HR VT     21/1800Z 63.0N  21.0W    50 KT...EXTRATROPICAL
 48HR VT     22/0600Z 67.0N  15.0W    50 KT...EXTRATROPICAL
 72HR VT     23/0600Z...ABSORBED
 
$$
FORECASTER PASCH
 

WTNT42 KNHC 201502
TCDAT2
TROPICAL STORM BERTHA DISCUSSION NUMBER  70
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
1100 AM EDT SUN JUL 20 2008
 
BERTHA IS RAPIDLY LOSING TROPICAL CHARACTERISTICS. THE WIND FIELD
HAS BECOME EXTREMELY ASYMMETRIC AND THE CONVECTION IS DIMINISHING
NEAR THE CENTER. THUS BERTHA IS BEING DECLARED EXTRATROPICAL AND
THIS IS THE LAST ADVISORY. SHIP ABCC4 AND QUIKSCAT SUGGEST THE
MAXIMUM WINDS REMAIN NEAR 60 KT. A SLOW WEAKENING IS FORECAST IN
LINE WITH GLOBAL MODEL GUIDANCE. THE TRACK FORECAST IS IN GOOD
AGREEMENT WITH THE MODEL CONSENSUS AND SIMILAR TO THE PREVIOUS
ADVISORY. 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      20/1500Z 51.3N  35.7W    60 KT...EXTRATROPICAL
 12HR VT     21/0000Z 55.2N  31.2W    55 KT...EXTRATROPICAL
 24HR VT     21/1200Z 61.0N  24.3W    50 KT...EXTRATROPICAL
 36HR VT     22/0000Z...DISSIPATED
 
$$
FORECASTER KNABB/BLAKE
 

