WTNT43 KNHC 152033
TCDAT3
TROPICAL STORM BILL DISCUSSION NUMBER   2
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL032009
500 PM AST SAT AUG 15 2009
 
SATELLITE IMAGERY INDICATES THAT THE DEPRESSION IN THE FAR EASTERN
ATLANTIC HAS CONTINUED TO BECOME BETTER ORGANIZED. THE CYCLONE IS
LARGE AND HAS NUMEROUS CYCLONICALLY-CURVED CONVECTIVE BANDS WITH
THE OUTFLOW PRIMARILY ON THE WESTERN SEMICIRCLE. DVORAK T-NUMBERS
HAVE INCREASED AND SUPPORT UPGRADING THE SYSTEM TO TROPICAL STORM
STATUS WITH AN INITIAL INTENSITY OF 35 KNOTS. BILL IS EXPECTED TO
REMAIN OVER WARM WATERS AND EMBEDDED WITHIN LIGHT SHEAR THROUGH THE
FORECAST PERIOD. STRENGTHENING IS INDICATED AND BILL IS EXPECTED TO
BECOME A HURRICANE IN 3 TO 4 DAYS. THIS IS CONSISTENT WITH THE
UPWARD INTENSITY TREND INDICATED BY THE GUIDANCE.

BILL IS IN THE DEEP TROPICS AND IS WELL-EMBEDDED WITHIN THE EASTERLY
TRADE WINDS. THE CYCLONE IS MOVING JUST SOUTH OF DUE WEST OR 265
DEGREES AT 14 KNOTS. IN GENERAL...NO SIGNIFICANT CHANGE IN THE
STEERING CURRENTS IS ANTICIPATED AND BILL SHOULD BEGIN TO TURN A
LITTLE MORE TO THE WEST-NORTHWEST AROUND THE PERIPHERY OF THE
SUBTROPICAL RIDGE IN A DAY OR SO...WITH LITTLE CHANGE IN FORWARD
SPEED. THERE HAS NOT BEEN A SIGNIFICANT CHANGE IN THE GUIDANCE...AND
THE BULK OF THE MODELS HAS BILL AS A HURRICANE JUST NORTH AND VERY
NEAR THE NORTHERN LEEWARD ISLANDS AND SO DOES THE OFFICIAL
FORECAST.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      15/2100Z 11.3N  35.2W    35 KT
 12HR VT     16/0600Z 11.2N  37.2W    35 KT
 24HR VT     16/1800Z 11.5N  40.0W    45 KT
 36HR VT     17/0600Z 12.0N  43.0W    50 KT
 48HR VT     17/1800Z 13.0N  46.0W    55 KT
 72HR VT     18/1800Z 14.5N  52.0W    60 KT
 96HR VT     19/1800Z 17.0N  58.0W    75 KT
120HR VT     20/1800Z 19.5N  63.5W    90 KT
 
$$
FORECASTER AVILA
 

WTNT43 KNHC 160247
TCDAT3
TROPICAL STORM BILL DISCUSSION NUMBER   3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL032009
1100 PM AST SAT AUG 15 2009
 
SATELLITE IMAGES CONTINUE TO SHOW THAT BILL IS GRADUALLY BECOMING
BETTER ORGANIZED WITH NUMEROUS CONVECTIVE BANDING FEATURES.
HOWEVER...THE CYCLONE LACKS AN INNER CORE AND DEEP CONVECTION NEAR
THE CENTER. INITIAL INTENSITY IS KEPT AT 35 KNOTS WHICH IS A BLEND
OF THE DVORAK CLASSIFICATIONS AND QUIKSCAT DATA.  WITH THE
CONDUCIVE ENVIRONMENT AHEAD...BILL IS FORECAST TO BECOME A
HURRICANE IN A COUPLE OF DAYS AND BECOME EVEN STRONGER THEREAFTER.
THIS IS CONSISTENT WITH SHIPS AND BOTH THE GFDL/HWRF MODEL PAIR.

BILL IS MOVING WESTWARD OR 270 DEGREES AT 14 KNOTS. THE CYCLONE IS
WELL-EMBEDDED IN THE TROPICAL TRADE WINDS AND WILL CONTINUE ON THIS
GENERAL TRACK WITH A GRADUAL TURN TO THE WEST-NORTHWEST. THE ECMWF
WAS THE LEADER SHOWING A GRADUAL NORTHWARD TREND AHEAD OF A TROUGH
OVER THE EASTERN UNITED STATES A FEW RUNS AGO.  NOW...THE REST OF
THE MODELS...WITH THE EXCEPTION OF THE UK MODEL...ARE FOLLOWING THE
ECMWF TUNE...AND ALL TURN BILL MORE THE WEST-NORTHWEST AND NORTHWEST
BY THE END OF THE FORECAST PERIOD. BASED ON THIS SHIFT IN THE
GUIDANCE...THE OFFICIAL FORECAST WAS ALSO SHIFTED A LITTLE
NORTHWARD AND IS IN THE MIDDLE OF THE TIGHTLY PACKED GUIDANCE
ENVELOPE.
  
  
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      16/0300Z 11.3N  36.6W    35 KT
 12HR VT     16/1200Z 11.2N  38.7W    40 KT
 24HR VT     17/0000Z 12.0N  41.5W    50 KT
 36HR VT     17/1200Z 12.8N  44.0W    55 KT
 48HR VT     18/0000Z 14.0N  47.0W    65 KT
 72HR VT     19/0000Z 15.5N  52.5W    75 KT
 96HR VT     20/0000Z 18.0N  58.5W    85 KT
120HR VT     21/0000Z 21.0N  64.0W    95 KT
 
$$
FORECASTER AVILA
 

WTNT43 KNHC 160857
TCDAT3
TROPICAL STORM BILL DISCUSSION NUMBER   4
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL032009
500 AM AST SUN AUG 16 2009
 
THE CENTER OF BILL HAS BEEN DIFFICULT TO FIND THIS MORNING...AND A
0419 UTC AMSR-E PASS INDICATED THAT IT HAS EITHER SLOWED DOWN OR
HAS BEEN RE-FORMING CLOSER TO THE DEEP CONVECTION.  DVORAK
T-NUMBERS ARE NOW 3.0 FROM TAFB AND 2.5 FROM SAB...SO THE INITIAL
INTENSITY IS RAISED TO 40 KT.  BILL IS EXPECTED TO GRADUALLY
STRENGTHEN OVER THE NEXT COUPLE OF DAYS...AND THE OFFICIAL FORECAST
FOLLOWS THE UPWARD TREND NOTED IN THE INTENSITY GUIDANCE.  BILL IS
NOW EXPECTED TO REACH MAJOR HURRICANE STATUS BY DAY 5...BUT IT
SHOULD BE NOTED THAT THE 100 KT SHOWN IN THE FORECAST IS STILL
BELOW THE INTENSITY CONSENSUS AND WELL BELOW THE HWRF MODEL.  THIS
IS TO ACCOUNT FOR INCREASED VERTICAL SHEAR THAT MAY DEVELOP BY DAYS
4 AND 5...AS INDICATED IN THE SHIPS GUIDANCE.

THE INITIAL MOTION IS AN UNCERTAIN 270/11.  BILL IS EXPECTED TO
GRADUALLY GAIN LATITUDE AND TURN TO THE WEST-NORTHWEST OVER THE
NEXT FEW DAYS.  THE NEW SUITE OF MODEL GUIDANCE HAS SHIFTED A
LITTLE NORTH OF THE PREVIOUS GUIDANCE ENVELOPE AS MOST OF THE
MODELS APPEAR TO BE SHOWING THE DEVELOPMENT OF A DEEP MID- TO
UPPER-LEVEL TROUGH OVER THE EASTERN UNITED STATES AT THE END OF THE
FORECAST PERIOD.  MOST OF THE MODELS...WITH THE EXCEPTION OF THE
UKMET AS A SOUTHERN OUTLIER...ARE IN REMARKABLY GOOD AGREEMENT
THROUGH DAY 5.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      16/0900Z 11.4N  37.2W    40 KT
 12HR VT     16/1800Z 11.8N  39.3W    45 KT
 24HR VT     17/0600Z 12.5N  41.9W    50 KT
 36HR VT     17/1800Z 13.4N  44.7W    60 KT
 48HR VT     18/0600Z 14.3N  47.5W    70 KT
 72HR VT     19/0600Z 16.5N  53.0W    85 KT
 96HR VT     20/0600Z 19.0N  58.5W    95 KT
120HR VT     21/0600Z 22.0N  64.0W   100 KT
 
$$
FORECASTER BERG
 

WTNT43 KNHC 161442
TCDAT3
TROPICAL STORM BILL DISCUSSION NUMBER   5
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL032009
1100 AM AST SUN AUG 16 2009
 
BILL IS DISPLAYING A BEAUTIFUL CURVED BAND PATTERN ON SATELLITE
IMAGERY THIS MORNING WITH A NEW BURST OF CONVECTION OCCURRING NEAR
THE CENTER.  A 0808 UTC QUIKSCAT PASS SHOWED MAXIMUM WINDS OF AT
LEAST 45 KT...AND DVORAK SATELLITE INTENSITY ESTIMATES ARE BETWEEN
45-55 KT.  THE INITIAL INTENSITY IS SET TO 50 KT AS A BLEND OF THE
ABOVE DATA.
 
A SERIES OF MICROWAVE PASSES AND VISIBLE IMAGES HAVE CONFIRMED THAT
THE CENTER HAS SHIFTED A LITTLE BIT TO THE NORTH AND THE INITIAL
MOTION IS ABOUT 285/14.  A CONTINUED WEST-NORTHWEST MOTION IS
EXPECTED FOR THE NEW FEW DAYS DUE TO SUBTROPICAL RIDGING TO THE
NORTH OF BILL.  ALL OF THE GLOBAL MODELS BESIDES THE UKMET SHOW
THE TROPICAL CYCLONE MOVING TO THE NORTH OF THE LEEWARD ISLANDS AS A
BREAK IN THE RIDGE FORMS AT ABOUT 65W.  MODEL GUIDANCE HAS SHIFTED
TO THE NORTHEAST THIS MORNING...AND THE OFFICIAL FORECAST FOLLOWS
THAT TREND.
 
ENVIRONMENTAL CONDITIONS APPEAR FAVORABLE FOR CONTINUED
INTENSIFICATION DUE TO LIGHT SHEAR AND WARM WATERS.  SSTS BEGIN TO
RISE MORE SIGNIFICANTLY IN A COUPLE OF DAYS AND THE NHC INTENSITY
FORECAST COULD BE CONSERVATIVE AFTER THAT TIME.  ALL RELIABLE
GUIDANCE SHOWS THIS SYSTEM EVENTUALLY BECOMING A MAJOR HURRICANE...
THOUGH AT DIFFERING TIME PERIODS WITH THE STATISTICAL GUIDANCE
SHOWING IT HAPPENING EARLIER THAN THE DYNAMICAL MODELS.  THE NHC
FORECAST IS RAISED FROM THE PREVIOUS ONE...AND IS IN GOOD AGREEMENT
WITH THE SHIPS/LGEM THROUGH 72 HOURS.  THE INTENSITY FORECAST IS
LEVELED OFF AFTER 96 HOURS DUE THE POSSIBILITY OF WESTERLY SHEAR
DEVELOPING...AS SUGGESTED BY THE GFS/ECMWF MODELS.
 
THE QUIKSCAT PASS FROM THIS MORNING SHOWED THAT THE WIND FIELD WITH
BILL HAS EXPANDED...AND CONSEQUENTLY THE INITIAL 12 FT SEAS AND
FORECAST WIND RADII ARE LARGER THAN THE PREVIOUS FORECAST.

 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      16/1500Z 12.1N  38.4W    50 KT
 12HR VT     17/0000Z 12.6N  40.4W    60 KT
 24HR VT     17/1200Z 13.4N  43.1W    70 KT
 36HR VT     18/0000Z 14.3N  45.9W    80 KT
 48HR VT     18/1200Z 15.2N  48.6W    90 KT
 72HR VT     19/1200Z 17.5N  54.0W   100 KT
 96HR VT     20/1200Z 20.5N  59.0W   105 KT
120HR VT     21/1200Z 24.0N  63.5W   105 KT
 
$$
FORECASTER BLAKE
 

WTNT43 KNHC 162040
TCDAT3
TROPICAL STORM BILL DISCUSSION NUMBER   6
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL032009
500 PM AST SUN AUG 16 2009
 
SATELLITE IMAGES SHOW THAT BILL HAS DEVELOPED A CENTRAL DENSE
OVERCAST ALONG WITH IMPRESSIVE BANDING AND OUTFLOW.  THESE FEATURES
SUGGEST THAT THE STORM CONTINUES TO INTENSIFY.  SATELLITE INTENSITY
ESTIMATES FROM TAFB/SAB HAVE INCREASED TO T3.5...55 KT ON THE
DVORAK SCALE AND THIS VALUE WILL BE USED FOR THE INITIAL WIND
SPEED.

BILL IS MOVING TOWARD THE WEST-NORTHWEST OR 285/14.  THIS GENERAL
MOTION IS EXPECTED FOR THE NEXT COUPLE OF DAYS AS A SUBTROPICAL
RIDGE SHOULD REMAIN FIRM TO THE NORTH OF THE TROPICAL CYCLONE. 
THEREAFTER...A COUPLE OF EVOLUTIONS TO THE SYNOPTIC PATTERN SEEM
POSSIBLE.  THE FIRST...FAVORED BY THE GFS/ECMWF/GFDL/HWRF...SHOWS A
MID-LATITUDE SHORTWAVE DIVING INTO THE SUBTROPICAL RIDGE...CAUSING
IT TO BREAK AROUND 65W.  THIS LEADS TO A NORTHWEST MOTION OF BILL
IN ABOUT THREE DAYS.  THE OTHER SOLUTION...SHOWN BY THE
NOGAPS/UKMET...IS THAT THE HURRICANE BYPASSES THE FIRST BREAK AND
CONTINUES MOVING TOWARD THE WEST-NORTHWEST...EVENTUALLY TURNING
NORTHWEST AT THE END OF THE FORECAST DUE TO A LARGE MID-LATITUDE
TROUGH APPROACHING THE EASTERN UNITED STATES.  THE OFFICIAL
FORECAST IS SHIFTED A LITTLE BIT TO THE RIGHT AT THE END...IN
DEFERENCE TO THE HIGHLY-SKILLED MODELS IN THE FORMER SOLUTION.

WATER VAPOR IMAGES SHOW THAT THE HURRICANE IS ON THE SOUTH SIDE OF
AN UPPER HIGH WITH LITTLE SHEAR LIKELY FOR THE NEXT SEVERAL DAYS. 
IN COMBINATION WITH WARM SSTS...THERE IS NO REASON NOT TO FORECAST
CONTINUED STRENGTHENING OF BILL.  IN FACT...THE SHIPS RAPID
INTENSIFICATION INDEX SHOWS A 38 PERCENT CHANCE OF A 30 KT INCREASE
IN WINDS DURING THE NEXT 24 HOURS.  ALL RELIABLE MODELS CONTINUE TO
SHOW THIS SYSTEM BECOMING A MAJOR HURRICANE...WITH THE
GFDL/HWRF/GFDN MODELS FORECASTING BILL TO REACH CATEGORY FOUR
STRENGTH BY DAY 5.  HOWEVER...THERE IS SOME EVIDENCE IN THE GLOBAL
MODEL FIELDS THAT THE UPPER-LEVEL WINDS WILL BECOME LESS FAVORABLE
AFTER 72 HOURS WITH SOME SOUTHWESTERLY SHEAR DEVELOPING AS BILL
BECOMES DISPLACED FROM AN UPPER-LEVEL HIGH.  THE OFFICIAL FORECAST
WILL SHOW THE INTENSITY LEVELING OFF AFTER THAT TIME DUE TO THAT
POSSIBILITY. THE NHC INTENSITY FORECAST IS CLOSE TO THE PREVIOUS
FORECAST AND IS SIMILAR TO THE SHIPS MODEL.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      16/2100Z 12.8N  40.0W    55 KT
 12HR VT     17/0600Z 13.4N  42.1W    65 KT
 24HR VT     17/1800Z 14.2N  45.0W    75 KT
 36HR VT     18/0600Z 15.0N  47.7W    85 KT
 48HR VT     18/1800Z 16.0N  50.4W    95 KT
 72HR VT     19/1800Z 18.5N  55.5W   105 KT
 96HR VT     20/1800Z 22.0N  60.5W   105 KT
120HR VT     21/1800Z 26.5N  65.0W   105 KT
 
$$
FORECASTER BLAKE
 

WTNT43 KNHC 170253
TCDAT3
TROPICAL STORM BILL DISCUSSION NUMBER   7
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL032009
1100 PM AST SUN AUG 16 2009
 
INFRARED SATELLITE IMAGERY REVEALS AN IMPRESSIVE MASS OF DEEP
CONVECTIVE TOPS TO -80C WITHIN A CENTRAL DENSE OVERCAST...ALONG
WITH AN EXPANDING UPPER-LEVEL OUTFLOW.  A LONG...WELL-DEFINED BAND
CONNECTED TO THE ITCZ IS NOTED IN THE SOUTHERN SEMICIRCLE...WHILE
LESSER BANDING COILS AROUND THE NORTHERN HALF OF THE CIRCULATION.
DVORAK T-NUMBERS ARE 3.5 AND 4.0 FROM SAB AND TAFB...RESPECTIVELY.
TAKING THE MEAN OF THESE INTENSITY ESTIMATES...THE ADVISORY WIND
SPEED IS SET AT 60 KT.
 
RECENT SATELLITE CENTER FIXES ARE SOMEWHAT UNCERTAIN BUT YIELD AN
INITIAL MOTION ESTIMATE OF 290/17...REPRESENTING A SLIGHTLY FASTER
FORWARD SPEED THAN BEFORE. UNDER THE INFLUENCE OF SUBTROPICAL
RIDGING TO THE NORTH...BILL IS EXPECTED TO MAINTAIN A GENERAL
WEST-NORTHWEST HEADING FOR THE NEXT 48-72 HOURS.  WITH LITTLE
SPREAD IN THE CURRENT MODEL CYCLE THROUGH THIS TIME...THE OFFICIAL
TRACK DEVIATES LITTLE FROM THE PREVIOUS ADVISORY. THEREAFTER...
MODEL GUIDANCE IS IN GOOD AGREEMENT THAT A RATHER SUBSTANTIAL BREAK
IN THE SUBTROPICAL RIDGE SHOULD DEVELOP ROUGHLY ALONG 60W...WHICH
SHOULD RESULT IN A MORE NORTHWESTWARD COURSE.  MOST OF THE MODEL
SOLUTIONS HAVE SHIFTED FARTHER NORTH FROM THE PREVIOUS RUNS...AND
SO HAS THE MODEL CONSENSUS.  ONLY THE UKMET FAVORS A MORE
WEST-NORTHWESTWARD PATH AND APPEARS AS THE LONE...SOUTHERN OUTLIER
AMONGST THE REMAINDER OF THE GLOBAL MODELS. THE OFFICIAL FORECAST
IS ADJUSTED NORTH OF THE PREVIOUS ONE...ESPECIALLY BEYOND 96
HOURS...BASED ON THE LATEST GUIDANCE.
 
EVEN THOUGH ENVIRONMENTAL SHEAR IS QUITE LOW...BILL HAS BEEN
TRACKING OVER MARGINAL SEA SURFACE TEMPERATURES AND WATERS ARE NOT
FORECAST TO WARM FURTHER UNTIL AFTER 24 HOURS.  INTERESTINGLY...THE
GFDL/HWRF SHOW A NEARLY FLAT INTENSIFICATION RATE FOR THE NEXT DAY
OR TWO...PERHAPS UNDERSCORING THE TEPID THERMODYNAMIC CONDITIONS. IT
SHOULD BE NOTED...HOWEVER...THAT THE SHIPS RAPID INTENSITY INDEX
SHOWS A 41% CHANCE OF A 30 KT INTENSITY INCREASE DURING THE NEXT 24
HOURS.  THEREAFTER...THE GUIDANCE IS IN GOOD AGREEMENT THAT LOW
SHEAR AND WARMING WATERS SHOULD PREVAIL FOR BILL...ALLOWING THE
CYCLONE TO EVOLVE INTO A MAJOR HURRICANE OVER THE FORECAST PERIOD.
THE OFFICIAL FORECAST IS CLOSEST TO THE SHIPS MODEL GUIDANCE...
WHICH PREDICTS A FAIRLY STEADY RATE OF DEVELOPMENT OVER THE NEXT
FEW DAYS.  TOWARD THE END OF THE FORECAST PERIOD...THE GLOBAL
MODELS HAVE BEEN HINTING AT INCREASING WESTERLY SHEAR AS BILL
OUTRUNS FAVORABLE ANTICYCLONIC FLOW TO THE SOUTHEAST.
ACCORDINGLY...THE OFFICIAL INTENSITY FORECAST SHOWS SLIGHT
WEAKENING NEAR THE END OF THE PERIOD.
  
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      17/0300Z 13.4N  41.7W    60 KT
 12HR VT     17/1200Z 14.1N  43.7W    70 KT
 24HR VT     18/0000Z 14.9N  46.5W    80 KT
 36HR VT     18/1200Z 15.8N  49.2W    85 KT
 48HR VT     19/0000Z 16.8N  51.8W    95 KT
 72HR VT     20/0000Z 19.7N  56.8W   105 KT
 96HR VT     21/0000Z 23.5N  61.5W   105 KT
120HR VT     22/0000Z 28.1N  65.5W   100 KT
 
$$
FORECASTER KIMBERLAIN/PASCH
 

WTNT43 KNHC 170856
TCDAT3
HURRICANE BILL DISCUSSION NUMBER   8
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL032009
500 AM AST MON AUG 17 2009
 
INFRARED SATELLITE PICTURES REVEAL AN IMPRESSIVE MASS OF DEEP
CONVECTION...WITH A LARGE AREA OF -70C AND EVEN -80C CLOUD
TOPS WITHIN A WELL-ORGANIZED CENTRAL DENSE OVERCAST. IN
ADDITION...SEVERAL WELL-DEFINED BANDS ARE NOTED OUTSIDE OF THE
CENTRAL CONVECTIVE CORE. A 0142 UTC TRMM PASS INDICATED A DISTINCT
CONVECTIVE RING AROUND THE CENTER...ALSO SUGGESTIVE OF INCREASED
ORGANIZATION.  DVORAK T-NUMBERS ARE AT 4.0 FROM TAFB AND SAB...ALONG
WITH CURRENT TRENDS...SUPPORT INCREASING THE INITIAL INTENSITY TO
65 KT. THIS MAKES BILL THE FIRST HURRICANE OF THE 2009 ATLANTIC
HURRICANE SEASON.
 
RECENT SATELLITE CENTER FIXES ARE LESS DOUBTFUL THAN EARLIER AND
YIELD A RATHER RAPID INITIAL MOTION ESTIMATE OF 285/19. GLOBAL
MODELS ARE IN GOOD AGREEMENT ON A GENERAL WEST-NORTHWEST TRACK FOR
THE NEXT DAY OR TWO...AS BILL IS STEERED BY A DEEP-LAYER RIDGE
NORTHEAST OF THE CYCLONE. HOWEVER...WATER VAPOR IMAGERY SHOWS A
WEAKNESS CURRENTLY ALONG 50W...WHICH IS FORECAST TO BEGIN ERODING A
PORTION OF THE SUBTROPICAL RIDGE OVER THE CENTRAL ATLANTIC OVER THE
NEXT 48 HOURS. AS THE BREAK IN THE RIDGE BECOMES MORE
SUBSTANTIAL...A MAJORITY OF THE MODEL GUIDANCE TURNS BILL ON A MORE
NORTHWESTWARD COURSE LATE IN THE FORECAST PERIOD. THE ONE EXCEPTION
IS THE UKMET WHICH INSISTS ON A MORE SOUTHERN SOLUTION. THE
OFFICIAL TRACK IS INITIALLY NUDGED SLIGHTLY SOUTHWARD IN THE
SHORT-TERM TO ACCOUNT FOR A MORE CERTAIN INITIAL POSITION...BUT
LITTLE CHANGE WAS MADE TO THE PREVIOUS TRACK THEREAFTER.
 
BILL IS EXPECTED TO TRACK THROUGH AN ENVIRONMENT CHARACTERIZED BY
LOW SHEAR AND SEA SURFACE TEMPERATURES JUST UNDER 27C THROUGH 24
HOURS. SIMILAR TO BEFORE...THE GFDL/HWRF INDICATE A NEARLY FLAT
RATE OF INTENSIFICATION FOR THE NEXT DAY OR TWO...PERHAPS
REFLECTING MARGINALLY WARM WATERS. IN SPITE OF THIS...THE SHIPS
RAPID INTENSIFICATION INDEX HAS CONTINUED FORECASTING A RATHER HIGH
PROBABILITY OF A 30 KT INTENSITY INCREASE DURING THE NEXT 24 HOURS.
THEREAFTER...ALL INTENSITY GUIDANCE INDICATES A CONDUCIVE
ENVIRONMENT FOR STRENGTHENING...WHICH SHOULD ALLOW BILL TO BECOME A
MAJOR HURRICANE. THE OFFICIAL FORECAST FOLLOWS SUIT...CLOSEST TO
THE SHIPS MODEL GUIDANCE. TOWARD THE END OF THE FORECAST
PERIOD...SEVERAL OF THE RELIABLE GLOBAL MODELS SUGGEST INCREASING
WESTERLY SHEAR AS BILL IS SEPARATED FROM ITS FAVORABLE...UPPER-
LEVEL SUPPORT. CONSEQUENTLY...THE OFFICIAL INTENSITY FORECAST
INDICATES MINOR WEAKENING NEAR THE END OF THE PERIOD.
 
IT APPEARS AS IF THE CENTER OF BILL WILL PASS VERY CLOSE TO NOAA
BUOY 41041 LATER THIS MORNING. 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      17/0900Z 13.8N  44.0W    65 KT
 12HR VT     17/1800Z 14.4N  46.4W    75 KT
 24HR VT     18/0600Z 15.1N  49.0W    85 KT
 36HR VT     18/1800Z 16.0N  51.6W    95 KT
 48HR VT     19/0600Z 17.3N  54.0W   105 KT
 72HR VT     20/0600Z 20.5N  59.0W   110 KT
 96HR VT     21/0600Z 25.0N  63.5W   105 KT
120HR VT     22/0600Z 30.1N  66.5W   100 KT
 
$$
FORECASTER KIMBERLAIN
 

WTNT43 KNHC 171435
TCDAT3
HURRICANE BILL DISCUSSION NUMBER   9
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL032009
1100 AM AST MON AUG 17 2009
 
SATELLITE IMAGERY INDICATES THAT BILL CONTINUES TO INTENSIFY THIS
MORNING...WITH A UNIFORM CENTRAL DENSE OVERCAST AROUND THE CENTER.
THE INTENSITY IS RAISED TO 80 KT BASED ON A DVORAK T-NUMBER OF 4.5
FROM TAFB AT 1200 UTC. MICROWAVE IMAGERY FROM A 1132 UTC TRMM PASS
SHOWS SEVERAL CONVECTIVE BANDS SPIRALING AROUND THE CENTER...BUT NO
EVIDENCE OF AN EYE. BILL SHOULD PASS VERY CLOSE TO NOAA BUOY 41041
IN THE NEXT FEW HOURS...WHICH SHOULD HELP PROVIDE INFORMATION ON
THE WINDS AND CENTRAL PRESSURE OF THE CYCLONE. 

THE OCEANIC AND ATMOSPHERIC ENVIRONMENT CONTINUES TO BE FAVORABLE
FOR INTENSIFICATION. WHILE THE SHIPS RI INDEX SHOWS A 35 PERCENT
CHANCE OF AN INCREASE OF 30 KT OR MORE IN THE NEXT 24 HOURS...
MICROWAVE IMAGERY SUGGESTS THAT BILL DOES NOT YET HAVE A WELL
DEFINED INNER CORE STRUCTURE. THE OFFICIAL INTENSITY FORECAST
IS ABOVE THE PREVIOUS PACKAGE FOR THE FIRST 36 HOURS DUE TO THE
OBSERVED INTENSIFICATION AND IS IN BEST AGREEMENT WITH SHIPS AND
LGEM. BEYOND THAT TIME...THE STATISTICAL MODELS SHOW THE INTENSITY
LEVELING OFF...WHILE THE HWRF AND GFDL SHOW STRENGTHENING THROUGH
THE END OF THE PERIOD. GIVEN THIS UNCERTAINTY...THE OFFICIAL
FORECAST SHOWS A PEAK IN INTENSITY AT DAYS 3 AND 4...AND A SLIGHT
DECREASE AT DAY 5. 

BILL CONTINUES ON A HEADING OF 285/14...WITHIN THE DEEP-LAYER FLOW
OF A RIDGE EXTENDING WESTWARD OVER THE CENTRAL ATLANTIC FROM
AFRICA. GLOBAL MODELS AND WATER VAPOR IMAGERY INDICATE A PERSISTENT
MID-ATLANTIC TROUGH SITUATED ALONG 53W WHICH SHOULD CAUSE THE
CYCLONE TO TURN MORE TOWARD THE NORTHWEST BY DAY 3. BEYOND THIS
TIME...THE FLOW AROUND A LARGE MID- TO UPPER-LEVEL LOW THAT
DEVELOPS OVER THE EASTERN UNITED STATES SHOULD INDUCE A MORE
NORTH-NORTHWESTWARD TURN. ALL OF THE TRACK MODEL GUIDANCE...WITH
THE EXCEPTION OF THE UKMET...IS IN GOOD AGREEMENT ON THIS SCENARIO.
THE UKMET HAS A MUCH STRONGER SUBTROPICAL RIDGE THAN THE REST OF
THE GLOBAL MODELS AND THE GFS AND ECMWF ENSEMBLE MEANS. AS A
RESULT...THIS MODEL KEEPS BILL TOO FAR SOUTH TO FEEL THE EFFECTS OF
THE CLOSED LOW LATE IN THE PERIOD. THE OFFICIAL FORECAST IS
ESSENTIALLY AN UPDATE OF THE PREVIOUS PACKAGE THROUGH DAY 3...AND
IS SHIFTED SLIGHTLY TO THE RIGHT TOWARD THE MODEL CONSENSUS AT DAYS
4 AND 5. 

THE INITIAL 34-KT WIND RADII WERE MODIFIED BASED ON A 0920 UTC
QUIKSCAT PASS. 

FORECAST POSITIONS AND MAX WINDS
 
INITIAL      17/1500Z 14.1N  45.2W    80 KT
 12HR VT     18/0000Z 14.7N  47.5W    90 KT
 24HR VT     18/1200Z 15.5N  50.1W    95 KT
 36HR VT     19/0000Z 16.6N  52.6W   100 KT
 48HR VT     19/1200Z 18.0N  55.1W   105 KT
 72HR VT     20/1200Z 21.5N  60.0W   110 KT
 96HR VT     21/1200Z 26.0N  64.0W   110 KT
120HR VT     22/1200Z 31.5N  66.5W   105 KT
 
$$
FORECASTER BRENNAN/ROBERTS
 

WTNT43 KNHC 172032
TCDAT3
HURRICANE BILL DISCUSSION NUMBER  10
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL032009
500 PM AST MON AUG 17 2009
 
BILL IS BEGINNING TO SHOW SIGNS OF DEVELOPING INNER CORE FEATURES...
WITH HINTS OF AN EYE FORMING IN RECENT SATELLITE IMAGERY AND
EXPANDING COLD CLOUD TOPS AROUND THE CENTER. DVORAK T-NUMBERS WERE
4.5 FROM SAB AND TAFB AT 1800 UTC...AND THE INITIAL INTENSITY IS
HELD AT 80 KT FOR THIS PACKAGE. BILL PASSED JUST TO THE NORTH OF
NOAA BUOY 40141 THIS AFTERNOON...WHICH REPORTED A MINIMUM PRESSURE
OF 972 MB AT 1800 UTC WITH A PEAK 1-MINUTE WIND OF 51 KT. BASED ON 
THESE DATA...THE CENTRAL PRESSURE ESTIMATE IS REDUCED TO 969 MB.

THE INTENSITY FORECAST IS UNCHANGED FROM THE PREVIOUS PACKAGE. THE
ENVIRONMENT AROUND THE CYCLONE APPEARS FAVORABLE FOR
INTENSIFICATION. OCEAN TEMPERATURES INCREASE ALONG THE TRACK...AND
THE GFS AND ECMWF BOTH SHOW AN UPPER-LEVEL ANTICYCLONE DEVELOPING
OVER THE SYSTEM. AS WAS THE CASE EARLIER...THE SHIPS AND LGEM SHOW
A BROAD PEAK IN INTENSITY IN 2 OR 3 DAYS...WHILE THE HWRF AND GFDL
SHOW ARE STRONGER LATER IN THE PERIOD. THE OFFICIAL FORECAST REMAINS
UNCHANGED FROM THE PREVIOUS ADVISORY...PEAKING A LITTLE HIGHER THAN
THE SHIPS AND LGEM BEFORE SHOWING SOME WEAKENING AT DAY 5.

THE INITIAL MOTION ESTIMATE IS 285/14. THE TRACK MODEL GUIDANCE IS
IN EXCELLENT AGREEMENT THROUGH 48 HOURS...AND THROUGH THAT TIME THE
OFFICIAL FORECAST IS SIMPLY AN EXTENSION OF THE PREVIOUS PACKAGE.
BEYOND THAT TIME ALMOST ALL OF THE TRACK GUIDANCE HAS SHIFTED TO
THE LEFT....WITH THE EXCEPTION OF THE UKMET...WHICH HAS FINALLY
TRENDED TOWARD A RECURVATURE SCENARIO. ALL OF THE GLOBAL MODELS NOW
SHOW BILL INTERACTING WITH A LARGE MID TO UPPER-LEVEL TROUGH
CENTERED OVER THE EASTERN UNITED STATES BY THE END OF THE
PERIOD...HOWEVER THERE ARE DIFFERENCES IN THE AMPLITUDE AND SPEED OF
THE TROUGH THAT WILL BE CRUCIAL TO WHEN AND WHERE BILL RECURVES.
INTERESTINGLY...THE GFS AND ECMWF ARE IN EXCELLENT AGREEMENT AT 5
DAYS...BUT NOW LIE ON THE EASTERN EDGE OF THE GUIDANCE ENVELOPE...
WITH THE GFS ENSEMBLE MEAN EVEN FARTHER EAST. GIVEN THE SPREAD IN 
THE GUIDANCE...THE OFFICIAL FORECAST IS SHIFTED ONLY SLIGHTLY TO
THE LEFT OF THE PREVIOUS PACKAGE AT DAYS 3 THROUGH 5...AND LIES
BETWEEN THE TVCN MULTI-MODEL CONSENSUS AND THE ECMWF/GFS BLEND.

THIS IS A GOOD TIME TO EMPHASIZE THE UNCERTAINTY THAT EXISTS IN
TRACK FORECASTING IN THE 3 TO 5 DAY PERIOD...WHERE AVERAGE NHC
TRACK ERRORS ARE TYPICALLY SEVERAL HUNDRED MILES.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      17/2100Z 14.6N  46.7W    80 KT
 12HR VT     18/0600Z 15.2N  48.7W    90 KT
 24HR VT     18/1800Z 16.2N  51.3W    95 KT
 36HR VT     19/0600Z 17.4N  53.8W   100 KT
 48HR VT     19/1800Z 18.8N  56.4W   105 KT
 72HR VT     20/1800Z 22.5N  61.0W   110 KT
 96HR VT     21/1800Z 27.0N  65.0W   110 KT
120HR VT     22/1800Z 33.1N  67.5W   105 KT
 
$$
FORECASTER BRENNAN/ROBERTS
 

WTNT43 KNHC 172101
TCDAT3
HURRICANE BILL DISCUSSION NUMBER  10...CORRECTED
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL032009
500 PM AST MON AUG 17 2009

CORRECTED BUOY ID TO 41041
 
BILL IS BEGINNING TO SHOW SIGNS OF DEVELOPING INNER CORE FEATURES...
WITH HINTS OF AN EYE FORMING IN RECENT SATELLITE IMAGERY AND
EXPANDING COLD CLOUD TOPS AROUND THE CENTER. DVORAK T-NUMBERS WERE
4.5 FROM SAB AND TAFB AT 1800 UTC...AND THE INITIAL INTENSITY IS
HELD AT 80 KT FOR THIS PACKAGE. BILL PASSED JUST TO THE NORTH OF
NOAA BUOY 41041 THIS AFTERNOON...WHICH REPORTED A MINIMUM PRESSURE
OF 972 MB AT 1800 UTC WITH A PEAK 1-MINUTE WIND OF 51 KT. BASED ON 
THESE DATA...THE CENTRAL PRESSURE ESTIMATE IS REDUCED TO 969 MB.

THE INTENSITY FORECAST IS UNCHANGED FROM THE PREVIOUS PACKAGE. THE
ENVIRONMENT AROUND THE CYCLONE APPEARS FAVORABLE FOR
INTENSIFICATION. OCEAN TEMPERATURES INCREASE ALONG THE TRACK...AND
THE GFS AND ECMWF BOTH SHOW AN UPPER-LEVEL ANTICYCLONE DEVELOPING
OVER THE SYSTEM. AS WAS THE CASE EARLIER...THE SHIPS AND LGEM SHOW
A BROAD PEAK IN INTENSITY IN 2 OR 3 DAYS...WHILE THE HWRF AND GFDL
SHOW ARE STRONGER LATER IN THE PERIOD. THE OFFICIAL FORECAST REMAINS
UNCHANGED FROM THE PREVIOUS ADVISORY...PEAKING A LITTLE HIGHER THAN
THE SHIPS AND LGEM BEFORE SHOWING SOME WEAKENING AT DAY 5.

THE INITIAL MOTION ESTIMATE IS 285/14. THE TRACK MODEL GUIDANCE IS
IN EXCELLENT AGREEMENT THROUGH 48 HOURS...AND THROUGH THAT TIME THE
OFFICIAL FORECAST IS SIMPLY AN EXTENSION OF THE PREVIOUS PACKAGE.
BEYOND THAT TIME ALMOST ALL OF THE TRACK GUIDANCE HAS SHIFTED TO
THE LEFT....WITH THE EXCEPTION OF THE UKMET...WHICH HAS FINALLY
TRENDED TOWARD A RECURVATURE SCENARIO. ALL OF THE GLOBAL MODELS NOW
SHOW BILL INTERACTING WITH A LARGE MID TO UPPER-LEVEL TROUGH
CENTERED OVER THE EASTERN UNITED STATES BY THE END OF THE
PERIOD...HOWEVER THERE ARE DIFFERENCES IN THE AMPLITUDE AND SPEED OF
THE TROUGH THAT WILL BE CRUCIAL TO WHEN AND WHERE BILL RECURVES.
INTERESTINGLY...THE GFS AND ECMWF ARE IN EXCELLENT AGREEMENT AT 5
DAYS...BUT NOW LIE ON THE EASTERN EDGE OF THE GUIDANCE ENVELOPE...
WITH THE GFS ENSEMBLE MEAN EVEN FARTHER EAST. GIVEN THE SPREAD IN 
THE GUIDANCE...THE OFFICIAL FORECAST IS SHIFTED ONLY SLIGHTLY TO
THE LEFT OF THE PREVIOUS PACKAGE AT DAYS 3 THROUGH 5...AND LIES
BETWEEN THE TVCN MULTI-MODEL CONSENSUS AND THE ECMWF/GFS BLEND.

THIS IS A GOOD TIME TO EMPHASIZE THE UNCERTAINTY THAT EXISTS IN
TRACK FORECASTING IN THE 3 TO 5 DAY PERIOD...WHERE AVERAGE NHC
TRACK ERRORS ARE TYPICALLY SEVERAL HUNDRED MILES.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      17/2100Z 14.6N  46.7W    80 KT
 12HR VT     18/0600Z 15.2N  48.7W    90 KT
 24HR VT     18/1800Z 16.2N  51.3W    95 KT
 36HR VT     19/0600Z 17.4N  53.8W   100 KT
 48HR VT     19/1800Z 18.8N  56.4W   105 KT
 72HR VT     20/1800Z 22.5N  61.0W   110 KT
 96HR VT     21/1800Z 27.0N  65.0W   110 KT
120HR VT     22/1800Z 33.1N  67.5W   105 KT
 
$$
FORECASTER BRENNAN/ROBERTS
 

WTNT43 KNHC 180233
TCDAT3
HURRICANE BILL DISCUSSION NUMBER  11
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL032009
1100 PM AST MON AUG 17 2009
 
BILL CONTINUES TO SLOWLY STRENGTHEN OVER THE TROPICAL ATLANTIC.  THE
HURRICANE IS GENERATING VERY DEEP...COLD-TOPPED CONVECTION...THOUGH
THERE ARE SOME EVIDENT ASYMMETRIES.  SATELLITE PICTURES ALSO REVEAL
AN EXPANSIVE CIRRUS CANOPY...SUGGESTIVE OF A WELL-ESTABLISHED
UPPER-LEVEL OUTFLOW.  EARLIER MICROWAVE PASSES INDICATED AN ABSENCE
OF INNER CORE FEATURES...BUT A 2229 SSMIS PASS SUGGESTS THAT BILL
MAY BE FINALLY FORMING AN INNER CORE.  DVORAK T-NUMBERS ARE 4.5 AND
5.0 FROM TAFB AND SAB...RESPECTIVELY. BASED UPON THESE ESTIMATES...
THE INITIAL INTENSITY IS RAISED TO 85 KT.
 
THERE ARE NO OBVIOUS REASONS TO PREVENT BILL FROM INTENSIFYING
FURTHER DURING THE SEVERAL DAYS...AS THE INTENSITY GUIDANCE AGREES
ON AN ENVIRONMENT CHARACTERIZED BY LOW SHEAR AND WARM SEA SURFACE
TEMPERATURES.  PERHAPS THE ONLY LIMITING FACTOR WILL BE
FLUCTUATIONS WITHIN THE INNER CORE FOR WHICH THERE IS VIRTUALLY NO
FORECAST SKILL.  THE GUIDANCE IS IN GENERAL AGREEMENT THAT BILL
SHOULD REACH A PEAK IN INTENSITY IN ABOUT 72 HOURS.  TOWARD THE END
OF THE PERIOD...GLOBAL MODELS HAVE BEEN PREDICTING A GRADUAL
INCREASE IN SOUTHWESTERLY SHEAR AS BILL BEGINS TO BECOME MORE
DISPLACED TO THE NORTH OF AN UPPER-LEVEL ANTICYCLONE.
CONSEQUENTLY...THE OFFICIAL FORECAST SHOWS A WEAKENING TREND AFTER
72 HOURS.
 
RECENT CENTER FIXES YIELD AN INITIAL MOTION ESTIMATE OF 285/15.  THE
FORECAST RATIONALE REMAINS UNCHANGED.  A WEAKNESS ALONG 50-55W IS
FORECAST TO ERODE A LARGE PORTION OF THE SUBTROPICAL RIDGE OVER THE
CENTRAL ATLANTIC BEGINNING AS SOON AS 24 HOURS FROM NOW.  AS A
RESULT...THE GENERAL WEST-NORTHWESTWARD TRACK THAT BILL HAS
MAINTAINED FOR SEVERAL DAYS SHOULD BEGIN TO BEND MORE TOWARD THE
NORTHWEST BY 48-72 HOURS.  BEYOND 72 HOURS...BILL SHOULD BE STEERED
ON A NORTH-NORTHWESTERLY TO NORTHERLY TRACK WHERE IT SHOULD BEGIN
ENCOUNTERING THE EFFECTS OF A DIGGING LONGWAVE TROUGH OVER THE
EASTERN UNITED STATES.  THE OFFICIAL FORECAST IS NOT ALL THAT
DIFFERENT FROM THE PREVIOUS ADVISORY PACKAGE...WITH ONLY COSMETIC
CHANGES MADE TO THE FORECAST TRACK.
 
THE WIND RADII WERE ADJUSTED SLIGHTLY BASED ON THE MOST RECENT
QUIKSCAT OVERPASS.  BILL IS FORECAST TO GROW A LITTLE MORE IN
SIZE DURING THE FORECAST PERIOD...ALTHOUGH SOME GUIDANCE SUCH AS THE
GFS SUGGESTS THAT IT MAY BECOME EVEN LARGER THAN INDICATED IN THE
NHC FORECAST.
  
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      18/0300Z 15.0N  48.3W    85 KT
 12HR VT     18/1200Z 15.7N  50.3W    95 KT
 24HR VT     19/0000Z 16.9N  52.8W   100 KT
 36HR VT     19/1200Z 18.1N  55.3W   105 KT
 48HR VT     20/0000Z 19.7N  57.8W   110 KT
 72HR VT     21/0000Z 23.5N  62.5W   110 KT
 96HR VT     22/0000Z 28.5N  66.0W   105 KT
120HR VT     23/0000Z 34.5N  68.5W   100 KT
 
$$
FORECASTER KIMBERLAIN/PASCH
 

WTNT43 KNHC 180837
TCDAT3
HURRICANE BILL DISCUSSION NUMBER  12
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL032009
500 AM AST TUE AUG 18 2009
 
TRMM DATA FROM 0223 UTC AND RECENT INFRARED IMAGERY SUGGEST THAT
BILL IS UNDERGOING AN EYEWALL REPLACEMENT CYCLE...WITH THE COLDEST
CLOUD TOPS CURRENTLY IN THE OUTER CONVECTIVE RING.  SATELLITE
INTENSITY ESTIMATES REMAIN 90 KT FROM SAB AND 77 KT FROM TAFB.  THE
INITIAL INTENSITY IS 85 KT...AND THIS COULD BE GENEROUS DUE TO THE
EYEWALL REPLACEMENT.

THE INITIAL MOTION IS 285/15.  BILL IS ON THE SOUTH SIDE OF A
LOW/MID-LEVEL RIDGE...WHICH SHOULD STEER THE HURRICANE GENERALLY
WEST-NORTHWESTWARD FOR THE NEXT COUPLE OF DAYS.  AFTER THAT...THE
LARGE-SCALE MODELS FORECAST THE RIDGE TO WEAKEN AS A SERIES OF
TROUGHS MOVE THROUGH THE WESTERN ATLANTIC AND THE EASTERN UNITED
STATES.  ONE MID/UPPER-LEVEL TROUGH IS CURRENTLY NORTHEAST OF
BERMUDA...MOVING SOUTHWARD.  A SECOND MID/UPPER-LEVEL TROUGH IS
ALONG THE EAST COAST OF THE UNITED STATES...FORECAST TO MOVE
EASTWARD AND THEN SOUTHWARD.  FINALLY...A STRONG DEEP-LAYER TROUGH
IS FORECAST TO DEVELOP OVER THE EASTERN UNITED STATES BETWEEN
72-120 HR.  ALL TRACK GUIDANCE INDICATES THAT BILL SHOULD TURN
NORTHWARD IN RESPONSE TO THE TROUGHS...BUT THERE IS SOME NOTABLE
SPREAD IN WHERE AND WHEN.  THE ECMWF...GFS...GFS ENSEMBLE MEAN...
AND THE BAM MODELS TURN BILL NORTHWARD BETWEEN 62W-65W IN RESPONSE
TO THE FIRST TWO TROUGHS.  THE REMAINDER OF THE TRACK GUIDANCE
CALLS FOR THE NORTHWARD TURN BETWEEN 65W-70W...DUE TO LESS RESPONSE
TO THE FIRST TWO TROUGHS AND THE EVENTUAL EFFECT OF THE THIRD
TROUGH.  THE PREVIOUS FORECAST TRACK WAS IN THE WESTERN CLUSTER...
AND THERE IS NO OBVIOUS REASON TO JUMP THE FORECAST TO THE EASTERN
CLUSTER.  THEREFORE...THE NEW TRACK IS DOWN THE MIDDLE OF THE
WESTERN GUIDANCE CLUSTER AND SIMILAR TO THE PREVIOUS FORECAST.

BILL IS IN A LIGHT VERTICAL WIND SHEAR ENVIRONMENT...AND THE SEA
SURFACE TEMPERATURES INCREASE ALONG THE FORECAST TRACK.  THE
HURRICANE SHOULD INTENSIFY AFTER THE EYEWALL REPLACEMENT CYCLE IS
OVER...WITH ALL GUIDANCE FORECASTING IT TO BECOME A MAJOR
HURRICANE.  THE INTENSITY FORECAST CALLS FOR A PEAK INTENSITY OF
110 KT IN 48 HR.  AFTER 48 HR...THE LARGE-SCALE MODELS FORECAST
BILL TO ENCOUNTER MODERATE SOUTHERLY OR SOUTHWESTERLY VERTICAL WIND
SHEAR...AND THE INTENSITY FORECAST THUS CALLS FOR GRADUAL WEAKENING
DURING THAT TIME.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      18/0900Z 15.5N  49.7W    85 KT
 12HR VT     18/1800Z 16.2N  51.7W    90 KT
 24HR VT     19/0600Z 17.4N  54.2W   100 KT
 36HR VT     19/1800Z 18.9N  56.7W   105 KT
 48HR VT     20/0600Z 20.5N  59.0W   110 KT
 72HR VT     21/0600Z 24.0N  63.5W   110 KT
 96HR VT     22/0600Z 29.5N  67.5W   105 KT
120HR VT     23/0600Z 35.5N  68.0W   100 KT
 
$$
FORECASTER BEVEN
 

WTNT43 KNHC 181500
TCDAT3
HURRICANE BILL DISCUSSION NUMBER  13
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL032009
1100 AM AST TUE AUG 18 2009
 
VISIBLE SATELLITE IMAGES REVEAL A VERY SYMMETRIC HURRICANE WITH
OUTFLOW WELL ESTABLISHED IN ALL QUADRANTS.  THE EYE OF BILL IS
QUITE LARGE...MEASURING ABOUT 35-40 NM IN DIAMETER.  SUBJECTIVE
DVORAK INTENSITY ESTIMATES ARE NOW T5.0 FROM BOTH TAFB AND SAB...
AND THE INITIAL INTENSITY IS INCREASED TO 90 KT.  A HURRICANE
HUNTER AIRCRAFT THAT WAS ORIGINALLY SCHEDULED TO INVESTIGATE THE
REMNANTS OF ANA HAS BEEN TASKED TO FLY INTO BILL THIS AFTERNOON.
DATA FROM THE AIRCRAFT WILL PROVIDE A BETTER ASSESSMENT OF THE
INTENSITY AND SIZE OF THE HURRICANE.
 
THE INITIAL MOTION IS 285/14.  BILL IS CURRENTLY BEING STEERED
WEST-NORTHWESTWARD BY THE SUBTROPICAL RIDGE TO THE NORTH OF THE
HURRICANE.  A COUPLE OF TROUGHS SEEN IN WATER VAPOR IMAGERY TO THE
NORTH AND NORTHWEST OF THE HURRICANE ARE FORECAST TO WEAKEN THE
RIDGE DURING THE NEXT COUPLE OF DAYS.  THIS SHOULD ALLOW BILL TO
TURN NORTHWESTWARD AND THE MODELS ARE IN GOOD AGREEMENT ON THIS
SCENARIO DURING THROUGH 48 HOURS.  AFTER THAT...A LARGE MID-LATITUDE
TROUGH IS FORECAST BY THE GLOBAL MODELS TO
MOVE INTO THE EASTERN UNITED STATES ON DAY 4 AND 5.  THE MODELS
RESPOND BY TURNING THE HURRICANE NORTHWARD AT THAT TIME...HOWEVER
THERE REMAINS SOME SPREAD AS TO WHEN AND WHERE THAT WILL OCCUR.
AS BEFORE...THE GFS AND ECMWF REMAIN ON THE RIGHT SIDE OF THE
MODEL ENVELOPE...WHILE THE UKMET AND HWRF ARE ON THE LEFT.  THE
OFFICIAL FORECAST IS VERY SIMILAR TO THE PREVIOUS NHC TRACK AND
NEAR THE MIDDLE OF THE GUIDANCE ENVELOPE THROUGH 72 HOURS.
THEREAFTER...THE NEW TRACK HAS BEEN SHIFTED EASTWARD...BUT REMAINS
TO THE WEST OF THE MODEL CONSENSUS.
 
BILL IS IN A CONDUCIVE ATMOSPHERIC ENVIRONMENT FOR STRENGTHENING
AND SSTS ALONG THE FORECAST TRACK WILL BE INCREASING DURING THE
NEXT COUPLE OF DAYS.  THE INTENSITY FORECAST SHOWS GRADUAL
STRENGTHENING AND TOPS OUT AT 110 KT...WHICH IS CLOSE TO THE
CONSENSUS OF THE INTENSITY GUIDANCE.  LATER IN THE FORECAST
PERIOD...MODERATE SOUTH TO SOUTHWESTERLY WIND SHEAR IS EXPECTED TO
INCREASE...AND THE OFFICIAL FORECAST PREDICTS GRADUAL WEAKENING AT
THAT TIME.
 
THE WIND RADII WERE EXPENDED OUTWARD BASED ON AN EARLIER QUIKSCAT
PASS.
  
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      18/1500Z 15.9N  51.2W    90 KT
 12HR VT     19/0000Z 16.8N  53.0W    95 KT
 24HR VT     19/1200Z 18.0N  55.3W   105 KT
 36HR VT     20/0000Z 19.6N  57.7W   110 KT
 48HR VT     20/1200Z 21.5N  60.3W   110 KT
 72HR VT     21/1200Z 25.9N  64.7W   110 KT
 96HR VT     22/1200Z 31.5N  67.5W   105 KT
120HR VT     23/1200Z 38.0N  66.5W    95 KT
 
$$
FORECASTER BROWN/CANGIALOSI
 

WTNT43 KNHC 182047
TCDAT3
HURRICANE BILL DISCUSSION NUMBER  14
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL032009
500 PM AST TUE AUG 18 2009
 
BILL REMAINS A VERY IMPRESSIVE AND SYMMETRIC HURRICANE IN SATELLITE
IMAGERY.  THE AIR FORCE HURRICANE HUNTER AIRCRAFT INVESTIGATING
BILL THIS AFTERNOON REPORTED PEAK 700 MB FLIGHT-LEVEL WINDS OF 114
KT IN THE NORTHEAST QUADRANT.  THE SFMR OBSERVED MAXIMUM WINDS
AROUND 85 KT IN EACH QUADRANT OF THE HURRICANE.  USING A BLEND OF
THESE DATA...THE INITIAL INTENSITY HAS BEEN INCREASED TO 95 KT.
THIS IS ALSO SUPPORTED BY SUBJECTIVE DVORAK INTENSITY ESTIMATES OF
90 AND 102 KT FROM SAB AND TAFB RESPECTIVELY.
 
THE INITIAL MOTION IS 290/14.  THE FORECAST SCENARIO REMAINS
UNCHANGED FROM THE PREVIOUS ADVISORY.  BILL IS EXPECTED TO
GRADUALLY TURN TO THE NORTHWEST DURING THE NEXT DAY OR TWO AS A
WEAKNESS DEVELOPS IN THE SUBTROPICAL RIDGE OVER THE WESTERN
ATLANTIC.  THEREAFTER...THE HURRICANE IS FORECAST TO TURN NORTHWARD
AHEAD OF A STRONG TROUGH MOVING INTO THE EASTERN UNITED STATES.
THE TRACK GUIDANCE ENVELOPE CHANGED VERY LITTLE THROUGH 48
HOURS...BUT HAS GENERALLY SHIFTED WESTWARD DURING THE REMAINDER OF
THE FORECAST PERIOD.  AS BEFORE THE ECMWF AND GFS ARE ON THE RIGHT
SIDE OF THE ENVELOPE WHILE THE UKMET IS ON THE LEFT.  THE OFFICIAL
FORECAST IS VIRTUALLY UNCHANGED THROUGH DAY 2...AND HAS NOT BEEN
ADJUSTED APPRECIABLY BEYOND THAT TIME AS WELL.  THE NEW FORECAST
LIES BETWEEN THE DYNAMICAL MODEL CONSENSUS AND THE USUALLY
WELL-PERFORMING ECMWF AND GFS MODELS.
 
VERTICAL WIND SHEAR IS EXPECTED TO REMAIN LOW AND SSTS GRADUALLY
INCREASE ALONG THE FORECAST TRACK DURING THE NEXT COUPLE OF DAYS.
THE INTENSITY FORECAST CALLS FOR ADDITIONAL STRENGTHENING DURING THE
NEXT COUPLE OF DAYS IN LINE WITH THE CONSENSUS OF THE INTENSITY
GUIDANCE.  BEYOND 72 HOURS...DECREASING SSTS AND INCREASING
SOUTHWESTERLY UPPER-LEVEL WINDS AHEAD OF THE AFOREMENTIONED TROUGH
SHOULD INDUCE SLOW WEAKENING.
  
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      18/2100Z 16.6N  52.2W    95 KT
 12HR VT     19/0600Z 17.5N  54.3W   105 KT
 24HR VT     19/1800Z 18.9N  56.9W   115 KT
 36HR VT     20/0600Z 20.7N  59.3W   115 KT
 48HR VT     20/1800Z 22.6N  61.8W   115 KT
 72HR VT     21/1800Z 27.3N  65.8W   110 KT
 96HR VT     22/1800Z 33.5N  68.0W   100 KT
120HR VT     23/1800Z 40.5N  65.5W    85 KT
 
$$
FORECASTER BROWN/CANGIALOSI
 

WTNT43 KNHC 190241
TCDAT3
HURRICANE BILL DISCUSSION NUMBER  15
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL032009
1100 PM AST TUE AUG 18 2009
 
REPORTS FROM A NOAA HURRICANE HUNTER AIRCRAFT CONDUCTING A RESEARCH
MISSION IN BILL AND INFRARED SATELLITE IMAGERY INDICATE THAT BILL
HAS UNDERGONE A PERIOD OF RAPID INTENSIFICATION AND IS NOW A MAJOR
HURRICANE.  HIGHEST FLIGHT-LEVEL WINDS SO FAR HAVE BEEN 126 KT AT
700 MB...WITH THE LATEST MINIMUM PRESSURE OF 952 MB AT 0202 UTC.
THE HIGHEST SFMR-OBSERVED SURFACE WIND SPEED WAS 100 KT.  THE LATEST
DVORAK T-NUMBERS ARE 6.0 FROM BOTH TAFB AND SAB...WHILE UW CIMSS
OBJECTIVE ADVANCED DVORAK VALUES HAVE BEEN AS HIGH AS 7.0. 
BLENDING THE AIRCRAFT FLIGHT-LEVEL...SFMR...AND DROPSONDE WINDS
WITH THE VARIOUS SATELLITE-DERIVED INTENSITY ESTIMATES...THE
INITIAL INTENSITY IS SET AT 110 KT.  FAVORABLE ENVIRONMENTAL
CONDITIONS COULD ALLOW FOR FURTHER STRENGTHENING DURING THE NEXT
24 TO 36 HOURS.  HOWEVER...EYEWALL REPLACEMENT CYCLES...WHICH ARE
VERY DIFFICULT TO ANTICIPATE...MAY PRODUCE SOME FLUCTUATIONS IN
INTENSITY.  REGARDLESS...BILL IS EXPECTED TO REMAIN A LARGE AND
POWERFUL HURRICANE FOR SEVERAL DAYS AS IT MARCHES INTO THE CENTRAL
NORTH ATLANTIC.  TOWARD THE END OF THE PERIOD...SEA SURFACE
TEMPERATURES WILL BE DECREASING ALONG THE FORECAST TRACK AND
SOUTHERLY TO SOUTHWESTERLY SHEAR SHOULD BEGIN TAKING A TOLL.  AS A
RESULT...THE OFFICIAL INTENSITY FORECAST CALLS FOR WEAKENING AROUND
96 HOURS...WITH A MORE DECIDED RATE OF WEAKENING NEAR THE END OF
THE PERIOD.
 
BASED ON AIRCRAFT AND SATELLITE FIXES...THE INITIAL MOTION IS
ESTIMATED TO BE 295/13...REPRESENTING A SLIGHTLY MORE NORTHERLY
COMPONENT OF MOTION.  THE TRACK FORECAST PHILOSOPHY HAS NOT
CHANGED.  BILL IS FORECAST TO BE STEERED NORTHWESTWARD INTO A
SIGNIFICANT BREAK IN THE SUBTROPICAL RIDGE OVER THE NEXT FEW
DAYS...WHERE IT WILL COME UNDER THE INFLUENCE OF AN UNUSUALLY DEEP
LONGWAVE TROUGH DIGGING INTO THE EASTERN UNITED STATES.  THIS
STEERING FEATURE SHOULD CAUSE BILL TO TURN NORTHWARD AND THEN
NORTH-NORTHEASTWARD...WITH SOME INCREASE IN FORWARD SPEED.  THE
TRACK GUIDANCE IS IN REASONABLY GOOD AGREEMENT ON THIS
SCENARIO...WITH THE OFFICIAL TRACK IN THE MIDDLE OF GUIDANCE
ENVELOPE.
  
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      19/0300Z 17.2N  53.4W   110 KT
 12HR VT     19/1200Z 18.4N  55.4W   120 KT
 24HR VT     20/0000Z 20.0N  58.0W   125 KT
 36HR VT     20/1200Z 21.8N  60.5W   125 KT
 48HR VT     21/0000Z 23.8N  62.9W   120 KT
 72HR VT     22/0000Z 29.0N  67.0W   115 KT
 96HR VT     23/0000Z 35.0N  68.0W   100 KT
120HR VT     24/0000Z 42.0N  64.0W    85 KT
 
$$
FORECASTER KIMBERLAIN/PASCH
 

WTNT43 KNHC 190844
TCDAT3
HURRICANE BILL DISCUSSION NUMBER  16
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL032009
500 AM AST WED AUG 19 2009

BILL HAS A WELL-DEFINED 25-30 N MI WIDE EYE WITH EYEWALL CLOUD TOPS
TO NEAR -80C.  SATELLITE INTENSITY ESTIMATES FROM TAFB AND SAB WERE
115 KT AT 06Z...AND THE CURRENT SATELLITE SIGNATURE SUGGESTS A
SLIGHTLY STRONGER SYSTEM.  BASED ON THE SATELLITE ESTIMATES...THE
INITIAL INTENSITY IS INCREASED TO 115 KT.  A NOAA HURRICANE HUNTER
AIRCRAFT IS CURRENTLY ENROUTE TO INVESTIGATE BILL.

THE MOTION IS WOBBLING BETWEEN 295-300 DEGREES AT 14 KT.  BILL IS ON
THE SOUTHWEST SIDE OF THE ATLANTIC SUBTROPICAL RIDGE.  WATER VAPOR
IMAGERY SHOWS A MID/UPPER-LEVEL LOW NEAR 32N60W AND A MID/UPPER-
LEVEL TROUGH N OF 30N BETWEEN 69W-75W.  THESE FEATURES ARE
CURRENTLY CREATING A WEAKNESS IN THE WESTERN PORTION OF THE
SUBTROPICAL RIDGE.  THE TRACK GUIDANCE MODELS FORECAST BILL TO
GRADUALLY TURN NORTHWESTWARD TOWARDS THIS WEAKNESS DURING THE NEXT
48-72 HR...WITH THE ECMWF SHOWING THE EARLIEST TURN AND THE
NOGAPS/UKMET SHOWING THE LATEST TURN.  AFTER THAT...A LARGE
DEEP-LAYER TROUGH MOVING INTO THE EASTERN UNITED STATES SHOULD
CAUSE BILL TO RECURVE NORTHWARD AND NORTHEASTWARD.  THERE IS A
LARGE MODEL SPREAD IN BOTH DIRECTION AND SPEED AFTER 72 HR...WITH
THE NOGAPS ON ONE SIDE BRINGING BILL NEAR NEW ENGLAND AND THE
CORRECTED CONSENSUS MODELS ON THE OTHER SIDE CALLING FOR A SHARP
TURN OUT TO SEA.  OVERALL...THE ENVELOPE OF MODEL GUIDANCE HAS
SHIFTED A LITTLE TO THE WEST...SO THE NEW OFFICIAL FORECAST WILL DO
LIKEWISE.  THE NEW FORECAST TRACK IS NEAR THE MODEL CONSENSUS AND
THE MIDDLE OF THE GUIDANCE ENVELOPE.

BILL HAS STRENGTHENED IN SPITE OF BEING IN AN ENVIRONMENT OF
10-15 KT OF SOUTHWESTERLY VERTICAL WIND SHEAR.  THE LARGE-SCALE
MODELS FORECAST THIS SHEAR SHOULD DECREASE AFTER 12 HR...SO
ADDITIONAL STRENGTHENING IS FORECAST.  BY 48-72 HR...BILL SHOULD
INTERACT WITH THE UPPER-LEVEL TROUGH CURRENTLY JUST OFF THE NORTH
CAROLINA COAST.  THIS IS LIKELY TO CAUSE ANOTHER ROUND OF SHEAR...SO
THE INTENSITY FORECAST CALLS FOR SLOW WEAKENING DURING THAT TIME. 
AFTER 72 HR...BILL SHOULD BECOME EMBEDDED IN THE WESTERLIES AS IT
MOVES OVER COLDER SEA SURFACE TEMPERATURES...AND A FASTER WEAKENING
IS EXPECTED.  IT SHOULD BE NOTED THAT EYEWALL REPLACEMENT CYCLES...
WHICH ARE VERY DIFFICULT TO ANTICIPATE...MAY PRODUCE SOME
FLUCTUATIONS IN INTENSITY SUPERIMPOSED ON THE GENERAL TREND OF THE
INTENSITY FORECAST.
  
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      19/0900Z 18.0N  54.9W   115 KT
 12HR VT     19/1800Z 19.0N  56.8W   120 KT
 24HR VT     20/0600Z 20.6N  59.4W   125 KT
 36HR VT     20/1800Z 22.5N  62.0W   125 KT
 48HR VT     21/0600Z 24.4N  64.4W   120 KT
 72HR VT     22/0600Z 29.5N  68.0W   115 KT
 96HR VT     23/0600Z 36.0N  68.5W   100 KT
120HR VT     24/0600Z 44.0N  62.0W    80 KT
 
$$
FORECASTER BEVEN
 

WTNT43 KNHC 191445
TCDAT3
HURRICANE BILL DISCUSSION NUMBER  17
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL032009
1100 AM AST WED AUG 19 2009
 
A NOAA P-3 PLANE ON A RESEARCH MISSION HAS BEEN PROVIDING EXCELLENT
DATA FROM BILL DURING THE PAST SEVERAL HOURS. THERE WAS A PEAK
FLIGHT-LEVEL WIND OF 132 KNOTS TWO HOURS AGO AND THE SFMR REPORTED
PEAK WINDS AROUND 105 KNOTS. DATA FROM THE PLANE ALSO SHOW THAT
BILL HAS A LARGE WIND FIELD AND A 30 NMI WIDE EYE. THE LATEST
EXTRAPOLATED MINIMUM CENTRAL PRESSURE WAS 950 MB. ALTHOUGH THE RING
OF DEEP CONVECTION SURROUNDING THE EYE OBSERVED ON SATELLITE HAS
WEAKENED DURING THE PAST COUPLE OF HOURS...THE T-NUMBERS REMAIN
AROUND 6.0 ON THE DVORAK SCALE. INITIAL INTENSITY IS KEPT AT 115 KT
IN THIS ADVISORY. THE LARGE SCALE ENVIRONMENT IS FAVORABLE FOR
ADDITIONAL INTENSIFICATION SINCE BILL IS HEADING FOR A WARMER OCEAN
AND THE SHEAR IS EXPECTED TO BE LOW FOR THE NEXT TWO TO THREE DAYS.
HOWEVER...MOST LIKELY THERE WILL BE FLUCTUATIONS IN INTENSITY IN
THIS PERIOD CONTROLLED BY EYEWALL REPLACEMENT CYCLES. BEYOND 72
HOURS...THE OCEAN IS COOLER AND A GRADUAL WEAKENING SHOULD BEGIN...
BUT BILL IS FORECAST TO REMAIN A HURRICANE THROUGH FIVE DAYS.     

THERE HAS BEEN NO CHANGE IN THE STEERING CURRENTS AND BILL CONTINUES
TO MOVE TOWARD THE WEST-NORTHWEST OR 300 DEGREES AT 16 KNOTS AROUND
THE AZORES-BERMUDA HIGH. THIS GENERAL MOTION SHOULD CONTINUE FOR A
COUPLE OF DAYS. THEREAFTER...A LARGE MID-LATITUDE TROUGH IS
EXPECTED TO SWING EASTWARD OVER THE EASTERN UNITED STATES...FORCING
BILL TO TURN NORTHWARD A GOOD DISTANCE AWAY FROM THE U.S. EAST
COAST. THIS IS IN AGREEMENT WITH THE SOLUTION PROVIDED BY MOST OF
THE DYNAMICAL MODELS...WHICH IN FACT HAVE BEEN QUITE CONSISTENT IN
TURNING BILL NORTHWARD FOR THE PAST SEVERAL RUNS. THE OFFICIAL
FORECAST IS VERY SIMILAR TO THE PREVIOUS ONE AND IS VERY CLOSE TO
THE MODEL CONSENSUS.

BECAUSE BILL IS A LARGE AND STRONG HURRICANE...SWELLS TRIGGERED BY
THE HURRICANE SHOULD AFFECT THE NORTHERN LEEWARD ISLANDS...BERMUDA
AND PORTIONS OF THE EASTERN UNITED STATES DURING THE NEXT FEW DAYS.  
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      19/1500Z 18.7N  56.3W   115 KT
 12HR VT     20/0000Z 19.9N  58.3W   120 KT
 24HR VT     20/1200Z 21.7N  61.0W   125 KT
 36HR VT     21/0000Z 23.5N  63.5W   125 KT
 48HR VT     21/1200Z 26.0N  65.5W   120 KT
 72HR VT     22/1200Z 32.0N  68.5W   115 KT
 96HR VT     23/1200Z 38.5N  67.0W   100 KT
120HR VT     24/1200Z 47.0N  58.0W    75 KT
 
$$
FORECASTER AVILA
 

WTNT43 KNHC 192031
TCDAT3
HURRICANE BILL DISCUSSION NUMBER  18
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL032009
500 PM AST WED AUG 19 2009
 
VISIBLE SATELLITE IMAGES SHOW THAT BILL IS AN IMPRESSIVE HURRICANE
WITH MESOCYCLONES NOTED IN THE EYE...CURVED BANDING FEATURES IN ALL
QUADRANTS AND A WELL-ESTABLISHED OUTFLOW PATTERN.  AN FORCE RESERVE
HURRICANE HUNTER RECENTLY MEASURED 135 KT AT 700 MB...ALONG WITH
SFMR WINDS OF 103 KT AND A MINIMUM PRESSURE OF 947 MB. IN
ADDITION...THERE WAS AN SFMR MEASUREMENT OF 106 KT FROM THE NOAA
MISSION THIS MORNING.  SATELLITE CLASSIFICATION ARE 127 KT FROM
TAFB/SAB AND THE INITIAL INTENSITY IS KEPT AT 115 KT AS A
COMPROMISE OF ALL THESE DATA.

VERY WARM WATERS ARE ALONG THE PATH OF THE HURRICANE FOR THE NEXT
FEW DAYS.  THE BIGGEST QUESTION IS WHETHER THE UPPER ENVIRONMENT
WILL REMAIN FAVORABLE FOR STRENGTHENING.   A PAIR OF UPPER-LEVEL
TROUGHS HAVE THE POTENTIAL TO INDUCE SOME SHEAR ON BILL...ONE ALONG
60W AND OTHER AT ABOUT 70W.  WHILE THE MODELS DISAGREE ON WHETHER
THE FIRST TROUGH WILL AFFECT THE HURRICANE MUCH...MOST MODELS SHOW
SOUTHWESTERLY SHEAR INCREASING IN A COUPLE DAYS AS A RESULT OF THE
SECOND FEATURE.  IN ADDITION...AN EYEWALL REPLACEMENT CYCLE COULD
OCCUR AT ANY TIME WITH A SECONDARY WIND MAXIMUM NOTED AT ABOUT 75 N
MI FROM THE CENTER IN AIRCRAFT DATA.  REGARDLESS...ALL OF THE
RELIABLE MODELS KEEP THE HURRICANE QUITE STRONG FOR THE NEXT
SEVERAL DAYS...AND THE OFFICIAL INTENSITY FORECAST REFLECTS THAT
LIKELIHOOD.  
 
THE ESTIMATED MOTION IS A LITTLE MORE TO THE RIGHT AND FASTER...NOW
305/17.  STRONG SUBTROPICAL RIDGING SHOULD KEEP BILL ON THIS
GENERAL TRACK FOR THE NEXT COUPLE OF DAYS WITH A GRADUAL BEND TOWARD
THE NORTH-NORTHWEST BY THE WEEKEND AS THE HURRICANE MOVES INTO A
BREAK IN THE RIDGE.  SOME OF THE MODELS...SUCH AS THE GFS...NOW
SHOW A SLIGHTLY STRONGER RIDGE OVER THE WESTERN ATLANTIC AND A
SLOWER MID-LATITUDE TROUGH MOVING ACROSS THE EASTERN UNITED STATES. 
IF THIS SOLUTION IS CORRECT...BILL WOULD BE ABLE TO MOVE A LITTLE
FARTHER TO THE WEST BEFORE TURNING TO THE NORTH AND NORTHEAST. 
THERE HAS BEEN A SMALL WESTWARD SHIFT IN MOST OF THE AFTERNOON
MODEL GUIDANCE...AND THE OFFICIAL FORECAST IS SHIFTED IN THAT
DIRECTION.  THIS IS A GOOD TIME TO POINT OUT THAT THERE IS A LOT OF
UNCERTAINTY IN THE LONG-RANGE TROPICAL CYCLONE FORECAST AND ONE
SHOULD NOT FOCUS ON THE EXACT TRACK AT THOSE TIME PERIODS.  

BECAUSE BILL IS A LARGE AND STRONG HURRICANE...SWELLS TRIGGERED BY
THE HURRICANE SHOULD AFFECT THE NORTHERN LEEWARD ISLANDS...THE
BAHAMAS...BERMUDA AND MOST OF THE EASTERN UNITED STATES DURING
THE NEXT FEW DAYS.  THESE SWELLS WILL LIKELY CAUSE EXTREMELY
DANGEROUS SURF AND LIFE-THREATENING RIP CURRENTS.  PLEASE CONSULT
STATEMENTS ISSUED BY YOUR LOCAL WEATHER OFFICE FOR MORE DETAILS.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      19/2100Z 19.8N  57.6W   115 KT
 12HR VT     20/0600Z 21.1N  59.7W   120 KT
 24HR VT     20/1800Z 23.0N  62.4W   125 KT
 36HR VT     21/0600Z 25.2N  64.6W   120 KT
 48HR VT     21/1800Z 27.9N  66.6W   120 KT
 72HR VT     22/1800Z 34.0N  69.0W   110 KT
 96HR VT     23/1800Z 42.0N  65.5W    95 KT
120HR VT     24/1800Z 51.5N  50.5W    55 KT...EXTRATROPICAL
 
$$
FORECASTER BLAKE
 

WTNT43 KNHC 200246
TCDAT3
HURRICANE BILL DISCUSSION NUMBER  19
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL032009
1100 PM AST WED AUG 19 2009
 
DATA FROM A NOAA AIRCRAFT FLYING A RESEARCH MISSION INTO BILL
INDICATE THAT IT IS MAINTAINING ITS INTENSITY.  THE AIRCRAFT
REPORTED PEAK 700 MB FLIGHT-LEVEL WINDS OF 140 KT...AND
A DROPSONDE RELEASED IN THE NORTHEASTERN EYEWALL MEASURED A MEAN
WIND OF 134 KT OVER THE THE LOWEST 150 METERS OF SOUNDING.  THE
SFMR MEASURED A PEAK SURFACE WINDS OF 108 KT.  USING A BLEND OF
THESE DATA SUPPORT A 115 KT INTENSITY FOR THIS ADVISORY.
 
BILL IS MOVING NORTHWESTWARD OR 305/15.  THE SUBTROPICAL RIDGE TO
THE NORTH OF THE HURRICANE IS EXPECTED TO KEEP IT ON THIS GENERAL
COURSE DURING THE NEXT DAY OR SO.  THEREAFTER...A BREAK IN THE
RIDGE IS FORECAST TO DEVELOP OVER THE WESTERN ATLANTIC...AND BILL
SHOULD BEGIN TO TURN NORTHWARD AHEAD OF A STRONG MID-LATITUDE
TROUGH THAT IS FORECAST TO MOVE INTO THE EASTERN UNITED STATES
BY THE WEEKEND.  OVERALL...THE TRACK MODELS HAVE SHOWN GOOD
CONSISTENCY DURING THE LAST DAY OR TWO...AND SO HAS THE OFFICIAL
FORECAST WHICH REMAINS NEAR THE CENTER OF THE TIGHTLY CLUSTERED
GUIDANCE.  THE NEW NHC TRACK FORECAST IS VERY SIMILAR TO THE
PREVIOUS ADVISORY THROUGH 72 HOURS...AND ONLY A SLIGHT WESTWARD
ADJUSTMENT WAS REQUIRED THEREAFTER.  IT IS IMPORTANT TO REMEMBER
THAT FORECAST UNCERTAINTY EXISTS IN THE LONGER RANGES...SO ONE
SHOULD NOT FOCUS ON THE EXACT FORECAST TRACK.
 
BILL IS PREDICTED TO REMAIN OVER WARM WATER FOR THE NEXT COUPLE OF
DAYS.  AN UPPER-LEVEL TROUGH SEEN IN WATER VAPOR IMAGERY ALONG 70W
MAY CAUSE IN INCREASE IN SOUTHWESTERLY UPPER-LEVEL WINDS OVER THE
HURRICANE IN A COUPLE OF DAYS.  HOWEVER...THE SHIPS MODEL SHOWS
THAT THE SHEAR WILL GENERALLY REMAIN LIGHT AND THE INTENSITY
GUIDANCE KEEPS THE HURRICANE STRONG DURING THE NEXT FEW DAYS.
AFTER 72 HOURS...INCREASING SOUTHWESTERLY UPPER-LEVEL FLOW AHEAD OF
THE STRONG TROUGH AND COOLING SSTS SHOULD IMPART A MORE RAPID RATE
OF WEAKENING.  THE GLOBAL MODELS SHOW BILL BEGINNING TO INTERACT
WITH A BAROCLINIC ZONE BY 96 HOURS...SO THE CYCLONE COULD BECOME
EXTRATROPICAL A LITTLE SOONER THAN INDICATED HERE.
 
LARGE SWELLS GENERATED BY THIS HURRICANE WILL AFFECT THE NORTHERN
LEEWARD ISLANDS...THE BAHAMAS...BERMUDA AND MOST OF THE EASTERN
U.S. COAST DURING THE NEXT FEW DAYS.  THESE SWELLS WILL LIKELY
CAUSE EXTREMELY DANGEROUS SURF AND LIFE-THREATENING RIP CURRENTS.
PLEASE CONSULT STATEMENTS ISSUED BY YOUR LOCAL WEATHER OFFICE FOR
MORE DETAILS.
  
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      20/0300Z 20.7N  58.9W   115 KT
 12HR VT     20/1200Z 22.1N  60.9W   120 KT
 24HR VT     21/0000Z 24.1N  63.4W   125 KT
 36HR VT     21/1200Z 26.6N  65.6W   120 KT
 48HR VT     22/0000Z 29.4N  67.5W   120 KT
 72HR VT     23/0000Z 36.0N  69.0W   105 KT
 96HR VT     24/0000Z 45.0N  62.5W    75 KT...INLAND
120HR VT     25/0000Z 53.0N  44.5W    55 KT...EXTRATROPICAL
 
$$
FORECASTER BROWN/PASCH
 

WTNT43 KNHC 200849
TCDAT3
HURRICANE BILL DISCUSSION NUMBER  20
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL032009
500 AM AST THU AUG 20 2009
 
DURING THE LAST PASS THROUGH THE NORTHEASTERN EYEWALL...AN AIR
FORCE RESERVE HURRICANE HUNTER AIRCRAFT REPORTED 123 KT WINDS AT
700 MB...WHICH IS DOWN ALMOST 20 KT FROM EARLIER.  AN EYEWALL
DROPSONDE SUGGESTS THE SURFACE WINDS IN THAT AREA WERE 105-110 KT. 
BASED ON THIS AND A SLIGHT WEAKENING OF THE SATELLITE CLOUD
PATTERN...THE INITIAL INTENSITY IS REDUCED TO 110 KT.  ANALYSES
FROM CIMSS AT THE UNIVERSITY OF WISCONSIN SHOW THAT BILL HAS BEEN
EXPERIENCING 10-15 KT OF WESTERLY VERTICAL WIND SHEAR.  THIS MAY BE
STARTING TO DIMINISH...AS THE CIRRUS OUTFLOW IS INCREASING IN THE
WESTERN SEMICIRCLE.

THE INITIAL MOTION IS 305/16.  BILL IS MOVING TOWARD A WEAKNESS IN
THE SUBTROPICAL RIDGE CAUSED BY TWO MID/UPPER-LEVEL TROUGHS...ONE
TO THE EAST-NORTHEAST OF BERMUDA AND ONE BETWEEN BERMUDA AND THE
UNITED STATES.  THE SECOND TROUGH IS FORECAST TO MOVE SOUTHWARD AND
WESTWARD DURING THE NEXT 24-48 HR...CAUSING BILL TO GRADUALLY TURN
MORE NORTHWARD AS THE SYSTEMS INTERACT.  AFTER 48 HR...ALL GUIDANCE
FORECASTS A LARGE DEEP-LAYER TROUGH TO MOVE INTO THE EASTERN UNITED
STATES...WITH A LARGE MID/UPPER-LEVEL RIDGE BUILDING OVER THE
CENTRAL ATLANTIC.  THIS COMBINATION SHOULD STEER BILL NORTHWARD AND
EVENTUALLY NORTHEASTWARD INTO THE WESTERLIES.  THE TRACK GUIDANCE
IS TIGHTLY CLUSTERED FOR THE FIRST 48-72 HR...THEN BECOME SOMEWHAT
DIVERGENT IN BOTH DIRECTION AND SPEED.  THE GFDN AND NOGAPS ARE ON
THE LEFT SIDE OF THE GUIDANCE ENVELOPE...BRINGING THE CENTER OF
BILL JUST SOUTHEAST OF NEW ENGLAND AND THEN OVER NOVA SCOTIA AND
NEWFOUNDLAND.  THE CORRECTED CONSENSUS MODELS CALL FOR A MUCH
SHARPER EASTWARD TURN...KEEPING THE CENTER WELL AWAY FROM NEW
ENGLAND AND CANADA.  THE TRACK FORECAST IS BETWEEN THESE EXTREMES
AND DOWN THE MIDDLE OF THE GUIDANCE ENVELOPE IN BEST OVERALL
AGREEMENT WITH THE GFDL.  IT SHOULD BE NOTED THAT BILL WILL
PROBABLY NOT TURN AS SHARPLY BETWEEN 72-96 HR AS IMPLIED BY THE
TRACK GRAPHIC...AND THUS IS LIKELY TO PASS CLOSER TO NEW ENGLAND
THAN THE GRAPHIC WOULD SUGGEST.
 
THE LARGE-SCALE MODELS SUGGEST THE CURRENT SHEAR SHOULD DIMINISH
DURING THE NEXT 24 HR...AND THIS BASIS SOME RE-INTENSIFICATION IS
EXPECTED.  THE INTENSITY FORECAST IS MOST UNCERTAIN DURING THE
24-72 HR TIME FRAME AS BILL INTERACTS WITH THE CURRENT WESTERN
ATLANTIC TROUGH.  THIS TROUGH COULD CAUSE SHEAR TO WEAKEN THE
SYSTEM.  HOWEVER...SOME OF THE LARGE-SCALE MODELS FORECAST
INCREASED UPPER-LEVEL DIVERGENCE OVER BILL...WHICH COULD STRENGTHEN
THE HURRICANE.  FOR NOW...THE INTENSITY FORECAST CALLS FOR LITTLE
CHANGE IN STRENGTH AS A COMPROMISE.  AFTER 72 HR...BILL SHOULD
WEAKEN RAPIDLY AS IT MOVES OVER COLDER SEA SURFACE TEMPERATURES AND
INTO STRONG VERTICAL WIND SHEAR.  EXTRATROPICAL TRANSITION SHOULD
BEGIN AROUND 96 HR AND BE COMPLETE BY 120 HR.
 
LARGE SWELLS GENERATED BY THIS HURRICANE WILL AFFECT THE NORTHERN
LEEWARD ISLANDS...THE BAHAMAS...BERMUDA AND MOST OF THE EASTERN
U.S. COAST DURING THE NEXT FEW DAYS.  THESE SWELLS WILL LIKELY
CAUSE EXTREMELY DANGEROUS SURF AND LIFE-THREATENING RIP CURRENTS.
PLEASE CONSULT STATEMENTS ISSUED BY YOUR LOCAL WEATHER OFFICE FOR
MORE DETAILS.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      20/0900Z 21.6N  60.3W   110 KT
 12HR VT     20/1800Z 23.0N  62.3W   115 KT
 24HR VT     21/0600Z 25.2N  64.7W   120 KT
 36HR VT     21/1800Z 27.8N  66.5W   120 KT
 48HR VT     22/0600Z 30.8N  68.1W   120 KT
 72HR VT     23/0600Z 38.5N  68.0W   105 KT
 96HR VT     24/0600Z 46.6N  59.0W    70 KT
120HR VT     25/0600Z 53.5N  36.0W    55 KT...EXTRATROPICAL
 
$$
FORECASTER BEVEN
 

WTNT43 KNHC 201447
TCDAT3
HURRICANE BILL DISCUSSION NUMBER  21
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL032009
1100 AM AST THU AUG 20 2009
 
CONVENTIONAL SATELLITE...MICROWAVE IMAGES AND NUMEROUS OBSERVATIONS
FROM A NOAA P-3 RESEARCH PLANE INDICATE THAT BILL HAS WEAKENED A
LITTLE BIT DURING THE PAST SEVERAL HOURS.  DVORAK T-NUMBERS HAVE
DECREASED SINCE YESTERDAY...THE EYEWALL HAS BECOME OPEN TO THE
SOUTHWEST AND THE MAXIMUM FLIGHT LEVEL AND SFMR WINDS WERE 121 AND
93 KNOTS...RESPECTIVELY...EARLIER THIS MORNING. IN FACT...SOME ARC
CLOUDS ARE MOVING AWAY FROM THE HURRICANE SUGGESTING THAT BILL IS
NOT STRENGTHENING AT THIS TIME.  BASED ON THESE DATA...THE INITIAL
INTENSITY HAS BEEN REDUCED TO 105 KNOTS...AND THIS IS PROBABLY ON
THE HIGH SIDE.  THE LARGE SCALE ENVIRONMENT IS CONDUCIVE FOR
REINTENSIFICATION SINCE BILL IS ABOUT TO ENCOUNTER THE WARMEST
WATERS ALONG ITS PATH SO FAR...AND THE SHEAR IS FORECAST TO BE
QUITE LIGHT.  HOWEVER...MOST OF THE INTENSITY CHANGE COULD BE
ASSOCIATED WITH EYEWALL REPLACEMENT CYCLES. THE OFFICIAL FORECAST
CALLS FOR RESTRENGTHENING AND BILL IS EXPECTED TO REACH CATEGORY
FOUR AGAIN IN A DAY OR SO.  THEREAFTER...THE HURRICANE SHOULD
GRADUALLY BEGIN TO INTERACT WITH A MID-LATITUDE TROUGH AND BY 96
HOURS IT SHOULD BE IN EXTRATROPICAL TRANSITION AND BE FULLY
EXTRATROPICAL IN FIVE DAYS.
 
BILL HAS CONTINUED TO MOVE ON A STEADY NORTHWEST TRACK OR 305
DEGREES AT 16 KNOTS...EMBEDDED WITHIN THE FLOW SURROUNDING THE
AZORES-BERMUDA HIGH.  IN ABOUT TWO DAYS...THE HURRICANE WILL BECOME
STEERED NORTHWARD AND THEN NORTHEASTWARD BY THE FLOW BETWEEN A
LARGE MID-LATITUDE TROUGH SWINGING EASTWARD ACROSS THE EASTERN
UNITED STATES AND THE SUBTROPICAL HIGH. ONCE THE RECURVATURE
BEGINS...THE HURRICANE SHOULD INCREASE IN FORWARD SPEED. MOST OF
THE TRACK GUIDANCE SHIFTED SLIGHTLY TO THE WEST COMPARED TO THE
PREVIOUS RUN. THIS SHIFT IN GUIDANCE JUSTIFIES A VERY SMALL SHIFT
TO THE WEST OF THE TRACK OFFICIAL FORECAST...WHICH INDEED IS VERY
CLOSE TO THE CONSENSUS.
 
LARGE SWELLS GENERATED BY THIS HURRICANE ARE AFFECTING THE NORTHERN
LEEWARD ISLANDS AND SHOULD BEGIN AFFECTING THE BAHAMAS...BERMUDA...
MOST OF THE EASTERN U.S. COAST...AND THE ATLANTIC MARITIMES OF
CANADA DURING THE NEXT FEW DAYS.  THESE SWELLS WILL LIKELY
CAUSE EXTREMELY DANGEROUS SURF AND LIFE-THREATENING RIP CURRENTS.
PLEASE CONSULT STATEMENTS ISSUED BY YOUR LOCAL WEATHER OFFICE FOR
MORE DETAILS.
 
THIS AFTERNOON NOAA AND THE 53RD HURRICANE HUNTERS WILL BE
CONDUCTING A TWO-AIRCRAFT SYNOPTIC SURVEILLANCE MISSION AROUND
HURRICANE BILL TO IMPROVE THE INITIAL ANALYSIS FOR THE NUMERICAL
MODELS.

 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      20/1500Z 22.6N  61.7W   105 KT
 12HR VT     21/0000Z 24.2N  63.8W   110 KT
 24HR VT     21/1200Z 26.6N  66.0W   115 KT
 36HR VT     22/0000Z 29.5N  67.5W   115 KT
 48HR VT     22/1200Z 32.5N  69.0W   110 KT
 72HR VT     23/1200Z 40.5N  66.5W   100 KT
 96HR VT     24/1200Z 48.0N  53.0W    65 KT...BECOMING EXTRATROPICAL
120HR VT     25/1200Z 55.0N  28.0W    50 KT...EXTRATROPICAL
 
$$
FORECASTER AVILA
 

WTNT43 KNHC 202036
TCDAT3
HURRICANE BILL DISCUSSION NUMBER  22
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL032009
500 PM AST THU AUG 20 2009
 
BOTH NOAA AND AIR FORCE RECONNAISSANCE PLANES HAVE BEEN SENDING VERY
VALUABLE DATA FROM HURRICANE BILL. THE LATEST MINIMUM PRESSURE WAS
DOWN TO 948 MB AND THE PEAK FLIGHT-LEVEL WIND WAS 135 KNOTS. THE
SFMR REPORTED EARLIER A PEAK WIND OF 101 KNOTS.  SINCE THEN...THE
SATELLITE PRESENTATION HAS IMPROVED AND THE EYE IS NOW BETTER
DEFINED. IN FACT...GOES SATELLITE SUPER-RAPID SCAN SHOWS THE
STRUCTURE OF THE EYEWALL AND SEVERAL MESOVORTICES INSIDE THE
EYE...TYPICAL OF STRONG HURRICANES. BASED ON THE AIRCRAFT DATA AND
THE CURRENT SATELLITE PRESENTATION...THE INITIAL INTENSITY IS
ADJUSTED UPWARD TO 110 KNOTS.  THE LARGE SCALE ENVIRONMENT
CONTINUES TO BE CONDUCIVE FOR REINTENSIFICATION SINCE BILL IS ABOUT
TO ENCOUNTER THE WARMEST WATERS ALONG ITS PATH SO FAR.
FURTHERMORE...GLOBAL MODELS SHOW BILL EMBEDDED IN A WELL DEFINED
200 MB ANTICYCLONE. GIVEN THE FAVORABLE ENVIRONMENT...THE OFFICIAL
FORECAST CALLS FOR RESTRENGTHENING AND BILL IS EXPECTED TO REACH
CATEGORY FOUR STATUS AGAIN WITHIN THE NEXT 12 TO 36 HOURS.
THEREAFTER...THE HURRICANE SHOULD GRADUALLY BEGIN TO INTERACT WITH
A MID-LATITUDE TROUGH AND BY 96 HOURS IT SHOULD BE EXTRATROPICAL.
 
THERE IS PRACTICALLY NO CHANGE IN THE FORECAST TRACK. BILL IS MOVING
TOWARD THE NORTHWEST OR 305 DEGREES AT 16 KNOTS EMBEDDED IN VERY
STRONG AND WELL DEFINED STEERING CURRENTS AROUND THE SOUTHWESTERN
PORTION OF THE AZORES-BERMUDA HIGH. HOWEVER...IN A DAY OR SO A
LARGE MID-LATITUDE TROUGH IS EXPECTED TO SWEEP ACROSS THE EASTERN
UNITED STATES AND THE FLOW BETWEEN THE TROUGH AND THE SUBTROPICAL
HIGH SHOULD FORCE THE HURRICANE TO MOVE ON A NORTHERLY AND THEN
NORTHEASTERLY TRACK.  THE DYNAMICAL TRACK GUIDANCE IS EXTREMELY
TIGHTLY CLUSTERED DURING THE FIRST 48 HOURS...INCREASING
CONSIDERABLY THE CONFIDENCE IN THE OFFICIAL TRACK FORECAST FOR THAT
PERIOD.  ON THIS TRACK...THE CORE OF THE HURRICANE WILL MOVE OVER
THE OPEN WATERS BETWEEN BERMUDA AND THE EAST COAST OF THE UNITED
STATES SATURDAY MORNING AND BY SUNDAY...THE HURRICANE WILL BE
APPROACHING THE WATERS SOUTH OF NOVA SCOTIA. 
 
LARGE SWELLS GENERATED BY THIS HURRICANE ARE AFFECTING THE NORTHERN
LEEWARD ISLANDS...PUERTO RICO...HISPANIOLA AND SHOULD BEGIN
AFFECTING THE BAHAMAS...BERMUDA...MOST OF THE EASTERN U.S.
COAST...AND THE ATLANTIC MARITIMES OF CANADA DURING THE NEXT FEW
DAYS.  THESE SWELLS WILL LIKELY CAUSE EXTREMELY DANGEROUS SURF AND
LIFE-THREATENING RIP CURRENTS. PLEASE CONSULT STATEMENTS ISSUED BY
YOUR LOCAL WEATHER OFFICE FOR MORE DETAILS.
 
THE NOAA AND THE 53RD AIR FORCE RESERVE HURRICANE HUNTERS ARE
CURRENTLY CONDUCTING A TWO-AIRCRAFT SYNOPTIC SURVEILLANCE MISSION
AROUND HURRICANE BILL TO IMPROVE THE INITIAL ANALYSIS FOR THE
NUMERICAL MODELS. THIS INFORMATION WILL BE INCLUDED FOR THE 0000
UTC MODEL RUN.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      20/2100Z 23.8N  63.2W   110 KT
 12HR VT     21/0600Z 25.6N  65.2W   115 KT
 24HR VT     21/1800Z 28.3N  67.1W   115 KT
 36HR VT     22/0600Z 31.0N  68.5W   115 KT
 48HR VT     22/1800Z 34.5N  69.0W   105 KT
 72HR VT     23/1800Z 42.5N  64.5W    85 KT
 96HR VT     24/1800Z 49.0N  49.5W    60 KT...EXTRATROPICAL
120HR VT     25/1800Z 53.5N  24.0W    50 KT...EXTRATROPICAL
 
$$
FORECASTER AVILA/BLAKE
 

WTNT43 KNHC 210248
TCDAT3
HURRICANE BILL DISCUSSION NUMBER  23
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL032009
1100 PM AST THU AUG 20 2009
 
THE SATELLITE PRESENTATION OF BILL HAS CHANGED LITTLE THIS EVENING.
THE LARGE EYE REMAINS VERY WELL-DEFINED...HOWEVER THE CLOUD TOPS
SURROUNDING THE EYE HAVE WARMED SLIGHTLY DURING THE PAST COUPLE OF
HOURS. THE NOAA RECONNAISSANCE AIRCRAFT THAT HAS BEEN SAMPLING THE
CORE OF THE HURRICANE THIS EVENING REPORTED A PEAK BELIEVABLE
FLIGHT-LEVEL WIND OF 127 KT.  ALTHOUGH HIGHER WIND SPEEDS WERE
REPORTED...THE METEOROLOGISTS ON THE AIRCRAFT DID NOT CONSIDER
THOSE HIGHER WINDS TO BE VALID.  DVORAK DATA T-NUMBERS HAVE
DECREASED SLIGHTLY.  BASED ON ALL OF THE DATA...THE INITIAL
INTENSITY IS HELD AT 110 KT.  ENVIRONMENTAL FACTORS ARE EXPECTED TO
REMAIN CONDUCIVE FOR SOME RESTRENGTHENING DURING THE NEXT 24 HOURS
OR SO.  AFTERWARDS...SOME COOLING OF THE SSTS WILL LIKELY INDUCE A
SLOW WEAKENING TREND.  VERTICAL WIND SHEAR IS PREDICTED BY THE
SHIPS MODEL TO REMAIN LIGHT UNTIL THE HURRICANE NEARS THE CANADIAN
MARITIMES IN ABOUT 72 HOURS.  HOWEVER...SSTS ALONG THE FORECAST
TRACK WILL BEGIN TO COOL MORE RAPIDLY AROUND THAT TIME...AND SHEAR
IS FORECAST TO INCREASE SIGNIFICANTLY VERY SOON THEREAFTER.  THE
OFFICIAL WIND SPEED FORECAST IS GENERALLY BETWEEN THE SHIPS AND
LGEM GUIDANCE  
 
BILL CONTINUES TO MOVE NORTHWESTWARD OR 310/16 KT. THERE IS NOT MUCH
NEW TO SAY ABOUT THE TRACK FORECAST.  BILL IS EXPECTED TO TURN
NORTHWARD AHEAD OF A STRONG MID-LATITUDE TROUGH THAT WILL MOVE INTO
THE EASTERN U.S. DURING THE NEXT COUPLE OF DAYS...AND RECURVE AHEAD
OF THAT TROUGH THEREAFTER.  THE NEW TRACK FORECAST IS VIRTUALLY
UNCHANGED FROM THE PREVIOUS ADVISORY AND IS ONCE AGAIN IN EXCELLENT
AGREEMENT WITH THE TIGHTLY CLUSTERED MODEL GUIDANCE.
 
LARGE SWELLS GENERATED BY THIS HURRICANE ARE AFFECTING...OR WILL
AFFECT...A LARGE PORTION OF THE WESTERN NORTH ATLANTIC COASTAL AREA
DURING THE NEXT FEW DAYS.  THESE SWELLS WILL LIKELY CAUSE EXTREMELY
DANGEROUS SURF AND LIFE-THREATENING RIP CURRENTS.  PLEASE CONSULT
STATEMENTS ISSUED BY YOUR LOCAL WEATHER OFFICE FOR MORE DETAILS.
 
DATA FROM A TWO-AIRCRAFT SYNOPTIC SURVEILLANCE MISSION CONDUCTED BY
NOAA AND U.S. AIR FORCE RESERVE AIRCRAFT THIS EVENING SHOULD BE
ASSIMILATED INTO THE INITIALIZATION OF THE 0000 UTC MODEL RUNS.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      21/0300Z 24.9N  64.3W   110 KT
 12HR VT     21/1200Z 26.9N  66.1W   115 KT
 24HR VT     22/0000Z 29.6N  67.9W   115 KT
 36HR VT     22/1200Z 32.7N  68.9W   110 KT
 48HR VT     23/0000Z 36.4N  68.6W   100 KT
 72HR VT     24/0000Z 44.3N  62.0W    80 KT
 96HR VT     25/0000Z 50.5N  43.0W    55 KT...EXTRATROPICAL
120HR VT     26/0000Z 55.0N  20.0W    50 KT...EXTRATROPICAL
 
$$
FORECASTER BROWN/PASCH
 

WTNT43 KNHC 210844
TCDAT3
HURRICANE BILL DISCUSSION NUMBER  24
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL032009
500 AM AST FRI AUG 21 2009

NEAR 06Z UTC..AN AIR FORCE RESERVE RECONNAISSANCE AIRCRAFT REPORTED
A 700 MB FLIGHT-LEVEL WINDS OF 128 KT...AND AN EYEWALL DROPSONDE
INDICATED SURFACE WINDS NEAR 105 KT.  SINCE THAT TIME...THE
SATELLITE APPEARANCE OF BILL HAS WEAKENED SIGNIFICANTLY...WITH THE
EYE NOW BARELY APPARENT.  THE INITIAL INTENSITY WILL BE A POSSIBLY
GENEROUS 105 KT BASED ON THE AIRCRAFT DATA.  ANALYSES FROM CIMSS AT
THE UNIVERSITY OF WISCONSIN SHOW 15 KT OF SOUTHERLY VERTICAL WIND
SHEAR AFFECTING BILL...AND THIS MAY BE ALLOWING DRY AIR SEEN IN
WATER VAPOR IMAGERY AND TOTAL PRECIPITABLE WATER DATA TO REACH THE
CORE OF THE HURRICANE.

THE INITIAL MOTION IS 315/15.  THERE IS NO CHANGE IN THE FORECAST
PHILOSOPHY SINCE THE PREVIOUS ADVISORY.  BILL IS MOVING TOWARD AN
INCREASING WEAKNESS IN THE SUBTROPICAL RIDGE...AND IS EXPECTED TO
RECURVE AHEAD OF A LARGE DEEP-LAYER TROUGH MOVING INTO THE EASTERN
UNITED STATES.  THE TIGHTLY-CLUSTERED TRACK GUIDANCE HAS CHANGED
ONLY SLIGHTLY SINCE THE PREVIOUS ADVISORY...WITH SOME NORTHWARD
SHIFT IN THE GUIDANCE ENVELOPE AFTER 48 HR.  THE NEW FORECAST TRACK
IS SIMILAR TO THE PREVIOUS TRACK THROUGH 48 HR...THEN IS ADJUSTED A
LITTLE TO THE NORTH AT SUBSEQUENT TIMES TO ALIGN WITH THE DYNAMICAL
MODEL CONSENSUS.

THE INTENSITY FORECAST IS BECOMING INCREASINGLY PROBLEMATIC.  THE
SHIPS MODEL IS FORECASTING BILL TO BE IN A LIGHT VERTICAL SHEAR
ENVIRONMENT THROUGH 72 HR...BUT THE MODEL HAS BEEN UNDERESTIMATING
THE ONGOING SHEAR FOR THE PAST 24 HR.  BILL IS CURRENTLY OVER SEA
SURFACE TEMPERATURES OF 28-29C...BUT THE SSTS ALONG THE FORECAST
TRACK DECREASE DRAMATICALLY AFTER 24 HR.  ANOTHER COMPLICATION IS
THE POSSIBLE IMPACT OF THE JET STREAM ASSOCIATED WITH THE EASTERN
U. S. TROUGH...WHICH COULD HELP THE HURRICANE MAINTAIN ITS STRENGTH
OR EVEN INTENSIFY IT A LITTLE.  AT THIS TIME...IT LOOKS LIKE THE
MOST FAVORABLE JET STREAM DYNAMICS WILL REMAIN WEST OF BILL.  BASED
ON THE CURRENT TRENDS...THE FIRST PART OF THE INTENSITY FORECAST
HAS BEEN NUDGED DOWNWARD...WITH ONLY A MODEST RE-INTENSIFICATION
BETWEEN 12-24 HR AS SHOWN IN THE SHIPS MODEL.  THEREAFTER...BILL
SHOULD STEADILY WEAKEN OVER COLDER WATERS...WITH EXTRATROPICAL
TRANSITION EXPECTED AT ABOUT 96 HR.  AN ALTERNATIVE SCENARIO IS
THAT BILL WEAKENS FURTHER EVEN BEFORE THE CENTER REACHES THE COLDER
WATER...AND WEAKENS FASTER THAN CURRENTLY FORECAST AFTER THAT. 

LARGE SWELLS GENERATED BY THIS HURRICANE WILL AFFECT A LARGE PORTION
OF THE WESTERN NORTH ATLANTIC COASTAL AREA DURING THE NEXT FEW
DAYS.  THESE SWELLS WILL LIKELY CAUSE EXTREMELY DANGEROUS SURF AND
LIFE-THREATENING RIP CURRENTS.  PLEASE CONSULT STATEMENTS ISSUED BY
YOUR LOCAL WEATHER OFFICE FOR MORE DETAILS.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      21/0900Z 26.2N  65.4W   105 KT
 12HR VT     21/1800Z 28.1N  66.9W   105 KT
 24HR VT     22/0600Z 31.1N  68.4W   110 KT
 36HR VT     22/1800Z 34.6N  68.8W   100 KT
 48HR VT     23/0600Z 38.6N  67.6W    90 KT
 72HR VT     24/0600Z 46.5N  58.5W    70 KT
 96HR VT     25/0600Z 52.5N  33.5W    55 KT...EXTRATROPICAL
120HR VT     26/0600Z 56.5N  15.0W    50 KT...EXTRATROPICAL
 
$$
FORECASTER BEVEN
 

WTNT43 KNHC 211448
TCDAT3
HURRICANE BILL DISCUSSION NUMBER  25
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL032009
1100 AM AST FRI AUG 21 2009
 
AFTER SOME DETERIORATION OF THE CLOUD PATTERN EARLY THIS
MORNING...VISIBLE SATELLITE IMAGES INDICATE THAT THE EYE HAS BECOME 
APPARENT AGAIN ALTHOUGH IS NOT AS DISTINCT IT WAS YESTERDAY. 
MICROWAVE IMAGES SHOW A CONVECTIVE RING ASSOCIATED WITH THE EYEWALL
WITH AN OUTER CONVECTIVE BAND.  AT THIS POINT IT IS DIFFICULT TO
KNOW WHETHER THIS IS THE BEGINNING OF THE FORMATION OF A SECONDARY
EYEWALL.  IT IS ALSO POSSIBLE THAT THE WEAKENING OVERNIGHT WAS 
RELATED TO AN EYEWALL REPLACEMENT CYCLE. THE AVERAGE OF THE LATEST
OBJECTIVE AND SUBJECTIVE DVORAK T-NUMBERS INDICATE THAT INITIAL
INTENSITY CAN BE ADJUSTED DOWN TO 100 KT.  AN AIR FORCE HURRICANE
HUNTER PLANE WILL CHECK THE INTENSITY LATER TODAY.  THE HURRICANE
STILL HAS TO MOVE OVER THE WARMEST OCEAN YET TODAY AND
SATURDAY...AND THE SHEAR IS LOW AS DIAGNOSED BY THE SHIPS MODEL.
BILL HAS THE POTENTIAL TO RESTRENGTHEN A LITTLE BUT MOST LIKELY THE
HURRICANE WILL EXPERIENCE SOME FLUCTUATIONS IN INTENSITY DURING THE
NEXT 24 HOURS. THEREAFTER...SHEAR AND A COLDER OCEAN SHOULD WORK
AGAINST INTENSIFICATION AND BILL SHOULD BEGIN ITS EXTRATROPICAL
TRANSITION BEYOND 72 HOURS.

BILL IS MOVING TOWARD THE NORTHWEST OR 325 DEGREES AT 16 KNOTS WHILE
EMBEDDED IN VERY WELL-ESTABLISHED STEERING CURRENTS ASSOCIATED WITH
THE AZORES-BERMUDA HIGH. BILL IS ALREADY REACHING THE SOUTHWESTERN
EDGE OF THE RIDGE AND SOON WILL BECOME STEERED NORTHWARD AND
NORTHEASTWARD BY THE FLOW BETWEEN THE HIGH AND A LARGE MID-LATITUDE
TROUGH DEVELOPING OVER THE EASTERN UNITED STATES. THESE TWO
FEATURES ARE BEING HANDLED CONSISTENTLY ACROSS MOST OF THE
DYNAMICAL MODELS AND CONSEQUENTLY THE TRACK GUIDANCE IS TIGHTLY
PACKED. THE FACT THAT TRACK GUIDANCE IS IN VERY GOOD AGREEMENT
INCREASES MY CONFIDENCE IN THE TRACK FORECAST.    

LARGE SWELLS GENERATED BY THIS HURRICANE WILL AFFECT A LARGE PORTION
OF THE WESTERN NORTH ATLANTIC COASTAL AREA DURING THE NEXT FEW
DAYS.  THESE SWELLS WILL LIKELY CAUSE EXTREMELY DANGEROUS SURF AND
LIFE-THREATENING RIP CURRENTS.  PLEASE CONSULT STATEMENTS ISSUED BY
YOUR LOCAL WEATHER OFFICE AND METEOROLOGICAL SERVICES FOR MORE
DETAILS.

 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      21/1500Z 27.6N  66.3W   100 KT
 12HR VT     22/0000Z 29.8N  67.7W   100 KT
 24HR VT     22/1200Z 33.0N  68.5W   100 KT
 36HR VT     23/0000Z 36.5N  68.4W    90 KT
 48HR VT     23/1200Z 41.0N  66.0W    80 KT
 72HR VT     24/1200Z 48.5N  52.0W    60 KT
 96HR VT     25/1200Z 53.5N  27.5W    50 KT...EXTRATROPICAL
120HR VT     26/1200Z 57.5N  10.0W    40 KT...EXTRATROPICAL
 
$$
FORECASTER AVILA
 

WTNT43 KNHC 212040
TCDAT3
HURRICANE BILL DISCUSSION NUMBER  26
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL032009
500 PM AST FRI AUG 21 2009
 
AN AIR FORCE HURRICANE HUNTER AIRCRAFT REACHED BILL THIS
AFTERNOON AND FOUND THAT THE CENTRAL PRESSURE HAS REMAINED AROUND
954 MB...BUT THE WINDS HAVE DECREASED AND INITIAL INTENSITY IS NOW
90 KT. THE PLANE REPORTED A SMALL EYE OF 14 N MI DIAMETER.
GIVEN THE CONCENTRIC RING STRUCTURE OBSERVED ON MICROWAVE AND THE
DOUBLE WIND MAXIMA PROVIDED BY THE PLANE...IT IS LIKELY THAT THE
HURRICANE IS GOING THROUGH AN EYEWALL REPLACEMENT AND THE REASON
FOR THE CURRENT WEAKENING. THERE IS AN OPPORTUNITY FOR BILL TO
REGAIN SOME STRENGTH DURING THE NEXT 12 TO 24 HOURS WHILE THE SHEAR
IS LOW AND BEFORE THE HURRICANE REACHES COOLER WATERS.
THEREAFTER...A STEADY WEAKENING IS INDICATED AND BY 72 HOURS...BILL
SHOULD ALREADY BE AN EXTRATROPICAL CYCLONE INTERACTING WITH THE
HIGH LATITUDE WESTERLIES.
 
BILL IS NOW MOVING TOWARD THE NORTH-NORTHWEST OR 340 DEGREES AT 17
KNOTS. THE HURRICANE SHOULD GRADUALLY TURN MORE TO THE NORTH AROUND
THE BERMUDA-AZORES HIGH TONIGHT AND SATURDAY AND SHOULD BE FORCED TO
RECURVE AS A LARGE MID-LATITUDE TROUGH MOVES EASTWARD ACROSS THE
EASTERN UNITED STATES.  THERE HAS NOT BEEN ANY CHANGE IN TRACK
GUIDANCE WHICH IN FACT CONTINUES TO BE TIGHTLY PACKED...MAINTAINING
HIGH CONFIDENCE IN THE TRACK FORECAST.
 
LARGE SWELLS GENERATED BY THIS HURRICANE WILL AFFECT A LARGE PORTION
OF THE WESTERN NORTH ATLANTIC COASTAL AREA DURING THE NEXT FEW
DAYS.  THESE SWELLS WILL LIKELY CAUSE EXTREMELY DANGEROUS SURF AND
LIFE-THREATENING RIP CURRENTS.  PLEASE CONSULT STATEMENTS ISSUED BY
YOUR LOCAL WEATHER OFFICE AND METEOROLOGICAL SERVICES FOR MORE
DETAILS.
 
AT THIS TIME...TROPICAL-STORM-FORCE WINDS ARE NOT FORECAST TO REACH
NEW ENGLAND.  HOWEVER...A SLIGHT SHIFT OF THE FORECAST TRACK TO THE
LEFT WOULD REQUIRE A TROPICAL STORM WATCH OR WARNING TONIGHT.  THE
WIND SPEED PROBABILITY PRODUCT INDICATES THAT THERE IS ROUGHLY A 25
PERCENT CHANCE OF THESE WINDS REACHING EXTREME SOUTHEASTERN NEW
ENGLAND.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      21/2100Z 29.4N  66.9W    90 KT
 12HR VT     22/0600Z 31.7N  68.0W   100 KT
 24HR VT     22/1800Z 35.1N  68.4W   100 KT
 36HR VT     23/0600Z 39.0N  67.2W    85 KT
 48HR VT     23/1800Z 43.0N  64.0W    75 KT
 72HR VT     24/1800Z 49.5N  47.0W    50 KT...EXTRATROPICAL
 96HR VT     25/1800Z 54.5N  20.0W    45 KT...EXTRATROPICAL
120HR VT     26/1800Z 60.0N   6.0W    35 KT...EXTRATROPICAL
 
$$
FORECASTER AVILA
 

WTNT43 KNHC 220245
TCDAT3
HURRICANE BILL DISCUSSION NUMBER  27
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL032009
1100 PM AST FRI AUG 21 2009
 
THE STRUCTURE OF BILL HAS CONTINUED TO EVOLVE THIS EVENING...WITH
MICROWAVE IMAGERY SHOWING THE REMNANT OF AN INNER EYEWALL AND THE
FORMATION OF AN OUTER EYEWALL. ALSO...THERE HAVE ALSO BEEN SIGNS OF
A LARGER EYE TRYING TO FORM IN GEOSTATIONARY INFRARED IMAGERY IN
THE PAST COUPLE OF HOURS. OVERALL...THE CLOUD PATTERN LOOKS LESS
IMPRESSIVE...AS COLD CLOUD TOPS HAVE DIMINISHED OVER THE WESTERN
SEMICIRCLE. ALL THAT BEING SAID...THE INITIAL INTENSITY IS HELD AT
90 KT BASED ON 0000 UTC DVORAK T-NUMBERS OF 5.0 FROM TAFB AND
SAB...BUT THIS COULD BE GENEROUS. AN AIR FORCE RESERVE HURRICANE
HUNTER AIRCRAFT IS CURRENTLY IN ROUTE TO INVESTIGATE BILL AND WILL
PROVIDE MORE INFORMATION ON THE INTENSITY AND STRUCTURE OF THE
CYCLONE IN THE NEXT FEW HOURS.

IF BILL IS ABLE TO COMPLETE THE EYEWALL REPLACEMENT CYCLE...THERE IS
SOME OPPORTUNITY FOR RESTRENGTHENING IN THE NEXT 24 HOURS BEFORE
THE HURRICANE CROSSES THE NORTHERN WALL OF THE GULF STREAM...AND
SOME STRENGTHENING IS SHOWN IN THE OFFICIAL FORECAST. THERE
IS THE POSSIBILITY THAT BILL COULD INTENSIFY A LITTLE MORE THAN
SHOWN HERE...AS THE INTENSITY PROBABILITY TABLE SHOWS ABOUT A 30 TO
35 PERCENT CHANCE THAT BILL WILL BE A CATEGORY 3 HURRICANE IN 12 TO
24 HOURS. BEYOND 24 HOURS...STEADY WEAKENING IS FORECAST AS THE
CYCLONE ENCOUNTERS MUCH LOWER SEA SURFACE TEMPERATURES AND
INCREASING WIND SHEAR. EXTRATROPICAL TRANSITION IS EXPECTED TO
OCCUR IN TWO OR THREE DAYS...AND THE WIND RADII AND INTENSITY
FORECASTS ATTEMPT TO ACCOUNT FOR THESE STRUCTURAL CHANGES. 

THE INITIAL MOTION ESTIMATE IS 345/17. THE TRACK GUIDANCE REMAINS IN
VERY GOOD AGREEMENT...ACCELERATING BILL TOWARD THE NORTH AND
NORTHEAST AHEAD OF A LARGE MID-LATITUDE TROUGH MOVING INTO THE
NORTHEASTERN UNITED STATES. AS A RESULT...ONLY MINOR CHANGES HAVE
BEEN MADE TO THE PREVIOUS PACKAGE. 
 
LARGE SWELLS GENERATED BY BILL ARE BEGINNING TO ARRIVE ALONG THE
EAST COAST OF THE UNITED STATES. THESE SWELLS WILL SPREAD NORTHWARD
OVER THE WEEKEND...CAUSING EXTREMELY DANGEROUS SURF AND
LIFE-THREATENING RIP CURRENTS. PLEASE CONSULT STATEMENTS ISSUED BY
YOUR LOCAL WEATHER OFFICE AND METEOROLOGICAL SERVICES FOR MORE
DETAILS.
 
WHILE TROPICAL-STORM-FORCE WINDS ARE NOT CURRENTLY FORECAST TO REACH
NEW ENGLAND...A SHIFT IN THE FORECAST TRACK TO THE LEFT COULD
REQUIRE THE ISSUANCE OF A TROPICAL STORM WATCH OR WARNING ON
SATURDAY. THE WIND SPEED PROBABILITY PRODUCT INDICATES A 15 TO 20
PERCENT CHANCE OF TROPICAL-STORM-FORCE WINDS REACHING EXTREME
SOUTHEASTERN NEW ENGLAND. 

THE INITIAL WIND RADII WERE ADJUSTED BASED ON DATA FROM A 2322 UTC
QUIKSCAT PASS...DATA FROM NOAA BUOY 41048 AND OBSERVATIONS FROM
BERMUDA. 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      22/0300Z 31.0N  67.5W    90 KT
 12HR VT     22/1200Z 33.5N  68.1W    95 KT
 24HR VT     23/0000Z 37.3N  67.8W    95 KT
 36HR VT     23/1200Z 41.3N  65.4W    80 KT
 48HR VT     24/0000Z 45.1N  59.9W    70 KT
 72HR VT     25/0000Z 50.5N  40.0W    45 KT...EXTRATROPICAL
 96HR VT     26/0000Z 55.0N  19.0W    40 KT...EXTRATROPICAL
120HR VT     27/0000Z 60.5N   6.0W    35 KT...EXTRATROPICAL
 
$$
FORECASTER BRENNAN
 

WTNT43 KNHC 220902
TCDAT3
HURRICANE BILL DISCUSSION NUMBER  28
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL032009
500 AM AST SAT AUG 22 2009

REPORTS FROM AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT INDICATE
THAT BILL HAS JUST ABOUT FINISHED ITS EYEWALL REPLACEMENT CYCLE...
AND NOW HAS A 48 N MI WIDE EYE.  THE AIRCRAFT ENCOUNTERED 120 KT
FLIGHT-LEVEL WINDS AT 700 MB IN THE NORTHEASTERN EYEWALL...AND A
DROPSONDE IN THE AREA SUGGESTS SURFACE WINDS OF 90 KT.  THE MINIMUM
CENTRAL PRESSURE WAS 960 MB.  BASED ON THIS DATA...THE INITIAL
INTENSITY REMAINS 90 KT.  THE CIRRUS OUTFLOW IS GOOD IN THE
NORTHWESTERN SEMICIRCLE AND POOR ELSEWHERE.

BILL HAS MOVED A LITTLE TO THE LEFT OF THE PREVIOUS FORECAST...WITH
AN INITIAL MOTION OF 345/19.  OTHER THAN THAT...THERE IS LITTLE
CHANGE IN THE FORECAST PHILOSOPHY OR THE TRACK FORECAST GUIDANCE. 
BILL IS EXPECTED TO RECURVE INTO THE WESTERLIES DURING THE NEXT
24-48 HR BETWEEN A LARGE DEEP-LAYER TROUGH OVER THE EASTERN UNITED
STATES AND A RIDGE OVER THE CENTRAL ATLANTIC.  AFTER 48 HR...THE
SYSTEM SHOULD MOVE QUICKLY EASTWARD IN THE WESTERLIES.  THE NEW
FORECAST TRACK IS SLIGHTLY NORTH AND WEST OF THE PREVIOUS TRACK FOR
THE FIRST 48 HR DUE TO THE INITIAL POSITION AND MOTION.  AFTER THAT
TIME...THE TRACK IS SHIFTED SOUTHWARD FROM THE PREVIOUS TRACK.  THE
NEW FORECAST IS DOWN THE MIDDLE OF THE DYNAMICAL GUIDANCE ENVELOPE.

BILL SHOULD REMAIN IN LIGHT VERTICAL WIND SHEAR AND OVER WARM SEA
SURFACE TEMPERATURES FOR THE NEXT 12-24 HOURS...AND THUS THE
INTENSITY FORECAST CALLS FOR SOME STRENGTHENING DURING THIS TIME. 
AFTER 24 HR...COLDER SSTS AND INCREASING SHEAR SHOULD CAUSE BILL TO
WEAKEN.  EXTRATROPICAL TRANSITION IS EXPECTED TO BEGIN AT ABOUT
THE 48 HR PERIOD AND BE COMPLETE BY 72 HR...AND THE EXTRATROPICAL
REMNANTS OF BILL ARE FORECAST TO GRADUALLY WEAKEN AS THEY CROSS THE
ATLANTIC.

LARGE SWELLS GENERATED BY BILL ARE BEGINNING TO ARRIVE ALONG THE
EAST COAST OF THE UNITED STATES. THESE SWELLS WILL SPREAD NORTHWARD
OVER THE WEEKEND...CAUSING EXTREMELY DANGEROUS SURF AND
LIFE-THREATENING RIP CURRENTS. PLEASE CONSULT STATEMENTS ISSUED BY
YOUR LOCAL WEATHER OFFICE AND METEOROLOGICAL SERVICES FOR MORE
DETAILS.

THE WESTWARD SHIFT IN THE FORECAST TRACK REQUIRES A TROPICAL STORM
WARNING FOR PORTIONS OF THE MASSACHUSETTS COAST...AND THE WIND
SPEED PROBABILITY PRODUCT NOW SHOWS A 40 PERCENT CHANCE OF
TROPICAL-STORM-FORCE WINDS IN THAT AREA.  ANY ADDITIONAL TRACK
DEVIATIONS TO THE WEST WOULD REQUIRE ADDITIONAL WARNINGS ALONG THE
NEW ENGLAND COAST.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      22/0900Z 33.0N  68.5W    90 KT
 12HR VT     22/1800Z 36.1N  68.7W    95 KT
 24HR VT     23/0600Z 40.1N  67.2W    90 KT
 36HR VT     23/1800Z 44.1N  63.1W    75 KT
 48HR VT     24/0600Z 48.0N  55.6W    60 KT...INLAND
 72HR VT     25/0600Z 51.0N  31.5W    40 KT...EXTRATROPICAL
 96HR VT     26/0600Z 54.0N  14.0W    30 KT...EXTRATROPICAL
120HR VT     27/0600Z 58.0N   4.0W    20 KT...EXTRATROPICAL
 
$$
FORECASTER BEVEN
 

WTNT43 KNHC 221442
TCDAT3
HURRICANE BILL DISCUSSION NUMBER  29
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL032009
1100 AM AST SAT AUG 22 2009
 
SATELLITE IMAGES INDICATE THAT BILL HAS NOT BECOME ANY BETTER
ORGANIZED AND THE T-NUMBERS HAVE CONTINUED TO DECREASE. INITIAL
INTENSITY HAS BEEN ADJUSTED DOWN TO 85 KNOTS AND THIS VALUE COULD
BE GENEROUS. AN AIR FORCE PLANE WILL CHECK BILL THIS AFTERNOON AND
WILL GIVE US A BETTER ESTIMATE OF THE INTENSITY AND WIND RADII. BILL
IS EXPECTED TO MAINTAIN ITS STRENGTH TODAY BUT WITH COLD WATERS
AHEAD...A GRADUAL WEAKENING SHOULD BEGIN TONIGHT. IN ABOUT 48
HOURS...THE EXTRATROPICAL TRANSITION SHOULD BEGIN AND BY 72 HOURS
BILL SHOULD BE FULLY EXTRATROPICAL.
 
THERE HAS BEEN NO SIGNIFICANT CHANGE IN TRACK. BILL IS MOVING
TOWARD THE NORTH OR 355 DEGREES ABOUT 20 KNOTS. THE HURRICANE IS
ALREADY EMBEDDED WITHIN THE FLOW BETWEEN THE AZORES-BERMUDA HIGH
AND A MID-LATITUDE TROUGH OVER THE EASTERN UNITED STATES. THIS
PATTERN SHOULD FORCE BILL TO RECURVE WITH A GRADUAL INCREASE IN
FORWARD SPEED. THE OFFICIAL FORECAST IS IN THE MIDDLE OF THE
GUIDANCE ENVELOPE AND BECAUSE THE GUIDANCE CONTINUES TO BE TIGHTLY
PACKED...THERE IS HIGH CONFIDENCE IN THE TRACK FORECAST. THE
FORECAST TRACK BRINGS BILL TO THE WATERS JUST SOUTH OF NOVA SCOTIA
IN 24 HOURS. THEREFORE...ENVIRONMENT CANADA HAS ISSUED WATCHES AND
WARNINGS FOR EASTERN REGIONS OF CANADA.
 
LARGE SWELLS GENERATED BY BILL ARE ARRIVING ALONG THE EAST COAST OF
THE UNITED STATES. THESE SWELLS WILL SPREAD NORTHWARD OVER THE
WEEKEND...CAUSING EXTREMELY DANGEROUS SURF AND LIFE-THREATENING RIP
CURRENTS. PLEASE CONSULT STATEMENTS ISSUED BY YOUR LOCAL WEATHER
OFFICE AND METEOROLOGICAL SERVICES FOR MORE DETAILS.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      22/1500Z 35.1N  68.6W    85 KT
 12HR VT     23/0000Z 38.0N  68.5W    85 KT
 24HR VT     23/1200Z 42.5N  65.5W    75 KT
 36HR VT     24/0000Z 46.0N  59.0W    65 KT
 48HR VT     24/1200Z 49.5N  49.4W    50 KT...BECOMING EXTRATROPICAL
 72HR VT     25/1200Z 52.0N  24.0W    40 KT...EXTRATROPICAL
 96HR VT     26/1200Z 58.0N   9.0W    30 KT...EXTRATROPICAL
120HR VT     27/1200Z 63.0N   5.0W    20 KT...EXTRATROPICAL
 
$$
FORECASTER AVILA
 

WTNT43 KNHC 222034
TCDAT3
HURRICANE BILL DISCUSSION NUMBER  30
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL032009
500 PM AST SAT AUG 22 2009
 
AN AIR FORCE PLANE JUST PENETRATED AND SURVEYED HURRICANE BILL AND
ALTHOUGH IT MEASURED A MINIMUM CENTRAL PRESSURE OF 961 MB...THE
SURFACE WINDS REPORTED BY THE PLANE HAVE DECREASED...AND THE
INITIAL INTENSITY IS LOWERED TO 75 KNOTS. THIS INTENSITY IS ALSO
SUPPORTED BY T-NUMBERS WHICH HAVE BEEN BETWEEN 4.0 AND 5.0 ON THE
DVORAK SCALE. BILL IS EXPECTED TO MAINTAIN ITS STRENGTH FOR THE
NEXT SEVERAL HOURS BUT WITH COLD WATERS AHEAD...A GRADUAL WEAKENING
SHOULD BEGIN TONIGHT. BILL SHOULD BE FULLY EXTRATROPICAL IN ABOUT
48 HOURS AFTER THE CENTER PASSES NEAR OR OVER NEWFOUNDLAND.
 
THERE HAS BEEN NO SIGNIFICANT CHANGE IN TRACK. BILL IS MOVING
TOWARD THE NORTH OR 360 DEGREES AT ABOUT 21 KNOTS. THE HURRICANE IS
ALREADY EMBEDDED WITHIN THE FLOW BETWEEN THE AZORES-BERMUDA HIGH
AND A MID-LATITUDE TROUGH OVER THE EASTERN UNITED STATES. THIS
PATTERN SHOULD FORCE BILL TO TURN TO THE NORTH-NORTHEAST TONIGHT
WITH A GRADUAL INCREASE IN FORWARD SPEED. THE GUIDANCE CONTINUES
TO BE TIGHTLY PACKED...RESULTING IN HIGH CONFIDENCE IN THE TRACK
FORECAST. THE FORECAST TRACK BRINGS BILL TO THE WATERS JUST SOUTH
OF NOVA SCOTIA IN 24 HOURS AND VERY NEAR OR OVER NEWFOUNDLAND
BETWEEN 24 AND 36 HOURS AS A WEAKENING CYCLONE.
 
LARGE SWELLS GENERATED BY BILL ARE STILL AFFECTING THE EAST COAST OF
THE UNITED STATES. THESE SWELLS WILL CONTINUE TO SPREAD NORTHWARD
TONIGHT AND SUNDAY...CAUSING EXTREMELY DANGEROUS SURF AND
LIFE-THREATENING RIP CURRENTS. PLEASE CONSULT STATEMENTS ISSUED BY
YOUR LOCAL WEATHER OFFICE AND METEOROLOGICAL SERVICES FOR MORE
DETAILS.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      22/2100Z 37.1N  68.8W    75 KT
 12HR VT     23/0600Z 40.2N  67.6W    75 KT
 24HR VT     23/1800Z 44.2N  63.2W    65 KT
 36HR VT     24/0600Z 48.0N  54.5W    45 KT...INLAND
 48HR VT     24/1800Z 50.0N  43.0W    40 KT...EXTRATROPICAL
 72HR VT     25/1800Z 52.0N  20.0W    30 KT...EXTRATROPICAL
 96HR VT     26/1800Z 57.0N   7.0W    25 KT...EXTRATROPICAL
120HR VT     27/1800Z 64.0N   2.5W    30 KT...EXTRATROPICAL
 
$$
FORECASTER AVILA
 

WTNT43 KNHC 230241
TCDAT3
HURRICANE BILL DISCUSSION NUMBER  31
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL032009
1100 PM AST SAT AUG 22 2009
 
AFTER DIMINISHING FOR A TIME...INFRARED SATELLITE IMAGERY SHOWS A
RECENT INCREASE OF COLD CLOUD TOPS NEAR AND TO THE NORTH OF THE
CENTER OF BILL. WHILE THE EYE IS NOT READILY APPARENT IN
GEOSTATIONARY IMAGERY...MICROWAVE IMAGERY STILL SHOWS AT LEAST A
PARTIAL EYEWALL NORTH OF THE CENTER. THE INITIAL INTENSITY IS HELD
AT 75 KT FOR THIS ADVISORY BASED ON FINAL CI-NUMBERS OF 4.5 FROM
TAFB AND SAB AT 0000 UTC. AN AIR FORCE RESERVE HURRICANE HUNTER
AIRCRAFT WILL BE INVESTIGATING BILL LATER TONIGHT AND SUNDAY
MORNING...AND WILL PROVIDE ADDITIONAL INFORMATION ON THE
LOCATION...STRUCTURE AND INTENSITY OF BILL.
 
OVER THE PAST FEW HOURS...BILL APPEARS TO HAVE BEEN MOVING JUST EAST
OF DUE NORTH...AND THE INITIAL MOTION ESTIMATE IS 015/22. THE TRACK
MODEL GUIDANCE REMAINS IN EXCELLENT AGREEMENT ON THE RECURVATURE OF
BILL IN THE NEXT COUPLE OF DAYS. THE OFFICIAL TRACK FORECAST IS
BASICALLY AN UPDATE OF THE PREVIOUS PACKAGE...AND LIES NEAR THE
MIDDLE OF THE TIGHTLY CLUSTERED TRACK GUIDANCE THROUGH 48 HOURS...
SHOWING A TURN TOWARD THE NORTHEAST AND EAST-NORTHEAST WITH AN
INCREASE IN FORWARD SPEED. BEYOND THAT TIME...THE TRACK FORECAST
LIES SOUTH OF THE MODEL CONSENSUS AND IS IN BEST AGREEMENT WITH THE
GFS ENSEMBLE MEAN AS THE POST-TROPICAL BILL APPROACHES THE BRITISH
ISLES LATE IN THE FORECAST PERIOD.
 
BILL WILL SOON BE MOVING ACROSS THE NORTH WALL OF THE GULF STREAM
AND INTO A MORE BAROCLINIC ENVIRONMENT. MOST OF THE GLOBAL MODEL
GUIDANCE SHOWS THAT BILL WILL BE EXTRATROPICAL BY 48 HOURS...AND
THE CYCLONE SHOULD BE WELL INTO THE TRANSITION PROCESS BY EARLY
MONDAY AS IT MOVES AWAY FROM NEWFOUNDLAND. THE OFFICIAL INTENSITY
FORECAST SHOWS SLOW WEAKENING THROUGH 24 HOURS DUE TO COOLER SEA
SURFACE TEMPERATURES AND INCREASING VERTICAL WIND SHEAR. BEYOND
THAT TIME...A MORE SIGNIFICANT DECREASE IN INTENSITY IS FORECAST...
ALONG WITH A LARGE EXPANSION OF THE 34-KT WIND RADII...AS BILL
COMPLETES EXTRATROPICAL TRANSITION. 
 
LARGE SWELLS GENERATED BY BILL ARE STILL AFFECTING THE EAST COAST OF
THE UNITED STATES. THESE SWELLS WILL CONTINUE TO SPREAD NORTHWARD
INTO THE CANADIAN MARITIMES ON SUNDAY...CAUSING EXTREMELY DANGEROUS
SURF AND LIFE-THREATENING RIP CURRENTS. PLEASE CONSULT STATEMENTS
ISSUED BY YOUR LOCAL WEATHER OFFICE AND METEOROLOGICAL SERVICES FOR
MORE DETAILS.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      23/0300Z 39.1N  67.8W    75 KT
 12HR VT     23/1200Z 42.3N  65.7W    70 KT
 24HR VT     24/0000Z 46.3N  59.2W    60 KT
 36HR VT     24/1200Z 49.3N  49.0W    45 KT
 48HR VT     25/0000Z 51.0N  37.0W    40 KT...EXTRATROPICAL
 72HR VT     26/0000Z 53.0N  16.5W    30 KT...EXTRATROPICAL
 96HR VT     27/0000Z 60.0N   6.0W    30 KT...EXTRATROPICAL
120HR VT     28/0000Z 64.0N   4.0W    25 KT...EXTRATROPICAL
 
$$
FORECASTER BRENNAN
 

WTNT43 KNHC 230851
TCDAT3
HURRICANE BILL DISCUSSION NUMBER  32
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL032009
500 AM AST SUN AUG 23 2009
 
INFRARED SATELLITE IMAGERY SHOWS COLD CONVECTIVE CLOUD TOPS CONTINUE
TO SURROUND THE CLOUD-FILLED EYE OF BILL.  RECENT AIRCRAFT FIXES
HAVE BEEN TO THE WEST AND SOUTHWEST OF THE EYE-FEATURE SEEN IN
SATELLITE IMAGERY...SUGGESTING SOME VERTICAL TILT TO THE HURRICANE. 
THE AIRCRAFT RECENTLY REPORTED A PEAK 700 MB FLIGHT-LEVEL WIND OF
93 KT AND A SFMR SURFACE WIND OF 67 KT TO THE SOUTHEAST OF THE
CENTER.  A DROPSONDE MEASURED A MEAN WIND OF 98 KT IN THE LOWEST
150 METERS OF THE SOUNDING.  THESE DATA SUPPORT MAINTAINING THE 
INITIAL INTENSITY AT 75 KT.
 
THE HURRICANE IS MOVING NORTH-NORTHEAST OR 025/23.  BILL IS
FORECAST TO TURN NORTHEASTWARD AND RECURVE AHEAD OF A STRONG
MID-LATITUDE TROUGH THAT IS MOVING ACROSS THE EASTERN UNITED
STATES.  THE NEW FORECAST TRACK IS VERY SIMILAR TO THE PREVIOUS
ADVISORY AND REMAINS NEAR THE MIDDLE OF THE TIGHTLY CLUSTERED
GUIDANCE THROUGH 36 HOURS.  THEREAFTER...THE TRACK HAS BEEN
ADJUSTED A LITTLE SOUTHWARD IN LINE WITH THE GFS AND UKMET
SOLUTIONS.
 
BILL WILL BE MOVING ACROSS THE NORTH WALL OF THE GULF STREAM AND
OVER MUCH COOLER WATERS VERY SOON.  THE INTENSITY FORECAST CALLS
FOR STEADY WEAKENING DURING THE NEXT 24 TO 36 HOURS.  BILL
SHOULD BEGIN ITS EXTRATROPICAL TRANSITION LATER TODAY AND BECOME
FULLY EXTRATROPICAL IN ABOUT 36 HOURS.  AFTER TRANSITION IS
COMPLETE...THE GLOBAL MODELS CONTINUE TO SHOW GRADUAL WEAKENING OF
THE CYCLONE...AS DOES THE OFFICIAL FORECAST.

THE 34-KT WIND RADII HAS BEEN EXPANDED OVER THE EASTERN SEMICIRCLE
BASED ON DATA FROM THE AIRCRAFT AND AN EARLIER QUIKSCAT PASS.
 
LARGE SWELLS GENERATED BY BILL ARE STILL AFFECTING THE EAST COAST OF
THE UNITED STATES. THESE SWELLS WILL CONTINUE TO SPREAD NORTHWARD
INTO THE CANADIAN MARITIMES TODAY...CAUSING EXTREMELY DANGEROUS
SURF AND LIFE-THREATENING RIP CURRENTS. PLEASE CONSULT STATEMENTS
ISSUED BY YOUR LOCAL WEATHER OFFICE AND METEOROLOGICAL SERVICES FOR
MORE DETAILS.
  
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      23/0900Z 41.2N  66.5W    75 KT
 12HR VT     23/1800Z 44.1N  63.0W    65 KT
 24HR VT     24/0600Z 47.5N  55.1W    55 KT
 36HR VT     24/1800Z 49.8N  43.8W    45 KT...EXTRATROPICAL
 48HR VT     25/0600Z 50.5N  31.0W    40 KT...EXTRATROPICAL
 72HR VT     26/0600Z 54.0N  10.0W    30 KT...EXTRATROPICAL
 96HR VT     27/0600Z 61.0N   2.0W    25 KT...EXTRATROPICAL
120HR VT     28/0600Z...ABSORBED
 
$$
FORECASTER BROWN
 

WTNT43 KNHC 230906
TCDAT3
HURRICANE BILL DISCUSSION NUMBER  32...CORRECTED
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL032009
500 AM AST SUN AUG 23 2009

CORRECTED MAXIMUM FLIGHT-LEVEL AND SFMR WIND MEASUREMENTS
 
INFRARED SATELLITE IMAGERY SHOWS COLD CONVECTIVE CLOUD TOPS CONTINUE
TO SURROUND THE CLOUD-FILLED EYE OF BILL.  RECENT AIRCRAFT FIXES
HAVE BEEN TO THE WEST AND SOUTHWEST OF THE EYE-FEATURE SEEN IN
SATELLITE IMAGERY...SUGGESTING SOME VERTICAL TILT TO THE HURRICANE. 
THE AIRCRAFT RECENTLY REPORTED A PEAK 700 MB FLIGHT-LEVEL WIND OF
97 KT AND A SFMR SURFACE WIND OF 68 KT TO THE SOUTHEAST OF THE
CENTER.  A DROPSONDE MEASURED A MEAN WIND OF 98 KT IN THE LOWEST
150 METERS OF THE SOUNDING.  THESE DATA SUPPORT MAINTAINING THE 
INITIAL INTENSITY AT 75 KT.
 
THE HURRICANE IS MOVING NORTH-NORTHEAST OR 025/23.  BILL IS
FORECAST TO TURN NORTHEASTWARD AND RECURVE AHEAD OF A STRONG
MID-LATITUDE TROUGH THAT IS MOVING ACROSS THE EASTERN UNITED
STATES.  THE NEW FORECAST TRACK IS VERY SIMILAR TO THE PREVIOUS
ADVISORY AND REMAINS NEAR THE MIDDLE OF THE TIGHTLY CLUSTERED
GUIDANCE THROUGH 36 HOURS.  THEREAFTER...THE TRACK HAS BEEN
ADJUSTED A LITTLE SOUTHWARD IN LINE WITH THE GFS AND UKMET
SOLUTIONS.
 
BILL WILL BE MOVING ACROSS THE NORTH WALL OF THE GULF STREAM AND
OVER MUCH COOLER WATERS VERY SOON.  THE INTENSITY FORECAST CALLS
FOR STEADY WEAKENING DURING THE NEXT 24 TO 36 HOURS.  BILL
SHOULD BEGIN ITS EXTRATROPICAL TRANSITION LATER TODAY AND BECOME
FULLY EXTRATROPICAL IN ABOUT 36 HOURS.  AFTER TRANSITION IS
COMPLETE...THE GLOBAL MODELS CONTINUE TO SHOW GRADUAL WEAKENING OF
THE CYCLONE...AS DOES THE OFFICIAL FORECAST.

THE 34-KT WIND RADII HAS BEEN EXPANDED OVER THE EASTERN SEMICIRCLE
BASED ON DATA FROM THE AIRCRAFT AND AN EARLIER QUIKSCAT PASS.
 
LARGE SWELLS GENERATED BY BILL ARE STILL AFFECTING THE EAST COAST OF
THE UNITED STATES. THESE SWELLS WILL CONTINUE TO SPREAD NORTHWARD
INTO THE CANADIAN MARITIMES TODAY...CAUSING EXTREMELY DANGEROUS
SURF AND LIFE-THREATENING RIP CURRENTS. PLEASE CONSULT STATEMENTS
ISSUED BY YOUR LOCAL WEATHER OFFICE AND METEOROLOGICAL SERVICES FOR
MORE DETAILS.
  
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      23/0900Z 41.2N  66.5W    75 KT
 12HR VT     23/1800Z 44.1N  63.0W    65 KT
 24HR VT     24/0600Z 47.5N  55.1W    55 KT
 36HR VT     24/1800Z 49.8N  43.8W    45 KT...EXTRATROPICAL
 48HR VT     25/0600Z 50.5N  31.0W    40 KT...EXTRATROPICAL
 72HR VT     26/0600Z 54.0N  10.0W    30 KT...EXTRATROPICAL
 96HR VT     27/0600Z 61.0N   2.0W    25 KT...EXTRATROPICAL
120HR VT     28/0600Z...ABSORBED
 
$$
FORECASTER BROWN
 

WTNT43 KNHC 231448
TCDAT3
HURRICANE BILL DISCUSSION NUMBER  33
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL032009
1100 AM AST SUN AUG 23 2009
 
AFTER THE LAST AIR FORCE MISSION INTO BILL....JUST BEFORE 1200
UTC...THE CLOUD PATTERN OF THE HURRICANE HAS BEGUN TO LOOK A LITTLE
LESS TROPICAL.  THE AIRCRAFT REPORTED A PEAK FLIGHT-LEVEL WIND OF
105 KT OVER THE EASTERN QUADRANT AROUND 1100 UTC.  TYPICALLY THIS
WOULD SUPPORT A HIGHER INTENSITY OF GREATER THAN 75 KT. 
HOWEVER...SINCE THE CYCLONE IS TRAVERSING COOLER WATERS...IT IS
BECOMING INCREASINGLY DIFFICULT FOR IT TO TRANSPORT STRONG WINDS TO
THE SURFACE.  GIVEN THAT...ALONG WITH THE DETERIORATION OF THE
CLOUD PATTERN...THE CURRENT INTENSITY IS HELD AT 75 KT.  BILL IS
EXPECTED TO BECOME AN EXTRATROPICAL STORM WITHIN A DAY OR SO AND
GRADUALLY WEAKEN AS IT MOVES RAPIDLY ACROSS THE NORTH ATLANTIC. 
GLOBAL MODELS SUGGEST THAT THE SYSTEM WILL MERGE WITH A BROADER
CYCLONIC CIRCULATION NEAR THE BRITISH ISLES IN 3-4 DAYS.
 
CURRENT MOTION IS AROUND 045/29.  BILL SHOULD CONTINUE ACCELERATING
OVER THE NEXT 24-36 HOURS AS IT BECOMES WELL EMBEDDED IN THE
MID-LATITUDE WESTERLIES.  SOME SLOWING OF THE FORWARD SPEED IS
LIKELY LATER IN THE PERIOD AS THE EXTRATROPICAL REMNANT OF BILL
INTERACTS WITH THE LARGE CYCLONIC CIRCULATION OVER THE NORTHEAST
ATLANTIC.  THE CURRENT OFFICIAL TRACK FORECAST IS SIMILAR TO THE
PREVIOUS ONE.
 
LARGE AND DANGEROUS SWELLS ASSOCIATED WITH BILL WILL BE IMPACTING
THE CANADIAN MARITIMES DURING THE NEXT 24 HOURS.  SWELLS ALONG THE
EAST COAST OF THE UNITED STATES SHOULD BE DIMINISHING TODAY.
  
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      23/1500Z 43.3N  64.0W    75 KT
 12HR VT     24/0000Z 46.3N  59.1W    65 KT
 24HR VT     24/1200Z 49.0N  49.7W    55 KT...EXTRATROPICAL
 36HR VT     25/0000Z 50.8N  37.4W    45 KT...EXTRATROPICAL
 48HR VT     25/1200Z 52.5N  26.5W    35 KT...EXTRATROPICAL
 72HR VT     26/1200Z 57.0N   8.0W    30 KT...EXTRATROPICAL
 96HR VT     27/1200Z...MERGED WITH ANOTHER LOW
 
$$
FORECASTER PASCH
 

WTNT43 KNHC 232036
TCDAT3
HURRICANE BILL DISCUSSION NUMBER  34
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL032009
500 PM AST SUN AUG 23 2009
 
BILL IS GRADUALLY WEAKENING WHILE LOSING SOME OF ITS TROPICAL
APPEARANCE. THE SATELLITE PRESENTATION HAS BEEN GRADUALLY
DETERIORATING...WITH THE CLOUD PATTERN BECOMING MORE ASYMMETRIC AND
THE DEEPEST CONVECTION CONFINED TO THE NORTHEAST SEMICIRCLE.
DVORAK T-NUMBERS OF 3.5 AND 4.0 FROM TAFB AND SAB...RESPECTIVELY
...AND THE ASSUMPTION OF A CONTINUED SLOW WEAKENING AS BILL
TRAVERSES COOLER WATERS...YIELD AN INITIAL INTENSITY ESTIMATE OF 65
KT FOR THIS ADVISORY. THE FORECAST CALLS FOR STEADY WEAKENING...
AND EXTRATROPICAL TRANSITION IS EXPECTED TO BE COMPLETE WITHIN 24
HOURS...IN AGREEMENT WITH THE GLOBAL MODEL GUIDANCE. BY 96 HOURS
BILL IS PREDICTED TO HAVE MERGED WITH A LARGER CYCLONIC CIRCULATION
NEAR THE BRITISH ISLES.
 
BILL HAS CONTINUED TO ACCELERATE...AND THE INITIAL MOTION ESTIMATE
IS NOW 050/030. SOME FURTHER ACCELERATION IS LIKELY DURING THE NEXT
24-36 HOURS AS THE CYCLONE BECOMES FULLY EMBEDDED WITHIN STRONG
WEST-SOUTHWESTERLY FLOW AHEAD OF A SHORTWAVE TROUGH LIFTING OUT OF
THE EASTERN UNITED STATES. BEYOND 36 HOURS...SOME SLOWING OF THE
FORWARD SPEED IS EXPECTED AS THE EXTRATROPICAL REMNANT OF BILL
INTERACTS WITH THE LARGE CYCLONIC CIRCULATION OVER THE NORTHEAST
ATLANTIC. THE OFFICIAL FORECAST REPRESENTS AN UPDATE OF THE
PREVIOUS ADVISORY...WITH NO SIGNIFICANT CHANGES.
 
LARGE AND DANGEROUS SWELLS ASSOCIATED WITH BILL WILL CONTINUE
IMPACTING THE CANADIAN MARITIMES DURING THE NEXT 12 TO 24 HOURS...
WHILE SWELLS ALONG THE EAST COAST OF THE UNITED STATES WILL CONTINUE
TO SUBSIDE TONIGHT.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      23/2100Z 45.1N  60.8W    65 KT
 12HR VT     24/0600Z 47.7N  54.5W    60 KT
 24HR VT     24/1800Z 50.0N  43.8W    50 KT...EXTRATROPICAL
 36HR VT     25/0600Z 51.5N  32.0W    40 KT...EXTRATROPICAL
 48HR VT     25/1800Z 52.5N  21.0W    35 KT...EXTRATROPICAL
 72HR VT     26/1800Z 57.0N   5.0W    30 KT...EXTRATROPICAL
 96HR VT     27/1800Z...DISSIPATED
 
$$
FORECASTER KIMBERLAIN/PASCH
 

WTNT43 KNHC 240234
TCDAT3
HURRICANE BILL DISCUSSION NUMBER  35
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL032009
1100 PM AST SUN AUG 23 2009
 
BILL STILL HAS STRUCTURAL CHARACTERISTICS OF A TROPICAL CYCLONE...
WITH DEEP CONVECTION NEAR THE CENTER AND A FRAGMENT OF AN EYEWALL
VISIBLE IN MICROWAVE IMAGERY FROM A 2304 UTC SSMIS PASS. BASED ON
THE INNER-CORE STRUCTURE...AND A DVORAK CI NUMBER OF 4.0 FROM TAFB
AT 0000 UTC...BILL IS MAINTAINED AS A 65 KT HURRICANE FOR THIS
ADVISORY.
 
BILL HAS ACCELERATED TOWARD THE EAST-NORTHEAST OVER THE PAST SEVERAL
HOURS...AND THE INITIAL MOTION ESTIMATE IS 060/35. BILL IS EXPECTED
TO REMAIN ON AN EAST-NORTHEASTWARD HEADING UNDER THE INFLUENCE OF
THE MID-LATITUDE WESTERLIES FOR THE NEXT COUPLE OF DAYS...AND THE
TRACK GUIDANCE REMAINS IN EXCELLENT AGREEMENT ON THIS SCENARIO.
AFTER 48 HOURS...BILL WILL SLOW DOWN AND TURN TOWARD THE NORTH AS
IT COMES UNDER THE INFLUENCE OF A MUCH LARGER EXTRATROPICAL CYCLONE
LOCATED SOUTHWEST OF ICELAND. BILL WILL EVENTUALLY BE ABSORBED INTO
THIS LARGER CIRCULATION BY 96 HOURS. THE NEW OFFICIAL FORECAST IS A
LITTLE FASTER THAN THE PREVIOUS PACKAGE...AND IS CLOSE TO THE
MULTI-MODEL CONSENSUS.

BILL IS BEGINNING TO UNDERGO EXTRATROPICAL TRANSITION...WITH THE
UPPER-LEVEL CLOUD PATTERN EXPANDING NORTH AND EAST OF THE CENTER IN
THE ENTRANCE REGION OF A 140-KT UPPER-LEVEL JET CORE CENTERED ALONG
55N. ALSO...DATA FROM A 2226 UTC QUIKSCAT PASS ALONG WITH NUMEROUS
SURFACE OBSERVATIONS SHOW THAT THE WIND FIELD OF BILL HAS BEGUN TO
EXPAND...PARTICULARLY IN THE SOUTHEASTERN QUADRANT. MOST OF THE
GLOBAL MODEL GUIDANCE INDICATES THAT BILL WILL COMPLETE THE
EXTRATROPICAL TRANSITION PROCESS WITHIN 12 TO 24 HOURS. AFTER THAT
TIME...UPPER-LEVEL DIVERGENCE ASSOCIATED WITH THE JET WILL HELP
MAINTAIN BILL AS AN EXTRATROPICAL CYCLONE...AND THE OFFICIAL
INTENSITY FORECAST SHOWS GRADUAL WEAKENING AS BILL MOVES ACROSS THE
NORTHERN ATLANTIC. AS BILL BECOMES FULLY EXTRATROPICAL...THE WIND
FIELD WILL CONTINUE TO EXPAND...ESPECIALLY IN THE SOUTHERN
SEMICIRCLE.
 
LARGE AND DANGEROUS SWELLS ASSOCIATED WITH BILL WILL CONTINUE
IMPACTING THE CANADIAN MARITIMES DURING THE NEXT 12 TO 24 HOURS...
WHILE SWELLS ALONG THE EAST COAST OF THE UNITED STATES WILL CONTINUE
TO SUBSIDE OVERNIGHT.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      24/0300Z 47.1N  55.5W    65 KT
 12HR VT     24/1200Z 49.1N  47.9W    55 KT
 24HR VT     25/0000Z 50.8N  36.0W    45 KT...EXTRATROPICAL
 36HR VT     25/1200Z 52.2N  24.5W    40 KT...EXTRATROPICAL
 48HR VT     26/0000Z 53.5N  14.7W    35 KT...EXTRATROPICAL
 72HR VT     27/0000Z 61.0N   2.0W    30 KT...EXTRATROPICAL
 96HR VT     28/0000Z...DISSIPATED
 
$$
FORECASTER BRENNAN
 

WTNT43 KNHC 240843
TCDAT3
TROPICAL STORM BILL DISCUSSION NUMBER  36
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL032009
500 AM AST MON AUG 24 2009
 
SATELLITE IMAGERY AS WELL AS RADAR AND SURFACE DATA FROM
NEWFOUNDLAND CANADA INDICATE THAT BILL HAS QUICKLY LOST TROPICAL
CHARACTERISTICS THIS MORNING.  THE CLOUD PATTERN HAS BECOME
INCREASING ASYMMETRIC WITH THE STRONGEST WINDS AND COLDEST CLOUD 
TOPS WELL REMOVED FROM THE CENTER. THE SYSTEM IS RAPIDLY MOVING
EAST-NORTHEASTWARD WITHIN A BAND OF STRONG UPPER-LEVEL WESTERLY
WINDS ASSOCIATED WITH THE SOUTHERN EXTENT OF A POLAR JET THAT IS
LOCATED JUST TO THE NORTH OF THE CYCLONE.  THE INITIAL INTENSITY
ESTIMATE IS 60 KT...WHICH IS BASED PRIMARILY ON BUOY...SHIP...AND
LAND OBSERVATIONS THAT RECORDED 50-56 KT WINDS DURING THE PAST 6
HOURS.  THE EXTRATROPICAL LOW IS FORECAST TO GRADUALLY WEAKEN
THROUGHOUT THE FORECAST PERIOD.
 
THE CYCLONE CONTINUES TO ACCELERATE EAST-NORTHWESTWARD WITH AN
INITIAL MOTION ESTIMATE OF 075/37.  BILL SHOULD CONTINUE TO MOVE
RAPIDLY EAST-NORTHEASTWARD ACROSS THE NORTH ATLANTIC DURING THE
NEXT DAY OR SO.  THE GLOBAL MODELS INDICATE THAT BILL WILL SLOW
DOWN AS IT INTERACTS WITH A LARGE EXTRATROPICAL LOW SOUTHWEST OF
ICELAND IN A COUPLE OF DAYS.  THE MODELS SUGGEST THAT THE
EXTRATROPICAL REMNANTS OF BILL WILL BE ABSORBED INTO THE LARGER LOW
SHORTLY THEREAFTER.  THE OFFICIAL FORECAST IS SIMILAR TO THE
PREVIOUS ADVISORY AND IS CLOSE TO THE MODEL CONSENSUS.

THIS WILL BE THE LAST NHC ADVISORY ON BILL.  ADDITIONAL INFORMATION
ON THIS SYSTEM CAN BE FOUND IN HIGH SEAS FORECASTS ISSUED BY THE
NATIONAL WEATHER SERVICE...UNDER AWIPS HEADER NFDHSFAT1 AND WMO
HEADER FZNT01 KWBC.

FORECAST POSITIONS AND MAX WINDS
 
INITIAL      24/0900Z 48.6N  50.2W    60 KT...EXTRATROPICAL
 12HR VT     24/1800Z 50.0N  41.5W    55 KT...EXTRATROPICAL
 24HR VT     25/0600Z 51.5N  29.5W    45 KT...EXTRATROPICAL
 36HR VT     25/1800Z 52.5N  19.0W    40 KT...EXTRATROPICAL
 48HR VT     26/0600Z 55.0N  11.0W    35 KT...EXTRATROPICAL
 72HR VT     27/0600Z 62.5N   1.0W    30 KT...EXTRATROPICAL
 96HR VT     28/0600Z...DISSIPATED
 
$$
FORECASTER BROWN/ROBERTS
 

