WTNT42 KNHC 062050
TCDAT2
SUBTROPICAL STORM OTTO DISCUSSION NUMBER   3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL172010
500 PM AST WED OCT 06 2010
 
SATELLITE IMAGERY AND DATA FROM AN AIR FORCE RESERVE RECONNAISSANCE
UNIT AIRCRAFT INDICATE THAT THE SUBTROPICAL DEPRESSION HAS
CONTINUED TO BECOME BETTER ORGANIZED AND HAS STRENGTHEN INTO
SUBTROPICAL STORM OTTO. CONVECTIVE BANDING NOW WRAPS ABOUT 75
PERCENT AROUND THE BROAD INNER CORE WIND FIELD. MAXIMUM 1500-FT
FLIGHT-LEVEL WINDS OBSERVED HAVE BEEN 63 KT IN THE SOUTHWESTERN
QUADRANT...WHICH CORRESPONDS TO ABOUT 50 KT AT THE SURFACE. THIS
VALUE IS CLOSE TO THE 48 KT CREDIBLE SFMR WINDS OBSERVED IN THE
SAME AREA...SO THE INITIAL INTENSITY IS SET AT 50 KT. VISIBLE AND
WATER VAPOR SATELLITE IMAGERY INDICATE THAT A SMALL UPPER-LEVEL
COLD LOW...LOCATED PREVIOUSLY IN THE SOUTHEAST QUADRANT...HAS MOVED
CYCLONICALLY AROUND THE LOW-LEVEL CIRCULATION AND IS NOW SITUATED
ABOUT 30 NMI WEST OF THE LOW-LEVEL CENTER. THIS SUGGESTS THAT OTTO
IS STILL A SUBTROPICAL CYCLONE...BUT THAT IT IS ALSO GRADUALLY
ACQUIRING TROPICAL CHARACTERISTICS.

THE INITIAL MOTION ESTIMATE IS 360/4. THERE ARE NO SIGNIFICANT
CHANGES TO THE PREVIOUS FORECAST TRACK OR REASONING. OTTO IS MOVING
NORTHWARD THROUGH A BROAD WEAKNESS IN A DEEP-LAYER RIDGE WHERE
STEERING CURRENTS ARE WEAK. HOWEVER...A STRONG MID-TROPOSPHERIC
TROUGH LOCATED OVER THE EASTERN U.S. IS FORECAST TO MOVE EASTWARD
AND GRADUALLY NUDGE OTTO ON A NORTHEASTWARD TRACK DURING THE NEXT
24 HOURS...AND THEN RAPIDLY ACCELERATE THE CYCLONE TO THE
EAST-NORTHEAST AHEAD OF A STRONG COLD FRONT BY 36 HOURS. BETWEEN 72
AND 96 HOURS...OTTO IS EXPECTED TO MERGE WITH THE COLD FRONT AND
BECOME A STRONG EXTRATROPICAL LOW PRESSURE SYSTEM THAT MAY POSE A
THREAT TO THE AZORES ISLANDS BY 120 HOURS. THE FORECAST TRACK IS
JUST AN UPDATE OF THE PREVIOUS ADVISORY TRACK AND IS DOWN THE
MIDDLE OF THE TIGHTLY PACKED NHC MODEL GUIDANCE.
 
OTTO IS EXPECTED TO TRANSITION INTO A TROPICAL CYCLONE WITHIN THE
NEXT 12 HOURS OR SO DUE TO A COMBINATION OF LIGHT VERTICAL WIND
SHEAR...WARM SSTS OF AT LEAST 28C...AND THE EXPECTED DISSIPATION OF
THE SMALL UPPER-LEVEL LOW. THE OFFICIAL INTENSITY FORECAST NOW
CALLS FOR OTTO TO REACH HURRICANE STRENGTH BY 36 HOURS...AND THEN
GRADUALLY WEAKEN AS THE WIND SHEAR INCREASES AHEAD OF THE
AFOREMENTIONED STRONG UPPER-LEVEL TROUGH. BY 96 HOURS...OTTO IS
EXPECTED TO TRANSITION INTO AN EXTRATROPICAL LOW. THE OFFICIAL
INTENSITY FORECAST IS A COMPROMISE OF THE STRONGER SHIPS/LGEM
MODELS AND THE WEAKER GFDL/HWRF MODELS.

 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      06/2100Z 23.2N  68.3W    50 KT
 12HR VT     07/0600Z 23.8N  68.5W    55 KT
 24HR VT     07/1800Z 24.5N  67.9W    60 KT
 36HR VT     08/0600Z 25.5N  66.4W    65 KT
 48HR VT     08/1800Z 26.8N  63.7W    65 KT
 72HR VT     09/1800Z 30.3N  55.8W    55 KT
 96HR VT     10/1800Z 34.5N  44.5W    40 KT...POST-TROP/EXTRATROP
120HR VT     11/1800Z 39.0N  31.0W    35 KT...POST-TROP/EXTRATROP
 
$$
FORECASTER STEWART
 

WTNT42 KNHC 070235
TCDAT2
SUBTROPICAL STORM OTTO DISCUSSION NUMBER   4
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL172010
1100 PM AST WED OCT 06 2010
 
AFTER THE LAST ADVISORY WAS ISSUED...THE HURRICANE HUNTER AIRCRAFT
MADE ONE MORE PASS THROUGH THE CENTER OF OTTO AND MEASURED A PEAK
1500-FT FLIGHT-LEVEL WIND OF 68 KT IN THE SOUTHEASTERN QUADRANT...
CORRESPONDING TO ABOUT 54 KT AT THE SURFACE.  AN SFMR WIND OF 55 KT
WAS ALSO REPORTED EARLIER IN THE MISSION...AND THAT WILL BE THE
INITIAL INTENSITY IN THIS ADVISORY.  WATER VAPOR AND INFRARED
IMAGERY SHOW THAT THE SURFACE AND UPPER-LEVEL LOW ARE ALMOST
COLLOCATED...BUT RECENT AMSU DATA INDICATE THAT THE WARM CORE IN
THE MID-LEVELS OF THE CIRCULATION IS STRENGTHENING.  ALTHOUGH OTTO
STILL LOOKS LIKE A CLASSIC SUBTROPICAL CYCLONE IN SATELLITE
IMAGERY...IT APPEARS TO BE SLOWLY GAINING TROPICAL CHARACTERISTICS.

VERTICAL SHEAR IS EXPECTED TO BE LIGHT FOR THE NEXT 48 HOURS OR
SO...AND THE CYCLONE HAS AN OPPORTUNITY TO STRENGTHEN DURING THAT
PERIOD.  THE STATISTICAL INTENSITY GUIDANCE SHOWS THE MOST
STRENGTHENING AND BRINGS OTTO TO AN 80-KT HURRICANE...BUT THESE
MODELS PROBABLY DO NOT HANDLE TRANSITIONING SUBTROPICAL CYCLONES AS
WELL AS PURE TROPICAL CYCLONES.  THE OFFICIAL FORECAST LEANS CLOSER
TO THE DYNAMICAL HURRICANE AND GLOBAL MODELS AND SHOWS OTTO
REACHING 65 KT FROM 24 TO 48 HOURS BEFORE THE SHEAR INCREASES. 
GRADUAL WEAKENING IS EXPECTED THEREAFTER WITH OTTO BECOMING AN
EXTRATROPICAL CYCLONE BY 96 HOURS...IF NOT SOONER.

THE INITIAL MOTION IS 360/3.  THE TRACK GUIDANCE REMAINS IN
GENERALLY GOOD AGREEMENT...AND LITTLE CHANGE WAS REQUIRED TO THE
PREVIOUS FORECAST TRACK.  OTTO SHOULD MOVE LITTLE FOR THE NEXT 12
HOURS OR SO BEFORE ACCELERATING NORTHEASTWARD BETWEEN A MID-LEVEL
HIGH OVER THE CENTRAL ATLANTIC AND A MID/UPPER-LEVEL TROUGH OVER
THE WESTERN ATLANTIC.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      07/0300Z 23.5N  68.2W    55 KT
 12HR VT     07/1200Z 23.9N  68.1W    60 KT
 24HR VT     08/0000Z 24.7N  66.9W    65 KT
 36HR VT     08/1200Z 26.0N  64.8W    65 KT
 48HR VT     09/0000Z 27.8N  61.6W    65 KT
 72HR VT     10/0000Z 32.0N  52.0W    60 KT
 96HR VT     11/0000Z 37.0N  38.5W    45 KT...POST-TROP/EXTRATROP
120HR VT     12/0000Z 42.0N  27.0W    40 KT...POST-TROP/EXTRATROP
 
$$
FORECASTER BERG
 

WTNT42 KNHC 070842
TCDAT2
SUBTROPICAL STORM OTTO DISCUSSION NUMBER   5
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL172010
500 AM AST THU OCT 07 2010

OTTO HAS BEEN STRUGGLING TO PRODUCE MUCH CONVECTION DURING THE
OVERNIGHT HOURS.  A CURVED OUTER BAND PERSISTS IN THE SOUTHERN
SEMICIRCLE OF THE STORM...WITH A SMALL AMOUNT OF CONVECTION NEAR
THE CENTER.  SINCE THE CLOUD PATTERN HAS DETERIORATED A LITTLE
BIT...THE MAXIMUM WINDS ARE REDUCED TO 50 KT...IN AGREEMENT WITH
VARIOUS SATELLITE INTENSITY ESTIMATES FROM 35 TO 50 KT.  IF THE
CONVECTION NEAR THE CENTER CONTINUES...THEN OTTO WILL LIKELY
TRANSITION INTO A TROPICAL STORM LATER TODAY.  THE SYSTEM STILL HAS
DAY OR TWO OF LIGHT SHEAR CONDITIONS AND WARM WATER TO INTENSIFY. 
IN FACT...ALL OF THE GUIDANCE SHOW OTTO BECOMING A HURRICANE...AND
THE NHC FORECAST WILL GO ALONG WITH THAT SCENARIO.  HOWEVER...OTTO
PROBABLY NEEDS TO SHED ITS SUBTROPICAL CHARACTERISTICS TO TAKE
ADVANTAGE OF THE FAVORABLE ENVIRONMENT.  SINCE THE SYSTEM IS STILL
RETAINING SOME SUBTROPICAL FEATURES...THE NHC FORECAST REMAINS
BELOW THE MODEL CONSENSUS.  GLOBAL MODELS SHOW OTTO BECOMING
EMBEDDED WITHIN A FRONTAL ZONE BY 72 HR...SO EXTRATROPICAL STATUS
IS INDICATED IN THE OFFICIAL FORECAST AT THAT TIME.

THE STORM HAS NOT BEEN MOVING MUCH DURING THE PAST FEW HOURS AND IS
ONLY DRIFTING NORTHWARD.  INITIALLY...OTTO IS IN AN AREA OF LIGHT
STEERING CURRENTS BETWEEN A DISTANT RIDGE OVER THE EAST-CENTRAL
ATLANTIC OCEAN AND A MID-LATITUDE TROUGH OVER THE WESTERN ATLANTIC. 
THE TROUGH IS EXPECTED TO DIG SOUTHEASTWARD TODAY...WHICH SHOULD
STEER OTTO MORE TO THE NORTHEAST AND CAUSE A FASTER FORWARD SPEED
AS THE STORM MOVES IN FASTER FLOW BETWEEN THE RIDGE AND THE TROUGH.
WHILE THE MODEL GUIDANCE REMAINS WELL CLUSTERED ON THIS SYNOPTIC
PATTERN...THERE ARE SOME NOTABLE SPEED DIFFERENCES...AS THE
GFDL/HWRF ARE MUCH FASTER THAN THE REST OF THE GUIDANCE.  FOR NOW
THE TRACK FORECAST WILL STAY CLOSER TO THE GLOBAL MODELS...SHOWING
A SLOWER FORWARD MOTION...AND THE PREVIOUS NHC FORECAST.  THE
96 AND 120 HR POSITIONS OF OTTO MAY HAVE TO BE ADJUSTED SOUTHWARD
LATER TODAY DUE TO THE POSSIBILITY THAT THE CYCLONE GETS CAUGHT UP
IN NORTHWESTERLY FLOW FROM A TROUGH EAST OF THE AZORES...RATHER
THAN MID-LATITUDE SOUTHWESTERLY FLOW AS EARLIER MODEL RUNS WERE
INDICATING.  
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      07/0900Z 23.6N  68.2W    50 KT
 12HR VT     07/1800Z 24.0N  67.7W    55 KT
 24HR VT     08/0600Z 25.1N  66.0W    60 KT
 36HR VT     08/1800Z 26.8N  63.3W    65 KT
 48HR VT     09/0600Z 28.8N  59.7W    60 KT
 72HR VT     10/0600Z 33.5N  48.5W    55 KT...POST-TROP/EXTRATROP
 96HR VT     11/0600Z 38.5N  35.0W    45 KT...POST-TROP/EXTRATROP
120HR VT     12/0600Z 41.0N  25.0W    35 KT...POST-TROP/EXTRATROP
 
$$
FORECASTER BLAKE
 

WTNT42 KNHC 071442
TCDAT2
TROPICAL STORM OTTO DISCUSSION NUMBER   6
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL172010
1100 AM AST THU OCT 07 2010
 
OTTO HAS FINALLY TRANSITIONED INTO A TROPICAL CYCLONE BASED ON A
07/0935Z AMSU VERTICAL TEMPERATURE ANALYSIS PROFILE FROM UW-CIMSS
THAT INDICATED THE WARM CORE HAD MOVED UPWARD FROM THE MID-LEVELS
TO THE UPPER-LEVELS OF THE CYCLONE. A RECENT BURST OF DEEP
CONVECTION WITH CLOUD TOP TEMPERATURES NEAR -80C THAT HAS DEVELOPED
OVER THE CENTER ALSO SUPPORTS A TRANSITION TO TROPICAL CYCLONE
STATUS. SATELLITE INTENSITY ESTIMATES ARE RUNNING BETWEEN T2.0/30
KT AND T2.5/35 KT FROM TAFB...SAB...AND UW-CIMSS USING A CURVED
BAND PATTERN. HOWEVER...USING A SHEAR PATTERN WITH THE RECENT BURST
OF CENTRAL CONVECTION YIELDS A VALUE OF T3.5/55 KT. SINCE THE
CONVECTION HAS ONLY PERSISTED FOR ABOUT 3-4 HOURS...THE INITIAL
INTENSITY WILL BE MAINTAINED AT 50 KT FOR THIS ADVISORY...BUT THE
50-KT WIND RADII DISTANCE HAS BEEN REDUCED FROM 45 NMI TO 15 NMI.

OTTO HAS ESSENTIALLY BEEN STATIONARY FOR THE PAST 6 HOURS...BUT A
SLOW DRIFT TO THE NORTHEAST...OR 325/02...IS EXPECTED TO BEGIN SOON
AND THAT IS THE MOTION USED FOR THIS ADVISORY. OTHERWISE...THERE
REMAINS NO SIGNIFICANT CHANGE TO THE PREVIOUS FORECAST TRACKS OR
PHILOSOPHIES FOR THE PAST 24 HOURS. A LARGE DEEP-LAYER TROUGH ALONG
THE U.S. EAST COAST IS EXPECTED TO CONTINUE ITS EASTWARD TREK AND
GRADUALLY NUDGE OTTO TO THE NORTHEAST DURING THE NEXT 24 HOURS. BY
36-48 HOURS...HOWEVER...THE LARGE TROUGH IS FORECAST TO CAPTURE
OTTO AND ACCELERATE IT TO THE NORTHEAST AHEAD OF A STRONG COLD
FRONT. OTTO IS EXPECTED TO MERGE WITH THE FRONTAL SYSTEM BY 72
HOURS AND BECOME A SIGNIFICANT EXTRATROPICAL CYCLONE THAT COULD
AFFECT THE AZORES ISLANDS IN 96 TO 120 HOURS. THE OFFICIAL FORECAST
TRACK IS BASICALLY JUST AN UPDATE OF THE PREVIOUS TRACK AND IS
CLOSE TO THE CONSENSUS MODEL...TVCN.

NOW THAT OTTO HAS TRANSITIONED INTO A TROPICAL CYCLONE...THE STORM
HAS A BETTER CHANCE OF REACHING HURRICANE STATUS AS FORECAST BY THE
GFDL AND HWRF MODELS. THE VERTICAL SHEAR IS EXPECTED TO REMAIN
AROUND 10 KT OR LESS FOR THE NEXT 24 HOURS WHILE OTTO WILL BE OVER
28C OR WARMER SSTS. THE MUCH SMALLER INNER CORE WIND FIELD ALSO
SHOULD ALLOW FOR A MORE RAPID RESPONSE TO DEEP CONVECTION THAT
DEVELOPS NEAR THE CENTER. IN THE LATER FORECAST PERIODS...THE
INTENSITY HAS BEEN HELD A LITTLE HIGHER THAN WHAT WOULD TYPICALLY
BE EXPECTED FOR A CYCLONE EXPERIENCING SHEAR CONDITIONS OF 40-50 KT
DUE TO EXTRATROPICAL TRANSITION AND AN EXPECTED INFUSION OF
BAROCLINIC ENERGY THAT SHOULD HELP TO SUSTAIN THE CIRCULATION. THE
OFFICIAL INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS ADVISORY AND
IS A BLEND OF THE NHC OBJECTIVE INTENSITY GUIDANCE.

 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      07/1500Z 23.8N  68.0W    50 KT
 12HR VT     08/0000Z 24.3N  67.1W    55 KT
 24HR VT     08/1200Z 25.7N  65.0W    60 KT
 36HR VT     09/0000Z 27.6N  61.8W    65 KT
 48HR VT     09/1200Z 29.8N  57.2W    60 KT
 72HR VT     10/1200Z 34.7N  45.2W    55 KT...POST-TROP/EXTRATROP
 96HR VT     11/1200Z 39.0N  32.5W    45 KT...POST-TROP/EXTRATROP
120HR VT     12/1200Z 39.0N  25.0W    35 KT...POST-TROP/EXTRATROP
 
$$
FORECASTER STEWART
 

WTNT42 KNHC 072035
TCDAT2
TROPICAL STORM OTTO DISCUSSION NUMBER   7
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL172010
500 PM AST THU OCT 07 2010
 
BURSTS OF DEEP CONVECTION WITH CLOUD TOP TEMPERATURES OF -70C TO
-80C HAVE CONTINUED TO DEVELOP OVER AND EAST OF THE LOW-LEVEL
CENTER DURING THE PAST 6 HOURS. SHEAR PATTERN SATELLITE INTENSITY
ESTIMATES HAVE BEEN VARYING BETWEEN T3.0/45 KT AND T3.5/55 KT.
THEREFORE...THE INITIAL INTENSITY WILL REMAIN AT 50 KT.  ALTHOUGH 
A SMALL UPPER-LEVEL ANTICYCLONE HAS DEVELOPED OVER THE CENTER OF
OTTO...LOWER CIRRUS CLOUD ELEMENTS CAN BE SEEN UNDERCUTTING THE
FAVORABLE OUTFLOW LAYER IN VISIBLE AND WATER VAPOR IMAGERY...WHICH
IS CREATING SOME MODEST UPPER-LEVEL SHEAR CONDITIONS ON THE CYCLONE.
 
THE INITIAL MOTION ESTIMATE IS 050/05. OTTO IS COMING UNDER THE
INCREASING INFLUENCE OF A LARGE DEEP-LAYER TROUGH THAT HAS MOVED
EASTWARD OFF THE U.S. EAST COAST. THE TROUGH IS FORECAST BY ALL OF
THE MODELS TO CONTINUE MOVING EASTWARD AND STEADILY ACCELERATE OTTO
TO THE NORTHEAST DURING THE NEXT 48 HOURS. BY 72 HOURS...OTTO IS
EXPECTED TO MERGE WITH A FRONTAL SYSTEM AND BECOME AN EXTRATROPICAL
CYCLONE AND GALE AREA THAT COULD AFFECT THE AZORES ISLANDS IN 96 TO
120 HOURS. THE OFFICIAL FORECAST TRACK IS SIMILAR TO THE PREVIOUS
ADVISORY TRACK AND IS CLOSE TO THE CONSENSUS MODEL...TVCN.

SLOW STRENGTHENING IS EXPECTED DURING THE NEXT 24 HOURS OR SO WHILE
OTTO REMAINS OVER WARM SSTS AND ALSO MOVES INTO AN AREA OF
INCREASING INSTABILITY LOCATED IN THE EASTERN SEMICIRCLE. VERTICAL
WIND SHEAR IS EXPECTED TO DECREASE SLIGHTLY BETWEEN 24 AND 36
HOURS...AND THAT IS WHEN OTTO COULD POSSIBLY REACH HURRICANE
STRENGTH AS SUGGESTED BY THE GFDL/HWRF MODELS. HOWEVER...THIS WOULD
LIKELY BE SHORT-LIVED DUE TO INCREASING WESTERLY SHEAR. BY 72
HOURS...OTTO IS EXPECTED TO ENCOUNTER STRONGER SHEAR OF 35-40
KT...WHICH SHOULD HASTEN THE WEAKENING PROCESS. HOWEVER...OTTO IS
EXPECTED TO BE AN EXTRATROPICAL GALE AREA BY THAT TIME...AND THE
INFUSION OF BAROCLINIC ENERGY SHOULD HELP MAINTAIN THE CYCLONE. THE
OFFICIAL OFFICIAL INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS
ADVISORY AND IS A BLEND OF THE NHC OBJECTIVE INTENSITY GUIDANCE.


FORECAST POSITIONS AND MAX WINDS
 
INITIAL      07/2100Z 24.0N  67.6W    50 KT
 12HR VT     08/0600Z 24.7N  66.3W    55 KT
 24HR VT     08/1800Z 26.1N  63.8W    60 KT
 36HR VT     09/0600Z 28.4N  59.7W    60 KT
 48HR VT     09/1800Z 30.8N  54.5W    55 KT
 72HR VT     10/1800Z 35.7N  42.3W    50 KT...POST-TROP/EXTRATROP
 96HR VT     11/1800Z 39.0N  29.0W    40 KT...POST-TROP/EXTRATROP
120HR VT     12/1800Z 37.0N  23.5W    35 KT...POST-TROP/EXTRATROP
 
$$
FORECASTER STEWART
 

WTNT42 KNHC 080241
TCDAT2
TROPICAL STORM OTTO DISCUSSION NUMBER   8
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL172010
1100 PM AST THU OCT 07 2010
 
A LITTLE BIT OF WESTERLY SHEAR IS AFFECTING OTTO...AND THE LOW-LEVEL
CENTER IS EMBEDDED BENEATH THE WESTERN SIDE OF A NEARLY CIRCULAR
AREA OF DEEP CONVECTION.  SATELLITE INTENSITY ESTIMATES ARE T3.5/55
KT AND T3.0/45 KT FROM TAFB AND SAB...RESPECTIVELY...AND THE
INITIAL INTENSITY WILL BE MAINTAINED AT 50 KT.  STRENGTHENING IS
STILL POSSIBLE DURING THE NEXT 48 HOURS SINCE THE VERTICAL SHEAR IS
EXPECTED TO BE RELATIVELY LIGHT.  THE ONE BIG CHANGE IN THE
INTENSITY GUIDANCE IS THAT MOST OF THE MODELS NOW SHOW A PEAK IN
INTENSITY OCCURRING AROUND 48 HOURS...WHICH IS ABOUT 12 HOURS LATER
THAN INDICATED IN THE PREVIOUS ADVISORY.  THE NEW FORECAST...
THEREFORE...DOES NOT SHOW WEAKENING COMMENCING UNTIL AFTER 48
HOURS.  THIS SOLUTION IS CLOSE TO THE STATISTICAL AND GLOBAL
GUIDANCE BUT TENDS TO DISREGARD THE HWRF AND GFDL SINCE THOSE
MODELS APPEAR TO DISSIPATE OTTO TOO SOON.

THE INITIAL MOTION IS 070/8.  THE CYCLONE IS BEING PICKED UP BY A
LARGE MID/UPPER-LEVEL TROUGH OVER THE WESTERN ATLANTIC AND IS
EXPECTED TO BECOME EMBEDDED WITHIN FAST MID-LATITUDE WESTERLIES
OVER THE NEXT 24-48 HOURS.  BY THE END OF THE FORECAST...MODEL
GUIDANCE SUGGESTS THAT THE FLOW WILL SPLIT WITH THE POST-TROPICAL
CYCLONE TAKING THE SOUTHERN ROUTE AND SLOWING DOWN AS IT NEARS THE
AZORES.  THE OFFICIAL FORECAST IS NOT MUCH DIFFERENT FROM THE
PREVIOUS ONE AND GENERALLY LIES BETWEEN THE FASTER ECMWF AND SLOWER
GFS.

THE FSU PHASE SPACE DIAGRAMS SHOW THAT OTTO SHOULD BEGIN
EXTRATROPICAL TRANSITION IN THE NEXT 24-36 HOURS...BUT THEY ALSO
SUGGEST THAT IT WILL NOT BECOME A DEEP COLD-CORE SYSTEM WITHIN THE
5-DAY FORECAST PERIOD.  AS SUCH...CONFIDENCE IS NOT HIGH THAT OTTO
WILL BECOME COMPLETELY EXTRATROPICAL BY 72 HOURS.

FORECAST POSITIONS AND MAX WINDS
 
INITIAL      08/0300Z 24.1N  66.6W    50 KT
 12HR VT     08/1200Z 24.9N  65.1W    55 KT
 24HR VT     09/0000Z 26.7N  62.0W    55 KT
 36HR VT     09/1200Z 29.0N  57.6W    60 KT
 48HR VT     10/0000Z 31.4N  52.1W    60 KT
 72HR VT     11/0000Z 36.5N  38.5W    50 KT...POST-TROP/EXTRATROP
 96HR VT     12/0000Z 39.0N  27.0W    45 KT...POST-TROP/EXTRATROP
120HR VT     13/0000Z 36.5N  23.0W    35 KT...POST-TROP/EXTRATROP
 
$$
FORECASTER BERG
 

WTNT42 KNHC 080842
TCDAT2
TROPICAL STORM OTTO DISCUSSION NUMBER   9
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL172010
500 AM AST FRI OCT 08 2010
 
SATELLITE IMAGES INDICATE THAT DEEP AND SYMMETRIC CONVECTION HAS
INTENSIFIED NEAR THE CENTER OF OTTO DURING THE PAST SEVERAL HOURS
WITH AN OCCASIONAL HINT OF A WARM SPOT IN THE INFRARED CHANNEL. 
UNFORTUNATELY THERE HAVE BEEN NO RECENT MICROWAVE OVERPASSES TO
HELP LOCATE THE CENTER...WHICH HANDICAPS THE INTENSITY ESTIMATE. 
DVORAK NUMBERS FROM TAFB/SAB ARE 65/55 KT...AND A BLEND OF THESE
DATA GIVE AN INITIAL WIND SPEED OF 60 KT.  THE SHIPS MODEL SUGGESTS
THAT SOUTHWESTERLY SHEAR WILL RELAX NEAR OTTO DURING THE NEXT 24
HOURS...WHICH SHOULD ALLOW THE STORM TO BECOME A HURRICANE. 
GUIDANCE IS NOW IN AGREEMENT ON OTTO ATTAINING HURRICANE STRENGTH
LATER TODAY.  SINCE ANY SUBTROPICAL CHARACTERISTICS ARE NOW
GONE...I DO NOT SEE A GOOD REASON TO DISCOUNT THE GUIDANCE...AND
THE OFFICIAL FORECAST IS RAISED FROM THE PREVIOUS ONE...JUST BELOW
THE MODEL CONSENSUS.  WEAKENING SEEMS LIKELY IN A COUPLE OF DAYS
DUE TO WATERS COOLING BELOW 26C AND INCREASING SOUTHWESTERLY SHEAR.   

BASED PRIMARILY ON CONTINUITY FROM THE PREVIOUS FORECAST TRACK...THE
INITIAL MOTION IS 060/12.  OTTO IS BEING ACCELERATED GENERALLY
NORTHEASTWARD BY A LARGE MID-LATITUDE TROUGH OVER THE WESTERN
ATLANTIC OCEAN.  THE TROPICAL CYCLONE SHOULD BECOME EMBEDDED WITHIN
FAST SOUTHWESTERLY FLOW FOR THE NEXT TWO TO THREE DAYS...AND MODEL
GUIDANCE IS IN GOOD AGREEMENT ON THE TRACK DURING THAT TIME. 
HOWEVER...LARGE DISAGREEMENTS OCCUR IN THE LONG RANGE AS IT IS NOT
CLEAR WHETHER OTTO WILL REMAIN WITHIN THE MID-LATITUDE FLOW OR TURN
MORE TO THE EAST AND SOUTHEAST AROUND THE WEST SIDE OF A TROUGH
OVER THE FAR NORTHEASTERN ATLANTIC OCEAN.  THE MOST RELIABLE
GUIDANCE SHOW THE LATTER SOLUTION...AND THE OFFICIAL FORECAST WILL
STAY WITH THAT SCENARIO.  

EXTRATROPICAL TRANSITION WILL PROBABLY BEGIN AFTER THE CYCLONE
CROSSES 30N AS THE CYCLONE MOVES OVER COOLER WATERS AND INTO HIGHER
SHEAR.  FSU PHASE SPACE DIAGRAMS...HOWEVER...SUGGEST THAT OTTO WILL
RETAIN ITS WARM CORE FOR SEVERAL DAYS.  THE MODEL THICKNESS FIELDS
DO SHOW THE CYCLONE DEVELOPING FRONTAL FEATURES IN ABOUT THREE
DAYS... THUS EXTRATROPICAL STATUS IS SHOWN AT THAT TIME.  

 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      08/0900Z 24.8N  65.5W    60 KT
 12HR VT     08/1800Z 25.9N  63.6W    65 KT
 24HR VT     09/0600Z 28.0N  60.1W    70 KT
 36HR VT     09/1800Z 30.3N  55.2W    75 KT
 48HR VT     10/0600Z 33.2N  49.0W    70 KT
 72HR VT     11/0600Z 38.5N  34.0W    55 KT...POST-TROP/EXTRATROP
 96HR VT     12/0600Z 39.0N  25.5W    45 KT...POST-TROP/EXTRATROP
120HR VT     13/0600Z 36.5N  21.5W    35 KT...POST-TROP/EXTRATROP
 
$$
FORECASTER BLAKE
 

WTNT42 KNHC 081431
TCDAT2
HURRICANE OTTO DISCUSSION NUMBER  10
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL172010
1100 AM AST FRI OCT 08 2010
 
SATELLITE IMAGES INDICATE THAT OTTO IS STEADILY INCREASING IN
ORGANIZATION.  THE CYCLONE HAS DEVELOPED A WELL DEFINED AND LARGE
CENTRAL DENSE OVERCAST DURING THE LAST 6-12 HOURS...WITH A CURVED
BAND OVER THE SOUTHEAST QUADRANT ATTACHED TO THE MAIN CONVECTIVE
MASS.  A 1059 UTC SSMIS OVERPASS SHOWED THE DEVELOPMENT OF A
MID-LEVEL EYEWALL...ALTHOUGH THE LOW-LEVEL CENTER APPEARS TO BE A
BIT TO THE WEST OF THAT FEATURE. DVORAK T-NUMBERS ARE AT 4.0 FROM
TAFB AND SAB...AND OTTO IS UPGRADED TO A HURRICANE BASED UPON THESE
DATA AND THE EARLIER MICROWAVE OVERPASS.  THE SHIPS MODEL OUTPUT
INDICATES THAT OTTO SHOULD REMAIN IN A GENERALLY LIGHT SHEAR
ENVIRONMENT DURING THE NEXT 24 HOURS AND OVER MARGINALLY WARM
WATERS...BOTH OF WHICH SHOULD LEAD TO SOME ADDITIONAL
INTENSIFICATION.  AFTER THAT...WEAKENING SHOULD OCCUR AS OTTO
ENCOUNTERS A RAPID INCREASE IN SOUTHWESTERLY SHEAR AND MOVES OVER
PROGRESSIVELY COOLER WATERS.  THE OFFICIAL INTENSITY FORECAST IS
SIMILAR TO THE PREVIOUS ONE AND CLOSE TO THE SHIPS/LGEM INTENSITY
GUIDANCE.
 
OTTO HAS CONTINUED TO ACCELERATE EAST-NORTHEASTWARD...AND THE LATEST
FIXES SUGGEST AN INITIAL MOTION OF 060/15.  THE TRACK GUIDANCE IS
IN GOOD AGREEMENT THAT OTTO SHOULD ACCELERATE FURTHER ON A
GENERALLY NORTHEASTWARD COURSE DURING THE NEXT 2-3 DAYS...EMBEDDED
IN A SWIFT SOUTHWESTERLY FLOW ASSOCIATED WITH A DEEP LAYER TROUGH
COVERING THE NORTHWEST ATLANTIC. BEYOND ABOUT 72 HOURS...OTTO IS
EXPECTED TO SEPARATE FROM THE MID-LATITUDE SOUTHWESTERLY FLOW AND
TURN EASTWARD AND THEN SOUTHEASTWARD ON THE WEST SIDE OF A TROUGH
OVER THE NORTHEAST ATLANTIC AND WESTERN EUROPE.  ALTHOUGH THIS
SOLUTION IS GENERALLY FAVORED BY GLOBAL MODELS...THERE REMAINS SOME
SPREAD IN THE GUIDANCE AS TO WHERE AND WHEN THE EXPECTED TURN
TOWARD THE EAST SHOULD OCCUR.  THE OFFICIAL FORECAST TRACK IS CLOSE
TO THE PREVIOUS ONE THROUGH 48 HOURS AND IS ADJUSTED A BIT TO THE
LEFT BEYOND THAT TIME...FOLLOWING THE TREND IN THE GUIDANCE.
 
EXTRATROPICAL TRANSITION WILL LIKELY BEGIN IN ABOUT 48 HOURS ONCE
OTTO BECOMES MORE DEEPLY INVOLVED WITH THE FAST-PACED...MID-
LATITUDE FLOW TO THE NORTH.  THERE IS STILL A FAIR AMOUNT OF
UNCERTAINTY REGARDING THE COMPLETION OF THIS PROCESS AS OTTO IS
FORECAST TO REMAIN TO THE SOUTH OF THE MAIN BAROCLINIC ZONE OVER
THE NORTH ATLANTIC.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      08/1500Z 25.9N  64.0W    65 KT
 12HR VT     09/0000Z 27.3N  61.7W    70 KT
 24HR VT     09/1200Z 29.7N  57.5W    75 KT
 36HR VT     10/0000Z 32.4N  51.9W    70 KT
 48HR VT     10/1200Z 35.5N  45.0W    65 KT
 72HR VT     11/1200Z 40.0N  31.0W    50 KT...POST-TROP/EXTRATROP
 96HR VT     12/1200Z 40.0N  24.0W    40 KT...POST-TROP/EXTRATROP
120HR VT     13/1200Z 37.0N  22.0W    35 KT...POST-TROP/EXTRATROP
 
$$
FORECASTER KIMBERLAIN
 

WTNT42 KNHC 082038
TCDAT2
HURRICANE OTTO DISCUSSION NUMBER  11
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL172010
500 PM AST FRI OCT 08 2010

OTTO CONTINUES TO MAINTAIN A CENTRAL DENSE OVERCAST WITH CLOUD TOPS
COLDER THAN -80C NEAR THE CENTER...ALONG WITH AN AREA OF OUTER
BANDING OVER THE EASTERN SEMICIRCLE.  SATELLITE INTENSITY ESTIMATES
ARE 77 KT FROM SAB AND 65 KT FROM TAFB...AND THERE IS A RECENT
CIMSS AMSU INTENSITY ESTIMATE OF 63 KT.  THE INITIAL INTENSITY IS
INCREASED TO 70 KT AS A BLEND OF THESE DATA.  THE CIRRUS OUTFLOW IS
GOOD IN THE NORTHEASTERN SEMICIRCLE AND FAIR/POOR ELSEWHERE.

THE INITIAL MOTION IS NOW 055/18.  THERE IS LITTLE CHANGE IN THE
FORECAST PHILOSOPHY...GUIDANCE...OR FORECAST TRACK DURING THE FIRST
72 HR OF THE FORECAST.  OTTO IS BECOMING EMBEDDED IN THE STRONG
SOUTHWESTERLY FLOW OVER THE CENTRAL ATLANTIC...AND IT SHOULD MOVE
RAPIDLY NORTHEASTWARD FOR THE NEXT THREE DAYS OR SO.  AFTER 72
HR...THE GUIDANCE HAS BECOME DIVERGENT.  WHILE THE GFS...GFS
ENSEMBLE MEAN...AND HWRF STILL SHOW A TURN TOWARD THE SOUTHEAST...
THE UKMET...CANADIAN...NOGAPS...AND GFDL NOW SHOW A CONTINUED
NORTHEASTWARD MOTION.  THE ECMWF IS IN BETWEEN THESE CAMPS...
FORECASTING OTTO TO MOVE NORTHEASTWARD FOR 84-96 HR BEFORE SHARPLY
TURNING IT DUE SOUTH.  THE NEW FORECAST TRACK GENERALLY FOLLOWS THE
GFS SCENARIO...BUT IS SHIFTED TO THE NORTH OUT OF RESPECT FOR THE
OTHER MODELS.  HOWEVER...THIS PART OF THE FORECAST TRACK STILL LIES
WELL TO THE RIGHT OF THE CENTER OF THE GUIDANCE ENVELOPE...AND MORE
NORTHWARD ADJUSTMENT OF THE TRACK COULD BE NEEDED LATER.
 
OTTO WILL SPEND 12-24 HR IN A LIGHT VERTICAL WIND SHEAR/WARM SEA
SURFACE TEMPERATURE ENVIRONMENT...AND THE INTENSITY FORECAST THUS
SHOWS A LITTLE MORE STRENGTHENING DURING THAT TIME.  AFTER 24 HR...
INCREASING SHEAR AND DECREASING SEA SURFACE TEMPERATURES SHOULD
START A WEAKENING TREND.  EXTRATROPICAL TRANSITION IS EXPECTED TO
BEGIN AT ABOUT 48 HR AND BE COMPLETE BY 72 HR.  HOWEVER...THERE IS
STILL A FAIR AMOUNT OF UNCERTAINTY REGARDING THE COMPLETION OF THIS
PROCESS DUE TO DISAGREEMENT IN THE DYNAMICAL MODELS ON HOW CLOSE
OTTO WILL BE TO THE MAIN BAROCLINIC ZONE OVER THE NORTH ATLANTIC.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      08/2100Z 26.8N  62.3W    70 KT
 12HR VT     09/0600Z 28.7N  59.5W    75 KT
 24HR VT     09/1800Z 31.3N  54.6W    75 KT
 36HR VT     10/0600Z 34.3N  48.2W    70 KT
 48HR VT     10/1800Z 38.2N  40.6W    65 KT
 72HR VT     11/1800Z 42.0N  30.0W    50 KT...POST-TROP/EXTRATROP
 96HR VT     12/1800Z 41.0N  25.0W    40 KT...POST-TROP/EXTRATROP
120HR VT     13/1800Z 39.0N  20.0W    40 KT...POST-TROP/EXTRATROP
 
$$
FORECASTER BEVEN
 

WTNT42 KNHC 090232
TCDAT2
HURRICANE OTTO DISCUSSION NUMBER  12
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL172010
1100 PM AST FRI OCT 08 2010
 
ALTHOUGH THE CENTRAL DENSE OVERCAST FEATURE HAS DECREASED IN AREAL
COVERAGE...CLOUD TOP TEMPERATURES COLDER THAN -80C HAVE PERSISTED
NEAR THE UPPER-LEVEL CENTER. A 08/2217Z SSMIS MICROWAVE OVERPASS
INDICATED THE EYE IS TILTED SIGNIFICANTLY DOWNSTREAM TO THE
NORTHEAST BY AT LEAST 35 NMI BETWEEN THE LOW- AND MID-LEVEL
CIRCULATIONS. SUBJECTIVE SATELLITE INTENSITY ESTIMATES ARE T5.0/90
KT FROM TAFB AND T4.5/77 KT FROM SAB...AND AROUND 67 KT FROM THE
UW-CIMSS ADT PROGRAM. THEREFORE...THE INITIAL INTENSITY IS BEING
INCREASED TO 75 KT...AND OTTO HAS LIKELY PEAKED IN STRENGTH GIVEN
THE EYEWALL WAS OPEN AT ALL LEVELS IN THE AFOREMENTIONED SSMIS
MICROWAVE IMAGES.
 
THE INITIAL MOTION IS 060/18. WATER VAPOR IMAGERY INDICATES OTTO IS
NOW EMBEDDED WITHIN A DEEP-LAYER WEST-SOUTHWESTERLY FLOW ON THE
EAST SIDE OF A MASSIVE MID-LATITUDE TROUGH THAT EXTENDS SOUTHWARD
FROM THE CANADIAN MARITIME PROVINCES TO THE NORTHERN BAHAMAS. THIS
FLOW REGIME SHOULD CONTINUE TO ACCELERATE OTTO TO THE NORTHEAST OR
EAST-NORTHEAST FOR THE NEXT 72 HOURS OR SO...WHICH IS CONSISTENT
WITH ALL OF THE NHC MODEL GUIDANCE. AFTER THAT...HOWEVER...THE
GUIDANCE REMAINS DIVERGENT ON WHETHER OTTO WILL CONTINUE TO MOVE TO
THE NORTHEAST OR SLOW DOWN AND TURN SOUTHEASTWARD TOWARD THE AZORES
ISLANDS.  THERE IS MUCH LESS SPREAD IN THE MODEL SOLUTIONS FOR THIS
RUN COMPARED TO THE PREVIOUS ADVISORY...SO THE FORECAST TRACK HAS
BEEN SHIFTED SLIGHTLY NORTHWARD WITH A NOTED DECREASE IN FORWARD
SPEED. OVERALL...THE OFFICIAL FORECAST IS SIMILAR TO THE CONSENSUS
MODEL...TVCN...THROUGH 72 HOURS...AND THEN A LITTLE SOUTH OF THAT
MODEL AT 96 AND 120 HOURS.
 
CONVENTIONAL INFRARED SATELLITE POSITION ESTIMATES INDICATE THAT THE
UPPER-LEVEL CIRCULATION IS OUTRUNNING THE LOW-LEVEL CENTER NOTED IN
MICROWAVE DATA BY MORE THAN 60 NMI...SO GRADUAL WEAKENING IS
FORECAST SINCE OTTO WILL BE MOVING OVER PROGRESSIVELY COOLER SSTS
AND EXPERIENCING INCREASING SOUTHWESTERLY VERTICAL SHEAR. TIMING
POSSIBLE DECOUPLING OF THE LOWER- AND UPPER-LEVEL CIRCULATIONS IS
TRICKY. HOWEVER...SINCE OTTO WILL BE MOVING OVER SUB-23C SSTS...BE
UNDERNEATH VERTICAL SHEAR CONDITIONS EXCEEDING 40 KT...AND POSSIBLY
MERGE WITH A FRONTAL ZONE BY 48 HOURS...OTTO IS EXPECTED TO BEGIN
EXTRATROPICAL TRANSITION BETWEEN 36-48 HOURS. THE INTENSITY
FORECAST IS SIMILAR TO BUT SLIGHTLY LOWER THAN A BLEND OF THE NHC
INTENSITY GUIDANCE...DUE IN PART TO THE TILTED VORTEX STRUCTURE.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      09/0300Z 27.8N  60.8W    75 KT
 12HR VT     09/1200Z 29.7N  57.4W    70 KT
 24HR VT     10/0000Z 32.6N  51.7W    70 KT
 36HR VT     10/1200Z 36.1N  44.4W    65 KT
 48HR VT     11/0000Z 40.0N  36.4W    60 KT...POST-TROP/EXTRATROP
 72HR VT     12/0000Z 43.0N  28.0W    50 KT...POST-TROP/EXTRATROP
 96HR VT     13/0000Z 43.0N  23.5W    40 KT...POST-TROP/EXTRATROP
120HR VT     14/0000Z 40.0N  20.0W    40 KT...POST-TROP/EXTRATROP
 
$$
FORECASTER STEWART
 

WTNT42 KNHC 090834
TCDAT2
HURRICANE OTTO DISCUSSION NUMBER  13
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL172010
500 AM AST SAT OCT 09 2010
 
OTTO CONTINUES TO PRODUCE DEEP CONVECTION IN A CDO WITH CLOUD TOPS
COLDER THAN -80C...HOWEVER THE CLOUD PATTERN IS BECOMING
INCREASINGLY DISTORTED DUE TO 20 TO 25 KT OF SOUTHWESTERLY SHEAR.
THIS SHEAR IS ALSO TILTING THE VORTEX NORTHEASTWARD WITH HEIGHT AS
SEEN IN A 0021 UTC SSMIS PASS. THE INITIAL INTENSITY OF 75 KT IS
BASED ON A BLEND OF DVORAK FINAL-T AND CI NUMBERS OF 4.0 TO 5.0
FROM TAFB AND SAB. SLOW WEAKENING IS EXPECTED OVER THE NEXT DAY OR
SO WHILE OTTO REMAINS A TROPICAL CYCLONE DUE TO SHEAR AND
DECREASING SEA SURFACE TEMPERATURES. GRADUAL WEAKENING SHOULD
CONTINUE BEYOND THAT TIME AS OTTO UNDERGOES EXTRATROPICAL
TRANSITION.
 
THE INITIAL MOTION ESTIMATE OF 055/21 IS UNCERTAIN DUE TO A LACK OF
RECENT MICROWAVE IMAGERY...AND IS BASED ON THE ASSUMPTION THAT THE
LOW-LEVEL CENTER CONTINUES TO LAG BEHIND THE COLDEST CLOUD TOPS.
OTTO WILL CONTINUE ACCELERATING NORTHEASTWARD OVER THE NEXT COUPLE
OF DAYS BETWEEN A LARGE DEEP-LAYER TROUGH OFF THE COAST OF NORTH
AMERICA AND A SUBTROPICAL RIDGE OVER THE EASTERN TROPICAL ATLANTIC.
THE OFFICIAL FORECAST IS A BLEND OF THE PREVIOUS PACKAGE AND THE
TVCN MULTI-MODEL CONSENSUS THROUGH 48 HOURS. BEYOND THAT TIME...
MOST OF THE GLOBAL MODELS AND THE GFS ENSEMBLE MEAN SUGGEST THAT
POST-TROPICAL OTTO WILL MOVE AROUND THE TOP OF A SHORTWAVE RIDGE
AND TURN SOUTHEASTWARD IN THE VICINITY OF THE AZORES. HOWEVER...
THERE ARE DIFFERENCES IN BOTH THE SHARPNESS OF THE SOUTHEASTWARD
TURN AND THE FORWARD SPEED. THE OFFICIAL FORECAST HAS BEEN ADJUSTED
SOUTHWARD AND WESTWARD AT DAYS 4 AND 5 TOWARD A BLEND OF THE UKMET
AND GFS MODELS...BUT CONFIDENCE IS LOWER THAN NORMAL AT THESE TIMES
DUE TO THE LARGE SPREAD IN THE GUIDANCE.
 
THE INITIAL 34-KT WIND RADII WERE ADJUSTED BASED ON A 0052 UTC ASCAT
PASS.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      09/0900Z 29.2N  58.5W    75 KT
 12HR VT     09/1800Z 31.1N  54.8W    70 KT
 24HR VT     10/0600Z 34.3N  48.3W    70 KT
 36HR VT     10/1800Z 37.7N  40.8W    65 KT
 48HR VT     11/0600Z 41.3N  33.4W    55 KT...POST-TROP/EXTRATROP
 72HR VT     12/0600Z 43.0N  27.0W    45 KT...POST-TROP/EXTRATROP
 96HR VT     13/0600Z 40.5N  24.5W    40 KT...POST-TROP/EXTRATROP
120HR VT     14/0600Z 37.0N  22.0W    40 KT...POST-TROP/EXTRATROP
 
$$
FORECASTER BRENNAN
 

WTNT42 KNHC 091435
TCDAT2
HURRICANE OTTO DISCUSSION NUMBER  14
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL172010
1100 AM AST SAT OCT 09 2010
 
THE CLOUD PATTERN ASSOCIATED WITH OTTO HAS GRADUALLY BEEN DECREASING
IN ORGANIZATION DURING THE LAST SEVERAL HOURS.  THE CENTRAL DENSE
OVERCAST THAT THE CYCLONE HAD BEEN MAINTAINING HAS BECOME
INCREASINGLY DISTORTED...AND CONVECTIVE CLOUD TOPS HAVE WARMED.  A
SERIES OF MICROWAVE OVERPASSES SUGGEST THAT THE CENTER IS LOCATED
ON THE SOUTHWEST SIDE OF THE DEEPEST CONVECTION...AND GIVE EVIDENCE
OF A PRONOUNCED TILT OF THE VORTEX DUE TO THE EFFECT OF MODERATE
SOUTHWESTERLY SHEAR.  THE INITIAL INTENSITY IS LOWERED TO 65 KT
BASED UPON DVORAK T-NUMBERS OF 3.5 AND 4.0 FROM SAB AND TAFB...
RESPECTIVELY.  FURTHER WEAKENING IS LIKELY OVER THE NEXT SEVERAL
DAYS AS OTTO ENTERS A STRONGLY SHEARED ENVIRONMENT AND MOVES OVER
PROGRESSIVELY COOLER WATERS.  GLOBAL MODELS SUGGEST THAT
EXTRATROPICAL TRANSITION MAY HAVE ALREADY BEGUN...AND THE COMPLETION
OF THIS PROCESS...ALTHOUGH STILL A BIT UNCERTAIN...IS FORECAST BY
ABOUT 48 HOURS.  THE OFFICIAL INTENSITY FORECAST IS ADJUSTED
DOWNWARD BASED UPON RECENT TRENDS AND IS IN GOOD AGREEMENT
WITH THE STATISTICAL-DYNAMICAL GUIDANCE.
 
THE MICROWAVE FIXES WERE HELPFUL IN FINDING THE CENTER OF OTTO AND
SUGGEST THAT THE HURRICANE HAS CONTINUED TO ACCELERATE...WITH AN
INITIAL MOTION ESTIMATE OF 055/25.  OTTO IS FORECAST TO ACCELERATE
FURTHER ON A GENERALLY NORTHEASTWARD COURSE DURING THE NEXT 24-36
HOURS IN BETWEEN A LARGE DEEP-LAYER TROUGH OVER THE NORTHWEST
ATLANTIC AND A SUBTROPICAL RIDGE TO ITS EAST.  ONCE POST-
TROPICAL...OTTO IS EXPECTED TO ABRUPTLY DECELERATE AND TURN
EASTWARD AND SOUTHEASTWARD AS IT ROUNDS THE TOP OF A SHORTWAVE
RIDGE AND DIVES INTO THE WEST SIDE OF A TROUGH OVER THE NORTHEAST
ATLANTIC.  ALTHOUGH THE MODEL GUIDANCE CONTINUES TO HAVE DIFFICULTY
IN PREDICTING THE SHARPNESS OF THIS TURN...THE SPREAD IN THE MODEL
SOLUTIONS HAS DECREASED SOME SINCE THE LAST CYCLE.  THE OFFICIAL
TRACK FORECAST IS BASICALLY AN UPDATE OF THE PREVIOUS ONE AND IS
CLOSE TO THE MULTI-MODEL CONSENSUS.
  
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      09/1500Z 30.7N  55.7W    65 KT
 12HR VT     10/0000Z 32.9N  51.4W    60 KT
 24HR VT     10/1200Z 36.2N  44.2W    55 KT
 36HR VT     11/0000Z 39.7N  36.7W    50 KT
 48HR VT     11/1200Z 42.5N  31.0W    45 KT...POST-TROP/EXTRATROP
 72HR VT     12/1200Z 43.0N  26.0W    35 KT...POST-TROP/EXTRATROP
 96HR VT     13/1200Z 39.6N  24.0W    30 KT...POST-TROP/EXTRATROP
120HR VT     14/1200Z 36.5N  21.5W    30 KT...POST-TROP/EXTRATROP
 
$$
FORECASTER KIMBERLAIN
 

WTNT42 KNHC 092031
TCDAT2
HURRICANE OTTO DISCUSSION NUMBER  15
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL172010
500 PM AST SAT OCT 09 2010
 
SATELLITE IMAGES INDICATE THAT OTTO IS GRADUALLY WEAKENING. WARMING
CLOUD TOPS ARE PRIMARILY LOCATED NORTH OF THE CIRCULATION CENTER AS
A CONSEQUENCE OF CONTINUED MODERATE SOUTHWESTERLY SHEAR. HOWEVER...
SATELLITE CLASSIFICATIONS SUPPORT MAINTAINING OTTO AS A HURRICANE
FOR THIS ADVISORY. FURTHER WEAKENING IS FORECAST AS OTTO ENCOUNTERS
A HIGH SHEAR ENVIRONMENT AND PASSES OVER PROGRESSIVELY COOLER
WATERS DURING THE NEXT FEW DAYS. EXTRATROPICAL TRANSITION APPEARS
TO BE UNDERWAY AS EVIDENCED BY CURRENT CONVECTIVE TRENDS AND
COLDER...DRIER AIR IMPINGING ON THE CIRCULATION FROM THE WEST.
GLOBAL MODELS INDICATE THAT THIS PROCESS SHOULD BE COMPLETE BY 36
HOURS...ALTHOUGH IT COULD FINISH EARLIER. THE OFFICIAL NHC
INTENSITY FORECAST IS ABOUT THE SAME AS THE PREVIOUS ONE AND IS IN
LINE WITH THE SHIPS/LGEM GUIDANCE.
 
OTTO IS STILL ACCELERATING...AND THE INITIAL MOTION ESTIMATE IS
055/28. SOME FURTHER ACCELERATION TOWARD THE NORTHEAST IS LIKELY
DURING THE NEXT 12-24 HOURS AS THE CYCLONE IS EMBEDDED IN A DEEP
LAYER OF STRONG SOUTHWESTERLY FLOW AHEAD OF A LARGE MID-LATITUDE
TROUGH OVER THE WESTERN ATLANTIC. AFTER 36 HOURS....OTTO SHOULD
ABRUPTLY DECELERATE AND TURN EASTWARD AND THEN SOUTHEASTWARD AS IT
STEERED AROUND THE CIRCULATION OF A DEEP LAYER CYCLONE OVER THE
NORTHEAST ATLANTIC. THE MODEL GUIDANCE...EXCEPT FOR THE NOGAPS AND
THE CANADIAN...IS IN GOOD AGREEMENT ON THIS SCENARIO...AND THE
OFFICIAL TRACK FORECAST IS CLOSE TO THE PREVIOUS ONE AND THE
MULTI-MODEL CONSENSUS.

 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      09/2100Z 32.4N  52.6W    65 KT
 12HR VT     10/0600Z 34.7N  47.6W    60 KT
 24HR VT     10/1800Z 38.0N  40.3W    55 KT
 36HR VT     11/0600Z 41.3N  33.6W    50 KT...POST-TROP/EXTRATROP
 48HR VT     11/1800Z 43.4N  29.4W    45 KT...POST-TROP/EXTRATROP
 72HR VT     12/1800Z 43.0N  25.5W    35 KT...POST-TROP/EXTRATROP
 96HR VT     13/1800Z 39.0N  24.0W    30 KT...POST-TROP/EXTRATROP
120HR VT     14/1800Z 37.0N  22.0W    30 KT...POST-TROP/EXTRATROP
 
$$
FORECASTER KIMBERLAIN
 

WTNT42 KNHC 100235
TCDAT2
TROPICAL STORM OTTO DISCUSSION NUMBER  16
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL172010
1100 PM AST SAT OCT 09 2010
 
CONVENTIONAL AND MICROWAVE SATELLITE IMAGERY INDICATE OTTO IS
QUICKLY COMING UNRAVELED. CLOUD TOPS HAVE WARMED SIGNIFICANTLY AND
THE OVERALL CONVECTIVE PATTERN HAS BECOME RATHER DISHEVELED
LOOKING. THE INITIAL INTENSITY OF 60 KT IS BASED ON A BLEND OF
SATELLITE CURRENT INTENSITY ESTIMATES OF T4.0/65 KT FROM TAFB AND
T3.5/55 KT FROM SAB...AND OTTO IS NOW A TROPICAL STORM. THE CENTRAL
PRESSURE IS BASED ON A PRESSURE REPORT OF 989.1 MB AT 23Z FROM
DRIFTING BUOY 62905 THAT OTTO PASSED OVER OR VERY CLOSE TO.

THE INITIAL MOTION ESTIMATE IS 060/33. OTTO CONTINUES TO ACCELERATE
AHEAD OF A SHARP DEEP-LAYERED TROUGH MOVING ACROSS THE CENTRAL
ATLANTIC. HOWEVER...ACCELERATION SHOULD LIKELY CEASE DURING THE
NEXT 12 HOURS OR SO AS THE LOW- AND UPPER-LEVEL CIRCULATIONS
DECOUPLE DUE TO VERTICAL SHEAR INCREASING TO MORE THAN 40 KT AND
SSTS COOLING TO BELOW 23C. BY 36 HOURS....OTTO SHOULD BE STEERED BY
THE WEAKER WESTERLY LOW-LEVEL FLOW AND SLOW DOWN AND TURN
EASTWARD...FOLLOWED BY A SOUTHEASTWARD TURN AS THE CYCLONE ROUNDS
THE TOP OF A MID-LEVEL RIDGE LOCATED WEST OF THE AZORES ISLANDS.
THE NHC TRACK GUIDANCE IS IN GOOD AGREEMENT ON THIS SCENARIO AND
THERE IS LESS SPREAD IN THE MODELS FOR THIS ADVISORY PACKAGE. THE
OFFICIAL FORECAST TRACK IS SIMILAR TO THE PREVIOUS ADVISORY...AND
REMAINS SOUTH OF THE MODEL CONSENSUS AFTER 48 HOURS.

INCREASING VERTICAL SHEAR...COMBINED WITH DECREASING SSTS AND DRY
AIR ENTRAINMENT FROM THE WEST...SHOULD HASTEN THE WEAKENING PROCESS
AND OTTO SHOULD TRANSITION TO AN EXTRATROPICAL CYCLONE IN 24 HOURS
OR LESS. THE NHC INTENSITY FORECAST IS SIMILAR TO THE SHIPS/LGEM
INTENSITY GUIDANCE.

FORECAST POSITIONS AND MAX WINDS
 
INITIAL      10/0300Z 33.9N  48.7W    60 KT
 12HR VT     10/1200Z 36.3N  43.4W    50 KT
 24HR VT     11/0000Z 39.7N  36.5W    45 KT...POST-TROP/EXTRATROP
 36HR VT     11/1200Z 42.0N  31.4W    40 KT...POST-TROP/EXTRATROP
 48HR VT     12/0000Z 43.5N  28.0W    40 KT...POST-TROP/EXTRATROP
 72HR VT     13/0000Z 42.0N  25.0W    35 KT...POST-TROP/EXTRATROP
 96HR VT     14/0000Z 39.0N  23.0W    30 KT...POST-TROP/EXTRATROP
120HR VT     15/0000Z 37.0N  21.5W    30 KT...POST-TROP/EXTRATROP
 
$$
FORECASTER STEWART
 

WTNT42 KNHC 100850
TCDAT2
TROPICAL STORM OTTO DISCUSSION NUMBER  17
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL172010
500 AM AST SUN OCT 10 2010
 
THE SATELLITE PRESENTATION OF OTTO CONTINUES TO DETERIORATE.  THE
LOW-LEVEL CENTER IS NOW COMPLETELY EXPOSED TO THE SOUTH OF A LARGE
SHIELD OF CIRRUS AND A FEW BURSTS OF CONVECTION...AND THE CYCLONE IS
LOOKING INCREASINGLY EXTRATROPICAL.  THE INTENSITY IS SET AT 55 KT
BASED ON A DVORAK ESTIMATE OF T3.0/4.0 FROM TAFB.  STRONG VERTICAL
SHEAR AND COLDER WATERS ARE EXPECTED TO CONTINUE WEAKENING
OTTO...AND THE NHC INTENSITY FORECAST IS BASED ON A BLEND OF THE
GFS...GFDL...AND HWRF MODELS.  THESE MODELS PROBABLY HAVE A BETTER
HANDLE ON THE MID-LATITUDE ENVIRONMENT THAN THE SHIPS/LGEM
MODELS...WHICH APPEAR TO WEAKEN THE CYCLONE TOO FAST.  IT SHOULD BE
NOTED THAT THE GFS AND ECMWF RE-ENERGIZE OTTO BY THE END OF THE
FORECAST PERIOD...SO THE OFFICIAL FORECAST COULD BE A LITTLE LOW ON
DAYS 4 AND 5.
 
OTTO IS EMBEDDED WITHIN STRONG FLOW TO THE SOUTH OF A MID/
UPPER-LEVEL TROUGH AND IS MOVING 65 DEGREES AT 34 KT.  THE FLOW
AHEAD OF OTTO IS EXPECTED TO SPLIT IN THE NEXT 24-36 HOURS...AND
THIS SHOULD CAUSE THE CYCLONE TO DECELERATE AND TURN
SOUTHEASTWARD...MOVING AROUND THE APEX OF A MID-LEVEL RIDGE
EXTENDING ACROSS THE AZORES.  THE EXTRATROPICAL LOW IS THEN
EXPECTED TO BECOME EMBEDDED WITHIN A LARGE CYCLONIC GYRE CURRENTLY
NEAR WESTERN EUROPE ON DAYS 3 THROUGH 5.  BASED ON THE NEW MODEL
GUIDANCE...THE OFFICIAL TRACK FORECAST IS A LITTLE FASTER THAN THE
PREVIOUS ONE FOR THE FIRST 36 HOURS OR SO.  THE ENTIRE FORECAST
TRACK IS MIRRORED MAINLY ON A CONSENSUS OF THE GFS...ECMWF...
UKMET...AND GFDL.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      10/0900Z 35.3N  45.0W    55 KT
 12HR VT     10/1800Z 38.1N  39.2W    50 KT...POST-TROP/EXTRATROP
 24HR VT     11/0600Z 41.5N  32.4W    45 KT...POST-TROP/EXTRATROP
 36HR VT     11/1800Z 43.4N  27.5W    45 KT...POST-TROP/EXTRATROP
 48HR VT     12/0600Z 42.4N  25.1W    40 KT...POST-TROP/EXTRATROP
 72HR VT     13/0600Z 39.5N  23.5W    35 KT...POST-TROP/EXTRATROP
 96HR VT     14/0600Z 37.0N  21.5W    30 KT...POST-TROP/EXTRATROP
120HR VT     15/0600Z 36.5N  19.0W    30 KT...POST-TROP/EXTRATROP
 
$$
FORECASTER BERG
 

WTNT42 KNHC 101435
TCDAT2
TROPICAL STORM OTTO DISCUSSION NUMBER  18
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL172010
1100 AM AST SUN OCT 10 2010
 
RECENT SATELLITE IMAGERY SHOWS THE DEVELOPMENT OF FRONTAL CLOUD
BANDS AND ALSO INDICATES THAT COOL DRY AIR HAS WRAPPED AROUND THE
SOUTHERN SEMICIRCLE OF OTTO AND INTO THE CENTER.  THE REMAINING
CONVECTION IS NOW NORTH AND WEST OF THE CENTER AND AMSU TEMPERATURE
PROFILES SHOW THAT THE UPPER-LEVEL WARM CORE HAS WEAKENED. BASED ON
ALL OF THIS...OTTO IS NOW A POST-TROPICAL EXTRATROPICAL CYCLONE...
AND THIS WILL BE THE LAST NHC ADVISORY. THE INITIAL INTENSITY IS
HELD AT 55 KT...AND SLOW WEAKENING SHOULD BEGIN LATER TODAY AS OTTO
MOVES AWAY FROM THE BEST BAROCLINIC DYNAMICS. GRADUAL WEAKENING IS
EXPECTED TO CONTINUE FOR THE REST OF THE PERIOD. HOWEVER...IT IS
WORTH NOTING THAT THE GFS AND ECMWF STRENGTHEN OTTO A LITTLE AT THE
END OF THE PERIOD...SO THE OFFICIAL FORECAST COULD BE A LITTLE LOW
ON DAYS 4 AND 5.

OTTO IS RACING TOWARD THE NORTHEAST AT 35 TO 40 KNOTS...EMBEDDED
WITHIN DEEP-LAYER SOUTHWESTERLY FLOW TO THE SOUTHEAST OF A LARGE
MID/UPPER-LEVEL TROUGH CENTERED BETWEEN 55W AND 60W.  THE GLOBAL
MODELS ARE IN GENERALLY GOOD AGREEMENT IN SHOWING POST-TROPICAL OTTO
ESCAPING THE WESTERN ATLANTIC TROUGH AND TURNING EASTWARD AND THEN
SOUTHEASTWARD WITHIN 48 HOURS AS IT COMES UNDER THE INFLUENCE OF A
DEEP-LAYER LOW CENTERED OVER THE IBERIAN PENINSULA AND WESTERN
MEDITERRANEAN SEA. LATE IN THE PERIOD THE DEEP-LAYER LOW MOVES
EAST...LEAVING OTTO BEHIND TO MOVE SLOWLY EASTWARD OR NORTHEASTWARD
BY DAY 5. THE OFFICIAL FORECAST IS BASED ON A CONSENSUS OF THE GFS
...UKMET...ECMWF...AND CANADIAN GLOBAL MODELS.

FUTURE INFORMATION ON POST-TROPICAL OTTO CAN BE FOUND IN HIGH SEAS
FORECASTS ISSUED BY THE NATIONAL WEATHER SERVICE UNDER AWIPS HEADER
NFDHSFAT1 AND WMO HEADER FZNT01 KWBC...AND BY METEO-FRANCE UNDER WMO
HEADER FQNT50 LFPW. 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      10/1500Z 37.3N  41.1W    55 KT...POST-TROP/EXTRATROP
 12HR VT     11/0000Z 40.0N  35.6W    50 KT...POST-TROP/EXTRATROP
 24HR VT     11/1200Z 42.6N  29.7W    45 KT...POST-TROP/EXTRATROP
 36HR VT     12/0000Z 43.0N  26.3W    45 KT...POST-TROP/EXTRATROP
 48HR VT     12/1200Z 41.5N  24.1W    40 KT...POST-TROP/EXTRATROP
 72HR VT     13/1200Z 37.0N  22.0W    35 KT...POST-TROP/EXTRATROP
 96HR VT     14/1200Z 36.0N  20.5W    30 KT...POST-TROP/EXTRATROP
120HR VT     15/1200Z 37.0N  19.5W    30 KT...POST-TROP/EXTRATROP
 
$$
FORECASTER BRENNAN
 

