WTNT44 KNHC 080802
TCDAT4
 
SUBTROPICAL STORM SEAN DISCUSSION NUMBER   1
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL192011
500 AM EDT TUE NOV 08 2011
 
SATELLITE INFORMATION AND SURFACE OBSERVATIONS INDICATE THE LARGE
NON-TROPICAL LOW PRESSURE SYSTEM THAT HAS BEEN MEANDERING BETWEEN
BERMUDA AND THE BAHAMAS THE PAST FEW DAYS HAS ACQUIRED ENOUGH
ORGANIZED TO BE CLASSIFIED AS SUBTROPICAL STORM SEAN. AN 08/1021Z
ASCAT OVERPASS INDICATED THE ENTIRE LOW-LEVEL CIRCULATION HAD
BECOME BETTER DEFINED...ESPECIALLY THE INNER CORE WIND FIELD. A
LARGE FIELD OF 34-KT WINDS EXTENDS A FEW HUNDRED MILES WEST THROUGH
NORTH OF THE CENTER...BUT THE ASCAT OVERPASS APPEARS TO HAVE
UNDERESTIMATED THE ACTUAL STRENGTH OF WINDS BASED ON WINDS OF 41 KT
REPORTED BY NOAA BUOYS 41047 AND 41048 AT 08/0100Z. SINCE THE TIME
OF THE ASCAT PASS...THUNDERSTORM ACTIVITY HAS INCREASED IN ALL
QUADRANTS...AND HAS BECOME MORE CONCENTRATED NEAR THE LOW-LEVEL
CENTER. FURTHERMORE...WEAK ANTICYCLONIC OUTFLOW HAS STARTED TO
DEVELOP DURING THE PAST FEW HOURS...AND THE 08/00Z FSU PHASE
EVOLUTION DIAGRAMS BASED OFF THE GFS...UKMET...AND CANADIAN MODELS
INDICATE THIS SYSTEM HAS DEVELOPED A SHALLOW-MODERATE DEPTH WARM
CORE. ALL OF THESE DATA GIVE CREDENCE THAT THIS SYSTEM IS AT LEAST
A SUBTROPICAL CYCLONE. THE INITIAL INTENSITY OF 40 KT IS BASED ON
THE NOAA BUOY REPORTS AND SATELLITE SUBTROPICAL CLASSIFICATIONS OF
ST2.5/35-40 KT FROM BOTH TAFB AND SAB.

THE INITIAL MOTION IS NEARLY STATIONARY. SEAN HAS BEEN MAKING A
SMALL CYCLONIC LOOP DURING THE PAST SEVERAL HOURS AND LITTLE
OVERALL MOTION IS EXPECTED TODAY AS THE CYCLONE REMAINS TRAPPED IN
WEAK STEERING FLOW. BY 12-24 HOURS...HOWEVER...SEAN IS EXPECTED TO
MOVE SLOWLY NORTHWESTWARD AS THE SUBTROPICAL RIDGE TO THE NORTH
BEGINS TO ERODE AND RETREAT TO THE EAST AS A STRONG FRONTAL SYSTEM
AND ASSOCIATED DEEP-LAYER TROUGH MOVE EASTWARD ACROSS THE EASTERN
UNITED STATES. BY 48-60 HOURS...THE AFOREMENTIONED FRONTAL SYSTEM
WILL BE MOVING OFF THE U.S. EAST COAST...AND THE STRONG
SOUTHWESTERLY FLOW ASSOCIATED WITH THE FRONT SHOULD BEGIN TO
ACCELERATE SEAN TOWARD THE NORTHEAST. IN THE 96-120 TIME FRAME...
THE CYCLONE IS EXPECTED TO MERGE WITH THE FRONTAL SYSTEM...ALTHOUGH
DISSIPATION OF SEAN DUE TO STRONG VERTICAL SHEAR IS A VERY DISTINCT
POSSIBILITY. THE OFFICIAL FORECAST TRACK IS TO THE RIGHT OF THE
CONSENSUS MODELS...AND IS A BLEND OF THE GFS AND ECMWF MODELS.

SEAN IS EXPECTED TO REMAIN OVER 26C SSTS FOR AT LEAST THE NEXT 48
HOURS...WHICH MEANS THE CYCLONE COULD POSSIBLY TRANSITION INTO A
TROPICAL STORM AS THE VERTICAL SHEAR WEAKENS. HOWEVER...ALL THIS
WOULD LIKELY DO IS CONTRACT THE WIND FIELD. OVERALL...ONLY A SLIGHT
INCREASE IN STRENGTH IS EXPECTED...ASSUMING THAT AN EYE FEATURE
DOES NOT DEVELOP. I SHOULD BE NOTED THAT SEAN IS A RELATIVELY
SHALLOW SYSTEM WHOSE VERTICAL EXTENT LIKELY ONLY EXTENDS UP TO THE
300 MB LEVEL. AS A RESULT...THE NORMAL SHEAR COMPUTATIONS MADE BY
THE SHIPS MODEL ARE LIKELY GOING TO BE TOO STRONG SINCE THAT MODELS
USES WINDS AT THE 200 MB LEVEL.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  08/0900Z 27.2N  69.4W   40 KT  45 MPH
 12H  08/1800Z 27.2N  69.7W   40 KT  45 MPH
 24H  09/0600Z 27.4N  70.0W   45 KT  50 MPH
 36H  09/1800Z 28.2N  70.5W   45 KT  50 MPH
 48H  10/0600Z 29.2N  70.8W   45 KT  50 MPH
 72H  11/0600Z 31.5N  68.8W   45 KT  50 MPH
 96H  12/0600Z 37.5N  59.0W   40 KT  45 MPH...POST-TROP/EXTRATROP
120H  13/0600Z...ABSORBED BY FRONTAL SYSTEM
 
$$
FORECASTER STEWART
 

WTNT44 KNHC 080927
TCDAT4
 
SUBTROPICAL STORM SEAN DISCUSSION NUMBER   1...CORRECTED
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL192011
400 AM EST TUE NOV 08 2011
 
CORRECTED TIME FROM EDT TO EST

SATELLITE INFORMATION AND SURFACE OBSERVATIONS INDICATE THE LARGE
NON-TROPICAL LOW PRESSURE SYSTEM THAT HAS BEEN MEANDERING BETWEEN
BERMUDA AND THE BAHAMAS THE PAST FEW DAYS HAS ACQUIRED ENOUGH
ORGANIZED CONVECTION TO BE CLASSIFIED AS SUBTROPICAL STORM SEAN. AN
08/1021Z ASCAT OVERPASS INDICATED THE ENTIRE LOW-LEVEL CIRCULATION
HAD BECOME BETTER DEFINED...ESPECIALLY THE INNER CORE WIND FIELD. A
LARGE FIELD OF 34-KT WINDS EXTENDS A FEW HUNDRED MILES WEST THROUGH
NORTH OF THE CENTER...BUT THE ASCAT OVERPASS APPEARS TO HAVE
UNDERESTIMATED THE ACTUAL STRENGTH OF WINDS BASED ON WINDS OF 41 KT
REPORTED BY NOAA BUOYS 41047 AND 41048 AT 08/0100Z. SINCE THE TIME
OF THE ASCAT PASS...THUNDERSTORM ACTIVITY HAS INCREASED IN ALL
QUADRANTS...AND HAS BECOME MORE CONCENTRATED NEAR THE LOW-LEVEL
CENTER. FURTHERMORE...WEAK ANTICYCLONIC OUTFLOW HAS STARTED TO
DEVELOP DURING THE PAST FEW HOURS...AND THE 08/00Z FSU PHASE
EVOLUTION DIAGRAMS BASED OFF THE GFS...UKMET...AND CANADIAN MODELS
INDICATE THIS SYSTEM HAS DEVELOPED A SHALLOW-MODERATE DEPTH WARM
CORE. ALL OF THESE DATA GIVE CREDENCE THAT THIS SYSTEM IS AT LEAST
A SUBTROPICAL CYCLONE. THE INITIAL INTENSITY OF 40 KT IS BASED ON
THE NOAA BUOY REPORTS AND SATELLITE SUBTROPICAL CLASSIFICATIONS OF
ST2.5/35-40 KT FROM BOTH TAFB AND SAB.
 
THE INITIAL MOTION IS NEARLY STATIONARY. SEAN HAS BEEN MAKING A
SMALL CYCLONIC LOOP DURING THE PAST SEVERAL HOURS AND LITTLE
OVERALL MOTION IS EXPECTED TODAY AS THE CYCLONE REMAINS TRAPPED IN
WEAK STEERING FLOW. BY 12-24 HOURS...HOWEVER...SEAN IS EXPECTED TO
MOVE SLOWLY NORTHWESTWARD AS THE SUBTROPICAL RIDGE TO THE NORTH
BEGINS TO ERODE AND RETREAT TO THE EAST AS A STRONG FRONTAL SYSTEM
AND ASSOCIATED DEEP-LAYER TROUGH MOVE EASTWARD ACROSS THE EASTERN
UNITED STATES. BY 48-60 HOURS...THE AFOREMENTIONED FRONTAL SYSTEM
WILL BE MOVING OFF THE U.S. EAST COAST...AND THE STRONG
SOUTHWESTERLY FLOW ASSOCIATED WITH THE FRONT SHOULD BEGIN TO
ACCELERATE SEAN TOWARD THE NORTHEAST. IN THE 96-120 TIME FRAME...
THE CYCLONE IS EXPECTED TO MERGE WITH THE FRONTAL SYSTEM...ALTHOUGH
DISSIPATION OF SEAN DUE TO STRONG VERTICAL SHEAR IS A VERY DISTINCT
POSSIBILITY. THE OFFICIAL FORECAST TRACK IS TO THE RIGHT OF THE
CONSENSUS MODELS...AND IS A BLEND OF THE GFS AND ECMWF MODELS.
 
SEAN IS EXPECTED TO REMAIN OVER 26C SSTS FOR AT LEAST THE NEXT 48
HOURS...WHICH MEANS THE CYCLONE COULD POSSIBLY TRANSITION INTO A
TROPICAL STORM AS THE VERTICAL SHEAR WEAKENS. HOWEVER...ALL THIS
WOULD LIKELY DO IS CONTRACT THE WIND FIELD. OVERALL...ONLY A SLIGHT
INCREASE IN STRENGTH IS EXPECTED...ASSUMING THAT AN EYE FEATURE
DOES NOT DEVELOP. I SHOULD BE NOTED THAT SEAN IS A RELATIVELY
SHALLOW SYSTEM WHOSE VERTICAL EXTENT LIKELY ONLY EXTENDS UP TO THE
300 MB LEVEL. AS A RESULT...THE NORMAL SHEAR COMPUTATIONS MADE BY
THE SHIPS MODEL ARE LIKELY GOING TO BE TOO STRONG SINCE THAT MODELS
USES WINDS AT THE 200 MB LEVEL.

FORECAST POSITIONS AND MAX WINDS
 
INIT  08/0900Z 27.2N  69.4W   40 KT  45 MPH
 12H  08/1800Z 27.2N  69.7W   40 KT  45 MPH
 24H  09/0600Z 27.4N  70.0W   45 KT  50 MPH
 36H  09/1800Z 28.2N  70.5W   45 KT  50 MPH
 48H  10/0600Z 29.2N  70.8W   45 KT  50 MPH
 72H  11/0600Z 31.5N  68.8W   45 KT  50 MPH
 96H  12/0600Z 37.5N  59.0W   40 KT  45 MPH...POST-TROP/EXTRATROP
120H  13/0600Z...DISSIPATED
 
$$
FORECASTER STEWART
 

WTNT44 KNHC 081443
TCDAT4
 
SUBTROPICAL STORM SEAN DISCUSSION NUMBER   2
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL192011
1100 AM AST TUE NOV 08 2011
 
SEAN APPEARS TO BE MAKING A TRANSITION INTO A MORE TROPICAL SYSTEM
WITH DEEP CONVECTION FORMING IN A CURVED BAND RELATIVELY CLOSE TO
THE CENTER.  THIS IS ALSO REFLECTED IN THE SATELLITE INTENSITY
ESTIMATE FROM TAFB...WHICH USED A CURVED BAND DVORAK PATTERN
INSTEAD OF A SUBTROPICAL CLASSIFICATION.  SINCE SEAN IS STILL NEAR
AN UPPER-LEVEL LOW...I HAVE CHOSEN TO KEEP IT SUBTROPICAL ON THIS
ADVISORY...AND THE WIND SPEED WILL REMAIN 40 KT.  THE CYCLONE WILL
LIKELY BECOME TROPICAL BY THE END OF THE DAY AS MOST OF THE MODEL
GUIDANCE SHOW AN UPPER-LEVEL ANTICYCLONE BUILDING OVER SEAN. SOME
MODEST STRENGTHENING IS ALSO POSSIBLE DURING THE NEXT COUPLE OF
DAYS WHILE THE SHEAR REMAINS LOW TO MODERATE.  THE NHC FORECAST IS
NEAR THE SHIPS/LGEM MODELS...AND A BIT HIGHER THAN THE MODEL
CONSENSUS.  AFTER 48 HOURS...SHEAR SHOULD MARKEDLY INCREASE
AS THE CYCLONE MOVES OVER COOLER WATERS...AND WEAKENING IS LIKELY.  
  
THE CYCLONE HAS BEEN MOVING ERRATICALLY DURING THE PAST SEVERAL
HOURS...RECENTLY ON A SLOW NORTHWARD DRIFT.  SEAN SHOULD BE STEERED
TO THE WEST AND NORTHWEST OVER THE NEXT DAY OR TWO AS SUBTROPICAL
RIDGING BRIEFLY BUILDS OVER THE WESTERN ATLANTIC.  THE STORM WILL
LIKELY TURN TOWARD THE NORTH AND NORTHEAST AWAY FROM THE UNITED
STATES ON THURSDAY DUE TO A DEEP TROUGH MOVING OVER EASTERN NORTH
AMERICA.   THE NHC FORECAST WILL STAY ON THE RIGHT SIDE OF THE
GUIDANCE ENVELOPE...BETWEEN THE GFS AND ECMWF MODELS...AND ASSUME
IT WILL NOT BE ABSORBED BY THAT TROUGH QUITE AS FAST AS MOST OF THE
MODELS SUGGEST.  
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  08/1500Z 27.7N  69.4W   40 KT  45 MPH
 12H  09/0000Z 27.8N  69.7W   45 KT  50 MPH
 24H  09/1200Z 28.2N  70.1W   45 KT  50 MPH
 36H  10/0000Z 29.2N  70.4W   45 KT  50 MPH
 48H  10/1200Z 30.2N  70.4W   45 KT  50 MPH
 72H  11/1200Z 33.5N  66.0W   40 KT  45 MPH
 96H  12/1200Z 40.0N  55.0W   35 KT  40 MPH...POST-TROP/EXTRATROP
120H  13/1200Z...ABSORBED
 
$$
FORECASTER BLAKE
 

WTNT44 KNHC 082035
TCDAT4
 
TROPICAL STORM SEAN DISCUSSION NUMBER   3
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL192011
500 PM AST TUE NOV 08 2011
 
CONVECTION HAS FORMED NEAR THE CENTER OF SEAN THIS AFTERNOON WITH A
BANDING FEATURE PERSISTING IN THE NORTHEASTERN QUADRANT.  SINCE THE
STORM IS A LITTLE FARTHER FROM THE UPPER-LEVEL LOW...WITH A WARM
CORE APPARENT ON AMSU ANALYSES AND A SMALLER RADIUS OF MAXIMUM
WINDS AS SEEN IN ASCAT DATA...SEAN NOW HAS ENOUGH CHARACTERISTICS
TO BE CONSIDERED TROPICAL.  THE MAXIMUM WINDS ARE SET TO 45 KT...IN
AGREEMENT WITH THE TAFB DVORAK ESTIMATE AND EARLIER ASCAT WINDS. 
WHILE THE REGIONAL HURRICANE MODELS DO NOT SHOW MUCH
INTENSIFICATION OF SEAN...THE SHEAR REMAINS RELATIVELY LIGHT FOR
THE NEXT 36 HR OR SO WHILE THE SYSTEM IS OVER MARGINAL SSTS.  SINCE
THE STORM IS EMBEDDED WITHIN COLDER-THAN-AVERAGE UPPER-AIR
TEMPERATURES...THE SST THRESHOLD FOR TROPICAL CYCLONE STRENGTHENING
IS LOWER THAN USUAL...AND SOME FURTHER STRENGTHENING IS
ANTICIPATED.  THE NEW NHC FORECAST IS HIGHER THAN THE PREVIOUS
ONE...AND REMAINS IN LINE WITH THE SHIPS/LGEM MODELS AND THE
EXPERIMENTAL SPC3 ENSEMBLE SHIPS GUIDANCE.  IN ABOUT TWO DAYS...
SEAN SHOULD ENCOUNTER A MORE HOSTILE UPPER-AIR ENVIRONMENT...WHICH
SHOULD INDUCE WEAKENING.  
 
THE CENTER OF THE CYCLONE HAS BEEN WOBBLING AROUND FOR QUITE SOME
TIME...BUT IT APPEARS THAT A MOTION TOWARD THE WEST-NORTHWEST HAS
BEGUN.  THIS GENERAL TRACK IS EXPECTED TO CONTINUE THROUGH TOMORROW
AS A RIDGE MOVES THROUGH THE WESTERN ATLANTIC.  THEREAFTER...THE
STORM SHOULD TURN TOWARD THE NORTH AND NORTHEAST BY THURSDAY AHEAD
OF A DEEP TROUGH OVER THE EASTERN UNITED STATES.  IT SEEMS THAT
BEING ON THE RIGHT SIDE OF THE GUIDANCE EARLIER WAS A GOOD CALL...
AS MOST OF THE MODELS HAVE SHIFTED IN THAT DIRECTION...APPARENTLY
BECAUSE OF FLATTER MID-LATITUDE FLOW FORECAST TO AFFECT SEAN.  ONLY
COSMETIC CHANGES WERE MADE TO THE NHC TRACK FOR THE FIRST COUPLE OF
DAYS...WITH A SHIFT TO THE SOUTHEAST MADE AT DAY 3...BETWEEN THE
ECMWF AND GFS MODELS.  ALL OF THE GLOBAL MODELS SHOW THE STORM
BEING ABSORBED BY A FRONTAL BOUNDARY BY DAY 4...AND THIS SCENARIO
IS REFLECTED IN THE NHC FORECAST.  
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  08/2100Z 27.8N  69.8W   45 KT  50 MPH
 12H  09/0600Z 27.9N  70.2W   50 KT  60 MPH
 24H  09/1800Z 28.4N  70.4W   50 KT  60 MPH
 36H  10/0600Z 29.0N  70.5W   55 KT  65 MPH
 48H  10/1800Z 29.9N  69.7W   50 KT  60 MPH
 72H  11/1800Z 34.0N  64.0W   45 KT  50 MPH
 96H  12/1800Z...ABSORBED
 
$$
FORECASTER BLAKE
 

WTNT44 KNHC 090240
TCDAT4
 
TROPICAL STORM SEAN DISCUSSION NUMBER   4
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL192011
1000 PM EST TUE NOV 08 2011
 
THE STRUCTURE OF SEAN HAS NOT CHANGED MUCH OVER THE PAST FEW HOURS.
THE CLOUD PATTERN CONSISTS OF A PRIMARY BAND OF RAGGED CONVECTION
THAT WRAPS MOST OF THE WAY AROUND THE CENTER...WHILE THE COLDEST
CLOUD TOPS AND LIGHTNING ACTIVITY ARE SEEN IN A SEPARATE BAND
DISPLACED ABOUT 175 NM EAST OF THE CENTER. DVORAK ESTIMATES FROM
TAFB AND SAB SUPPORT MAINTAINING THE INITIAL INTENSITY OF 45 KT FOR
THIS ADVISORY. WHILE SEAN IS CURRENTLY SITUATED OVER MARGINAL
SSTS...THE UPPER LEVELS OF THE ATMOSPHERE ARE COOLER THAN NORMAL...
WHICH SHOULD SUSTAIN ENOUGH CONVECTION TO ALLOW FOR SOME
STRENGTHENING. THE NHC INTENSITY FORECAST REFLECTS THIS REASONING
AND IS UNCHANGED FROM THE PREVIOUS ADVISORY...SHOWING SEAN PEAKING
IN AROUND 36 HOURS. THIS FORECAST IS A LITTLE ABOVE THE LGEM AND
CLOSE TO THE SPC3 SHIPS ENSEMBLE. AFTER 48 HOURS SEAN WILL MOVE
OVER COOLER WATERS AND INTO A HIGHER SHEAR ENVIRONMENT...WHICH
SHOULD RESULT IN SOME WEAKENING AS THE CYCLONE BECOMES
EXTRATROPICAL BY 72 HOURS. SEAN SHOULD BE ABSORBED BY A SURFACE
FRONT SHORTLY AFTER TRANSITION...AND IN FACT SOME GLOBAL MODEL
FIELDS SHOW THAT OCCURRING EARLIER THAN INDICATED HERE.

SEAN HAS MOVED SLOWLY WESTWARD OVER THE PAST FEW HOURS...WITH AN
INITIAL MOTION ESTIMATE OF 270/03. A NARROW MID-LEVEL RIDGE
BUILDING NORTH OF THE CYCLONE SHOULD RESULT IN A SLOW WEST-
NORTHWESTWARD MOTION DEVELOPING IN THE NEXT 12 HOURS OR SO...
FOLLOWED BY A TURN TOWARD THE NORTH IN ABOUT 24 HOURS AS THE
RIDGE WEAKENS. SEAN SHOULD THEN BEGIN TO ACCELERATE NORTHEASTWARD BY
48 HOURS AS A DEEP-LAYER TROUGH MOVES OFF THE EAST COAST OF THE
UNITED STATES. DUE TO THE MORE WESTERLY INITIAL MOTION THE NHC
FORECAST HAS BEEN ADJUSTED A BIT TO THE LEFT OF THE PREVIOUS ONE
FOR THE FIRST 12 TO 24 HOURS. BEYOND 24 HOURS...THE LATEST RUN OF
THE GFS HAS SHIFTED TO THE LEFT...BUT THE NHC FORECAST HAS ONLY
BEEN NUDGED A LITTLE IN THAT DIRECTION AT 48 AND 72 HOURS...AND
STILL LIES ON THE EASTERN SIDE OF THE GUIDANCE ENVELOPE.
 
THE INITIAL 34-KT WIND RADII WERE EXPANDED IN THE NORTHERN
SEMICIRCLE BASED ON SEVERAL PEAK 1-MINUTE WIND OBSERVATIONS ABOVE
TROPICAL STORM FORCE AT NOAA BUOY 41048.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  09/0300Z 27.9N  70.1W   45 KT  50 MPH
 12H  09/1200Z 28.0N  70.5W   50 KT  60 MPH
 24H  10/0000Z 28.6N  70.6W   50 KT  60 MPH
 36H  10/1200Z 29.5N  70.1W   55 KT  65 MPH
 48H  11/0000Z 31.0N  68.4W   50 KT  60 MPH
 72H  12/0000Z 36.5N  61.0W   45 KT  50 MPH...POST-TROP/EXTRATROP
 96H  13/0000Z...ABSORBED BY FRONT
 
$$
FORECASTER BRENNAN
 

WTNT44 KNHC 090837
TCDAT4
 
TROPICAL STORM SEAN DISCUSSION NUMBER   5
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL192011
400 AM EST WED NOV 09 2011

SEAN HAS AGAIN CHANGED LITTLE IN STRUCTURE DURING THE PAST SEVERAL
HOURS.  A CENTRAL CONVECTIVE BAND IS PRESENT WITHIN 60-75 N MI OF
THE CENTER...MAINLY IN THE SOUTHEASTERN SEMICIRCLE...WHILE OUTER
CONVECTIVE BANDS ARE PRESENT UP TO 240 N MI FROM THE CENTER IN THE
NORTHEASTERN SEMICIRCLE.  SATELLITE INTENSITY ESTIMATES FROM SAB
AND TAFB ARE 45 KT...AND THAT REMAINS THE INITIAL INTENSITY FOR
THIS ADVISORY.  THE CENTRAL PRESSURE HAS BEEN ADJUSTED DOWNWARD
BASED ON OBSERVATIONS FROM NOAA BUOY 41047.

THE INITIAL MOTION REMAINS 270/3.  SEAN IS EMBEDDED IN A DEEP-LAYER
CYCLONIC CIRCULATION THAT IS CUT OFF FROM THE WESTERLIES SOUTH OF A
RIDGE OVER THE NORTHWESTERN ATLANTIC.  A STRONG MID/UPPER-LEVEL
TROUGH AND ASSOCIATED SURFACE COLD FRONT ARE MOVING EASTWARD
THROUGH THE MISSISSIPPI VALLEY...AND THE DYNAMICAL MODELS FORECAST
THIS SYSTEM TO REACH THE WESTERN ATLANTIC IN ABOUT 36 HOURS.  THIS
EVOLUTION SHOULD CAUSE SEAN TO TURN NORTHWARD DURING THE NEXT
24 HOURS...AND THEN TURN NORTHEASTWARD IN DEEP-LAYER SOUTHWESTERLY
FLOW AHEAD OF THE APPROACHING TROUGH.  WHILE THE DYNAMICAL MODELS
AGREE ON THIS SCENARIO...THERE IS SOME SPREAD IN BOTH THE DIRECTION
AND SPEED OF FORWARD MOTION AFTER 24 HOURS.  THE ECMWF MODEL IS ON
THE RIGHT SIDE OF THE GUIDANCE ENVELOPE AND TAKES THE CENTER NEAR
BERMUDA...WHILE THE GFDL AND UKMET ARE ON THE LEFT SIDE FORECASTING
A TRACK CLOSER TO NOVA SCOTIA AND NEWFOUNDLAND.  THE GUIDANCE
ENVELOPE HAS SHIFTED TO THE LEFT/NORTH COMPARED TO 6 HOURS AGO...
AND THE NEW FORECAST TRACK IS ALSO SHIFTED IN THAT DIRECTION. 
HOWEVER...OUT OF RESPECT FOR THE ECMWF AND THE PREVIOUS FORECAST
THE NEW FORECAST TRACK LIES TO THE RIGHT OF THE CENTER OF THE
GUIDANCE ENVELOPE AND THE CONSENSUS MODELS.

SEAN IS IN A REGION OF LIGHT/MODERATE VERTICAL WIND SHEAR NEAR THE
CENTER OF THE CUT-OFF LOW.  THE DYNAMICAL MODELS SUGGEST THE
PRESENT SHEAR SHOULD CONTINUE FOR THE NEXT 12-24 HOURS...FOLLOWED
BY A SIGNIFICANT INCREASE IN SHEAR CAUSED BY THE TROUGH APPROACHING
FROM THE WEST.  THIS SHOULD ALLOW SEAN TO STRENGTHEN SOME TODAY...
FOLLOWED BY A WEAKENING TREND AFTER 24 HOURS.  SEAN IS FORECAST TO
BECOME EXTRATROPICAL AS IT MERGES WITH THE APPROACHING COLD FRONT
BETWEEN 48-72 HOURS...WITH THE CIRCULATION BECOMING TOTALLY
ABSORBED BY THE FRONT BY 96 HOURS.  THE NEW INTENSITY FORECAST IS
SIMILAR TO THE PREVIOUS FORECAST...WITH JUST A LITTLE LESS
STRENGTHENING DURING THE FIRST 24-36 HOURS.  IT SHOULD BE NOTED
THAT MANY OF THE DYNAMICAL MODELS SHOW THE CIRCULATION OF SEAN
DISSIPATING BEFORE 72 HOURS...SO THE CURRENT FORECAST LIFETIME
COULD BE GENEROUS.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  09/0900Z 27.9N  70.4W   45 KT  50 MPH
 12H  09/1800Z 28.4N  70.7W   50 KT  60 MPH
 24H  10/0600Z 29.4N  70.7W   50 KT  60 MPH
 36H  10/1800Z 30.6N  69.7W   50 KT  60 MPH
 48H  11/0600Z 33.1N  67.4W   45 KT  50 MPH
 72H  12/0600Z 38.5N  59.0W   45 KT  50 MPH...POST-TROP/EXTRATROP
 96H  13/0600Z...DISSIPATED
 
$$
FORECASTER BEVEN
 

WTNT44 KNHC 091448
TCDAT4
 
TROPICAL STORM SEAN DISCUSSION NUMBER   6
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL192011
1000 AM EST WED NOV 09 2011

DURING THE PAST FEW HOURS...CONVECTION HAS BECOME BETTER ORGANIZED
IN A BROKEN RING AROUND THE CENTER OF SEAN...WITH THE POSSIBILITY
THAT AN EYE FEATURE IS FORMING.  SUBJECTIVE SATELLITE INTENSITY
ESTIMATES FROM TAFB/SAB ARE 45/55 KT...AND A BLEND OF THESE DATA
GIVES AN INITIAL WIND SPEED OF 50 KT.  SEAN HAS ABOUT 24 TO 36
HOURS OF RELATIVELY LOW SHEAR CONDITIONS...WHICH WOULD SEEM TO
FAVOR SOME INTENSIFICATION.  MODEL GUIDANCE IS A BIT HIGHER...AND
THE OFFICIAL WIND SPEED FORECAST IS RAISED FROM THE LAST ONE...
BETWEEN THE STATISTICAL MODELS AND THE INTENSITY CONSENSUS.  THE
OFFICIAL FORECAST MIGHT BE CONSERVATIVE IF A CENTRAL CORE BECOMES
WELL ESTABLISHED.  

THE GRADUAL POLEWARD TURN OF THE CYCLONE HAS BEGUN...WITH AN
INITIAL MOTION ESTIMATE OF 320/3.  SHORTWAVE RIDGING OVER THE
WESTERN ATLANTIC WILL MOVE TO THE EAST LATER TODAY...STEERING SEAN
ON A PATH TOWARD THE NORTH AND NORTH-NORTHEAST BY EARLY TOMORROW. 
AS A TROUGH OVER THE EASTERN UNITED STATES APPROACHES THE
STORM...AN INCREASE IN MID-TROPOSPHERIC FLOW SHOULD CAUSE THE
TROPICAL CYCLONE TO ACCELERATE NORTHEASTWARD.  THERE CONTINUES TO
BE A FAIR AMOUNT OF SPREAD...HOWEVER...ON HOW FAR SEAN MOVES FROM
BERMUDA.  THE GFS AND ECMWF HAVE BEEN MORE CONSISTENT THAN THE REST
OF THE GUIDANCE SHOWING A CLOSER TRACK TO BERMUDA...SO THE OFFICIAL
FORECAST WILL STAY NEAR THOSE HISTORICALLY RELIABLE MODELS.  MOST OF
THE GLOBAL MODELS SHOW THIS SYSTEM BEING ABSORBED WITHIN A FRONT
BETWEEN DAY 3 AND DAY 4...AND THE NHC FORECAST CONTINUES TO FOLLOW
THIS SCENARIO.  
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  09/1500Z 27.9N  70.5W   50 KT  60 MPH
 12H  10/0000Z 28.4N  70.6W   55 KT  65 MPH
 24H  10/1200Z 29.6N  70.2W   55 KT  65 MPH
 36H  11/0000Z 31.5N  68.4W   55 KT  65 MPH
 48H  11/1200Z 33.8N  65.3W   50 KT  60 MPH
 72H  12/1200Z 41.0N  53.0W   45 KT  50 MPH...POST-TROP/EXTRATROP
 96H  13/1200Z...ABSORBED
 
$$
FORECASTER BLAKE
 

WTNT44 KNHC 092042
TCDAT4
 
TROPICAL STORM SEAN DISCUSSION NUMBER   7
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL192011
400 PM EST WED NOV 09 2011
 
SATELLITE IMAGERY INDICATES THAT SEAN IS STRENGTHENING.  THE CLOUD
PATTERN CONSISTS OF A LARGE COILED BAND...WHICH APPEARS TO BE
WRAPPING UP INTO A BANDING EYE FEATURE.  DVORAK ESTIMATES ARE 55 KT
FROM BOTH TAFB/SAB...SO THIS WILL BE THE INITIAL WIND SPEED.  WITH
THE DEVELOPMENT OF THE CENTRAL CORE AND ABOUT A DAY OF LIGHT SHEAR
CONDITIONS REMAINING...FURTHER INTENSIFICATION SEEMS PROBABLE.  IT
IS A LITTLE PUZZLING WHY NONE OF THE MODELS MAKE THIS A HURRICANE...
ALTHOUGH THE INTENSITY GUIDANCE HAS GENERALLY HAD A LOW BIAS WITH
THIS SYSTEM.  GIVEN THE DEVELOPING EYE FEATURE...THE NEW NHC
FORECAST SHOWS SEAN REACHING HURRICANE STRENGTH...WHICH IS A BIT
HIGHER THAN THE SHIPS/LGEM MODELS.
 
THE STORM HAS TURNED TOWARD THE NORTH AT ABOUT 5 KT...A LITTLE
FASTER THAN EARLIER. A GRADUAL TURN TOWARD THE NORTHEAST WITH SOME
ACCELERATION IS EXPECTED TOMORROW AS THE TROPICAL CYCLONE FEELS THE
INFLUENCE OF A TROUGH MOVING INTO THE EASTERN UNITED STATES.
ALTHOUGH THERE IS STILL SOME SPREAD...THE GUIDANCE IS PRETTY
CONSISTENT IN SHOWING SEAN MOVING A FAIR DISTANCE TO THE NORTHWEST
OF BERMUDA. THE LATEST GFS/ECMWF MODELS CAME IN VERY CLOSE TO THE
PREVIOUS NHC FORECAST...AND ONLY SMALL CHANGES WERE MADE TO THE NEW
NHC TRACK. ALL OF THE GLOBAL MODELS SHOW SEAN BECOMING
EXTRATROPICAL IN TWO DAYS...AND THEN BEING ABSORBED BY A FRONTAL
BOUNDARY BY DAY 3.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  09/2100Z 28.7N  70.5W   55 KT  65 MPH
 12H  10/0600Z 29.4N  70.5W   60 KT  70 MPH
 24H  10/1800Z 30.6N  69.5W   65 KT  75 MPH
 36H  11/0600Z 32.7N  67.0W   60 KT  70 MPH
 48H  11/1800Z 35.8N  62.7W   50 KT  60 MPH...POST-TROP/EXTRATROP
 72H  12/1800Z...ABSORBED
 
$$
FORECASTER BLAKE
 

WTNT44 KNHC 100240
TCDAT4
 
TROPICAL STORM SEAN DISCUSSION NUMBER   8
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL192011
1000 PM EST WED NOV 09 2011
 
RECENT SATELLITE TRENDS SUGGEST THAT THE INTENSITY OF SEAN HAS
LEVELED OFF THIS EVENING. CLOUD TOP TEMPERATURES NEAR THE CENTER
HAVE WARMED...ALTHOUGH RECENT MICROWAVE IMAGERY FROM THE U.S. NAVY
FNMOC TC WEBPAGE STILL SHOWS A BANDING EYE FEATURE. BASED ON DVORAK
CURRENT INTENSITY ESTIMATE FROM TAFB AND SAB...THE INITIAL
INTENSITY REMAINS 55 KT. GIVEN THE CONTINUED PRESENCE OF SOME INNER
CORE STRUCTURE...SEAN STILL HAS AN OPPORTUNITY TO STRENGTHEN IN THE
NEXT 12 TO 24 HOURS BEFORE VERTICAL WIND SHEAR INCREASES. THE NHC
INTENSITY FORECAST REMAINS UNCHANGED FROM THE PREVIOUS ADVISORY AND
IS A LITTLE ABOVE THE LGEM AT 24 HOURS...SHOWING SEAN REACHING
HURRICANE STRENGTH. AFTER THAT TIME...SEAN SHOULD WEAKEN DUE TO
COOLER WATERS AND INCREASING SHEAR. MODEL FIELDS SHOW THE CYCLONE
BECOMING EXTRATROPICAL BY 48 HOURS AND BEING ABSORBED BY A FRONTAL
BOUNDARY SHORTLY THEREAFTER...BUT THIS COULD OCCUR EVEN SOONER.

SEAN HAS JOGGED QUICKLY NORTHWARD THIS EVENING...AND THE INITIAL
MOTION ESTIMATE IS 360/07. SEAN SHOULD TURN NORTHEASTWARD ON
THURSDAY FOLLOWED BY A STEADY INCREASE IN FORWARD SPEED THURSDAY
NIGHT AND FRIDAY AS THE CYCLONE BECOMES EMBEDDED IN THE
SOUTHWESTERLY FLOW AHEAD OF A TROUGH MOVING OFF OF THE EAST COAST
OF THE UNITED STATES. THE NEW NHC FORECAST IS A LITTLE FASTER AND A
LITTLE TO THE LEFT OF THE PREVIOUS ONE IN THE FIRST 12 TO 24 HOURS
DUE TO THE FASTER NORTHWARD MOTION THIS EVENING. AFTER THAT TIME
ONLY MINOR CHANGES WERE MADE TO THE OFFICIAL FORECAST...WHICH
REMAINS CLOSE TO THE GFS AND ECMWF MODELS UNTIL DISSIPATION.
 

FORECAST POSITIONS AND MAX WINDS
 
INIT  10/0300Z 29.5N  70.7W   55 KT  65 MPH
 12H  10/1200Z 30.3N  70.2W   60 KT  70 MPH
 24H  11/0000Z 31.8N  68.3W   65 KT  75 MPH
 36H  11/1200Z 34.5N  64.9W   55 KT  65 MPH
 48H  12/0000Z 38.5N  59.3W   45 KT  50 MPH...POST-TROP/EXTRATROP
 72H  13/0000Z...ABSORBED BY FRONT
 
$$
FORECASTER BRENNAN
 

WTNT44 KNHC 100836
TCDAT4
 
TROPICAL STORM SEAN DISCUSSION NUMBER   9
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL192011
400 AM EST THU NOV 10 2011

INFRARED AND MICROWAVE SATELLITE IMAGERY THIS MORNING SHOWS THAT
SEAN IS SLOWLY BECOMING BETTER ORGANIZED...WITH INCREASING
CONVECTIVE BANDING AROUND THE CENTER AND OCCASIONAL ATTEMPTS AT EYE
FORMATION.  SATELLITE INTENSITY ESTIMATES FROM SAB AND TAFB ARE 55
KT...AND THAT REMAINS THE INITIAL INTENSITY.  THE CYCLONE CURRENTLY
HAS GOOD CIRRUS OUTFLOW IN THE NORTH SEMICIRCLE.

SEAN CONTINUES ITS NORTHERLY TRACK WITH AN INITIAL MOTION OF 355/7. 
WATER VAPOR IMAGERY SHOWS SOUTHWESTERLY MID/UPPER-LEVEL FLOW
ASSOCIATED WITH A TROUGH OVER THE EASTERN UNITED STATES APPROACHING
THE CYCLONE...AND THE GUIDANCE IS IN GOOD AGREEMENT THAT THIS
SHOULD CAUSE SEAN TO TURN NORTHEASTWARD IN THE NEXT 12 HOURS. 
AFTER THAT...THE CYCLONE SHOULD ACCELERATE NORTHEASTWARD DURING THE
REMAINDER OF ITS LIFETIME.  THE NEW FORECAST TRACK FOLLOWS THIS
SCENARIO AND IS SIMILAR TO...BUT NORTH OF...THE PREVIOUS TRACK. 
THE FORECAST TRACK IS NEAR THE CENTER OF THE TRACK GUIDANCE
ENVELOPE.
 
THERE IS PERHAPS 12-24 HOURS FOR SEAN TO STRENGTHEN BEFORE STRONG
VERTICAL WIND SHEAR IMPACTS THE STORM.  GIVEN THE CURRENT
STRUCTURE...THE INTENSITY FORECAST CALLS FOR SEAN TO REACH HURRICANE
STRENGTH IN 24 HOURS IN AGREEMENT WITH THE PREVIOUS FORECAST. 
AFTER THAT...STRONG SHEAR AND THE START OF EXTRATROPICAL TRANSITION
SHOULD CAUSE WEAKENING.  EXTRATROPICAL TRANSITION IS EXPECTED TO BE
COMPLETE BY 48 HOURS...AND BY 72 HOURS SEAN IS EXPECTED TO BE
ABSORBED BY A LARGER BAROCLINIC SYSTEM TO ITS NORTH.  AS NOTED IN
THE PREVIOUS DISCUSSION...IT IS POSSIBLE THAT SEAN COULD DISSIPATE
EARLIER THAN CURRENTLY FORECAST.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  10/0900Z 30.2N  70.9W   55 KT  65 MPH
 12H  10/1800Z 31.2N  69.8W   60 KT  70 MPH
 24H  11/0600Z 33.4N  67.2W   65 KT  75 MPH
 36H  11/1800Z 37.0N  63.0W   55 KT  65 MPH
 48H  12/0600Z 41.5N  56.5W   45 KT  50 MPH...POST-TROP/EXTRATROP
 72H  13/0600Z...ABSORBED BY EXTRATROPICAL LOW
 
$$
FORECASTER BEVEN
 

WTNT44 KNHC 101432
TCDAT4
 
TROPICAL STORM SEAN DISCUSSION NUMBER  10
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL192011
1000 AM EST THU NOV 10 2011
 
THERE HAS NOT BEEN MUCH CHANGE WITH SEAN OVER THE PAST SEVERAL
HOURS. THE STORM CONTINUES TO SHOW A RAGGED EYE...WITH A MORE
COMPACT APPEARANCE ON SATELLITE THAN YESTERDAY. DVORAK ESTIMATES
REMAIN THE SAME...SO THE INITIAL WIND SPEED WILL REMAIN AT 55 KT.
AN AIR FORCE RESERVE RECONNAISSANCE AIRCRAFT IS SCHEDULED TO BE IN
THE CYCLONE AROUND 1800 UTC TO PROVIDE A BETTER ESTIMATE OF THE
INITIAL WINDS. SEAN STILL HAS A DAY OR SO OF MARGINAL WATER
TEMPERATURES AND MODERATE SHEAR LEFT TO INTENSIFY. SOUTHWESTERLY
SHEAR SHOULD NOTABLY INCREASE AFTER THAT TIME...WHICH SHOULD CAUSE
WEAKENING OF THE STORM. MODEL GUIDANCE IS A LITTLE LOWER THAN SIX
HOURS AGO...AND THE NHC FORECAST IS REDUCED FROM THE PREVIOUS ONE.
SEAN COULD STILL BECOME A HURRICANE...ALTHOUGH IT IS NOT EXPLICITLY
FORECAST.
 
THE STORM HAS MADE THE TURN TO THE NORTHEAST...MOVING ABOUT 035/6.
GUIDANCE IS IN GOOD AGREEMENT ON THIS TRACK CONTINUING WITH A
SIGNIFICANT INCREASE IN FORWARD SPEED BY FRIDAY MORNING DUE TO AN
APPROACHING MID-LATITUDE TROUGH.  THE NEW FORECAST IS BASICALLY AN
UPDATE OF THE PREVIOUS ONE...SHOWING THE CYCLONE PASSING A FAIR
DISTANCE NORTHWEST OF BERMUDA.  STRONG SHEAR...COOLER WATERS...AND
A COLD FRONT ARE EXPECTED TO CAUSE EXTRATROPICAL TRANSITION IN
ABOUT 36 HOURS...WITH SEAN BECOMING ABSORBED BY THAT FRONT WITHIN
48 HOURS.  IT WOULD NOT BE SURPRISING IF SEAN DISSIPATED A LITTLE
FASTER THAN SHOWN BELOW...AS INDICATED BY THE GFS AND UKMET MODELS.
  
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  10/1500Z 30.4N  70.5W   55 KT  65 MPH
 12H  11/0000Z 31.8N  69.0W   60 KT  70 MPH
 24H  11/1200Z 34.7N  65.6W   60 KT  70 MPH
 36H  12/0000Z 39.0N  60.0W   50 KT  60 MPH...POST-TROP/EXTRATROP
 48H  12/1200Z...ABSORBED
 
$$
FORECASTER BLAKE
 

WTNT44 KNHC 102035
TCDAT4
 
TROPICAL STORM SEAN DISCUSSION NUMBER  11
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL192011
500 PM AST THU NOV 10 2011

SATELLITE IMAGES SHOW THAT THE STRUCTURE OF SEAN HAS BECOME A LITTLE
LESS ORGANIZED...WITH CONVECTION AROUND THE EYE FEATURE APPEARING
TO WEAKEN A BIT AND BECOME LESS SYMMETRIC. AN AIR FORCE RESERVE
AIRCRAFT MISSION THIS AFTERNOON INTO SEAN FOUND PEAK FLIGHT-LEVEL
WINDS OF 63 KT...SFMR MEASUREMENTS OF 52 KT...ALONG WITH A CENTRAL
PRESSURE OF 983 MB. THESE DATA SUPPORT MAINTAINING THE INTENSITY AT
55 KT. THE CHANCES OF SEAN BECOMING A HURRICANE APPEAR TO BE
DIMINISHING DUE TO THE DEGRADED STRUCTURE. SINCE THE MODELS
GENERALLY SHOW NO SIGNIFICANT INTENSIFICATION...THE INTENSITY
FORECAST WILL BE HELD AT 55 KT DURING THE SHORT-TERM PERIOD. BY
TOMORROW...WEAKENING IS LIKELY...AND THIS IS ALREADY BEING HERALDED
BY THE ERODING CIRRUS OVERFLOW ON THE NORTHWESTERN SIDE OF THE
CIRCULATION. THE NHC FORECAST IS REDUCED FROM THE PREVIOUS ONE...
AND IS SIMILAR TO THE MODEL CONSENSUS.

SEAN IS ACCELERATING TOWARD THE NORTHEAST...NOW MOVING AT ABOUT 
11 KT...ALTHOUGH RECENTLY IT MIGHT BE WOBBLING A LITTLE TO THE RIGHT
OF THAT ESTIMATE. THE MODEL GUIDANCE CONTINUES TO BE VERY
CONSISTENT IN SHOWING A NORTHEASTWARD ACCELERATION AS SEAN PASSES
TO THE NORTHWEST OF BERMUDA. THE LATEST MODEL SUITE HAS SHIFTED A
BIT TO THE SOUTHEAST...SO THE NHC TRACK FORECAST WAS BE NUDGED IN
THAT DIRECTION. IN A DAY OR SO...A COLD FRONT IS EXPECTED TO
OVERTAKE SEAN AND ABSORB THE SYSTEM. THE NEW FORECAST IS CONSISTENT
WITH THE LARGE-SCALE GUIDANCE...ALTHOUGH A FEW OF THE MODELS NOW
SHOW SEAN DISSIPATED AS EARLY AS 24 HOURS. 
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  10/2100Z 30.9N  69.4W   55 KT  65 MPH
 12H  11/0600Z 32.5N  67.4W   55 KT  65 MPH
 24H  11/1800Z 36.1N  62.9W   50 KT  60 MPH
 36H  12/0600Z...ABSORBED
 
$$
FORECASTER BLAKE
 

WTNT44 KNHC 110236
TCDAT4
 
TROPICAL STORM SEAN DISCUSSION NUMBER  12
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL192011
1100 PM AST THU NOV 10 2011
 
SATELLITE TRENDS HAVE PROVIDED MIXED SIGNALS REGARDING THE INTENSITY
OF SEAN OVER THE PAST FEW HOURS. ON ONE HAND...VERTICAL SHEAR OF
ABOUT 20 KT AS ANALYZED BY UW-CIMSS HAS DISPLACED THE MID-LEVEL
CENTER EAST OF THE LOW-LEVEL CENTER...AS SEEN IN RECENT MICROWAVE
IMAGERY FROM THE FNMOC TC WEBPAGE. HOWEVER...CONVECTIVE CLOUD TOPS
HAVE COOLED AND EXPANDED IN COVERAGE OVER THE PAST FEW HOURS.
THEREFORE...THE INITIAL INTENSITY WILL BE HELD AT 55 KT IN
AGREEMENT WITH 00Z DVORAK CI-NUMBERS FROM TAFB AND SAB. THE NHC
FORECAST SHOWS NO CHANGE IN INTENSITY DURING THE NEXT 12 HOURS...IN
AGREEMENT WITH MOST OF THE GUIDANCE. BY 24 HOURS...SEAN SHOULD BE
ABSORBED BY THE FRONTAL BOUNDARY NOW MOVING OFFSHORE OF THE EAST
COAST OF THE UNITED STATES.
 
RECENT DVORAK AND MICROWAVE FIXES SUGGEST THAT THE LOW-LEVEL CENTER
HAS BEEN MOVING A BIT TO THE RIGHT OF THE PREVIOUS FORECAST...WITH
AN INITIAL MOTION OF 060/11. THIS RIGHTWARD JOG SHOULD BE TEMPORARY
HOWEVER...AS ALL OF THE GUIDANCE SHOWS A NORTHEASTWARD MOTION
DEVELOPING OVERNIGHT AS THE DEEP-LAYER FLOW BECOMES SOUTHWESTERLY
AHEAD OF THE MID/UPPER-LEVEL TROUGH MOVING OFF THE U.S. EAST COAST.
GIVEN THE INITIAL POSITION AND MOTION...THE NEW NHC TRACK FORECAST
HAS BEEN ADJUSTED TO THE RIGHT...OR SOUTHEAST...OF THE PREVIOUS
ONE...AND LIES A LITTLE TO THE RIGHT OF THE GFS AND ECMWF AND CLOSE
TO THE GEFS ENSEMBLE MEAN.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  11/0300Z 31.5N  68.2W   55 KT  65 MPH
 12H  11/1200Z 33.6N  65.3W   55 KT  65 MPH
 24H  12/0000Z...ABSORBED BY FRONT
 
$$
FORECASTER BRENNAN
 

WTNT44 KNHC 110845
TCDAT4
 
TROPICAL STORM SEAN DISCUSSION NUMBER  13
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL192011
500 AM AST FRI NOV 11 2011

SEAN IS SHOWING A SHEARED CLOUD PATTERN IN INFRARED AND TRMM
MICROWAVE SATELLITE IMAGERY THIS MORNING...WITH THE LOW-LEVEL
CENTER NEAR THE WESTERN EDGE OF THE CONVECTIVE OVERCAST.  WHILE
SUBJECTIVE SATELLITE INTENSITY ESTIMATES FROM SAB AND TAFB ARE
UNCHANGED SINCE THE PREVIOUS ADVISORY...INTENSITY ESTIMATES FROM
THE AMSU MICROWAVE SOUNDER AND THE CIMSS ADVANCED DVORAK TECHNIQUE
HAVE DECREASED A LITTLE DURING THE PAST 6-12 HOURS.  IN ADDITION...
AN ASCAT OVERPASS NEAR 0200 UTC SHOWED WINDS NEAR 45 KT IN THE
SOUTHEASTERN QUADRANT.  BASED ON THESE DATA...THE INITIAL INTENSITY
IS DECREASED TO 50 KT.  LITTLE CHANGE IN STRENGTH IS LIKELY BEFORE
SEAN GETS ABSORBED BY A FRONTAL SYSTEM IN 18-24 HOURS.

SEAN IS ACCELERATING TOWARD THE NORTHEAST ON THE SOUTH SIDE OF A
DEVELOPING DEEP-LAYER CYCLONE OVER NEW ENGLAND AND THE CANADIAN
MARITIMES...WITH THE INITIAL MOTION NOW 050/19.  AN EVEN FASTER
MOTION TOWARD THE NORTHEAST IS EXPECTED DURING THE REMAINDER OF THE
LIFE OF THE CYCLONE.

THE WIND RADII HAVE BEEN REVISED BASED ON THE ASCAT DATA.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  11/0900Z 32.9N  66.3W   50 KT  60 MPH
 12H  11/1800Z 35.2N  62.8W   50 KT  60 MPH
 24H  12/0600Z...ABSORBED BY FRONTAL SYSTEM.
 
$$
FORECASTER BEVEN
 

WTNT44 KNHC 111443
TCDAT4

TROPICAL STORM SEAN DISCUSSION NUMBER 14 
NWS NATIONAL HURRICANE CENTER MIAMI FL      AL192011 
1100 AM AST FRI NOV 11 2011

SEAN IS A STRONGLY SHEARED TROPICAL CYCLONE WITH THE LOW-LEVEL
CENTER LOCATED ABOUT 70 N MI TO THE WEST OF THE SHRINKING DENSE
OVERCAST. SATELLITE INTENSITY ESTIMATES FROM TAFB AND SAB HAVE
DECREASED... AND THE INITIAL WIND SPEED IS LOWERED TO 45 KT. A COLD
FRONT... CURRENTLY SITUATED A COUPLE OF HUNDRED N MI TO THE WEST OF
SEAN...IS EXPECTED TO MERGE WITH THE CYCLONE LATER TODAY CAUSING IT
TO LOSE TROPICAL CHARACTERISTICS BY THEN.

THE TROPICAL STORM IS GAINING FORWARD SPEED...AND THE LATEST INITIAL
MOTION ESTIMATE IS 050/20. THE CENTER OF SEAN IS CURRENTLY PASSING
JUST NORTH OF BERMUDA...AND IT IS EXPECTED TO MOVE MORE RAPIDLY
NORTHEASTWARD OVER THE NORTH ATLANTIC UNTIL IT DISSIPATES TONIGHT
OR EARLY SATURDAY.

FORECAST POSITIONS AND MAX WINDS

INIT 11/1500Z 34.0N 64.1W 45 KT 50 MPH 
 12H 12/0000Z 37.2N 59.9W 45 KT 50 MPH...POST-TROP/EXTRATROP 
 24H 12/1200Z...DISSIPATED

$$ FORECASTER CANGIALOSI/STEWART

WTNT44 KNHC 111445
TCDAT4

TROPICAL STORM SEAN DISCUSSION NUMBER 14 
NWS NATIONAL HURRICANE CENTER MIAMI FL      AL192011 
1100 AM AST FRI NOV 11 2011

SEAN IS A STRONGLY SHEARED TROPICAL CYCLONE WITH THE LOW-LEVEL
CENTER LOCATED ABOUT 70 N MI TO THE WEST OF THE SHRINKING DENSE
OVERCAST. SATELLITE INTENSITY ESTIMATES FROM TAFB AND SAB HAVE
DECREASED... AND THE INITIAL WIND SPEED IS LOWERED TO 45 KT. A COLD
FRONT... CURRENTLY SITUATED A COUPLE OF HUNDRED N MI TO THE WEST OF
SEAN...IS EXPECTED TO MERGE WITH THE CYCLONE LATER TODAY CAUSING IT
TO LOSE TROPICAL CHARACTERISTICS BY THEN.

THE TROPICAL STORM IS GAINING FORWARD SPEED...AND THE LATEST INITIAL
MOTION ESTIMATE IS 050/20. THE CENTER OF SEAN IS CURRENTLY PASSING
JUST NORTH OF BERMUDA...AND IT IS EXPECTED TO MOVE MORE RAPIDLY
NORTHEASTWARD OVER THE NORTH ATLANTIC UNTIL IT DISSIPATES TONIGHT
OR EARLY SATURDAY.

FORECAST POSITIONS AND MAX WINDS

INIT 11/1500Z 34.0N 64.1W 45 KT 50 MPH 
 12H 12/0000Z 37.2N 59.9W 45 KT 50 MPH...POST-TROP/EXTRATROP 
 24H 12/1200Z...DISSIPATED

$$ 
FORECASTER CANGIALOSI/STEWART

WTNT44 KNHC 112108
TCDAT4
 
TROPICAL STORM SEAN DISCUSSION NUMBER  15...RETRANSMITTED
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL192011
500 PM AST FRI NOV 11 2011
 
SEAN IS QUICKLY LOSING TROPICAL CHARACTERISTICS. VISIBLE SATELLITE
IMAGES SHOW STABLE STRATOCUMULUS CLOUDS ENTRAINING INTO THE
SOUTHERN HALF OF THE CIRCULATION. THIS STABLE AIR IS ALSO EVIDENT
IN SURFACE OBSERVATIONS...WITH THE DEWPOINT IN BERMUDA FALLING
ABOUT 3C DURING THE LAST FEW HOURS. MEANWHILE...A RAGGED CURVED
BAND OF CONVECTION STILL EXISTS ON THE EAST SIDE OF THE
CIRCULATION...AND THAT IS THE BASIS FOR MAINTAINING ADVISORIES ON
THIS SYSTEM. NONETHELESS...SEAN IS EXPECTED TO BECOME POST-TROPICAL
SOON AND WILL LIKELY BE ABSORBED BY A COLD FRONT...WHICH IS NOW
VERY NEAR THE CYCLONE...TONIGHT OR EARLY SATURDAY.
 
SEAN IS RACING NORTHEASTWARD AND SHOULD CONTINUE MOVING IN THAT
DIRECTION OVER THE NORTH ATLANTIC UNTIL DISSIPATION.

FORECAST POSITIONS AND MAX WINDS
 
INIT  11/2100Z 35.5N  61.3W   45 KT  50 MPH
 12H  12/0600Z 38.2N  56.2W   45 KT  50 MPH...POST-TROP/EXTRATROP
 24H  12/1800Z...DISSIPATED
 
$$
FORECASTER CANGIALOSI
 

