ATL: SEAN - Post-Tropical - Discussion

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Re: ATL: INVEST 98L - Discussion

#21 Postby MGC » Mon Nov 07, 2011 1:39 pm

Convection starting to wrap around the CC.....looks like an upgrade if this trend continues.....MGC
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#22 Postby CrazyC83 » Mon Nov 07, 2011 2:47 pm

Any Recon planned? That would help determine the core data. It doesn't appear frontal to me...
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Re:

#23 Postby cycloneye » Mon Nov 07, 2011 2:54 pm

CrazyC83 wrote:Any Recon planned? That would help determine the core data. It doesn't appear frontal to me...


Nothing planned.

NOUS42 KNHC 071745
WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
1245 PM EST MON 07 NOVEMBER 2011
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
VALID 08/1100Z TO 09/1100Z NOVEMBER 2011
TCPOD NUMBER.....11-160

I. ATLANTIC REQUIREMENTS
1. NEGATIVE RECONNAISSANCE REQUIREMENTS
2. OUTLOOK FOR SUCCEEDING DAY.....NEGATIVE.
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Re: ATL: INVEST 98L - Discussion

#24 Postby bg1 » Mon Nov 07, 2011 2:57 pm

Finally! Some action! Between this and the Mediterranean cyclone, I think there will be interesting hours (at least) ahead.
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Re: ATL: INVEST 98L - Models

#25 Postby cycloneye » Mon Nov 07, 2011 2:58 pm

18z models.

Code: Select all

WHXX01 KWBC 071823
CHGHUR
TROPICAL CYCLONE GUIDANCE MESSAGE
NWS NATIONAL HURRICANE CENTER MIAMI FL
1823 UTC MON NOV 7 2011
 
DISCLAIMER...NUMERICAL MODELS ARE SUBJECT TO LARGE ERRORS.
PLEASE REFER TO NHC OFFICIAL FORECASTS FOR TROPICAL CYCLONE
AND SUBTROPICAL CYCLONE INFORMATION.
 
ATLANTIC OBJECTIVE AIDS FOR
 
DISTURBANCE INVEST (AL982011) 20111107 1800 UTC
 
        ...00 HRS...   ...12 HRS...   ...24 HRS. ..   ...36 HRS...
        111107  1800   111108  0600   111108  1800   111109  0600
 
         LAT    LON     LAT    LON     LAT    LON     LAT    LON
BAMS    27.5N  69.3W   27.5N  71.2W   27.2N  73.3W   27.0N  74.9W
BAMD    27.5N  69.3W   28.0N  68.9W   28.1N  69.5W   28.1N  69.9W
BAMM    27.5N  69.3W   27.5N  70.1W   27.4N  71.2W   27.0N  72.1W
LBAR    27.5N  69.3W   27.8N  68.9W   28.7N  68.9W   29.9N  69.1W
SHIP        40KTS          40KTS          40KTS          39KTS
DSHP        40KTS          40KTS          40KTS          39KTS
 
        ...48 HRS...   ...72 HRS...   ...96 HRS. ..   ..120 HRS...
        111109  1800   111110  1800   111111  1800   111112  1800
 
         LAT    LON     LAT    LON     LAT    LON     LAT    LON
BAMS    27.0N  75.9W   26.5N  76.5W   28.5N  70.0W   30.3N  66.1W
BAMD    28.8N  69.9W   29.7N  69.7W   37.7N  63.8W   53.1N  54.0W
BAMM    27.0N  72.3W   26.9N  72.2W   32.0N  66.6W   41.0N  54.2W
LBAR    31.2N  69.7W   34.7N  68.8W   40.3N  61.0W   45.9N  44.8W
SHIP        35KTS          22KTS           0KTS           0KTS
DSHP        35KTS          22KTS           0KTS           0KTS
 
         ...INITIAL CONDITIONS...
LATCUR =  27.5N LONCUR =  69.3W DIRCUR = 250DEG SPDCUR =   2KT
LATM12 =  27.7N LONM12 =  68.8W DIRM12 = 233DEG SPDM12 =   2KT
LATM24 =  28.0N LONM24 =  68.6W
WNDCUR =   40KT RMAXWD =  120NM WNDM12 =   40KT
CENPRS = 1005MB OUTPRS = 1010MB OUTRAD =  275NM SDEPTH =   M
RD34NE =  360NM RD34SE =    0NM RD34SW =  150NM RD34NW = 360NM
 


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#26 Postby TheEuropean » Mon Nov 07, 2011 6:41 pm

Up to 70 Percent:

ABNT20 KNHC 072334
TWOAT

TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
700 PM EST MON NOV 7 2011

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

A NON-TROPICAL LOW PRESSURE SYSTEM LOCATED ABOUT 435 MILES SOUTHWEST
OF BERMUDA CONTINUES TO PRODUCE GALE FORCE WINDS OVER AN AREA
EXTENDING SEVERAL HUNDRED MILES TO THE NORTH AND WEST OF THE
CENTER. SHOWER AND THUNDERSTORM ACTIVITY ASSOCIATED WITH THIS LOW
HAS CHANGED LITTLE OVER THE PAST FEW HOURS...AND THIS SYSTEM STILL
HAS SOME FRONTAL CHARACTERISTICS. HOWEVER...CONDITIONS APPEAR
CONDUCIVE FOR THIS LOW TO GRADUALLY ACQUIRE SUBTROPICAL
CHARACTERISTICS TONIGHT OR TUESDAY. THIS SYSTEM HAS A HIGH
CHANCE...70 PERCENT...OF BECOMING A SUBTROPICAL CYCLONE DURING THE
NEXT 48 HOURS AS IT MOVES SLOWLY WESTWARD TONIGHT AND MOVES
NORTHWESTWARD ON TUESDAY. ADDITIONAL INFORMATION ON THIS GALE AREA
CAN BE FOUND IN HIGH SEAS FORECASTS ISSUED BY THE NOAA NATIONAL
WEATHER SERVICE UNDER AWIPS HEADER NFDHSFAT1...AND UNDER WMO HEADER
FZNT01 KWBC.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER BRENNAN
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#27 Postby AdamFirst » Mon Nov 07, 2011 8:01 pm

Hoping this gets a name. I really want my name on a storm this year. 8-)
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Re: ATL: INVEST 98L - Discussion

#28 Postby cycloneye » Mon Nov 07, 2011 8:07 pm

00z Best Track

No renumber.

AL, 98, 2011110800, , BEST, 0, 276N, 695W, 40, 1004, LO

ftp://ftp.tpc.ncep.noaa.gov/atcf/tcweb/ ... 011.invest
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Re:

#29 Postby fci » Tue Nov 08, 2011 12:37 am

AdamFirst wrote:Hoping this gets a name. I really want my name on a storm this year. 8-)


Is your name Sean?
Or Adam?
Or First?
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#30 Postby Extratropical94 » Tue Nov 08, 2011 12:49 am

80%

A LARGE NON-TROPICAL LOW PRESSURE SYSTEM CENTERED ABOUT 460 MILES
SOUTHWEST OF BERMUDA CONTINUES TO PRODUCE GALE-FORCE WINDS OVER
AN AREA EXTENDING SEVERAL HUNDRED MILES WEST THROUGH NORTHEAST OF
THE CENTER. RECENT SATELLITE INFORMATION INDICATES THE LOW-LEVEL
CIRCULATION HAS BECOME BETTER DEFINED AND THAT GALE-FORCE WINDS
HAVE ALSO DEVELOPED CLOSE TO THE SURFACE CENTER. IN ADDITION...
THUNDERSTORM ACTIVITY HAS INCREASED AND BECOME BETTER ORGANIZED
DURING THE PAST FEW HOURS AND IF THIS TREND CONTINUES...THEN
ADVISORIES COULD BEEN INITIATED ON THIS LOW PRESSURE AREA LATER
THIS MORNING. THIS SYSTEM HAS A HIGH CHANCE...80 PERCENT...OF
BECOMING A SUBTROPICAL CYCLONE DURING THE NEXT 48 HOURS AS IT
DRIFTS WESTWARD TODAY...AND THEN TURNS NORTHWESTWARD BY WEDNESDAY.
ADDITIONAL INFORMATION ON THIS GALE AREA CAN BE FOUND IN HIGH SEAS
FORECASTS ISSUED BY THE NOAA NATIONAL WEATHER SERVICE UNDER AWIPS
HEADER NFDHSFAT1...AND UNDER WMO HEADER FZNT01 KWBC.
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Re: ATL: INVEST 98L - Discussion

#31 Postby Brent » Tue Nov 08, 2011 2:46 am

lol Advisory is out early

SUBTROPICAL STORM SEAN ADVISORY NUMBER 1
NWS NATIONAL HURRICANE CENTER MIAMI FL AL192011
500 AM EDT TUE NOV 08 2011


...NEW SUBTROPICAL STORM DEVELOPS MIDWAY BETWEEN BERMUDA AND
THE BAHAMAS...


SUMMARY OF 500 AM EDT...0900 UTC...INFORMATION
----------------------------------------------
LOCATION...27.2N 69.4W
ABOUT 445 MI...720 KM SW OF BERMUDA
MAXIMUM SUSTAINED WINDS...45 MPH...75 KM/H
PRESENT MOVEMENT...STATIONARY
MINIMUM CENTRAL PRESSURE...1002 MB...29.59 INCHES
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Re:

#32 Postby rog » Tue Nov 08, 2011 5:05 am

AdamFirst wrote:Hoping this gets a name. I really want my name on a storm this year. 8-)


Looks like you got your wish. :)
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ATL: SEAN - Advisories

#33 Postby cycloneye » Tue Nov 08, 2011 5:34 am

BULLETIN
SUBTROPICAL STORM SEAN ADVISORY NUMBER 1...CORRECTED
NWS NATIONAL HURRICANE CENTER MIAMI FL AL192011
400 AM EST TUE NOV 08 2011

CORRECTED MOTION IN SUMMARY SECTION

...NEW SUBTROPICAL STORM DEVELOPS MIDWAY BETWEEN BERMUDA AND
THE BAHAMAS...


SUMMARY OF 400 AM EST...0900 UTC...INFORMATION
----------------------------------------------
LOCATION...27.2N 69.4W
ABOUT 445 MI...720 KM SW OF BERMUDA
MAXIMUM SUSTAINED WINDS...45 MPH...75 KM/H
PRESENT MOVEMENT...STATIONARY
MINIMUM CENTRAL PRESSURE...1002 MB...29.59 INCHES


WATCHES AND WARNINGS
--------------------
THERE ARE NO COASTAL WATCHES OR WARNINGS IN EFFECT.


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 400 AM EST...0900 UTC...THE CENTER OF SUBTROPICAL STORM SEAN WAS
LOCATED NEAR LATITUDE 27.2 NORTH...LONGITUDE 69.4 WEST. THE STORM IS
NEARLY STATIONARY...AND LITTLE MOTION IS EXPECTED TODAY. A SLOW
WESTWARD OR NORTHWESTWARD MOTION IS FORECAST TO BEGIN BY TONIGHT OR
WEDNESDAY.

MAXIMUM SUSTAINED WINDS ARE NEAR 45 MPH...75 KM/H...WITH HIGHER
GUSTS. LITTLE CHANGE IN STRENGTH IS FORECAST DURING THE NEXT 48
HOURS.

WINDS OF 40 MPH EXTEND OUTWARD UP TO 380 MILES...610 KM...PRIMARILY
WEST THROUGH NORTHEAST OF THE CENTER.

THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 1002 MB...29.59 INCHES.


HAZARDS AFFECTING LAND
----------------------
NONE


NEXT ADVISORY
-------------
NEXT COMPLETE ADVISORY...1000 AM EST.

$$
FORECASTER STEWART




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
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Re: ATL: SEAN - Subtropical Storm - Discussion

#34 Postby cycloneye » Tue Nov 08, 2011 6:45 am

The question now is if Sean makes the transition to a pure tropical storm before it gets caught in the SW flow out to sea.

First visible image.

Image
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Re: ATL: SEAN - Subtropical Storm - Discussion

#35 Postby cycloneye » Tue Nov 08, 2011 7:47 am

12z Best Track still has Sean as Subtropical storm.

AL, 19, 2011110812, , BEST, 0, 276N, 694W, 40, 1002, SS

ftp://ftp.tpc.ncep.noaa.gov/atcf/tcweb/ ... 011.invest
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#36 Postby brunota2003 » Tue Nov 08, 2011 8:16 am

Of note:

SUBTROPICAL STORM SEAN TROPICAL CYCLONE UPDATE
NWS NATIONAL HURRICANE CENTER MIAMI FL AL192011
700 AM EST TUE NOV 08 2011

AT 700 AM EST...1200 UTC...THE BERMUDA WEATHER SERVICE HAS ISSUED A
TROPICAL STORM WATCH FOR BERMUDA.

$$
FORECASTER BLAKE

Also, quite an interesting system. What's up with this line?

OVERALL...ONLY A SLIGHT INCREASE IN STRENGTH IS EXPECTED...ASSUMING THAT AN EYE FEATURE DOES NOT DEVELOP.

Stewart is generally more clear about things, I just thought that was an interesting statement.
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Re: ATL: SEAN - Subtropical Storm - Discussion

#37 Postby Macrocane » Tue Nov 08, 2011 8:36 am

The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products


Very interesting discussion, shallow systems could intensify more than expected: 2009 Grace, Vince, Epsilon, to name a few. In my unofficial opinion Sean is transitioning to a tropical system as it has got rid of the dry air in its circulation and the strongest convection is near the center.
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Re: ATL: SEAN - Subtropical Storm - Discussion

#38 Postby Thunder44 » Tue Nov 08, 2011 8:49 am

cycloneye wrote:The question now is if Sean makes the transition to a pure tropical storm before it gets caught in the SW flow out to sea.

First visible image.
http://www.nrlmry.navy.mil/htdocs_dyn_a ... .100pc.jpg


I think it will make the transition to a TS in 24-36hrs. Convection is already getting deeper and more consolidated around the center. On water vapor imagery, the ULL appears to be filling in, as well.
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Re: ATL: SEAN - Advisories

#39 Postby cycloneye » Tue Nov 08, 2011 9:44 am

BULLETIN
SUBTROPICAL STORM SEAN ADVISORY NUMBER 2
NWS NATIONAL HURRICANE CENTER MIAMI FL AL192011
1100 AM AST TUE NOV 08 2011

...SEAN EXPECTED TO BECOME A TROPICAL STORM LATER TODAY...


SUMMARY OF 1100 AM AST...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...27.7N 69.4W
ABOUT 420 MI...675 KM SW OF BERMUDA
MAXIMUM SUSTAINED WINDS...45 MPH...75 KM/H
PRESENT MOVEMENT...N OR 360 DEGREES AT 2 MPH...4 KM/H
MINIMUM CENTRAL PRESSURE...1002 MB...29.59 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY...

NONE.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A TROPICAL STORM WATCH IS IN EFFECT FOR...
* BERMUDA

A TROPICAL STORM WATCH MEANS THAT TROPICAL STORM CONDITIONS ARE
POSSIBLE WITHIN THE WATCH AREA...GENERALLY WITHIN 48 HOURS.

INTERESTS IN BERMUDA SHOULD MONITOR PRODUCTS ISSUED BY THE BERMUDA
WEATHER SERVICE.


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 1100 AM AST...1500 UTC...THE CENTER OF SUBTROPICAL STORM SEAN WAS
LOCATED NEAR LATITUDE 27.7 NORTH...LONGITUDE 69.4 WEST. THE STORM IS
MOVING TOWARD THE NORTH NEAR 2 MPH...4 KM/H. A SLOW MOTION TOWARD
THE WEST-NORTHWEST IS EXPECTED TO BEGIN LATER TODAY...WITH A TURN
TOWARD THE NORTHWEST FORECAST BY WEDNESDAY.

MAXIMUM SUSTAINED WINDS ARE NEAR 45 MPH...75 KM/H...WITH HIGHER
GUSTS. LITTLE CHANGE IN STRENGTH IS FORECAST DURING THE NEXT 48
HOURS.

WINDS OF 40 MPH EXTEND OUTWARD UP TO 380 MILES...610 KM...PRIMARILY
TO THE NORTH OF THE CENTER.

ESTIMATED MINIMUM CENTRAL PRESSURE IS 1002 MB...29.59 INCHES.


HAZARDS AFFECTING LAND
----------------------
WIND...TROPICAL STORM CONDITIONS ARE POSSIBLE ON BERMUDA LATE
THURSDAY.

SURF...SWELLS GENERATED BY SEAN ARE EXPECTED TO AFFECT PORTIONS OF
THE SOUTHEASTERN COAST OF THE UNITED STATES DURING THE NEXT COUPLE
OF DAYS. THESE SWELLS WILL CAUSE LIFE-THREATENING SURF AND RIP
CURRENTS. PLEASE SEE STATEMENTS FROM YOUR LOCAL NATIONAL WEATHER
SERVICE OFFICE FOR MORE DETAILS.


NEXT ADVISORY
-------------
NEXT INTERMEDIATE ADVISORY...200 PM AST.
NEXT COMPLETE ADVISORY...500 PM AST.

$$
FORECASTER BLAKE


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
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cycloneye
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Re: ATL: SEAN - Subtropical Storm - Discussion

#40 Postby cycloneye » Tue Nov 08, 2011 9:44 am

...SEAN EXPECTED TO BECOME A TROPICAL STORM LATER TODAY...


SUMMARY OF 1100 AM AST...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...27.7N 69.4W
ABOUT 420 MI...675 KM SW OF BERMUDA
MAXIMUM SUSTAINED WINDS...45 MPH...75 KM/H
PRESENT MOVEMENT...N OR 360 DEGREES AT 2 MPH...4 KM/H
MINIMUM CENTRAL PRESSURE...1002 MB...29.59 INCHES
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