[Tropical] Tropical Cyclone Discussion

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WTNT44 KNHC 130233
TCDAT4

TROPICAL STORM MARIA DISCUSSION NUMBER  26
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL142011
1100 PM AST MON SEP 12 2011

ALTHOUGH UNDER THE INFLUENCE OF STRONG SOUTHWESTERLY SHEAR...MARIA
CONTINUES TO PRODUCE DEEP CONVECTION WHICH APPEARS TO HAVE RECENTLY
DEVELOPED A BIT CLOSER TO THE CENTER.  HOWEVER...LAST-LIGHT VISIBLE
IMAGES SUGGESTED THAT THE LOW-LEVEL CIRCULATION IS LESS DEFINED AND
THE COVERAGE OF COLD CLOUD TOPS IS NOT AS WIDESPREAD AS 24 HOURS
AGO. WITH DVORAK T-NUMBERS FROM TAFB AND SAB UNCHANGED AND THE
SATELLITE PRESENTATION GENERALLY NO DIFFERENT THAN EARLIER...THE
INITIAL INTENSITY IS HELD AT 45 KT.  THE PREVAILING WESTERLY SHEAR
OVER MARIA IS NOT LIKELY TO DECREASE SUBSTANTIALLY DURING THE NEXT
COUPLE OF DAYS WHICH SUGGESTS THAT ANY INTENSIFICATION WILL BE
SHORT-LIVED.  THE SHEAR IS FORECAST TO INCREASE EVEN FURTHER AFTER
ABOUT 60 HOURS...MAKING THE SURVIVAL OF MARIA AS A TROPICAL CYCLONE
BEYOND THAT TIME QUESTIONABLE.  THE OFFICIAL INTENSITY FORECAST IS
ESSENTIALLY AN UPDATE OF THE PREVIOUS ONE AND SHOWS LITTLE CHANGE
IN STRENGTH DURING THE FORECAST PERIOD.  A 96-HOUR FORECAST POINT IS
INDICATED...THOUGH THE GUIDANCE IS AMBIGUOUS AS TO WHETHER THE
POST-TROPICAL CYCLONE WILL BE A VIABLE ENTITY AT THAT TIME. AN
ALTERNATIVE AND EQUALLY PLAUSIBLE SCENARIO WOULD BE FOR MARIA TO
SUCCUMB TO THE HIGH SHEAR...BECOME A SHALLOW CYCLONE..AND
DISSIPATE.

THE POOR DEFINITION OF THE CENTER AND NO RECENT MICROWAVE DATA HAS
MADE IT DIFFICULT TO ASSESS THE INITIAL MOTION...BUT IT APPEARS AS
IF MARIA HAS BEEN NEARLY STATIONARY OR DRIFTING NORTHWESTWARD.  THE
STORM HAS TEMPORARILY BEEN TRAPPED IN A WEAK STEERING FLOW BETWEEN
MID-LEVEL ANTICYCLONES TO ITS EAST AND WEST.  WITHIN ABOUT 24
HOURS...THE STORM IS FORECAST TO BE CAUGHT UP IN A DEEP-LAYER
SOUTHERLY FLOW ON THE WEST SIDE OF A CENTRAL ATLANTIC RIDGE.  AN
ACCELERATION TOWARD THE NORTH-NORTHEAST TO NORTHEAST SHOULD OCCUR
IN 48-72 HOURS AHEAD OF A LARGE MID-LATITUDE TROUGH SWINGING
THROUGH NEW ENGLAND.  THE TRACK GUIDANCE IS RELATIVELY STABLE AND
THE SPREAD IS REASONABLY SMALL...MAKING ONLY COSMETIC CHANGES
NECESSARY TO THE PREVIOUS NHC TRACK FORECAST.

A CREDIBLE 40-KT SHIP REPORT ABOUT 175 N MI EAST-NORTHEAST OF THE
CENTER OF MARIA WAS USED TO EXPAND THE WIND RADIUS IN THE NORTHEAST
QUADRANT.

FORECAST POSITIONS AND MAX WINDS

INIT  13/0300Z 21.3N  67.5W   45 KT  50 MPH
 12H  13/1200Z 22.3N  68.1W   45 KT  50 MPH
 24H  14/0000Z 24.0N  68.8W   45 KT  50 MPH
 36H  14/1200Z 26.3N  69.1W   50 KT  60 MPH
 48H  15/0000Z 29.3N  68.8W   50 KT  60 MPH
 72H  16/0000Z 37.5N  64.0W   50 KT  60 MPH
 96H  17/0000Z 48.5N  50.0W   50 KT  60 MPH...POST-TROP/EXTRATROP
120H  18/0000Z...DISSIPATED

$$
FORECASTER KIMBERLAIN


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