[Tropical] Tropical Cyclone Discussion

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WTNT44 KNHC 120844
TCDAT4

TROPICAL STORM MARIA DISCUSSION NUMBER  23
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL142011
500 AM AST MON SEP 12 2011

MARIA REMAINS A STRONGLY SHEARED TROPICAL CYCLONE WITH DEEP
CONVECTION CONFINED TO THE EASTERN HALF OF THE CIRCULATION. DVORAK
CLASSIFICATIONS WERE ESSENTIALLY UNCHANGED SINCE 0000 UTC...SO THE
INITIAL WIND SPEED IS HELD AT 50 KT.  BUOY 41043 LOCATED ABOUT 75
N MI EAST OF THE ESTIMATED CENTER HAS REPORTED SUSTAINED WINDS AS
HIGH AS 41 KT DURING THE PAST FEW HOURS.

THE LOW-LEVEL CENTER OF MARIA IS VERY DIFFICULT TO LOCATE. USING A
SSMIS PASS AROUND 0000 UTC AND CONTINUITY...THE INITIAL MOTION
ESTIMATE IS 305/8. GLOBAL MODELS ARE IN GOOD AGREEMENT ON THE LARGE
SCALE PATTERN EVOLUTION THAT WILL AFFECT THE FUTURE TRACK OF MARIA.
A MID- TO UPPER-LEVEL TROUGH CURRENTLY OVER THE EASTERN UNITED
STATES IS EXPECTED TO MOVE EASTWARD AND CAUSE MARIA TO GRADUALLY
TURN TOWARD THE NORTH DURING THE NEXT 48 HOURS. ANOTHER
TROUGH...THIS ONE BEING LARGER AND STRONGER...WILL MOVE OVER
ATLANTIC CANADA AND THE NORTHEAST UNITED STATES LATE THIS WEEK.
THIS FLOW PATTERN SHOULD THEN TURN MARIA TO THE NORTHEAST WITH A
SIGNIFICANT INCREASE IN FORWARD SPEED.

WESTERLY SHEAR OF ABOUT 20 KT...PRIMARILY ASSOCIATED WITH AN
UPPER-LEVEL LOW TO THE NORTHWEST OF THE CYCLONE...IS CURRENTLY
AFFECTING MARIA. THE SHIPS MODEL ONLY SHOWS A SLIGHT DECREASE IN
THE SHEAR DURING THE NEXT COUPLE OF DAYS BEFORE IT INCREASES
SHARPLY IN ABOUT 72 HOURS. THIS UNFAVORABLE ATMOSPHERIC
ENVIRONMENT...COMBINED WITH A COLD WATER WAKE LEFT BY HURRICANE
KATIA SHOULD LIMIT THE INTENSIFICATION PROCESS. THE OFFICIAL
FORECAST REMAINS ON THE LOW END OF THE MODEL GUIDANCE NEAR THE
LGEM. THE AFOREMENTIONED STRONG SHEAR...THE INTERACTION WITH A
FRONT...AND SEA SURFACE TEMPERATURES LOWER THAN 20C SHOULD CAUSE
MARIA TO TRANSITION TO AN EXTRATROPICAL CYCLONE IN ABOUT FOUR DAYS.

THE 12-FT SEA RADII HAVE BEEN MODIFIED BASED ON A 0340 UTC ALTIMETER
PASS.

FORECAST POSITIONS AND MAX WINDS

INIT  12/0900Z 20.8N  66.3W   50 KT  60 MPH
 12H  12/1800Z 21.5N  67.2W   50 KT  60 MPH
 24H  13/0600Z 22.7N  68.3W   50 KT  60 MPH
 36H  13/1800Z 24.0N  69.0W   55 KT  65 MPH
 48H  14/0600Z 26.1N  69.2W   55 KT  65 MPH
 72H  15/0600Z 32.8N  67.6W   65 KT  75 MPH
 96H  16/0600Z 41.5N  60.5W   60 KT  70 MPH...POST-TROP/EXTRATROP
120H  17/0600Z 51.0N  46.0W   50 KT  60 MPH...POST-TROP/EXTRATROP

$$
FORECASTER CANGIALOSI



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