[Tropical] Tropical Cyclone Discussion

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WTNT44 KNHC 091448
TCDAT4

TROPICAL STORM MARIA DISCUSSION NUMBER  12
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL142011
1100 AM AST FRI SEP 09 2011

THERE HAS BEEN A SIGNIFICANT INCREASE IN DEEP CONVECTION OVERNIGHT
AND THIS MORNING IN ASSOCIATION WITH MARIA.  HOWEVER...THE OVERALL
ORGANIZATION OF THE CYCLONE DOES NOT APPEAR TO HAVE CHANGED VERY
MUCH.  THE AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT HAS FOUND
SOUTHWEST AND LIGHT WEST WINDS...BUT IT HAS NOT BEEN ABLE TO LOCATE
A WELL-DEFINED LOW-LEVEL CENTER.  HOWEVER...THERE ARE ENOUGH
FLIGHT-LEVEL WINDS INDICATING A BROAD CLOSED CIRCULATION THAT
JUSTIFIES MAINTAINING ADVISORIES ON THIS SYSTEM.

THE AIRCRAFT HAS MEASURED A PEAK FLIGHT-LEVEL WIND OF 42 KT TO THE
EAST OF THE CENTER...BUT HAS NOT YET SAMPLED THE NORTHEAST QUADRANT
WHERE THE STRONGEST WINDS ARE LIKELY OCCURRING.  THE INITIAL
INTENSITY...THEREFORE HAS BEEN RAISED TO 40 KT...BASED ON DVORAK
ESTIMATES OF 45 KT AND THE RECENT INCREASE IN DEEP CONVECTION.  THE
UPPER-LEVEL PATTERN AHEAD OF MARIA DOES NOT APPEAR TO BE VERY
CONDUCIVE FOR SIGNIFICANT STRENGTHENING.  AN UPPER-LEVEL LOW
LOCATED TO THE NORTH OF THE LEEWARD ISLANDS IS EXPECTED TO PRODUCE
MODERATE WEST TO SOUTHWEST SHEAR OVER THE CYCLONE DURING THE NEXT
2-3 DAYS...AND THE OFFICIAL FORECAST ONLY CALLS FOR SLIGHT
STRENGTHENING DURING THAT TIME.  LATER IN THE PERIOD THE
UPPER-LEVEL ENVIRONMENT IS FORECAST TO BECOME MORE CONDUCIVE AND
THE NHC FORECAST CALLS FOR STRENGTHENING...BUT NOT QUITE AS MUCH
AS SHOWN BY MOST OF THE GUIDANCE.

THE BEST ESTIMATE OF THE INITIAL MOTION IS 285/15. MARIA IS EXPECTED
TO CONTINUE MOVING WEST-NORTHWESTWARD TO THE SOUTH OF A SUBTROPICAL
RIDGE OVER THE CENTRAL AND WESTERN ATLANTIC.  IN ABOUT 72 HOURS...
THE WESTERN PORTION OF THE RIDGE IS FORECAST TO WEAKEN AS A TROUGH
MOVES INTO THE SOUTHEASTERN UNITED STATES. THIS SHOULD RESULT IN A
TURN TOWARD THE NORTHWEST AND NORTH NEAR THE END OF THE FORECAST
PERIOD.  HOWEVER...IT SHOULD BE NOTED THAT THE ECMWF MODEL DEPICTS A
WEAKER CYCLONE THAT CONTINUES MORE WESTWARD.  THE UPDATED NHC
FORECAST IS SIMILAR TO THE PREVIOUS ADVISORY AND IS BETWEEN THE
GFS..WHICH TURNS MARIA NORTHWARD IN 4-5 DAYS...AND THE
AFOREMENTIONED ECMWF.


FORECAST POSITIONS AND MAX WINDS

INIT  09/1500Z 14.2N  57.5W   40 KT  45 MPH
 12H  10/0000Z 15.1N  59.9W   45 KT  50 MPH
 24H  10/1200Z 16.5N  62.4W   45 KT  50 MPH
 36H  11/0000Z 17.9N  64.5W   45 KT  50 MPH
 48H  11/1200Z 19.3N  66.5W   50 KT  60 MPH
 72H  12/1200Z 22.0N  69.8W   55 KT  65 MPH
 96H  13/1200Z 24.0N  72.0W   65 KT  75 MPH
120H  14/1200Z 27.5N  73.5W   70 KT  80 MPH

$$
FORECASTER BROWN



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