044
WTNT44 KNHC 050851
TCDAT4
TROPICAL STORM GRACE DISCUSSION NUMBER 2
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL092009
500 AM AST MON OCT 05 2009
DESPITE ITS ENVIRONMENT AND UNUSUAL LOCATION...INFRARED SATELLITE
IMAGERY INDICATES THAT GRACE HAS BEEN MAINTAINING A SMALL BUT
IMPRESSIVE INNER CORE OF RELATIVELY DEEP CONVECTION. MORE
RECENTLY...THERE HAS BEEN AN EXPANSION OF COLD-TOPPED CONVECTION IN
A RING SURROUNDING A RAGGED EYE-TYPE FEATURE. BASED ON SUBJECTIVE
DVORAK CLASSIFICATIONS AND THE CURRENT TREND OF INCREASING
ORGANIZATION...THE INITIAL INTENSITY IS RAISED TO 60 KT. IT IS
UNCLEAR WHETHER SURFACE WINDS MATCH THE SATELLITE SIGNATURE...
ESPECIALLY SINCE CONVECTIVE TOPS MIGHT LACK SOME VIGOR OVER 20C
SSTS. HOWEVER...THERE HAVE BEEN NO RECENT DATA TO CONFIRM OR DENY
DVORAK ESTIMATES...OTHER THAN AN ASCAT PASS OF 45-50 KT FROM MUCH
EARLIER.
RECENT FIXES INDICATE THAT GRACE HAS ACCELERATED WHILE MOVING A
LITTLE TO THE LEFT OF ITS PREVIOUS HEADING AND IS NOW MOVING
045/24. THE CYCLONE IS MOVING NORTHEASTWARD IN A DEEP LAYER OF
SOUTHWESTERLY FLOW...BUT IS EXPECTED TO TURN NORTH-NORTHEAST AND
DECELERATE AS A POTENT SHORTWAVE NEARS IT FROM THE SOUTHWEST. ON
THIS TRACK...A STEADY WEAKENING IS FORECAST AS GRACE MOVES OVER
SUB-20C WATER TEMPERATURES IN AN ENVIRONMENT OF MODERATE TO STRONG
WESTERLY SHEAR. GRACE SHOULD MERGE WITH A LARGER EXTRATROPICAL
CYCLONE OR ITS ASSOCIATED COLD FRONT OVER THE NORTHEAST ATLANTIC
WITHIN 24 TO 36 HOURS...IF NOT SOONER.
FORECAST POSITIONS AND MAX WINDS
INITIAL 05/0900Z 43.0N 18.0W 60 KT
12HR VT 05/1800Z 45.5N 16.5W 50 KT
24HR VT 06/0600Z 49.0N 15.0W 45 KT
36HR VT 06/1800Z...DISSIPATED
FORECASTER KIMBERLAIN
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