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| #58228 (Received by flhurricane at: 3:40 AM 24.Nov.2005) TCDAT3 TROPICAL STORM DELTA DISCUSSION NUMBER 3 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 4 AM EST THU NOV 24 2005 INFRARED IMAGERY THIS MORNING INDICATES THAT DELTA IS A LITTLE BETTER ORGANIZED...WITH SOMEWHAT INCREASED CONVECTIVE BANDING AND SOME ANTICYCLONIC OUTFLOW IN THE EASTERN SEMICIRCLE. WHILE THE CONVECTIVE AREA ASSOCIATED WITH THE STORM IS FAIRLY SMALL...DELTA HAS A LARGE CYCLONIC ENVELOPE PROVIDED BY ITS DEVELOPMENT AS A NON-TROPICAL LOW. SATELLITE INTENSITY ESTIMATES ARE 55 KT FROM TAFB AND SAB...AND THAT IS THE INITIAL INTENSITY. IT SHOULD BE NOTED THAT A TRMM OVERPASS AT 0403Z SUGGESTS THE CENTER IS NORTHEAST OF THE POSTIONS FROM TAFB AND SAB...AND IF LATER INFORMATION CONFIRMS THIS THE POSITION AND MOTION MAY NEED SOME ADJUSTMENT ON THE NEXT ADVISORY. THE INITIAL MOTION IS A SOMEWHAT UNCERTAIN 155/7. DELTA IS CURRENTLY BEING STEERED BY A MID/UPPER-LEVEL TROUGH TO THE NORTH AND EAST...AND A HIGH-AMPLITUDE DEEP-LAYER RIDGE TO THE WEST. LARGE-SCALE MODELS FORECAST THE RIDGE TO SLOWLY WEAKEN DURING THE NEXT 48 HR AS A SHORTWAVE TROUGH CURRENTLY OVER FLORIDA MOVES EASTWARD. BY 72 HR...THIS TROUGH WILL BE AMPLIFYING JUST WEST OF DELTA...WITH THE LARGE-SCALE MODELS EITHER FORMING ANOTHER AREA OF LOW PRESSURE WEST OF THE STORM OR SPLITTING THE STORM IN TWO AS A RESULT. THIS PATTERN EVOLUTION SHOULD ALLOW DELTA TO CONTINUE MORE SOUTHWARD OR SOUTHEASTWARD FOR 24 HR OR SO...FOLLOWED BY A TURN BACK TOWARD THE NORTH AS THE RIDGE WEAKENS. BY 72 HR...THE FALLING PRESSURES WEST OF THE STORM SHOULD MOVE IT ALONG FASTER TOWARD THE NORTH OR NORTH-NORTHWEST. THE NEW FORECAST TRACK CALLS FOR DELTA TO CONTINUE SOUTH-SOUTHEASTWARD FOR 24 HR...BUT NOT AS FAR SOUTH AS MOST OF THE MODELS ARE SUGGESTING. AFTER THAT...THE FORECAST CALLS FOR A TURN TOWARD THE NORTH. THE NEW FORECAST IS SIMILAR TO...BUT SLOWER THAN...THE PREVIOUS FORECAST AND IS IN BEST AGREEMENT WITH THE GFDL. ANALYSES FROM CIMSS AT THE UNIVERSITY OF WISCONSIN INDICATE ABOUT 30 KT OF VERTICAL SHEAR OVER DELTA. HOWEVER...THE STORM DOES NOT APPEAR QUITE THAT BADLY SHEARED IN SATELLITE IMAGERY. THE LARGE-SCALE MODELS FORECAST A STRONG NORTHERLY UPPER-LEVEL JET STREAM TO PERSIST NEAR OR JUST WEST OF DELTA THROUGH 48 HR...AND HOW MUCH THE STORM STRENGTHENS WILL DEPEND ON HOW FAR AWAY IT CAN STAY FROM THAT SHEAR. BETWEEN 48-72 HR...THERE IS A CHANCE THE SHEAR COULD DECREASE FOR A SHORT TIME AS THE NEW SHORTWAVE AMPLIFIES WEST OF DELTA...BUT BY THAT TIME THE STORM WILL LIKELY BE MOVING INTO COOLER SEA SURFACE TEMPERATES. THE INTENSITY FORECAST IS BASED ON THE PREMISE THAT DELTA WILL AVOID THE WORST OF THE SHEAR THROUGH 72 HR...WITH SLIGHT STRENGTHENING DURING THE NEXT 24 HR FOLLOWED BY GRADUAL WEAKENING AFTER 48 HR. AFTER 72 HR... INCREASING SHEAR...COOLER WATERS...AND THE DEVELOPMENT OF THE NEW LOW WEST OF DELTA COULD CAUSE THE STORM TO START EXTRATROPICAL TRANSITION AS SHOWN IN THE FORECAST. THE 12 FT SEAS HAVE BEEN EXPANDED IN THE NORTHERN SEMICIRCLE BASED ON SHIP REPORTS. FORECASTER BEVEN FORECAST POSITIONS AND MAX WINDS INITIAL 24/0900Z 24.7N 39.8W 55 KT 12HR VT 24/1800Z 24.2N 39.6W 55 KT 24HR VT 25/0600Z 23.9N 39.4W 60 KT 36HR VT 25/1800Z 24.2N 39.3W 60 KT 48HR VT 26/0600Z 24.9N 39.4W 55 KT 72HR VT 27/0600Z 27.0N 39.5W 55 KT 96HR VT 28/0600Z 31.0N 40.0W 50 KT...BECOMING EXTRATROPICAL 120HR VT 29/0600Z 34.0N 41.0W 50 KT...EXTRATROPICAL |
