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| #59187 (Received by flhurricane at: 10:17 PM 29.Nov.2005) TCDAT4 TROPICAL STORM EPSILON DISCUSSION NUMBER 3 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 10 PM EST TUE NOV 29 2005 WHILE ITS POSITION NEAR THE CENTER OF A LARGE UPPER-LEVEL LOW SUGGESTS THAT EPSILON HAS NOT FULLY SHED SUBTROPICAL CHARACTERISTICS...THE LOW-LEVEL CENTER HAS REMAINED BENEATH THE PERSISTENT CENTRAL CONVECTION DURING THE PAST SEVERAL HOURS. ADDITIONALLY...A TRMM OVERPASS AT 2051Z AND A QUIKSCAT OVERPASS AT 2155Z BOTH SUGGEST THAT THE CYCLONE HAS FORMED AN INNER WIND CORE MORE CHARACTERISTIC OF A TROPICAL CYCLONE...WITH THE QUIKSCAT DATA SHOWING 40 KT WINDS NEAR THE CENTER. SATELLITE INTENSITY ESTIMATES ARE SUBTROPICAL 45-50 KT FROM TAFB...AND TROPICAL 35 KT FROM SAB AND AFWA. BASED ON THE ABOVE...EPSILON REMAINS A 45 KT TROPICAL STORM FOR THIS PACKAGE. AN AMSU OVERPASS AT ABOUT 02Z MAY PROVIDE MORE INFORMATION ON THE THERMAL STRUCTURE OF THE STORM. THE INITIAL MOTION REMAINS 270/7. EPSILON...AND THE UPPER-LEVEL LOW IT IS EMBEDDED IN....ARE SOUTH OF A DEEP-LAYER RIDGE THAT IS MOVING EASTWARD FROM SOUTHEASTERN CANADA INTO THE ATLANTIC. THE LARGE- SCALE MODELS FORECAST THIS RIDGE TO PASS NORTH OF THE CYCLONE DURING THE NEXT 24 HR...THEN CONTINUE EASTWARD AND WEAKEN AS A DEEP-LAYER TROUGH AND ASSOCIATED SURFACE CYCLONE MOVE INTO THE EASTERN UNITED STATES AND NORTHWESTERN ATLANTIC. THIS EVOLUTION SHOULD STEER THE STORM WESTWARD FOR 12-24 HR...THEN ALLOW RECURVATURE TOWARD THE NORTHEAST. ALL THE TRACK GUIDANCE AGREES WITH THIS SCENARIO THROUGH ABOUT 72 HR. AFTER THAT TIME...THE GFS AND NOGAPS MODELS FORECAST EPSILON TO MOVE MORE EASTWARD...WHILE THE ECMWF...UKMET...AND CANADIAN MODELS CALL FOR A NORTHEASTWARD MOTION. THE OFFICIAL FORECAST WILL LIE BETWEEN THESE TWO EXTREMES IN BEST AGREEMENT WITH THE GFDL. OVERALL...THE NEW FORECAST TRACK IS A LITTLE TO THE WEST AND NORTH OF THE PREVIOUS TRACK. THE LARGE-SCALE MODELS FORECAST EPSILON TO REMAIN NEAR THE CENTER OF THE UPPER-LEVEL LOW FOR 24-36 HR. WHILE THIS IS NOT THE BEST PLACE FOR TROPICAL CYCLONES FROM A THERMODYNAMIC STANDPOINT...THIS WILL LIKELY KEEP THE VERTICAL SHEAR AT LIGHT TO MODERATE LEVELS AND ALLOW SOME STRENGTHENING. THE INTENSITY FORECAST THUS CALLS FOR THE STORM TO REACH 60 KT IN 36 HR...WHICH IS A LITTLE STRONGER THAN THE SHIPS GUIDANCE. AFTER THAT...THE UPPER LOW SHOULD WEAKEN AND MOVE EASTWARD...EXPOSING THE STORM TO SHEAR. ALSO...THE FORECAST NORTHEASTWARD TURN SHOULD BRING THE SYSTEM OVER SEA SURFACE TEMPERATURES COLDER THAN THE CURRENTLY MARGINAL-AT-BEST 23C. THIS COMBINATION SHOULD CAUSE WEAKENING. THEN...THE FRONTAL SYSTEM ASSOCIATED WITH THE APPROACHING DEEP-LAYER TROUGH SHOULD BEGIN TO MERGE WITH EPSILON IN ABOUT 72 HR...EVENTUALLY CAUSING THE STORM TO BECOME EXTRATROPICAL. THE TRMM AND QUIKSCAT DATA SUGGEST THE WIND FIELD OF EPSILON IS ABOUT TO JOIN THE LARGE AREA OF NORTHEASTERLY FLOW LOCATED NORTHWEST OF THE STORM. IF THIS HAPPENS...THE WIND RADII IN THE NORTHWESTERN QUADRANT MAY NEED SIGNIFICANT REVISION. IN THE LONGER TERM...THE SIZE OF THE 34 KT WIND FIELD AT 72 HR WAS REDUCED BASED ON THE LARGE-SCALE MODELS NOT SHOWING A VIGOROUS OUTER ENVELOPE. FORECASTER BEVEN FORECAST POSITIONS AND MAX WINDS INITIAL 30/0300Z 31.4N 51.9W 45 KT 12HR VT 30/1200Z 31.4N 53.1W 50 KT 24HR VT 01/0000Z 31.6N 53.9W 55 KT 36HR VT 01/1200Z 32.0N 53.9W 60 KT 48HR VT 02/0000Z 32.8N 53.0W 60 KT 72HR VT 03/0000Z 34.5N 48.5W 55 KT...BECOMING EXTRATROPICAL 96HR VT 04/0000Z 37.0N 43.5W 50 KT...EXTRATROPICAL 120HR VT 05/0000Z 40.5N 39.0W 40 KT...EXTRATROPICAL |
