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#106150 (Received by flhurricane at: 10:55 PM 25.Aug.2006) TCDAT4 TROPICAL STORM DEBBY DISCUSSION NUMBER 18 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL042006 1100 PM EDT FRI AUG 25 2006 DESPITE CURRENT INTENSITY NUMBERS FROM TAFB AND SAB WHICH SUPPORT DOWNGRADING DEBBY TO A DEPRESSION...A QUIKSCAT PASS FROM EARLIER THIS AFTERNOON INDICATED THAT TROPICAL STORM FORCE WINDS ARE STILL POSSIBLE IN A SMALL AREA ABOUT 90 NM NORTHEAST OF THE CENTER. SATELLITE IMAGERY AND QUIKSCAT DATA ALSO INDICATE THAT WHILE THERE IS A DEFINITE LOW-LEVEL CENTER...THE SYSTEM IS BECOMING INCREASINGLY ELONGATED AND ASYMMETRIC. AN UPPER LEVEL LOW IS EXPECTED TO MAINTAIN SOUTHERLY SHEAR OVER DEBBY FOR THE NEXT 2 TO 3 DAYS...SO IT IS UNLIKELY THAT THE CYCLONE...IN ITS CURRENT FRAGILE STATE...WOULD BE ABLE TO SURVIVE THE FRONTAL SYSTEM WHICH WILL BE APPROACHING FROM THE NORTHWEST. CYCLONE PHASE DIAGRAMS AND MODEL FIELDS SUGGEST THAT DEBBY SHOULD BEGIN EXTRATROPICAL TRANSITION IN 36 HOURS THEN BECOME FULLY ABSORBED IN THE FRONTAL ZONE BY 72 HOURS. THE OFFICIAL INTENSITY FORECAST CLOSELY FOLLOWS THE SHIPS AND FSU SUPERENSEMBLE GUIDANCE IN MAINTAINING A MARGINAL TROPICAL STORM. HOWEVER...IT COULD WEAKEN TO A DEPRESSION AT ANY TIME. DEBBY HAS TAKEN A SLIGHT WESTWARD JOG WITH AN INITIAL MOTION OF 300/12. THE SYSTEM WILL BEGIN TO RECURVE TO THE NORTH IN THE NEXT 24 TO 48 HOURS IN RESPONSE TO AN APPROACHING UPPER TROUGH AND ITS ASSOCIATED COLD FRONT. DEBBY WILL THEN ACCELERATE NORTHEASTWARD BEYOND 48 HOURS AS IT BECOMES ABSORBED INTO THE FRONTAL ZONE. THE OFFICIAL TRACK FORECAST IS ONLY SLIGHTLY LEFT OF THE PREVIOUS FORECAST AND VERY CLOSE TO THE MODEL CONSENSUS. FORECAST POSITIONS AND MAX WINDS INITIAL 26/0300Z 25.2N 45.6W 35 KT 12HR VT 26/1200Z 26.5N 47.1W 35 KT 24HR VT 27/0000Z 28.5N 48.5W 35 KT 36HR VT 27/1200Z 30.8N 48.7W 40 KT...BECOMING EXTRATROPICAL 48HR VT 28/0000Z 33.6N 47.5W 50 KT...EXTRATROPICAL 72HR VT 29/0000Z...ABSORBED BY A FRONT |