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#105979 (Received by flhurricane at: 10:55 PM 24.Aug.2006) TCDAT4 TROPICAL STORM DEBBY DISCUSSION NUMBER 14 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL042006 1100 PM EDT THU AUG 24 2006 DEBBY STILL LOOKS MUCH LIKE IT DID SIX HOURS AGO...WITH A RELATIVELY SMALL AREA OF DEEP CONVECTION AND CIRRUS SPREADING OUT TO THE NORTH DUE TO SOUTHERLY SHEAR. DVORAK DATA-T NUMBERS HAVE NOT CHANGED AND THE CURRENT INTENSITY ESTIMATES ARE 30-35 KT. HOWEVER...THE STRONGEST WINDS RETRIEVED BY QUIKSCAT IN AN OVERPASS AROUND 21Z WERE 45 KT...AND THAT REMAINS THE ADVISORY INTENSITY. MANUAL ANALYSIS OF THE QUIKSCAT DIRECTIONAL AMBIGUITIES CONFIRMS THAT THE LOW-LEVEL CIRCULATION CENTER REMAINS BENEATH THE SOUTHERN PORTIONS OF THE MASS OF DEEP CONVECTION. THE INITIAL MOTION OF 295/16 IS JUST A LITTLE LEFT OF WHAT IT WAS EARLIER...BUT STILL WEST-NORTHWESTWARD. ONCE AGAIN THERE IS LITTLE CHANGE TO THE FORECAST OR THE UNDERLYING REASONING. THE STEERING MECHANISMS LEADING TO RECURVATURE REMAIN FAIRLY STRAIGHTFORWARD...AND THE OFFICIAL TRACK FORECAST IS ESSENTIALLY AN UPDATE OF THE PREVIOUS ADVISORY AND REMAINS CLOSE TO THE CONSENSUS OF THE TIGHTLY-CLUSTERED DYNAMICAL MODEL GUIDANCE. THE SOUTHERLY SHEAR WILL PROBABLY NOT ABATE MUCH DURING THE NEXT COUPLE OF DAYS DUE TO A PERSISTENT MID- TO UPPER-LEVEL TROUGH TO THE WEST OF DEBBY...SO ONLY VERY GRADUAL STRENGTHENING IS FORECAST DURING THAT PERIOD. THE UPPER-LEVEL WINDS MIGHT SLACKEN A BIT ON DAY 3 AND ALLOW DEBBY TO STRENGTHEN A LITTLE FASTER...BUT THEREAFTER A MID-LATITUDE TROUGH TRAVERSING THE NORTH-CENTRAL ATLANTIC WILL AGAIN INCREASE THE SHEAR. THE CHANCES OF DEBBY REACHING HURRICANE INTENSITY BEFORE EXTRATROPICAL TRANSITION APPEAR TO BE QUITE MARGINAL...AND THE NEW OFFICIAL INTENSITY FORECAST IS NUDGED DOWNWARD SLIGHTLY ON DAYS 4 AND 5...VERY CLOSE TO THE SHIPS GUIDANCE. FORECAST POSITIONS AND MAX WINDS INITIAL 25/0300Z 21.9N 41.1W 45 KT 12HR VT 25/1200Z 22.9N 43.4W 45 KT 24HR VT 26/0000Z 24.6N 46.2W 45 KT 36HR VT 26/1200Z 26.2N 48.5W 50 KT 48HR VT 27/0000Z 28.1N 50.2W 55 KT 72HR VT 28/0000Z 32.0N 51.0W 55 KT 96HR VT 29/0000Z 36.0N 48.0W 60 KT 120HR VT 30/0000Z 41.0N 42.0W 60 KT...EXTRATROPICAL |