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| #150957 (Received by flhurricane at: 10:34 AM 15.Sep.2007) TCDAT3 TROPICAL DEPRESSION INGRID DISCUSSION NUMBER 13 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082007 1100 AM EDT SAT SEP 15 2007 AN UPPER-LEVEL MID-OCEANIC TROUGH...MUCH STRONGER THAN NORMAL FOR SEPTEMBER...HAS BECOME ESTABLISHED OVER THE ATLANTIC RESULTING IN STRONG WESTERLY FLOW OVER INGRID. CONSEQUENTLY...THE CLOUD PATTERN HAS DETERIORATED AND INGRID IS BECOMING A JUST LARGE SWIRL OF LOW CLOUDS WITH A FEW PATCHES OF INTERMITTENT CONVECTION. THE LOW-LEVEL CIRCULATION IS STILL VIGOROUS AS INDICATED BY A NOAA AIRCRAFT AND BY THE LATEST QUIKSCAT...AND BASED ON DATA FROM THESE OBSERVING TOOLS...THE INITIAL INTENSITY HAS BEEN LOWERED TO 30 KNOTS. THE STRONG UPPER-LEVEL WESTERLIES ARE FORECAST TO INCREASE EVEN FURTHER...SO IT IS FAIR TO SAY THAT INGRID WILL MOST LIKELY CONTINUE TO WEAKEN AS INDICATED IN THE OFFICIAL FORECAST. THE MAIN REASON INGRID IS KEPT AS A 25-KNOT DEPRESSION THROUGH FIVE DAYS...WITHOUT FORECASTING DISSIPATION...IS BECAUSE GLOBAL MODELS MAINTAIN A CIRCULATION WHICH TRAVERSES THE BAND OF STRONG WESTERLIES. SOME MODELS...INCLUDING ALL VERSIONS OF SHIPS...SUGGEST A SLIGHT REJUVENATION OF INGRID BY DAYS 4 AND 5 AS IT MOVES NORTHWARD INTO A LOWER SHEAR ENVIRONMENT OVER THE OPEN SUBTROPICAL ATLANTIC. THE CENTER OF THE LOW-LEVEL CIRCULATION OR SWIRL HAS BEEN MOVING TOWARD THE WEST-NORTHWEST OR 290 DEGREES AT 9 KNOTS. BECAUSE THE CYCLONE HAS WEAKENED...IT IS BECOMING STEERED BY THE FLOW AT LOWER LEVELS. NEVERTHELESS...A GRADUAL TURN TO THE NORTHWEST AROUND A LOWER TROPOSPHERIC HIGH PRESSURE SYSTEM SHOULD BEGIN LATER TODAY...AND WHATEVER IS LEFT OF INGRID SHOULD BE PASSING WELL TO THE NORTHEAST OF THE LEEWARD ISLANDS IN A DAY OR TWO. IN FACT...THIS IS THE SOLUTION OF THE MODEL CONSENSUS. FORECAST POSITIONS AND MAX WINDS INITIAL 15/1500Z 16.4N 53.7W 30 KT 12HR VT 16/0000Z 17.0N 55.0W 25 KT 24HR VT 16/1200Z 18.0N 56.5W 25 KT 36HR VT 17/0000Z 19.0N 58.0W 25 KT 48HR VT 17/1200Z 20.5N 59.5W 25 KT 72HR VT 18/1200Z 22.5N 61.0W 25 KT 96HR VT 19/1200Z 25.0N 63.0W 25 KT 120HR VT 20/1200Z 26.0N 64.0W 25 KT $$ FORECASTER AVILA |
