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#453177 (Received by flhurricane at: 10:46 AM 25.Aug.2011) TCDAT5 TROPICAL DEPRESSION TEN DISCUSSION NUMBER 2 NWS NATIONAL HURRICANE CENTER MIAMI FL AL102011 1100 AM EDT THU AUG 25 2011 AFTER BEING CLOSE TO A TROPICAL STORM OVERNIGHT...THE CLOUD PATTERN OF THE DEPRESSION HAS BECOME LESS ORGANIZED WITH A DECREASE IN CONVECTION AND CURVED BANDING. ALTHOUGH DVORAK ESTIMATES REMAIN AT STORM STRENGTH...AN ASCAT PASS AT 1126 UTC SUGGESTED MAXIMUM WINDS OF 25 TO 30 KT...WHICH WAS LESS THAN WHAT WAS MEASURED ON THE LAST PASS. THE INITIAL WIND SPEED WILL STAY AT 30 KT FOR THIS ADVISORY. THE ASCAT DATA SHOWED THAT THE CIRCULATION OF THE DEPRESSION IS ELONGATED FROM NORTHEAST TO SOUTHWEST...WHICH IS NOT EXACTLY A FAVORABLE STRUCTURE FOR MUCH NEAR-TERM INTENSIFICATION. IN ADDITION...NORTHEASTERLY SHEAR IS FORECAST TO REMAIN MODERATE TO STRONG TODAY. THUS THE NHC FORECAST IS REDUCED FROM THE PREVIOUS ONE IN THE SHORT-TERM. SOME INTENSIFICATION SEEMS LIKELY ON FRIDAY WITH LESS SHEAR WHILE THE CYCLONE REMAINS OVER WARM WATERS. HOWEVER...THERE IS A BIG SPLIT BETWEEN THE DYNAMICAL AND STATISTICAL GUIDANCE...WITH THE GFDL/HWRF MODELS SHOWING LITTLE STRENGTHENING FOR THE NEXT SEVERAL DAYS WHILE THE SHIPS/LGEM MODELS FORECAST THE DEPRESSION TO BECOME HURRICANE. WITH SUCH A LARGE SPREAD IN THE GUIDANCE...NO CHANGE IS MADE TO THE PREVIOUS FORECAST BEYOND FRIDAY. WEAKENING SHOULD COMMENCE BY DAY THREE DUE TO AN INCREASE IN SHEAR AND DECREASE IN SSTS. AN UNCERTAIN ESTIMATE OF INITIAL MOTION IS 290/10. A MID-LEVEL RIDGE TO THE NORTH OF THE DEPRESSION SHOULD BREAK DOWN AS A TROUGH FORMS OVER THE EASTERN ATLANTIC OCEAN. THIS SHOULD CAUSE THE CYCLONE TO TURN TOWARD THE NORTHWEST AND NORTH-NORTHWEST DURING THE NEXT FEW DAYS. ALTHOUGH THE GUIDANCE HAS THIS GENERAL IDEA...THERE ARE A VARIETY OF SOLUTIONS ON HOW QUICKLY THE MORE NORTHWARD MOTION STARTS. PART OF THE PROBLEM IS THAT THE TRACK FORECAST IS RATHER DEPENDENT ON THE INTENSITY FORECAST WITH A DEEPER SYSTEM MORE LIKELY TO BE PULLED MORE TO THE NORTH THAN A WEAKER ONE. THE NHC FORECAST WILL SHOW A NORTH-NORTHWEST MOTION BY DAY 3 AND ASSUMES THE CYCLONE GAINS SOME STRENGTH. THE NEW FORECAST IS TO THE RIGHT OF THE PREVIOUS ONE DURING THE DAY OR SO...CLOSE TO A BLEND OF THE ECMWF MODEL AND THE HURRICANE FORECAST IMPROVEMENT PROGRAM EXPERIMENTAL CONSENSUS. MOST OF THE MODELS SHOW A SHARPER LEFT TURN IN THE LONGER-RANGE PERIOD...SO THE TRACK AT THAT TIME IS WEST OF THE PREVIOUS FORECAST. FORECAST POSITIONS AND MAX WINDS INIT 25/1500Z 13.3N 31.8W 30 KT 35 MPH 12H 26/0000Z 13.9N 32.9W 30 KT 35 MPH 24H 26/1200Z 14.7N 34.1W 35 KT 40 MPH 36H 27/0000Z 15.6N 35.2W 45 KT 50 MPH 48H 27/1200Z 16.6N 35.9W 50 KT 60 MPH 72H 28/1200Z 18.7N 37.0W 45 KT 50 MPH 96H 29/1200Z 20.5N 38.0W 35 KT 40 MPH 120H 30/1200Z 22.0N 40.5W 30 KT 35 MPH $$ FORECASTER BLAKE |