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| #288546 (Received by flhurricane at: 4:49 PM 15.Aug.2009) TCDAT2 TROPICAL STORM ANA DISCUSSION NUMBER 15 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL022009 500 PM AST SAT AUG 15 2009 THE CENTER OF ANA CONTINUES TO BE EXPOSED TO THE WEST OF THE CONVECTION BY MODERATE VERTICAL WIND SHEAR. THE UPPER-LEVEL WINDS NEAR ANA ARE CURRENTLY LIGHT AND SOUTHERLY...MOST OF THE CONTRIBUTION TO THE SHEAR SEEMS TO BE FROM THE FAST LOW-LEVEL FLOW THE CENTER IS EMBEDDED IN. SATELLITE INTENSITY ESTIMATES FROM TAFB AND SAB REMAIN 35 KT...AND THAT REMAINS THE INITIAL INTENSITY. THE INITIAL MOTION IS 270/15. OVERALL...A LOW/MID-LEVEL RIDGE SHOULD STEER ANA QUICKLY WESTWARD TO WEST-NORTHWESTWARD...WITH ALL THE TRACK GUIDANCE AGREEING WITH THIS SCENARIO. HOWEVER...THERE REMAINS A SIGNIFICANT SPREAD IN THE 120 HR FORECAST POINTS. THE ECMWF AND BAMS ARE AT THE NORTHERN EXTREME...FORECASTING ANA TO PASS OVER OR NEAR THE SOUTHERN FLORIDA PENINSULA BY 120 HR. AT THE OTHER EXTREME ARE THE UKMET...GFDN...AND BAMM...WHICH FORECAST ANA TO PASS SOUTH OF HISPANIOLA AND BE OVER THE NORTHWESTERN CARIBBEAN AT 120 HR. THE NEW FORECAST TRACK IS AGAIN SHIFTED SOUTHWARD FROM THE PREVIOUS TRACK IN BEST AGREEMENT WITH THE NOGAPS. HOWEVER...THE NEW TRACK IS STILL ON THE NORTHERN SIDE OF THE GUIDANCE ENVELOPE AND NOTABLY NORTH OF THE CONSENSUS MODELS. IT IS UNCLEAR WHETHER THE CURRENT SHEAR IS A TEMPORARY TREND OR A SIGN OF LONG-TERM TROUBLE FOR ANA. THE LARGE-SCALE MODELS SUGGEST THE FORMER IS THE CASE...AND SO THE INTENSITY FORECAST CONTINUES TO CALL FOR STRENGTHENING. HOWEVER...THE CYCLONE IS STILL SURROUNDED BY DRY AIR IN WATER VAPOR IMAGERY...AND THE NEW FORECAST TRACK NOW CALLS FOR THE SYSTEM TO MAKE LANDFALL ON HISPANIOLA...AN OCCURRENCE THAT HAS DESTROYED STORMS MUCH STRONGER THAN ANA. THE INTENSITY FORECAST ASSUMES THAT THE CIRCULATION WILL SURVIVE THIS PASSAGE AND INTENSIFY OVER THE WATERS NORTH OF CUBA. AS BEFORE...THIS INTENSITY FORECAST HAS GREATER THAN NORMAL UNCERTAINTY. FORECAST POSITIONS AND MAX WINDS INITIAL 15/2100Z 14.4N 50.0W 35 KT 12HR VT 16/0600Z 14.7N 52.5W 35 KT 24HR VT 16/1800Z 15.4N 56.0W 40 KT 36HR VT 17/0600Z 16.1N 59.5W 45 KT 48HR VT 17/1800Z 17.2N 63.2W 50 KT 72HR VT 18/1800Z 19.0N 70.0W 50 KT...INLAND 96HR VT 19/1800Z 21.5N 76.0W 55 KT...OVER WATER 120HR VT 20/1800Z 24.5N 82.0W 60 KT $$ FORECASTER BEVEN |
