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#371827 (Received by flhurricane at: 10:59 PM 27.Aug.2010) TCDAT2 TROPICAL STORM EARL DISCUSSION NUMBER 11 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL072010 1100 PM AST FRI AUG 27 2010 SATELLITE IMAGES INDICATE THAT CONVECTION HAS INCREASED IN THE WESTERN SEMICIRCLE OF EARL. BANDING FEATURES ARE BECOMING BETTER DEFINED...AND A THUNDERSTORM CLUSTER IS LOCATED NEAR OR JUST SOUTHWEST OF THE CENTER. SATELLITE ESTIMATES ARE A CONSENSUS 45 KT FROM TAFB/SAB...AND THAT WILL BE THE INITIAL INTENSITY. THE CLOUD PATTERN SUGGESTS THAT NORTHEASTERLY SHEAR HAS INCREASED DURING THE PAST SEVERAL HOURS...AND GLOBAL MODELS SUGGEST THIS SHEAR WILL CONTINUE FOR THE NEXT DAY OR SO. THERE IS ALSO EVIDENCE THAT SOME DRIER AIR IS LURKING NEAR THE CYCLONE. THUS THE INTENSITY FORECAST WILL BE A BIT BELOW MOST OF THE MODEL GUIDANCE FOR THE FIRST 36 HOURS. THEREAFTER...EARL WILL BE MOVING CLOSER TO THE CENTER OF A LARGE UPPER-LEVEL ANTICYCLONE NORTHEAST OF THE LESSER ANTILLES. THIS PATTERN IS QUITE FAVORABLE FOR INTENSIFICATION...ESPECIALLY CONSIDERING THE 29C PLUS SSTS IN THE PATH OF THE HURRICANE. THE GFDL/GFDN RESPOND TO THESE CONDITIONS BY FORECASTING EARL TO BECOME A CATEGORY 4 HURRICANE IN THE LONG-RANGE. WHILE THE NEW NHC FORECAST WILL NOT BE THAT AGGRESSIVE...IT IS INCREASED FROM THE PREVIOUS ONE AND IS CLOSE TO A BLEND OF THE ABOVE DYNAMICAL GUIDANCE AND THE LGEM MODEL. A SERIES OF MICROWAVE PASSES SUGGESTS THE CENTER REMAINS A BIT ELONGATED...THUS CONFIDENCE IN MY INITIAL MOTION OF 275/18 IS LOWER THAN AVERAGE. A STRONG RIDGE BETWEEN EARL AND DANIELLE IS EXPECTED TO KEEP THE TROPICAL STORM MOVING GENERALLY WESTWARD FOR THE NEXT DAY OR SO. AFTER THAT TIME...EARL WILL REACH THE WESTERN PERIPHERY OF THE RIDGE AND IS EXPECTED TO TURN TOWARD THE WEST-NORTHWEST. ALTHOUGH ALL OF THE GUIDANCE SHOWS THE CENTER NORTHEAST OF THE LEEWARD ISLANDS...THERE REMAINS SOME UNCERTAINTY ON HOW CLOSE EARL WILL COME. THE GFS HAS THE STRONGEST RIDGE IN THE GLOBAL MODELS AND MOVES THE CYCLONE CLOSER TO THE LEEWARD ISLANDS THAN MOST OF THE OTHER GUIDANCE. AT THIS POINT...IT IS PRUDENT NOT TO MAKE ANY CHANGES IN THE TRACK FORECAST IN THE FIRST COUPLE OF DAYS... ESPECIALLY SINCE THE CYCLONE HAS MOVED FASTER TOWARDS THE WEST THAN PREVIOUSLY FORECAST. THE NHC FORECAST REMAINS ON THE LEFT EDGE OF THE GUIDANCE ENVELOPE THROUGH THE FIRST THREE DAYS...THEN IS JUST LEFT OF THE MODEL CONSENSUS AT THE END. RESIDENTS IN THE LESSER ANTILLES SHOULD CLOSELY MONITOR THE PROGRESS OF EARL THROUGHOUT THE WEEKEND. WATCHES MAY BE REQUIRED AS EARLY AS SATURDAY MORNING. FORECAST POSITIONS AND MAX WINDS INITIAL 28/0300Z 16.0N 47.9W 45 KT 12HR VT 28/1200Z 16.2N 50.7W 50 KT 24HR VT 29/0000Z 16.6N 54.0W 55 KT 36HR VT 29/1200Z 17.3N 56.8W 65 KT 48HR VT 30/0000Z 18.1N 59.1W 80 KT 72HR VT 31/0000Z 20.5N 63.0W 100 KT 96HR VT 01/0000Z 24.5N 66.0W 110 KT 120HR VT 02/0000Z 29.0N 68.5W 105 KT $$ FORECASTER BLAKE |