000 WTNT42 KNHC 310250 TCDAT2 HURRICANE EARL DISCUSSION NUMBER 23 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL072010 1100 PM AST MON AUG 30 2010 THE INTENSITY OF EARL APPEARS TO HAVE LEVELED OFF FOR THE TIME BEING. DROPSONDE MEASUREMENTS FROM THE AIR FORCE RESERVE HURRICANE HUNTERS INDICATE LITTLE CHANGE IN CENTRAL PRESSURE OVER THE PAST FEW HOURS. THERE WAS ALSO AN UNFLAGGED SFMR-MEASURED SURFACE WIND OF 111 KT. THE CURRENT INTENSITY IS HELD AT 115 KT FOR THIS ADVISORY. WSR-88D RADAR DATA FROM SAN JUAN SUGGEST THAT A CONCENTRIC EYEWALL OR CONVECTIVE RING MAY BE FORMING. THIS WOULD AT LEAST TEMPORARILY HALT FURTHER INTENSIFICATION. WATER VAPOR IMAGERY CONTINUES TO DEPICT A BROAD UPPER-LEVEL TROUGH TO THE NORTHWEST OF THE HURRICANE. GLOBAL MODELS FORECAST AN UPPER-LEVEL LOW TO CUT OFF FROM THE TROUGH AND MOVE SOUTHWARD...WHICH IS AN UPPER-LEVEL FLOW EVOLUTION THAT IS USUALLY CONDUCIVE FOR STRENGTHENING. HOWEVER THE GFS PREDICTS AROUND 18-20 KT OF SOUTH-SOUTHWESTERLY VERTICAL SHEAR OVER EARL IN 24-48 HOURS. THE OFFICIAL INTENSITY FORECAST HAS BACKED OFF SOME FROM THE PREVIOUS ONE...AND SHOWS ONLY SLIGHT STRENGTHENING OVER THE NEXT DAY OR SO. ALSO...SOME OSCILLATIONS IN INTENSIYY DUE TO EYEWALL REPLACEMENTS OR OTHER INNER-CORE CONVECTIVE PROCESSES ARE ALSO POSSIBLE. THERE HAVE BEEN SOME WOBBLES IN THE TRACK OF EARL BUT THE MEAN MOTION HAS BEEN ABOUT 300/12 OVER THE PAST 6 HOURS. A GRADUAL TURN TOWARD THE NORTHWEST IS LIKELY IN 12 TO 24 HOURS AS EARL MOVES AROUND THE SOUTHWESTERN PERIPHERY OF THE SUBTROPICAL RIDGE. BY DAY 3...A GENERALLY NORTHWARD TRACK IS EXPECTED AS THE HURRICANE MOVES ALONG THE WESTERN SIDE OF THE RIDGE. A STRONG MID-TROPOSPHERIC TROUGH MOVING THROUGH THE GREAT LAKES SHOULD PROVIDE AN EASTWARD COMPONENT OF STEERING BY DAY 4...AND EARL IS LIKELY TO ACCELERATE NORTH-NORTHEASTWARD AHEAD OF THE TROUGH NEAR THE END OF THE FORECAST PERIOD. THE TRACK GUIDANCE SUITE IS IN RATHER CLOSE AGREEMENT UP TO 72 HOURS...BUT BECOMES MORE DIVERGENT AFTER THAT FORECAST TIME. THE OFFICIAL TRACK FORECAST IS...ONCE AGAIN... SHIFTED SLIGHTLY WESTWARD FROM THE PREVIOUS ONE AND IS VERY CLOSE TO THE MULTI-MODEL CONSENSUS. INTERESTS FROM THE CAROLINAS NORTHWARD TO NEW ENGLAND SHOULD MONITOR THE PROGRESS OF EARL. THERE IS STILL CONSIDERABLE UNCERTAINTY AS TO HOW CLOSE THE HURRICANE WILL COME TO THE U.S. EAST COAST. FORECAST POSITIONS AND MAX WINDS INITIAL 31/0300Z 19.9N 65.8W 115 KT 12HR VT 31/1200Z 20.9N 67.2W 120 KT 24HR VT 01/0000Z 22.6N 69.2W 120 KT 36HR VT 01/1200Z 24.6N 71.4W 120 KT 48HR VT 02/0000Z 26.9N 73.4W 120 KT 72HR VT 03/0000Z 32.5N 75.0W 110 KT 96HR VT 04/0000Z 38.5N 70.5W 90 KT 120HR VT 05/0000Z 46.0N 62.0W 60 KT $$ FORECASTER PASCH