000 WTNT42 KNHC 310902 TCDAT2 HURRICANE EARL DISCUSSION NUMBER 24 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL072010 500 AM AST TUE AUG 31 2010 AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT EARLIER REPORTED 700 MB FLIGHT-LEVEL WINDS OF 124 KT...AND ESTIMATED SURFACE WINDS OF 112 KT FROM THE SFMR. THE PLANE ALSO REPORTED A CENTRAL PRESSURE OF 931 MB. BASED ON THIS...THE INITIAL INTENSITY IS SET AT 115 KT. SINCE THE PLANE LEFT...A TRMM OVERPASS AND DATA FROM THE SAN JUAN WSR-88D RADAR INDICATE THAT EARL HAS STARTED AN EYEWALL REPLACEMENT CYCLE. ANOTHER HURRICANE HUNTER AIRCRAFT WILL ARRIVE IN EARL NEAR 12Z TO DETERMINE IF IT HAS PEAKED IN INTENSITY FOR NOW. THE INITIAL MOTION IS A WOBBLY 295/11. THERE IS LITTLE CHANGE TO THE TRACK FORECAST PHILOSOPHY FROM THE PREVIOUS ADVISORY. EARL SHOULD MOVE GENERALLY NORTHWESTWARD FOR THE NEXT 48 HR OR SO ON THE SOUTHWESTERN SIDE OF THE SUBTROPICAL RIDGE. AFTER THAT...THE HURRICANE SHOULD TURN NORTHWARD AROUND THE WESTERN END OF THE RIDGE...FOLLOWED BY A TURN TO THE NORTH-NORTHEAST AND ACCELERATION ON THE EAST SIDE OF A STRONG DEEP-LAYER TROUGH MOVING INTO THE NORTHEASTERN UNITED STATES. THE TRACK GUIDANCE IS TIGHTLY CLUSTERED FOR THE FIRST 72 HR...WITH SOME SPREAD IN THE TRACK DIRECTIONS BETWEEN THE LEFT-MOST HWRF AND THE RIGHT-MOST GFS ENSEMBLE MEAN THEREAFTER. THE NEW FORECAST TRACK IS AN UPDATE OF THE PREVIOUS TRACK AND LIES JUST LEFT OF THE CENTER OF THE GUIDANCE ENVELOPE. THE INTENSITY FORECAST IS A LITTLE PROBLEMATIC. THE GFDL AND GFDN MODELS SUGGEST THAT EARL COULD STRENGTHEN DURING THE NEXT 24 HR OR SO...AND THIS COULD OCCUR IF THE HURRICANE COMPLETES THE EYEWALL REPLACEMENT QUICKLY ENOUGH. ON THE OTHER HAND...EARL IS FORECAST TO BE IN AN ENVIRONMENT OF MODERATE SOUTHWESTERLY VERTICAL WIND SHEAR...AND WATER VAPOR IMAGERY SHOWS VERY DRY MID/UPPER-LEVEL AIR APPROACHING THE HURRICANE FROM THE NORTH. THESE FACTORS COULD PREVENT ADDITIONAL STRENGTHENING. THE INTENSITY FORECAST WILL FOLLOW THE GFDL/GFDN SCENARIO WITH A LITTLE MORE STRENGTHENING DURING THE NEXT 12-24 HR...BASED ON THE HURRICANE COMPLETING THE EYEWALL REPLACEMENT AND THE DRY AIR NOT REACHING THE HURRICANE CORE. THE FORECAST TRACK TAKES EARL OVER COLDER SEA SURFACE TEMPERATURES AND INTO INCREASING SHEAR AFTER 72 HR...WHICH SHOULD CAUSE STEADY WEAKENING AND EVENTUAL EXTRATROPICAL TRANSITION. 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 31/0900Z 20.5N 66.7W 115 KT 12HR VT 31/1800Z 21.4N 68.2W 120 KT 24HR VT 01/0600Z 23.3N 70.3W 120 KT 36HR VT 01/1800Z 25.5N 72.3W 120 KT 48HR VT 02/0600Z 28.0N 73.8W 115 KT 72HR VT 03/0600Z 33.5N 74.5W 105 KT 96HR VT 04/0600Z 40.0N 69.5W 85 KT 120HR VT 05/0600Z 48.0N 60.5W 60 KT...POST-TROP/EXTRATROP $$ FORECASTER BEVEN