000 WTNT42 KNHC 010903 TCDAT2 HURRICANE EARL DISCUSSION NUMBER 28 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL072010 500 AM EDT WED SEP 01 2010 THE EYE OF EARL HAS BECOME LESS DISTINCT IN SATELLITE IMAGERY DURING THE PAST FEW HOURS...AND THE EYEWALL CLOUD TOPS HAVE WARMED A LITTLE. AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT REPORTED A CENTRAL PRESSURE OF 941 MB...WHICH IS LITTLE CHANGED FROM EARLIER. HOWEVER...THE MAXIMUM FLIGHT-LEVEL WINDS WERE 116 KT...WHICH WAS LOWER THAN THE PREVIOUS MISSION...AND SURFACE WIND ESTIMATES FROM THE SFMR WERE UNDER 100 KT. THE INITIAL INTENSITY IS DECREASED TO 110 KT...AND THIS COULD BE A LITTLE GENEROUS. EARL IS MOVING 310-315 DEGREES AT ABOUT 14 KT. FOR THE NEXT 36 OR SO...THE HURRICANE SHOULD CONTINUE TO MOVE GENERALLY NORTHWESTWARD ON THE SOUTHWESTERN SIDE OF A LOW/MID-LEVEL RIDGE OVER THE CENTRAL ATLANTIC. AFTER THAT...EARL IS EXPECTED TO TURN NORTHWARD AND THEN NORTH-NORTHEASTWARD AS IT ROUNDS THE END OF THE RIDGE AND ENTERS THE WESTERLIES ASSOCIATED WITH A DEEP-LAYER TROUGH MOVING INTO THE NORTHEASTERN UNITED STATES. THE TRACK GUIDANCE IS IN GOOD AGREEMENT WITH THIS SCENARIO. HOWEVER...THERE ARE SOME SMALL DIFFERENCE IN THE MODEL GUIDANCE THAT COULD HAVE LARGE IMPLICATIONS IN TERMS OF IMPACTS. THE GFDN...NOGAPS...AND UKMET FORECAST THE CENTER TO PASS NEAR OR OVER THE NORTH CAROLINA COAST AND NEW ENGLAND. THE OTHER MODELS ARE FARTHER TO THE EAST...KEEPING THE CENTER OFFSHORE. THROUGH 48 HR...THE NEW FORECAST TRACK IS SIMILAR TO THE PREVIOUS TRACK...KEEPS THE CENTER OFF THE NORTH CAROLINA COAST...AND LIES JUST WEST OF THE CENTER OF THE GUIDANCE ENVELOPE. AFTER 48 HR...THE GUIDANCE ENVELOPE HAS SHIFTED A LITTLE TO THE WEST...AND THE NEW FORECAST TRACK DOES LIKEWISE TO BE IN THE CENTER OF THE ENVELOPE. THIS PART OF THE TRACK IS CLOSER TO THE NEW ENGLAND STATES THAN THE PREVIOUS FORECAST. THE INTENSITY FORECAST IS A CONUNDRUM. ON THE FAVORABLE SIDE...THE HURRICANE IS OVER VERY WARM SEA SURFACE TEMPERATURES...HAS GOOD CIRRUS OUTFLOW IN ALL DIRECTIONS EXCEPT TO THE SOUTH...AND HAS A GOOD CONVECTIVE STRUCTURE. ON THE NEGATIVE SIDE...EARL IS EXPERIENCING 15-20 KT OF SOUTHWESTERLY VERTICAL WIND SHEAR...AND WATER VAPOR IMAGERY SHOWS A TONGUE OF MID/UPPER-LEVEL DRY AIR WRAPPED MORE THAN HALFWAY AROUND THE CYCLONE. SOME SHEAR IS LIKELY TO CONTINUE FOR THE NEXT 36-48 HR...AND NONE OF THE INTENSITY GUIDANCE CALLS FOR MUCH STRENGTHENING AT THIS TIME. BASED ON THIS...THE NHC INTENSITY FORECAST CALLS FOR LITTLE CHANGE IN STRENGTH FOR 36 HR...FOLLOWED BY WEAKENING AS EARL ENCOUNTERS COOLER SEA SURFACE TEMPERATURES AND INCREASING SHEAR. EARL IS EXPECTED TO BECOME EXTRATROPICAL BY 96 HR. HURRICANE WARNINGS WILL LIKELY BE REQUIRED FOR PORTIONS OF THE NORTH CAROLINA COAST LATER THIS MORNING. FORECAST POSITIONS AND MAX WINDS INITIAL 01/0900Z 24.0N 71.2W 110 KT 12HR VT 01/1800Z 25.8N 72.9W 110 KT 24HR VT 02/0600Z 28.5N 74.6W 110 KT 36HR VT 02/1800Z 31.3N 75.2W 110 KT 48HR VT 03/0600Z 34.6N 74.4W 105 KT 72HR VT 04/0600Z 42.0N 68.0W 85 KT 96HR VT 05/0600Z 50.0N 61.5W 60 KT...POST-TROP/EXTRATROP 120HR VT 06/0600Z 57.0N 58.0W 45 KT...POST-TROP/EXTRATROP $$ FORECASTER BEVEN