000 WTNT44 KNHC 141440 TCDAT4 POST-TROPICAL CYCLONE HUMBERTO DISCUSSION NUMBER 24 NWS NATIONAL HURRICANE CENTER MIAMI FL AL092013 1100 AM AST SAT SEP 14 2013 HUMBERTO CONTINUES TO MAINTAIN A LARGE AND WELL-DEFINED CIRCULATION...BUT HAS BEEN WITHOUT ORGANIZED DEEP CONVECTION FOR ABOUT 24 HOURS. GIVEN THE LACK OF DEEP CONVECTION...HUMBERTO IS BEING DECLARED A POST-TROPICAL CYCLONE ON THIS ADVISORY...WITH WINDS ESTIMATED TO BE 35 KT BASED ON A RECENT ASCAT PASS. VERY STRONG WEST-SOUTHWESTERLY SHEAR...DRY MID-TROPOSPHERIC AIR...AND A TRACK OVER MARGINALLY WARM SEA SURFACE TEMPERATURES COULD RESULT IN A CONTINUED GRADUAL SPIN-DOWN OF THE CYCLONE DURING THE NEXT DAY OR POSSIBLY TWO. AFTER THAT...REGENERATION OF HUMBERTO INTO A TROPICAL CYCLONE SEEMS LIKELY SINCE THE CYCLONE WILL BE MOVING OVER WARMER WATERS AND EXPERIENCING A GRADUAL DECREASE IN SHEAR. GLOBAL MODELS SHOW HUMBERTO INTERACTING WITH A LARGE MID-LATITUDE TROUGH IN ABOUT 3 DAYS. THIS INTERACTION COULD BE THE IMPETUS FOR A FASTER RATE OF INTENSIFICATION LATE IN THE FORECAST PERIOD. THE NHC INTENSITY PREDICTION IS KEPT HIGHER INITIALLY ASSUMING A SLOWER RATE OF DECAY. THE EXTENDED FORECAST IS KEPT THE SAME AND IS SLIGHTLY ABOVE THE BULK OF THE INTENSITY GUIDANCE. THE POST-TROPICAL CYCLONE IS MOVING WEST-NORTHWESTWARD...285/11... AROUND A LOW- TO MID-LEVEL RIDGE OVER THE NORTHEASTERN ATLANTIC. THE FORWARD MOTION OF HUMBERTO SHOULD GRADUALLY TURN NORTHWESTWARD AND SLOW DOWN DURING THE NEXT COUPLE OF DAYS WHEN IT MOVES INTO A WEAKNESS OVER THE CENTRAL ATLANTIC. A STRONG TROUGH IN THE WESTERLIES APPROACHING HUMBERTO IN ABOUT 3 DAYS SHOULD LEAD TO A TURN NORTHEASTWARD WITH ACCELERATION ON DAYS 4 AND 5. THE NHC TRACK FORECAST IS ABOUT THE SAME AS BEFORE BUT SLOWER ON DAYS 3 TO 5... LYING IN BETWEEN THE ECMWF AND GFS AND CLOSE TO THE MULTI-MODEL CONSENSUS TVCA. ADDITIONAL INFORMATION ON HUMBERTO CAN BE FOUND IN HIGH SEAS FORECASTS ISSUED BY THE NATIONAL WEATHER SERVICE...UNDER AWIPS HEADER NFDHSFAT1 AND WMO HEADER FZNT01 KWBC. FORECAST POSITIONS AND MAX WINDS INIT 14/1500Z 25.4N 35.4W 35 KT 40 MPH...POST-TROPICAL 12H 15/0000Z 25.8N 37.1W 30 KT 35 MPH...POST-TROP/REMNT LOW 24H 15/1200Z 26.7N 39.3W 30 KT 35 MPH...POST-TROP/REMNT LOW 36H 16/0000Z 27.5N 41.2W 35 KT 40 MPH...POST-TROPICAL 48H 16/1200Z 28.6N 42.6W 35 KT 40 MPH...POST-TROPICAL 72H 17/1200Z 30.9N 44.1W 45 KT 50 MPH 96H 18/1200Z 33.7N 44.1W 55 KT 65 MPH 120H 19/1200Z 37.5N 41.5W 65 KT 75 MPH $$ FORECASTER KIMBERLAIN