ZCZC MIATCDAT5 ALL TTAA00 KNHC DDHHMM HURRICANE OMAR DISCUSSION NUMBER 10 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL152008 500 PM EDT WED OCT 15 2008 TWO RECENT PASSES THROUGH OMAR'S EYE INDICATE THE CENTRAL PRESSURE DECREASED BY AT LEAST 4 MB...DOWN TO 973 MB. THE AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT ALSO MEASURED A PEAK 700 MB FLIGHT-LEVEL WIND OF 89 KT IN THE SOUTHEAST QUADRANT...WHICH EQUATES TO ABOUT AN 80-KT SURFACE WIND...DESPITE THE HIGHEST SFMR SURFACE MEASURED HAVING ONLY BEEN 74 KT. HOWEVER...THE RECON AIRCRAFT AND THE CONVECTION HAVE BEEN PLAYING A GAME OF CAT-AND-MOUSE...AND I DO NOT BELIEVE THAT THE AIRCRAFT HAS BEEN SAMPLING THE STRONGEST WINDS IN THE STRONGEST CONVECTION. THE ADVISORY INTENSITY HAS BEEN INCREASED TO 80 KT...WHICH COULD BE A LITTLE LOW GIVEN THAT THE PRESSURE-WIND RELATIONSHIP FOR 973 MB CORRESPONDS TO ABOUT 85 KT. THE INITIAL MOTION ESTIMATE IS 050/013. AFTER AN EARLIER JOG TO THE EAST-NORTHEAST...IT APPEARS THAT OMAR HAS RESUMED ITS BASE COURSE BACK TOWARD THE NORTHEAST. THERE REMAINS NO SIGNIFICANT CHANGE TO THE PREVIOUS TRACK FORECAST OR PHILOSOPHY AS ALL OF THE TRACK MODELS REMAIN TIGHTLY CLUSTERED ABOUT A NORTHEASTWARD MOTION THROUGH THE NORTHERN LEEWARD ISLANDS AND THE VIRGIN ISLANDS IN 12-18 HOURS HOURS. AFTER THAT...OMAR IS FORECAST TO ACCELERATE AS IT GETS DRAWN RAPIDLY NORTHEASTWARD IN SOUTHWESTERLY STEERING FLOW ON THE EAST SIDE OF A LARGE MID-TROPOSPHERIC TROUGH THAT IS FORECAST TO MOVE OFF THE U.S. EAST COAST AND INTO THE WESTERN AND CENTRAL ATLANTIC BY DAY 3. DURING DAYS 4-5...OMAR IS EXPECTED TO ACCELERATE THE EAST-NORTHEAST OR EASTWARD AT FORWARD SPEEDS IN EXCESS OF 35 KT AND BECOME EXTRATROPICAL OVER THE MUCH COOLER WATERS OF THE NORTH ATLANTIC. THE OFFICIAL FORECAST TRACK IS SLIGHTLY TO THE RIGHT OF PREVIOUS TRACK...AND REMAINS SLOWER THAN THE NHC MODEL CONSENSUS...WHICH HAS HAD A NOTICEABLE FAST FORWARD SPEED BIAS. STRONG CONVECTIVE BURSTS HAVE CONTINUED TO DEVELOP IN THE EYEWALL AND RADAR DATA FROM SAN JUAN HAS INDICATED OCCASIONAL DISTINCT MESOVORTICES ROTATING AROUND THE INNER PORTION OF THE EYEWALL. THIS FAVORABLE SMALL-SCALE INTENSIFICATION SHOULD PERSISTS FOR ANOTHER 12 HOURS OR SO...WHICH MEANS THAT OMAR HAS A GOOD CHANCE OF REACHING AT LEAST CATEGORY 2 INTENSITY BEFORE IT MOVES THROUGH THE NORTHERN LEEWARD ISLANDS LATER TONIGHT AND THURSDAY MORNING. THE GFDL MODEL WAS MUCH MORE BULLISH WITH OMAR ON THE 12Z MODEL RUN AND BRINGS THE HURRICANE UP TO 109 KT BY 18-24 HOURS. THAT MUCH INTENSIFICATION IS LIKELY OVERDONE GIVEN SATELLITE INDICATIONS OF A RAPIDLY SHRINKING CDO FEATURE...PLUS THE INTRUSION OF DRY MID-LEVEL INTO THE NORTHWEST QUADRANT OF THE CYCLONE. HOWEVER...SINCE OMAR IS EXPECTED TO REMAIN IN A RELATIVELY LOW SHEAR ENVIRONMENT AND OVER 29C SSTS...ADDITIONAL STRENGTHENING TO 90 KT SEEMS VERY PLAUSIBLE ...AND WOULD MOST LIKELY OCCUR LATER TONIGHT DURING THE USUAL NOCTURNAL CONVECTIVE MAXIMUM PERIOD. ALSO...INTERESTS IN THE LEEWARD ISLANDS ARE REMINDED THAT STRONGER WINDS...POSSIBLY ONE CATEGORY HIGHER...CAN BE EXPECTED OVER HIGHER TERRAIN...ESPECIALLY ABOVE 500 FT ELEVATION. FORECAST POSITIONS AND MAX WINDS INITIAL 15/2100Z 15.9N 66.1W 80 KT 12HR VT 16/0600Z 17.6N 64.8W 85 KT...NRN LEEWARD ISLANDS 24HR VT 16/1800Z 20.4N 62.9W 90 KT 36HR VT 17/0600Z 23.2N 60.9W 90 KT 48HR VT 17/1800Z 26.1N 59.2W 85 KT 72HR VT 18/1800Z 31.7N 54.8W 75 KT 96HR VT 19/1800Z 39.0N 44.5W 60 KT...BECOMING EXTRATROPICAL 120HR VT 20/1800Z 48.0N 27.0W 50 KT...EXTRATROPICAL $$ FORECASTER STEWART NNNN
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Page last modified: Tuesday, 21-Apr-2009 12:09:25 UTC