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| #222727 (Received by flhurricane at: 10:37 PM 17.Oct.2008) TCDAT5 TROPICAL STORM OMAR DISCUSSION NUMBER 19 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL152008 1100 PM EDT FRI OCT 17 2008 THE CONVECTION ASSOCIATED WITH OMAR HAS DECREASED AGAIN THIS EVENING...WITH THE REMAINING CONVECTION IN A RAGGED BAND WELL SOUTHEAST OF THE CENTER. HOWEVER...AN AMSU OVERPASS NEAR 20Z SHOWS THAT THE CYCLONE HAS A DEEP-LAYER WARM CORE...WHICH SSM/I IMAGERY SHOWS IS SURROUNDED BY MID/UPPER-LEVEL DRY/COOL AIR. A QUIKSCAT OVERPASS NEAR 22Z SHOWS A SIGNIFICANT DECREASE IN THE WINDS FROM THE EARLIER OVERPASS...WITH NO RELIABLE-LOOKING VECTORS SHOWING WINDS OF MORE THAN 45 TO 50 KT. AMSU INTENSITY ESTIMATES AT 20Z WERE 55 TO 60 KT...WHILE REGULAR SATELLITE INTENSITY ESTIMATES WERE TROPICAL 65 KT FROM TAFB AND SUBTROPICAL 35-40 KT FROM SAB. THE INITIAL INTENSITY IS DECREASED TO 55 KT BASED ON AN AVERAGE OF THESE ESTIMATES...AND THIS MIGHT BE A BIT GENEROUS. THE INITIAL WIND RADII HAVE BEEN REVISED BASED ON THE QUIKSCAT DATA. OMAR HAS SLOWED ITS FORWARD MOTION DURING THE PAST FEW HOURS AND THE INITIAL MOTION IS NOW 040/14. IN THE SHORT TERM...OMAR SHOULD CONTINUE A GENERAL NORTHEASTWARD MOTION BETWEEN A DEEP-LAYER RIDGE OVER THE EAST CENTRAL ATLANTIC AND THE MID-LATITUDE WESTERLIES TO THE NORTH. THE FIRST 48 HR OF THE FORECAST IS DOWN THE MIDDLE OF THE FAIRLY TIGHTLY CLUSTERED GUIDANCE. AFTER 48 HR...THE GFS... ECMWF...UKMET..AND HWRF SHOW OMAR BEING ABSORBED INTO A BAROCLINIC LOW MOVING EASTWARD FROM THE WESTERN ATLANTIC...THIS AFTER OMAR TURNS MORE NORTHWARD IN ADVANCE OF THE LOW. THE NOGAPS...THE BAMD...THE BAMM...AND THE LBAR FORECAST OMAR TO TURN EASTWARD AND EVENTUALLY SOUTHWARD AROUND THE EASTERN ATLANTIC RIDGE. THE NEW FORECAST TRACK WILL LEAN MORE TOWARD THE GFS/UKMET/ECMWF/HWRF SOLUTION...CALLING FOR OMAR TO TURN MORE NORTHWARD AFTER 72 HR. HOWEVER...OUT OF DEFERENCE TO THE OTHER MODELS AND THE PREVIOUS FORECAST...THE NEW FORECAST IS NOT AS FAR NORTH AS THAT OF THOSE MODELS. OMAR IS MOVING OVER SEA SURFACE TEMPERATURES OF LESS THAN 26C...AND IS LIKELY TO ENCOUNTER INCREASING WESTERLY VERTICAL WIND SHEAR AFTER 24 HR. WHILE ANOTHER CONVECTIVE FLARE-UP CANNOT BE RULED OUT...THESE CONDITIONS INDICATE THE STORM SHOULD GENERALLY WEAKEN THROUGH THE FORECAST PERIOD. THIS IS SUPPORTED BY ALL THE INTENSITY GUIDANCE. OMAR SHOULD BECOME EXTRATROPICAL IN 48-72 HR AS IT MERGES WITH A FRONTAL SYSTEM OVER THE NORTH ATLANTIC. IF THE GFS/UKMET/ECMWF/HWRF SCENARIO VERIFIES...OMAR WILL BE ABSORBED BY THE WARM FRONT OF THE ONCOMING BAROCLINIC LOW...WITH THE FORMER TROPICAL CYCLONE SHOWING LITTLE RE-INTENSIFICATION AS AN EXTRATROPICAL LOW. THIS IS REFLECTED IN THE 48-96 HR PORTION OF THE INTENSITY FORECAST. FORECAST POSITIONS AND MAX WINDS INITIAL 18/0300Z 31.5N 52.8W 55 KT 12HR VT 18/1200Z 33.3N 51.1W 50 KT 24HR VT 19/0000Z 35.1N 48.7W 45 KT 36HR VT 19/1200Z 36.7N 46.2W 40 KT 48HR VT 20/0000Z 38.3N 43.2W 35 KT...BECOMING EXTRATROPICAL 72HR VT 21/0000Z 39.5N 39.0W 35 KT...EXTRATROPICAL 96HR VT 22/0000Z 42.0N 36.0W 35 KT...EXTRATROPICAL 120HR VT 23/0000Z...ABSORBED BY FRONTAL SYSTEM $$ FORECASTER BEVEN |
