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| #534889 (Received by flhurricane at: 10:41 AM 17.Aug.2012) TCDAT3 TROPICAL STORM GORDON DISCUSSION NUMBER 8 NWS NATIONAL HURRICANE CENTER MIAMI FL AL082012 1100 AM AST FRI AUG 17 2012 THE SATELLITE APPEARANCE OF GORDON REMAINS RATHER UNIMPRESSIVE... WITH CLOUD TOP TEMPERATURES WARMING OVER THE PAST FEW HOURS AND THE COLDEST CLOUD TOPS DISPLACED NORTH AND WEST OF THE CENTER. UW-CIMSS SATELLITE ANALYSIS AND SHIPS DIAGNOSTICS SHOW AROUND 15 KT OF WEST-NORTHWESTERLY SHEAR OVER THE CYCLONE...WHILE MET-9 AIRMASS IMAGERY AND MICROWAVE IMAGERY SHOW SOME DRY AIR WRAPPING INTO THE CIRCULATION FROM THE SOUTHWEST. THE INITIAL INTENSITY IS HELD AT 55 KT BASED ON A BLEND OF THE LATEST DVORAK FINAL-T AND CI-NUMBERS FROM TAFB AND SAB. THE CENTRAL PRESSURE OF 997 MB IS BASED ON AN OBSERVATION OF 999 MB FROM A DRIFTING BUOY THAT THE CENTER PASSED JUST NORTH OF AROUND 1000 UTC. THE SHEAR IS FORECAST TO DECREASE A LITTLE IN THE SHORT TERM...WHICH SHOULD ALLOW GORDON TO STRENGTHEN A BIT BEFORE THE CYCLONE REACHES SUB-26C WATERS AND THE SHEAR INCREASES IN 36 TO 48 HOURS. THE NHC FORECAST SHOWS THE CYCLONE PEAKING AT 60 KT IN 24 TO 36 HOURS AND IS CLOSE TO A BLEND OF THE SHIPS AND LGEM MODELS UNTIL EXTRATROPICAL TRANSITION OCCURS. THE INITIAL MOTION ESTIMATE IS A LITTLE SOUTH OF DUE EAST...095/16. GORDON WILL BE STEERED GENERALLY EASTWARD FOR THE NEXT DAY OR SO TO THE SOUTH OF A LARGE MID/UPPER-LEVEL TROUGH OVER THE NORTHEASTERN ATLANTIC. BY 48 HOURS...A SHORTWAVE TROUGH IS EXPECTED TO APPROACH THE CYCLONE FROM THE WEST AND INDUCE AN EAST-NORTHEASTWARD TURN AS THE CYCLONE BECOMES EXTRATROPICAL IN ABOUT 3 DAYS. A SLOW EAST- NORTHEASTWARD MOTION IS EXPECTED AT DAYS 4 AND 5 AS THE CYCLONE WEAKENS. OVERALL THE TRACK MODEL GUIDANCE REMAINS IN GOOD AGREEMENT ON THIS SCENARIO. THE NEW NHC FORECAST IS LARGELY AN UPDATE OF THE PREVIOUS ONE AND IS CLOSE TO A CONSENSUS OF THE GFS AND ECMWF. THE 34-KT WIND RADII WERE ADJUSTED OUTWARD BASED ON A PARTIAL ASCAT PASS FROM AROUND 1250 UTC. FORECAST POSITIONS AND MAX WINDS INIT 17/1500Z 34.5N 46.3W 55 KT 65 MPH 12H 18/0000Z 34.2N 43.4W 55 KT 65 MPH 24H 18/1200Z 34.1N 39.6W 60 KT 70 MPH 36H 19/0000Z 34.4N 35.6W 60 KT 70 MPH 48H 19/1200Z 35.2N 31.8W 55 KT 65 MPH 72H 20/1200Z 38.0N 24.0W 45 KT 50 MPH...POST-TROP/EXTRATROP 96H 21/1200Z 39.0N 19.5W 40 KT 45 MPH...POST-TROP/EXTRATROP 120H 22/1200Z 39.5N 16.5W 35 KT 40 MPH...POST-TROP/EXTRATROP $$ FORECASTER BRENNAN |
