ZCZC MIATCDAT1 ALL TTAA00 KNHC DDHHMM TROPICAL STORM KIRK DISCUSSION NUMBER 4 NWS NATIONAL HURRICANE CENTER MIAMI FL AL112012 1100 AM AST WED AUG 29 2012 WHILE KIRK HAS A DISTINCT MID-LEVEL CENTER ON THE SOUTHWEST SIDE OF THE RELATIVELY DISORGANIZED CONVECTIVE CANOPY...THE LOW-LEVEL CIRCULATION APPEARS TO BE DISPLACED A LITTLE TO THE WEST DUE TO ABOUT 15 KT OF WESTERLY SHEAR OVER THE CYCLONE. THE INITIAL INTENSITY IS HELD AT 40 KT BASED ON A BLEND OF DVORAK FINAL-T NUMBERS FROM SAB AND TAFB. IN THE SHORT TERM THE COMBINATION OF DRY AIR AROUND THE CYCLONE AND SHEAR OF 10 TO 15 KT SUGGESTS THAT ANY INTENSIFICATION WILL BE GRADUAL FOR THE NEXT DAY OR SO. THE NEW NHC FORECAST HAS BEEN NUDGED SLIGHTLY DOWNWARD THROUGH 36 HOURS BUT IS STILL ABOVE MOST OF THE GUIDANCE THROUGH THAT TIME. AFTER THAT TIME AS KIRK RECURVES AND THE SHEAR DECREASES...STRENGTHENING TO HURRICANE INTENSITY IS FORECAST BY 72 HOURS IN AGREEMENT WITH THE INTENSITY CONSENSUS. KIRK IS EXPECTED TO BECOME EXTRATROPICAL BY THE END OF THE PERIOD WITH SLOW WEAKENING UNDERWAY BY THAT TIME. MICROWAVE IMAGERY SUGGESTS THAT THE CENTER WAS LOCATED WEST OF PREVIOUS ESTIMATES OVERNIGHT...AND THE INITIAL MOTION ESTIMATE IS A RATHER UNCERTAIN 290/10. KIRK WILL TURN NORTHWESTWARD IN THE NEXT 36 HOURS INTO A BREAK IN THE SUBTROPICAL RIDGE...AND THEN TURN NORTHWARD AND NORTHEASTWARD AS THE CYCLONE RECURVES INTO THE MID-LATITUDE WESTERLIES LATE IN THE PERIOD. WHILE THE MODEL GUIDANCE IS IN AGREEMENT ON THIS OVERALL SCENARIO...THERE REMAIN SOME SIGNIFICANT DETAIL DIFFERENCES IN THE MOTION IN THE SHORT TERM. THE ECMWF MODEL KEEPS KIRK WEAKER AND SHOWS MORE GRADUAL RECURVATURE...WHILE THE GFS...GEFS ENSEMBLE MEAN...AND THE REGIONAL HURRICANE MODELS SHOW A SHARPER RECURVATURE. THE NEW NHC TRACK IS FASTER THROUGH 36 HOURS AND A LITTLE TO THE LEFT OF THE PREVIOUS FORECAST THROUGH THE PERIOD...LARGELY DUE TO THE INITIAL POSITION AND MOTION. THE NHC TRACK IS CLOSE TO THE LATEST TVCA CONSENSUS THROUGH 48 HOURS AND A LITTLE TO THE LEFT AFTERWARD...CLOSE TO A BLEND OF THE GFS AND ECMWF AT DAYS 3 THROUGH 5. FORECAST POSITIONS AND MAX WINDS INIT 29/1500Z 24.7N 46.9W 40 KT 45 MPH 12H 30/0000Z 25.3N 48.4W 45 KT 50 MPH 24H 30/1200Z 26.2N 50.2W 45 KT 50 MPH 36H 31/0000Z 27.8N 51.7W 50 KT 60 MPH 48H 31/1200Z 29.8N 52.2W 55 KT 65 MPH 72H 01/1200Z 34.5N 50.5W 65 KT 75 MPH 96H 02/1200Z 40.5N 44.0W 65 KT 75 MPH 120H 03/1200Z 48.5N 32.5W 55 KT 65 MPH...POST-TROP/EXTRATROP $$ FORECASTER BRENNAN NNNN
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Page last modified: Monday, 31-Dec-2012 12:09:29 UTC