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| #455382 (Received by flhurricane at: 10:52 AM 01.Sep.2011) TCDAT2 HURRICANE KATIA DISCUSSION NUMBER 14 NWS NATIONAL HURRICANE CENTER MIAMI FL AL122011 1100 AM AST THU SEP 01 2011 KATIA HAS CHANGED LITTLE IN STRUCTURE DURING THE LAST SEVERAL HOURS. BASED ON MICROWAVE DATA...THE LOW-LEVEL CENTER IS LOCATED NEAR THE WESTERN PERIPHERY OF THE CORE CONVECTION. A CURVED BAND STILL EXISTS OVER THE SOUTHERN SEMICIRCLE OF THE STORM...BUT CLOUD TOPS HAVE BEEN WARMING IN THIS BAND DURING THE PAST FEW HOURS. THE INITIAL WIND SPEED REMAINS AT 65 KT FOR THIS ADVISORY...IN AGREEMENT WITH THE LATEST SATELLITE CLASSIFICATIONS. SOUTHWESTERLY SHEAR OF ABOUT 15 KT...AS ANALYZED BY UW-CIMSS...IS CURRENTLY AFFECTING KATIA. THIS SHEAR IS ASSOCIATED WITH AN UPPER-LEVEL LOW LOCATED TO THE NORTHWEST OF THE HURRICANE. THE UPPER LOW IS EXPECTED TO CONTINUE TO IMPOSE MODERATE SHEAR OVER KATIA FOR ANOTHER 24 TO 36 HOURS. IN ADDITION...SOME DRY AIR APPEARS TO BE ENTRAINING INTO THE CIRCULATION OF KATIA AND THIS...IN COMBINATION WITH THE AFOREMENTIONED SHEAR...COULD INHIBIT SIGNIFICANT DEVELOPMENT IN THE SHORT-TERM. BEYOND 36 HOURS...THE GLOBAL MODELS SHOW THE UPPER LOW LIFTING OUT...CREATING A MORE FAVORABLE UPPER-LEVEL WIND PATTERN. THEREFORE...STEADY STRENGTHENING IS FORECAST IN THE LONGER RANGE. THE OFFICIAL FORECAST IS LOWERED SLIGHTLY FROM THE PREVIOUS ONE IN THE SHORT-TERM...BUT STILL BRINGS KATIA TO A MAJOR HURRICANE IN A FEW DAYS. KATIA IS MOVING WESTWARD AT 16 KT TO THE SOUTH OF A SUBTROPICAL HIGH. THE HURRICANE IS EXPECTED TO SLOW DOWN AND TURN TO THE WEST-NORTHWEST DURING THE NEXT 12-24 HOURS AS IT APPROACHES A WEAKNESS IN THE RIDGE. THE MODEL GUIDANCE BECOMES VERY DIVERGENT IN 4 TO 5 DAYS WITH THE UKMET...NOGAPS...AND GFDL MODELS ON THE SOUTH SIDE OF THE ENVELOPE AND THE GFS...ECMWF...AND HWRF MODELS ON THE NORTH SIDE. THIS SPREAD APPEARS TO BE ASSOCIATED WITH THE STRENGTH OF A TROUGH MOVING OVER THE NORTHEASTERN UNITED STATES AND THE POSITION OF THE SUBTROPICAL HIGH. THE OFFICIAL TRACK FORECAST IS ONLY NUDGED A LITTLE TO THE LEFT...IN PART BECAUSE OF THE INITIAL MOTION AND POSITION...AND IS VERY NEAR THE MULTI-MODEL CONSENSUS. FORECAST POSITIONS AND MAX WINDS INIT 01/1500Z 15.5N 47.5W 65 KT 75 MPH 12H 02/0000Z 16.1N 49.5W 70 KT 80 MPH 24H 02/1200Z 17.0N 51.7W 75 KT 85 MPH 36H 03/0000Z 18.0N 53.4W 85 KT 100 MPH 48H 03/1200Z 19.0N 55.0W 95 KT 110 MPH 72H 04/1200Z 20.8N 58.0W 100 KT 115 MPH 96H 05/1200Z 22.3N 61.0W 105 KT 120 MPH 120H 06/1200Z 23.8N 64.0W 105 KT 120 MPH $$ FORECASTER CANGIALOSI/ZELINSKY |
