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| #456990 (Received by flhurricane at: 10:42 PM 05.Sep.2011) TCDAT2 HURRICANE KATIA DISCUSSION NUMBER 32 NWS NATIONAL HURRICANE CENTER MIAMI FL AL122011 1100 PM AST MON SEP 05 2011 SATELLITE IMAGES INDICATE THAT KATIA HAS STRENGTHENED CONSIDERABLY DURING THE PAST SEVERAL HOURS. AS THE ASSOCIATED DEEP CONVECTION BECAME MUCH MORE SYMMETRIC AND THE EYE WARMED DURING THE EVENING HOURS...DVORAK CLASSIFICATIONS FROM TAFB AND SAB INCREASED TO 6.0/115 KT AT 0000 UTC. DESPITE SOME FLUCTUATIONS IN THE APPEARANCE OF THE EYE OVER THE LAST HOUR OR TWO...ADT ESTIMATES FROM UW-CIMSS ARE STILL 6.2/122 KT...SO THE INITIAL INTENSITY IS INCREASED TO 115 KT...MAKING KATIA A CATEGORY FOUR HURRICANE. THE LATEST 12-HOUR INITIAL MOTION ESTIMATE IS 315/9...A TOUCH SLOWER THAN NOTED IN THE PREVIOUS PACKAGE. THE TRACK FORECAST REASONING IS UNCHANGED. KATIA IS EXPECTED TO CONTINUE MOVING NORTHWESTWARD FOR THE NEXT 36 HOURS AS IT REMAINS ON THE SOUTHWESTERN PERIPHERY OF THE SUBTROPICAL RIDGE. A TURN TOWARD THE NORTH IS FORECAST IN 48 TO 72 HOURS AS THE HURRICANE BECOMES EMBEDDED IN SOUTHERLY FLOW BETWEEN THE RIDGE AND A LARGE CUTOFF LOW OVER THE EASTERN UNITED STATES. THIS STEERING PATTERN WILL ALLOW KATIA TO MOVE BETWEEN BERMUDA AND THE UNITED STATES EAST COAST DURING THAT TIME PERIOD. AFTER THAT...A SHARP NORTHEASTWARD AND EAST-NORTHEASTWARD TURN WITH AN INCREASE IN FORWARD SPEED IS FORECAST AS KATIA GETS CAUGHT IN THE MID-LATITUDE WESTERLIES. THE MODEL SOLUTIONS HAVE BEEN CONVERGING DURING THE PAST FEW CYCLES AND ARE NOW IN RELATIVELY GOOD AGREEMENT...INCREASING CONFIDENCE IN THE TRACK FORECAST. THE OFFICIAL FORECAST IS SIMILAR TO THE PREVIOUS ONE AND NEAR THE MIDDLE OF THE GUIDANCE ENVELOPE. FLUCTUATIONS IN THE INTENSITY OF KATIA ARE LIKELY DURING THE NEXT 12 TO 24 HOURS...PERHAPS DUE TO EYEWALL REPLACEMENT CYCLES...AS THE MAJOR HURRICANE REMAINS IN A FAVORABLE ENVIRONMENT. SLOW WEAKENING IS EXPECTED BEYOND THAT TIME AS KATIA MOVES INTO AN ENVIRONMENT OF MODERATE SHEAR AND SLIGHTLY COOLER WATERS. THE NEW NHC INTENSITY FORECAST HAS BEEN ADJUSTED UPWARD THROUGH 36 HOURS BASED ON THE OBSERVED STRENGTHENING AND IS NEAR THE MODEL CONSENSUS. KATIA IS NOW FORECAST TO BE A POST-TROPICAL CYCLONE BY DAY 5...AS IT IS EXPECTED TO BE WELL-EMBEDDED IN THE WESTERLIES AND OVER 20-21C WATERS BY THAT TIME. DRIFTING BUOY 41855...WHICH WAS LOCATED ABOUT 20 N MI NORTHEAST OF THE EYE OF KATIA AT 0000 UTC...REPORTED A MINIMUM PRESSURE OF 952 MB. FORECAST POSITIONS AND MAX WINDS INIT 06/0300Z 25.8N 64.4W 115 KT 135 MPH 12H 06/1200Z 26.9N 65.5W 115 KT 135 MPH 24H 07/0000Z 28.1N 66.9W 115 KT 135 MPH 36H 07/1200Z 29.4N 68.3W 110 KT 125 MPH 48H 08/0000Z 30.9N 69.5W 100 KT 115 MPH 72H 09/0000Z 35.4N 69.7W 90 KT 105 MPH 96H 10/0000Z 39.5N 63.5W 75 KT 85 MPH 120H 11/0000Z 42.5N 48.0W 65 KT 75 MPH $$ FORECASTER CANGIALOSI |
