ZCZC MIATCDAT2 ALL TTAA00 KNHC DDHHMM HURRICANE KATIA DISCUSSION NUMBER 38 NWS NATIONAL HURRICANE CENTER MIAMI FL AL122011 1100 AM AST WED SEP 07 2011 THE CLOUD PATTERN OF KATIA HAS CHANGED LITTLE SINCE EARLY THIS MORNING. RECENT MICROWAVE IMAGES SHOW THE REMAINING FRAGMENTS OF AN INNER EYE WALL WITH A COUPLE OF CONVECTIVE BANDS OVER THE NORTHEASTERN SEMICIRCLE. IT APPEARS THAT DRY AIR HAS WRAPPED AROUND THE SOUTHWESTERN SIDE OF THE CIRCULATION WITH DEEP CONVECTION NON EXISTENT OVER THAT PORTION OF THE CYCLONE. THE DVORAK T- AND CI-NUMBERS FROM TAFB HAVE DECREASED AND CI-NUMBERS FROM BOTH AGENCIES ARE NOW T4.5. THIS SUPPORTS LOWERING THE INITIAL INTENSITY TO 75 KT. GIVEN THE MODERATE WESTERLY SHEAR AND THE LACK OF A TIGHT-INNER CORE...SOME SLIGHT WEAKENING IS ANTICIPATED DURING THE NEXT 24 HOURS. AS KATIA BEGINS MOVING NORTH-NORTHEASTWARD IN A DAY OR SO...THE SHIPS GUIDANCE SHOWS THAT THE SHEAR WILL DECREASE...HOWEVER THE HURRICANE WILL BE MOVING OVER COOLER SSTS...WHICH SHOULD NEGATE THE SLIGHTLY MORE FAVORABLE ATMOSPHERIC ENVIRONMENT. THE OFFICIAL FORECAST CALLS FOR VERY LITTLE CHANGE IN INTENSITY UNTIL THE SYSTEM BECOMES AN EXTRATROPICAL CYCLONE IN 3-4 DAYS. THE INITIAL MOTION ESTIMATE IS 315/9. THE MODELS ARE IN EXCELLENT AGREEMENT SHOWING A TURN TOWARD THE NORTH DURING THE NEXT 24 HOURS...FOLLOWED BY A TURN TOWARD THE NORTHEAST IN A COUPLE OF DAYS. AFTER THAT TIME...THE CYCLONE IS EXPECTED TO ACCELERATE INTO THE WESTERLIES AHEAD OF A TROUGH THAT MOVES OVER THE CANADIAN MARITIMES IN 3-4 DAYS. THE GFS AND ECMWF ARE IN VERY GOOD AGREEMENT EVEN DURING THE EXTRATROPICAL PORTION OF THE TRACK. THE NEW NHC FORECAST IS CLOSE TO THESE RELIABLE MODELS AND ONLY SLIGHT ADJUSTMENTS WERE MADE TO THE PREVIOUS FORECAST. THE WIND RADII OVER THE NORTHWEST QUADRANT OF THE HURRICANE WERE EXPANDED OUTWARD BASED ON DATA FROM NOAA BUOY 41048. THE CENTER OF KATIA IS FORECAST TO PASS VERY NEAR THAT BUOY TONIGHT. FORECAST POSITIONS AND MAX WINDS INIT 07/1500Z 29.2N 68.8W 75 KT 85 MPH 12H 08/0000Z 30.6N 69.6W 70 KT 80 MPH 24H 08/1200Z 32.8N 69.8W 70 KT 80 MPH 36H 09/0000Z 35.4N 69.0W 70 KT 80 MPH 48H 09/1200Z 38.1N 66.6W 70 KT 80 MPH 72H 10/1200Z 42.5N 52.5W 65 KT 75 MPH 96H 11/1200Z 51.0N 29.0W 65 KT 75 MPH...POST-TROP/EXTRATROP 120H 12/1200Z 60.0N 8.0W 65 KT 75 MPH...POST-TROP/EXTRATROP $$ FORECASTER BROWN NNNN
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Page last modified: Tuesday, 17-Jul-2012 13:43:55 UTC