000 WTNT42 KNHC 051447 TCDAT2 HURRICANE KATIA DISCUSSION NUMBER 30 NWS NATIONAL HURRICANE CENTER MIAMI FL AL122011 1100 AM AST MON SEP 05 2011 KATIA APPEARS TO HAVE GONE THROUGH AN EYEWALL REPLACEMENT AND NOW HAS A 30 N MI WIDE EYE SURROUNDED BY A RELATIVELY NARROW BAND OF THE COLDEST CLOUD TOPS. DVORAK INTENSITY ESTIMATES HAVE RISEN TO T5.0 FROM TAFB AND SAB...AND THE OBJECTIVE NUMBERS ARE AT T5.5. THE INITIAL INTENSITY IS THEREFORE BEING RAISED TO 95 KT. THE EYE HAS BEEN WOBBLING A BIT...BUT THE 12-HOUR SMOOTHED MOTION IS 310/11 KT. KATIA IS MOVING AROUND THE SOUTHWESTERN PERIPHERY OF A CENTRAL ATLANTIC MID-LEVEL ANTICYCLONE AND TOWARDS DEEP-LAYER TROUGHING OVER THE EASTERN UNITED STATES AND WESTERN ATLANTIC. THE TRACK GUIDANCE IS IN GOOD AGREEMENT IN MAINTAINING A NORTHWESTWARD HEADING WITH SOME DECREASE IN FORWARD SPEED DURING THE FIRST 48 HOURS. ALTHOUGH ALL THE GUIDANCE SHOWS SHARP RE-CURVATURE BETWEEN BERMUDA AND THE U.S. EAST COAST IN ABOUT 3 DAYS...THERE IS STILL A LARGE DIVERGENCE IN FORWARD SPEED WITH GREATER-THAN-NORMAL SPREAD AT DAYS 4 AND 5. FOR THIS CYCLE...THE GUIDANCE IS BOUNDED BY THE SLOWER-MOVING ECMWF AND UKMET...AND THE FASTER-MOVING GFS. IF TRENDS FROM THE PAST FEW DAYS CONTINUE TODAY...I WOULD EXPECT THE 12Z GUIDANCE TO SHOW LESS SPREAD AND FOR NOW WILL MAINTAIN THE OFFICIAL FORECAST AS BEING SLOWER THAN THE CONSENSUS MODELS. THE UPPER-LEVEL ENVIRONMENT NEAR KATIA APPEARS CONDUCIVE FOR FURTHER STRENGTHENING OVER THE NEXT SEVERAL DAYS. HOWEVER...WITHIN THE NEXT 24 HOURS OR SO...THE HURRICANE WILL BE MOVING OVER OCEAN HEAT CONTENT VALUES THAT DO NOT NORMALLY SUPPORT SIGNIFICANT INTENSIFICATION. THE OFFICIAL FORECAST THEREFORE INDICATES GRADUAL STRENGTHENING OVER THE NEXT 24 HOURS AND THEN MAINTAINS THE INTENSITY THROUGH DAYS 2 AND 3. WEAKENING IS FORECAST ON DAYS 4 AND 5 AS VERTICAL SHEAR INCREASES...AND AS KATIA MOVES OVER EVEN LESS CONDUCIVE OCEAN WATERS. THE OFFICIAL INTENSITY FORECAST IS AT THE UPPER END OF THE GUIDANCE FOR MOST OF THE FORECAST PERIOD. DUE TO THE EYEWALL REPLACEMENT...IT APPEARS THAT THE WIND FIELD HAS EXPANDED A BIT...AND THIS IS REFLECTED IN THE ANALYSIS AND FORECAST. FORECAST POSITIONS AND MAX WINDS INIT 05/1500Z 24.6N 63.3W 95 KT 110 MPH 12H 06/0000Z 25.6N 64.2W 100 KT 115 MPH 24H 06/1200Z 26.9N 65.7W 105 KT 120 MPH 36H 07/0000Z 28.1N 67.3W 105 KT 120 MPH 48H 07/1200Z 29.2N 68.7W 100 KT 115 MPH 72H 08/1200Z 32.5N 70.5W 95 KT 110 MPH 96H 09/1200Z 37.0N 67.5W 80 KT 90 MPH 120H 10/1200Z 40.0N 60.0W 70 KT 80 MPH $$ FORECASTER BERG