ZCZC MIATCDEP4 ALL TTAA00 KNHC DDHHMM TROPICAL STORM NORMA DISCUSSION NUMBER 2 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 2 AM PDT FRI SEP 23 2005 TROPICAL DEPRESSION 14-E HAS CONTINUED TO BECOME BETTER ORGANIZED DURING THE PAST 6 HOURS AND HAS STRENGTHENED INTO TROPICAL STORM NORMA. SATELLITE INTENSITY ESTIMATES AT 06Z WERE 30 KT FROM BOTH TAFB AND SAB. HOWEVER...CONVECTION HAS SINCE INCREASED CLOSE TO THE CENTER WITH CLOUD TOPS NEAR -80C. DATA T-NUMBERS USING A SHEAR PATTERN ARE 35-45 KT...DEPENDING ON THE PLACEMENT OF THE CENTER RELATIVE TO DEEP CONVECTION... AND RAW ODT VALUES ARE 45 KT USING A CURVED BAND PATTERN AND 45-55 KT USING A SHEAR PATTERN. THE RAW ODT VALUES ARE LIKELY TOO HIGH...BUT A 22/2205Z CIRA-AMSU INTENSITY ESTIMATE INDICATED A CENTRAL PRESSURE OF 998 MB AND 40 KT. DUE TO THE UNCERTAINTY IN THE EXACT LOCATION OF THE LOW-LEVEL CENTER... THE INTENSITY IS HAS BEEN CONSERVATIVELY INCREASED TO 35 KT. THE INITIAL MOTION ESTIMATE IS 295/5. THE LOW-LEVEL CENTER HAS BEEN TRYING TO RE-ORGANIZE CLOSER TO THE DEEP CONVECTION...OR VICE VERSA ...SO THERE IS SOME UNCERTAINTY IN THE EXACT LOCATION USING NIGHTTIME IMAGERY. A LARGE BUT WEAK MID-LEVEL RIDGE LOCATED TO THE NORTH AND EAST OF NORMA IS EXPECTED TO STEER THE CYCLONE SLOWLY WEST-NORTHWESTWARD THROUGHOUT THE FORECAST PERIOD. THE OFFICIAL FORECAST TRACK IS CLOSE TO THE PREVIOUS TRACK AND THE MEDIUM BAM MODEL... AND IS CONSISTENT WITH THE GENERAL MEAN MOTION OF THE WIDELY DIVERGENT GLOBAL MODELS. THE CURRENT EAST-SOUTHEASTERLY UPPER-LEVEL SHEAR OF 15 KT IS FORECAST TO DECREASE TO LESS THAN 10 KT DURING THE 12-36 HOUR PERIOD BEFORE IT INCREASES AGAIN AFTERWARDS. WITH NORMA EXPECTED TO MOVE OVER 28C-28.5C SSTS DURING THAT TIME PERIOD... AT LEAST STEADY INTENSIFICATION SHOULD OCCUR UNTIL THE VERTICAL SHEAR INCREASES ONCE AGAIN. HOWEVER... AS MENTIONED IN THE PREVIOUS DISCUSSION ... IF THE VERTICAL SHEAR HOLDS OFF THROUGH 48 HOURS... THEN NORMA COULD BECOME A 65-KT HURRICANE. FORECASTER STEWART FORECAST POSITIONS AND MAX WINDS INITIAL 23/0900Z 15.1N 109.3W 35 KT 12HR VT 23/1800Z 15.6N 110.3W 40 KT 24HR VT 24/0600Z 16.2N 111.5W 45 KT 36HR VT 24/1800Z 16.9N 112.8W 55 KT 48HR VT 25/0600Z 17.5N 114.0W 50 KT 72HR VT 26/0600Z 18.7N 116.4W 45 KT 96HR VT 27/0600Z 20.0N 119.0W 40 KT 120HR VT 28/0600Z 21.0N 121.5W 35 KT $$ NNNN
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Page last modified: Friday, 23-Sep-2005 08:40:20 UTC