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Tropical Storm NORMA

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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

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