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TROPICAL STORM MANUEL DISCUSSION NUMBER 24
NATIONAL WEATHER SERVICE MIAMI FL
8 AM PDT TUE OCT 16 2001
DURING THE PAST 6 HOURS...MANUEL HAS GONE THROUGH A TEMPORARY
BURSTING PHASE WITH DEEP CONVECTION WEAKENING AND NOW REFORMING NEAR
THE LOW-LEVEL CENTER. THE INITIAL INTENSITY OF 45 KT IS MAINTAINED
BASED ON SATELLITE INTENSITY ESTIMATES OF 45 KT FROM BOTH TAFB AND
SAB. OUTFLOW IS LESS RESTRICTED AND THE OVERALL CLOUD PATTERN HAS
BECOME MORE SYMMETRICAL.
THE INITIAL MOTION ESTIMATE IS 305/10. DUE TO THE UNCERTAINITY OF
CENTER POSITIONING FROM INFARED IMAGERY...WE DID NOT WANT TO DEVIATE
MUCH FROM THE PREVIOUS ADVISORY MOTION. HOWEVER...LONG TERM
SATELLITE ANIMATION SUGGESTS THAT MANUEL IS CONTINUING IN A GENERAL
NORTHWESTERLY DIRECTION. WATER VAPOR IMAGERY INDICATES A DEEP LAYER
RIDGE IS LOCATED TO THE NORTH AND NORTHEAST OF THE CYCLONE WITH A
MID-LEVEL TROUGH APPROACHING FROM THE WEST. THE TROUGH APPEARS TO BE
LIFTING OUT TO THE NORTHEAST...THEREFORE THE RIDGE SHOULD REMAIN
INTACT TO THE NORTH OF THE CYCLONE. THIS SHOULD KEEP MANUEL ON A
GENERAL NORTHWEST TO WEST-NORTHWESTERLY TRACK. FORECAST GUIDANCE
REMAINS IN GOOD AGREEMENT ON A NORTHWESTERLY TRACK THROUGH 36
HOURS...AND THEN DIVERGE SIGNIFICANTLY AFTERWARDS. THE BAM MODELS
TAKE MANUEL RAPIDLY NORTH AND NORTHEAST TOWARDS SOUTHERN
CALIFORNIA...WHICH SEEMS UNREASONABLE GIVEN THE STRENGTH OF THE
RIDGE TO THE NORTH. THE REMAINING MODELS TAKE MANUEL WEST-NORTHWEST
TO NORTHWEST...WITH THE AVN BEING THE FASTEST OF THE MODELS. ONCE
WEAKENING BEGINS IN 36 TO 48 HOURS...MANUEL SHOULD BE STEERED MORE
WESTWARD BY THE DOMINATE LOW-LEVEL RIDGE. THE OFFICIAL FORECAST IS
TO THE LEFT OF THE PREVIOUS FORECAST TRACK AND IS BETWEEN THE GFDL
AND UKMET MODELS.
SINCE CONVECTION HAS REDEVELOPED NEAR THE LOW-LEVEL CENTER...MANUEL
IS EXPECTED TO STRENGTHEN SLIGHTLY DURING THE NEXT 24 HOURS WHILE IT
REMAINS OVER MARGINAL SSTS. THEREAFTER...INCREASING UPPER-LEVEL
SHEAR AND COOLER SSTS ARE EXPECTED TO RESULT IN STEADY WEAKENING.
THE SHIPS INTENSITY MODEL MAINTAINS THE CURRENT INTENSITY THROUGH 36
HOURS...WITH STEADY WEAKENING AFTERWARDS AND DISSIPATION IN 72
HOURS.
FORECASTER STEWART/BROWN
FORECAST POSITIONS AND MAX WINDS
INITIAL 16/1500Z 18.1N 118.3W 45 KTS
12HR VT 17/0000Z 19.0N 119.7W 50 KTS
24HR VT 17/1200Z 19.9N 121.1W 55 KTS
36HR VT 18/0000Z 21.0N 122.5W 50 KTS
48HR VT 18/1200Z 21.8N 123.7W 40 KTS
72HR VT 19/1200Z 23.5N 125.5W 30 KTS
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