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TROPICAL STORM MANUEL DISCUSSION NUMBER   7
NATIONAL WEATHER SERVICE MIAMI FL
2 AM PDT FRI OCT 12 2001

CONVECTION NEAR THE CENTER OF MANUEL HAS DECREASED MARKEDLY
DURING THE NIGHT...WITH THE STRONGEST CONVECTION REMAINING IN
THE STORM ABOUT A DEGREE OR SO SOUTHWEST OF THE ESTIMATED CENTER
POSITION.  A TRMM OVERPASS AT 0355Z HINTED THAT THE LOW LEVEL
CENTER WAS BECOMING ELONGATED...SUGGESTING THE POSSIBILITY THAT
IT MIGHT REFORM CLOSER TO THAT CONVECTION.  DAYLIGHT VISIBLE 
IMAGES SHOULD HELP DETERMINE WHETHER THAT HAS ACTUALLY HAPPENED
OR NOT.  SATELLITE INTENSITY ESTIMATES REMAIN AT 45 KT...AS DOES
THE INITIAL INTENSITY.

THE INITIAL MOTION IS NOW ESTIMATED AT 280/11.  WATER VAPOR IMAGERY
INDICATES A DEEP-LAYER TROUGH OVER THE WESTERN UNITED STATES
EXTENDING TO ABOUT 29N...AND MODEL ANALYSES INDICATE MID LEVEL
RIDGING BETWEEN THE TROUGH AND THE STORM.  THE LARGE-SCALE MODELS
SUGGEST THE LOW AND MID LEVEL PARTS OF THE TROUGH WILL MOVE EASTWARD
AND BYPASS MANUEL...ALLOWING IT TO CONTINUE GENERALLY WESTWARD OR
WEST-NORTHWESTWARD.  NHC HURRICANE GUIDANCE IS SOMEWHAT DIVERSE.
THE GFDL AND GFDN BOTH FORECAST ERRATIC MOTION...NEVER MOVING MANUEL
WEST OF 112W.  THE LBAR CALLS FOR A NORTHWESTWARD TRACK...WHILE THE
NHC91 CALLS FOR A WEST-SOUTHWESTWARD MOTION.  THE REMAINDER OF THE
GUIDANCE CALLS FOR A WESTWARD MOTION WITH A TURN TO THE WEST-
NORTHWEST IN 36-48 HR...AND THE OFFICIAL FORECAST FOLLOWS THIS
SCENARIO.
 
IN ADDITION TO THE CONVECTIVE DISORGANIZATION...THE OUTFLOW OF
MANUEL LOOKS UNIMPRESSIVE.  THERE IS EVIDENCE THAT NORTHWESTERLY 
FLOW IS UNDERCUTTING THE OUTFLOW AND PARTIALLY SHEARING THE SYSTEM.
LARGE-SCALE MODELS SUGGEST THAT THE SHEAR WILL GRADUALLY INCREASE
BY 36-48 HR...ALTHOUGH IF MANUEL STAYS SOUTH OF THE CURRENT FORECAST
TRACK THE ENVIRONMENT COULD BE MORE FAVORABLE.  BASED ON THIS...AND
THE POSSIBILITIES OF NEW CONVECTIVE FLARE-UPS NEAR THE CENTER OR A
REFORMATION OF THE CENTER...THE INTENSITY FORECAST WILL CALL FOR
MODEST STRENGTHENING FOLLOWED BY SLIGHT WEAKENING.  THIS IS IN
AGREEMENT WITH THE SHIPS MODEL.
 
FORECASTER BEVEN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     12/0900Z 16.2N 108.6W    45 KTS
12HR VT     12/1800Z 16.4N 110.0W    45 KTS
24HR VT     13/0600Z 16.7N 111.8W    50 KTS
36HR VT     13/1800Z 16.9N 114.4W    50 KTS
48HR VT     14/0600Z 17.2N 116.8W    45 KTS
72HR VT     15/0600Z 18.0N 119.5W    45 KTS
 
 
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