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TROPICAL STORM ROSA DISCUSSION NUMBER  11
NATIONAL WEATHER SERVICE MIAMI FL
1 AM PST MON NOV 06 2000

WHEREAS THE SYSTEM IS BETTER ORGANIZED THAN IT WAS 24 HOURS
AGO...THE EARLIER DEVELOPMENT TREND SEEMS TO HAVE LEVELLED OFF.  THE
INNER CORE DOES NOT YET APPEAR TO BE WELL DEFINED.  INITIAL WINDS
ARE SET AT 55 KNOTS IN CONCURRENCE WITH DVORAK INTENSITY ESTIMATES
FROM BOTH TAFB AND SAB.  SINCE CONDITIONS APPEAR TO BE FAVORABLE...
ROSA COULD BECOME A HURRICANE IN A DAY OR SO.  INCREASING SHEAR
AND/OR THE PROXIMITY TO LAND SHOULD CURTAIL STRENGTHENING LATER IN
THE PERIOD.  THE OFFICIAL INTENSITY FORECAST LEANS TOWARD...BUT IS A
LITTLE MORE CONSERVATIVE THAN...THE LATEST SHIPS GUIDANCE.  THE GFDL
MODEL SHOWS WEAKENING COMMENCING WITHIN 24 HOURS...EVEN THOUGH IT
PREDICTS THE CENTER TO REMAIN OVER WARM WATERS.  

CENTER POSITIONS USING INFRARED IMAGERY ARE SOMEWHAT UNCERTAIN...BUT
EARLIER TRMM AND SSM/I IMAGERY SUGGEST THAT THE CENTER IS A LITTLE
TO THE NORTH AND EAST OF EARLIER ESTIMATES.  THE INITIAL MOTION
ESTIMATE IS NOW 325/6.  ROSA APPEARS TO BE RESPONDING THE FLOW AHEAD
OF A BROAD MID-TROPOSPHERIC TROUGH WHICH EXTENDS FROM THE WESTERN
U.S. SOUTHWARD INTO NORTHERN MEXICO.  GLOBAL MODELS SHOW ADDITIONAL
VORTICITY ENTERING THE TROUGH...FORMING A  CUT-OFF LOW NEAR THE NEW
MEXICO/OLD MEXICO BORDER IN A COUPLE OF DAYS.  ROSA IS EXPECTED TO
TURN NORTHWARD AND NORTH-NORTHEASTWARD IN RESPONSE TO THIS STEERING
REGIME.  THE CURRENT OFFICIAL FORECAST IS SHIFTED A BIT TO THE EAST
OF THE PREVIOUS ONE.  THIS IS FAIRLY CLOSE TO THE LATEST U.K. MET.
OFFICE MODEL RUN.  THE LATEST AVN RUN ALSO SHOWS THE STORM TURNING
TOWARD THE NORTH-NORTHEAST...BUT GIVEN THE LARGE SCALE STEERING
PATTERN...IT SEEMS TO MOVE ROSA TOO SLOWLY.

INTERESTS ALONG THE SOUTH COAST OF MEXICO SHOULD CLOSELY MONITOR THE
PROGRESS OF ROSA.  A HURRICANE WATCH MAY BE REQUIRED FOR A PORTION
OF THE COAST LATER TODAY.
 
FORECASTER PASCH
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     06/0900Z 12.3N  99.1W    55 KTS
12HR VT     06/1800Z 13.0N  99.4W    55 KTS
24HR VT     07/0600Z 14.1N  99.3W    60 KTS
36HR VT     07/1800Z 15.3N  98.9W    65 KTS
48HR VT     08/0600Z 16.5N  98.3W    60 KTS...INLAND
72HR VT     09/0600Z 19.0N  97.0W    30 KTS...INLAND
 
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