Tropical Storm MARIE

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TROPICAL STORM MARIE DISCUSSION NUMBER   5
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP142008
200 AM PDT THU OCT 02 2008

RECENT MICROWAVE IMAGERY SHOWS THAT THE CENTER OF MARIE IS EXPOSED
TO THE EAST OF THE MAIN CONVECTION...UNDERNEATH THE OUTFLOW CIRRUS. 
ANALYSES FROM CIMSS AT THE UNIVERSITY OF WISCONSIN INDICATE ABOUT
15 KT OF EASTERLY VERTICAL WIND SHEAR AFFECTING THE STORM.  WHILE
THE CENTRAL CONVECTION HAS INCREASED DURING THE PAST FEW HOURS...
THE OVERALL AMOUNT OF CONVECTION HAS DECREASED SIGNIFICANTLY DURING
THE PAST 24 HOURS.  THIS MAY BE DUE TO A TONGUE OF STABLE STRATUS
CLOUDS SEEN IN THE WESTERN SEMICIRCLE.  SATELLITE INTENSITY
ESTIMATES FROM TAFB AND SAB REMAIN 45 KT...AND THIS REMAINS THE
INITIAL INTENSITY.
 
THE MICROWAVE DATA SUGGESTS THAT THE FORWARD MOTION HAS SLOWED...
WITH THE INITIAL MOTION NOW 280/10.  WATER VAPOR IMAGERY SHOWS A
LARGE MID/UPPER-LEVEL TROUGH OVER THE NORTHEASTERN PACIFIC NEAR THE
U. S. WEST COAST...AND THIS IS LIKELY WEAKENING THE RIDGE NORTH OF
MARIE AS FORECAST BY THE DYNAMICAL MODELS LAST NIGHT.  HOWEVER...
THE TROUGH IS NOT DIGGING SOUTHWARD ENOUGH TO CAUSE MARIE TO TURN
NORTHWARD.  THE TRACK GUIDANCE CALLS FOR A GENERAL WESTWARD TO
WEST-NORTHWESTWARD MOTION UNDER THE RIDGE...WITH THE HWRF...GFS...
AND BAMD SHOWING A MORE NORTHERLY MOTION WHILE THE NOGAPS AND THE
UKMET SHOW A SOUTH OF WEST MOTION.  THERE IS ALSO SPREAD IN THE
FORWARD SPEED BETWEEN THE RATHER SLOW ECMWF AND GFDN...AND THE
FASTER UKMET AND HWRF.  GIVEN THE SPREAD...THE NEW FORECAST TRACK
CALLS FOR A SLOW WESTWARD MOTION IN BEST OVERALL AGREEMENT WITH THE
NOGAPS AND THE TVCN CONSENSUS MODEL.  THE NEW TRACK IS SIMILAR TO
BUT A LITTLE SOUTH OF THE PREVIOUS FORECAST.

MARIE IS MOVING OVER GRADUALLY COOLER SEA SURFACE TEMPERATURES AND
SHOULD REACH THE 26C ISOTHERM IN ABOUT 24 HOURS.  AFTER THAT...THE
FORECAST TRACK IS NEARLY PARALLEL TO THE ISOTHERMS WITH THE CENTER
OVER 25-26C SSTS.  THE VERTICAL SHEAR IS FORECAST TO BE LIGHT TO
MODERATE THROUGH THE FORECAST PERIOD.  THE CURRENT SATELLITE
APPEARANCE SUGGESTS THAT STABLE AIR AND COOLER WATERS MAY ALREADY
BE AFFECTING THE SYSTEM.  HOWEVER...THE INTENSITY GUIDANCE
CONTINUES TO FORECAST SOME STRENGTHENING DURING THE NEXT 24 HOURS
OR SO.  BASED ON THIS AND THE UPCOMING DIURNAL CONVECTIVE
MAXIMUM...THE NEW INTENSITY FORECAST CALLS FOR SLIGHT STRENGTHENING
DURING THE NEXT 12 HOURS FOLLOWED BY GRADUALLY WEAKENING.  AN
ALTERNATIVE SCENARIO IS THAT MARIE HAS ALREADY PEAKED IN INTENSITY
AND WILL GRADUALLY WEAKEN FROM THIS TIME ON.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      02/0900Z 18.0N 120.0W    45 KT
 12HR VT     02/1800Z 18.2N 121.1W    50 KT
 24HR VT     03/0600Z 18.3N 122.3W    50 KT
 36HR VT     03/1800Z 18.2N 123.3W    45 KT
 48HR VT     04/0600Z 18.1N 124.1W    45 KT
 72HR VT     05/0600Z 18.0N 126.0W    40 KT
 96HR VT     06/0600Z 18.0N 128.0W    35 KT
120HR VT     07/0600Z 18.0N 130.0W    30 KT
 
$$
FORECASTER BEVEN
 
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