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Tropical Storm MARIE (Text)

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TROPICAL STORM MARIE DISCUSSION NUMBER   9
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP142008
200 AM PDT FRI OCT 03 2008

MARIE HAS BECOME BETTER ORGANIZED THIS MORNING.  AN SSM/IS OVERPASS
AT 0329Z SHOWED CONVECTION WRAPPING AROUND A MID-LEVEL EYE...WITH
EARLIER MICROWAVE DATA SUGGESTING THAT THE LOW-LEVEL AND MID-LEVEL
CENTERS WERE GETTING CLOSER TOGETHER.  INFRARED SATELLITE IMAGERY
SHOWS INCREASED CONVECTIVE BANDING WITH CLOUD TOPS COLDER THAN -80C
TO THE SOUTHEAST OF THE CENTER.  SATELLITE INTENSITY ESTIMATES ARE
55 KT FROM SAB AND 45 KT FROM TAFB.  BASED ON THIS...THE INITIAL
INTENSITY IS INCREASED TO 50 KT.  THE MODERATE EASTERLY VERTICAL
WIND SHEAR PREVIOUSLY AFFECTING THE CYCLONE HAS BECOME LIGHT
NORTHERLY SHEAR...AND MARIE CURRENTLY HAS FAIR TO GOOD CIRRUS
OUTFLOW IN ALL DIRECTIONS.

THE INITIAL MOTION IS 270/5.  MARIE IS SOUTH OF A BREAK IN THE
SUBTROPICAL RIDGE...WITH A SERIES OF SHORTWAVE TROUGHS SEEN IN
WATER VAPOR IMAGERY MOVING ACROSS THE NORTHEASTERN PACIFIC NORTH OF
THE BREAK.  THE LARGE-SCALE MODELS FORECAST THAT THESE TROUGHS WILL
NOT DIG FAR ENOUGH SOUTH TO AFFECT MARIE...AND WATER VAPOR IMAGERY
SUPPORTS THIS BY SHOWING MID/UPPER-LEVEL NORTHERLY FLOW TO THE
NORTH OF THE STORM.  THE DYNAMICAL MODELS FORECAST THE RIDGE TO
BUILD NORTH AND NORTHWEST OF MARIE AFTER 36-48 HR.  BASED ON THE
PATTERN AND TRENDS...MARIE IS EXPECTED TO MOVE SLOWLY WESTWARD
DURING THE NEXT 36-48 HR...WITH THE GUIDANCE SUGGESTING THE
POSSIBILITY OF ERRATIC MOTION.  AFTER THAT...THE BUILDING RIDGE
SHOULD STEER MARIE WESTWARD OR WEST-NORTHWESTWARD AT A SLIGHTLY
FASTER FORWARD SPEED.  SOME SPREAD IS PRESENT IN THE MODEL GUIDANCE
LATER IN THE FORECAST PERIOD...AS THE GFS...HWRF... BAMD...AND BAMM
MODELS CALLING FOR A FASTER WEST-NORTHWESTWARD MOTION THAN THE
OTHER GUIDANCE.  THE NEW FORECAST TRACK STAYS WITH THE SLOWER
GUIDANCE...CALLING FOR A SLOW WESTWARD MOTION THROUGH 120 HR.  THE
NEW TRACK IS SHIFTED A LITTLE NORTH OF THE PREVIOUS TRACK AND IS IN
BEST AGREEMENT WITH THE GUNA AND TVCN CONSENSUS MODELS.
 
MARIE IS EXPECTED TO REMAIN IN AN ENVIRONMENT OF LIGHT VERTICAL WIND
SHEAR FOR SEVERAL DAYS.  THUS...THE INTENSITY WILL LARGELY BE
CONTROLLED BY SEA SURFACE TEMPERATURES.  MARIE IS CURRENTLY NEAR
THE 26C ISOTHERM...WHICH IS LIKELY TO PREVENT SIGNIFICANT
STRENGTHENING.  HOWEVER...THE SLOW MOTION AND A FORECAST TRACK
ROUGHLY PARALLEL TO THE ISOTHERMS SUGGEST THAT THE SSTS WILL BE
SLOW TO COOL UNDER THE SYSTEM.  THE INTENSITY GUIDANCE SHOWS SOME
ADDITIONAL STRENGTHENING FOR 12-24 HR...WITH GRADUAL WEAKENING
BEGINNING IN 36-48 HR.  THE INTENSITY FORECAST FOLLOWS THIS
SCENARIO...WITH A PEAK INTENSITY OF 55 KT IN 12 HR AND A GRADUAL
DECAY AFTER 36 HR.  THE INTENSITY FORECAST IS IN BEST AGREEMENT
WITH THE SHIPS MODEL...AND IS SIMILAR TO THE PREVIOUS FORECAST.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      03/0900Z 17.8N 121.9W    50 KT
 12HR VT     03/1800Z 17.7N 122.5W    55 KT
 24HR VT     04/0600Z 17.8N 123.1W    55 KT
 36HR VT     04/1800Z 18.0N 123.6W    55 KT
 48HR VT     05/0600Z 18.2N 124.2W    50 KT
 72HR VT     06/0600Z 18.5N 126.5W    45 KT
 96HR VT     07/0600Z 19.0N 129.0W    40 KT
120HR VT     08/0600Z 19.0N 131.5W    35 KT
 
$$
FORECASTER BEVEN
 
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