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Tropical Storm MARTY (Text)

ZCZC MIATCDEP1 ALL
TTAA00 KNHC DDHHMM
TROPICAL STORM MARTY DISCUSSION NUMBER   3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP162009
200 PM PDT WED SEP 16 2009
 
VISIBLE SATELLITE IMAGERY INDICATES THAT MARTY HAS MOVED VERY LITTLE
SINCE THIS MORNING.  THE CLOUD PATTERN IS THAT OF A VERY ASYMMETRIC
TROPICAL CYCLONE...WITH ALL OF THE DEEP CONVECTION OVER THE WESTERN
SEMICIRCLE OF THE STORM.  DVORAK T-NUMBERS OF 2.5 AND 3.0 SUPPORT
INCREASING THE INITIAL INTENSITY TO 40 KT.  A SHEAR ANALYSIS FROM
UW-CIMSS SHOWS ABOUT 15 KT OF SOUTHEASTERLY SHEAR OVER THE CYCLONE. 
THE SHEAR IS FORECAST TO BECOME SOUTHERLY...THEN TURN SOUTHWESTERLY
IN ABOUT 24 HOURS.  IT APPEARS THAT THERE IS SMALL WINDOW OF
OPPORTUNITY FOR MARTY TO STRENGTHEN DURING THE NEXT DAY...
THEREAFTER INCREASING SHEAR AND A LESS FAVORABLE THERMODYNAMIC
ENVIRONMENT SHOULD INDUCE A MORE RAPID RATE OF WEAKENING.  THE
OFFICIAL INTENSITY FORECAST IS CLOSEST TO THE STATISTICAL GUIDANCE
FOR THE FIRST 24 HOURS...THEN IS IN GOOD AGREEMENT WITH THE
INTENSITY CONSENSUS THEREAFTER.

MARTY IS EXPECTED TO BEGIN MOVING SLOWLY NORTH-NORTHWESTWARD SOON 
AS A WEAK RIDGE BUILDS TO THE EAST OF THE CYCLONE.  THE NEW
FORECAST IS CLOSE TO THE PREVIOUS ADVISORY AND NEAR THE MIDDLE OF
THE GUIDANCE ENVELOPE DURING THE FIRST 48 HOURS.  THEREAFTER...A
SIGNIFICANT WESTWARD SHIFT HAS BEEN MADE TO THE NHC TRACK...AS
NEARLY ALL OF THE DYNAMICAL MODELS TURN MARTY WESTWARD IN THE
LOW-LEVEL FLOW AS IT WEAKENS AND BECOME A SHALLOW SYSTEM.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      16/2100Z 18.9N 112.6W    40 KT
 12HR VT     17/0600Z 19.2N 112.7W    45 KT
 24HR VT     17/1800Z 19.7N 113.0W    50 KT
 36HR VT     18/0600Z 20.4N 113.4W    45 KT
 48HR VT     18/1800Z 21.2N 113.9W    35 KT
 72HR VT     19/1800Z 22.6N 115.3W    30 KT...REMNANT LOW
 96HR VT     20/1800Z 23.5N 117.0W    25 KT...REMNANT LOW
120HR VT     21/1800Z 23.5N 120.0W    20 KT...REMNANT LOW
 
$$
FORECASTER BROWN
 
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