000
WTPZ41 KNHC 172037
TCDEP1
TROPICAL STORM MARTY DISCUSSION NUMBER   7
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP162009
200 PM PDT THU SEP 17 2009
 
THE OVERALL CLOUD PATTERN HAS CHANGED LITTLE SINCE THIS MORNING.
MICROWAVE IMAGERY SHOWS THAT THE CENTER HAS MOVED VERY LITTLE
DURING THE PAST 12 HOURS...AND IS LOCATED NEAR THE SOUTHERN EDGE
OF THE DEEP CONVECTION.  DVORAK T-NUMBERS ARE 3.0 AND 2.0
RESPECTIVELY FROM TAFB AND SAB...AND A RECENT ASCAT PASS SHOWED A
SOLID AREA OF WINDS AROUND 35 KT.  BASED ON THE SCATTEROMETER DATA
THE INITIAL INTENSITY REMAINS 40 KT.
 
MARTY IS FORECAST TO MOVE INTO A LESS FAVORABLE ENVIRONMENT...
CHARACTERIZED BY INCREASING SOUTHWESTERLY SHEAR AND A DRIER AND
MORE STABLE AIRMASS.  THIS SHOULD RESULT IN GRADUAL WEAKENING
DURING THE NEXT DAY OR TWO...AND MARTY IS PREDICTED TO BECOME
A REMNANT LOW IN ABOUT 48 HOURS.  THE OFFICIAL FORECAST REMAINS
AT OR JUST BELOW THE CONSENSUS OF THE INTENSITY GUIDANCE.
 
MARTY IS EXPECTED TO BEGIN MOVING ON A TRACK BETWEEN NORTHWEST
AND NORTH-NORTHWEST TONIGHT.  THE TRACK MODELS ARE IN GOOD AGREEMENT
ON THIS MOTION DURING THE NEXT DAY OR SO.  THEREAFTER...MARTY IS
EXPECTED TO TURN WESTWARD AS IT WEAKENS AND BECOMES A SHALLOW
SYSTEM.  THE LATEST RUNS OF THE DYNAMICAL MODELS HAVE SHIFTED SOUTH
AND WESTWARD AND SO HAS THE OFFICIAL FORECAST.  THE NEW FORECAST IS
SOMEWHAT TO THE LEFT OF THE PREVIOUS ADVISORY AND LIES JUST NORTH OF
THE MODEL CONSENSUS.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      17/2100Z 19.7N 113.2W    40 KT
 12HR VT     18/0600Z 20.1N 113.7W    35 KT
 24HR VT     18/1800Z 20.8N 114.6W    35 KT
 36HR VT     19/0600Z 21.7N 115.7W    30 KT
 48HR VT     19/1800Z 22.3N 116.9W    25 KT...REMNANT LOW
 72HR VT     20/1800Z 22.5N 119.0W    20 KT...REMNANT LOW
 96HR VT     21/1800Z 22.5N 121.0W    20 KT...REMNANT LOW
120HR VT     22/1800Z...DISSIPATED
 
$$
FORECASTER BROWN