889 
 WTPZ41 KNHC 162040
 TCDEP1
 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