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 989 
 WTPZ42 KNHC 230246
 TCDEP2
 TROPICAL DEPRESSION SEVENTEEN-E DISCUSSION NUMBER   1
 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP172009
 800 PM PDT TUE SEP 22 2009
  
 SATELLITE IMAGERY INDICATES THAT THE BROAD AREA OF LOW PRESSURE
 LOCATED SEVERAL HUNDRED MILES SOUTHWEST OF THE SOUTHERN TIP OF BAJA
 CALIFORNIA HAS ACQUIRED SUFFICIENT CONVECTION ORGANIZATION TO BE
 DESIGNATED AS A TROPICAL DEPRESSION...THE SEVENTEENTH OF THE
 SEASON. THE DEPRESSION IS COMPRISED OF AN ELONGATED AND FAIRLY
 SHAPELESS MASS OF CENTRAL CONVECTION...DISPLACED NORTHWEST OF THE
 ESTIMATED CENTER DUE TO SOUTHEASTERLY SHEAR. DVORAK T-NUMBERS ARE
 T 2.0 FROM BOTH TAFB AND SAB AND SERVE AS THE BASIS FOR SETTING THE
 ADVISORY INTENSITY AT 30 KT. WITHIN 24 HOURS... SOUTHWESTERLY SHEAR
 IS EXPECTED TO BEGIN INCREASING AND SHOULD BECOME PROHIBITIVELY
 STRONG BY 48 HOURS. HOWEVER...PRIOR TO ENCOUNTERING THIS HIGH SHEAR
 ENVIRONMENT...THE DEPRESSION HAS SOME OPPORTUNITY TO BECOME A
 TROPICAL STORM. WEAKENING IS THEN FORECAST AFTER 36 HOURS...WITH
 THE DEPRESSION FORECAST TO BECOME A REMNANT LOW BY 72 HOURS. THE
 OFFICIAL FORECAST IS IN BEST AGREEMENT WITH THE SHIPS/LGEM GUIDANCE
 AND DOES NOT CONSIDER THE GFDL/HWRF INTENSITY FORECASTS WHICH CALL
 FOR THE DEPRESSION TO BECOME A HURRICANE. THESE FORECASTS APPEAR TO
 BE UNREALISTIC..GIVEN THE STRONG SHEAR FORECAST BY THE GLOBAL
 MODELS. 
  
 THERE IS MORE UNCERTAINTY THAN NORMAL IN THE INITIAL MOTION...WHICH
 IS ESTIMATED AT 320/08.  GLOBAL MODELS SHOW A BREAK IN THE
 SUBTROPICAL RIDGE BETWEEN 115 WEST AND 120 WEST...WHICH SHOULD
 STEER THE DEPRESSION ON A GENERAL NORTHWESTWARD COURSE FOR THE NEXT
 24 HOURS. THEREAFTER...THE STRONG SHEAR FORECAST BY THE GLOBAL
 MODELS SHOULD CAUSE A DECOUPLING OF THE CYCLONE...WITH THE LOW-
 LEVEL CENTER EXPECTED TO TURN TOWARD THE WEST AT A REDUCED
 FORWARD SPEED UNTIL DISSIPATION.
  
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      23/0300Z 15.7N 115.7W    30 KT
  12HR VT     23/1200Z 16.4N 116.5W    35 KT
  24HR VT     24/0000Z 17.3N 117.5W    40 KT
  36HR VT     24/1200Z 17.6N 118.2W    35 KT
  48HR VT     25/0000Z 17.7N 119.0W    30 KT
  72HR VT     26/0000Z 17.8N 120.5W    20 KT...REMNANT LOW
  96HR VT     27/0000Z...DISSIPATED
  
 $$
 FORECASTER KIMBERLAIN
  
 
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