134 
 WTPZ42 KNHC 221434
 TCDEP2
 TROPICAL STORM IVO DISCUSSION NUMBER  17
 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP122007
 800 AM PDT SAT SEP 22 2007
 
 THE SATELLITE PRESENTATION OF IVO CONSISTS OF ONLY A BURST OF
 CONVECTION OVER THE NORTHERN SEMICIRCLE...RESULTANT FROM THE
 SOUTH-SOUTHWESTERLY SHEAR.  WHILE DVORAK CURRENT INTENSITIES ARE 65
 KT AND 45 KT FROM TAFB AND SAB RESPECTIVELY...THE DATA T-NUMBERS
 ARE 45 KT FROM BOTH AGENCIES.  THE INITIAL INTENSITY WILL BE HELD
 AT 50 KT FOR THIS ADVISORY.
 
 THE INITIAL MOTION IS ESTIMATED AT 025/5.  WATER VAPOR IMAGERY
 SUGGESTS THAT THE LARGE MID- TO UPPER-LEVEL LOW JUST WEST OF THE
 SOUTHERN COAST OF CALIFORNIA IS BEGINNING TO LIFT NORTHEASTWARD AS
 FORECAST.  THE MAJORITY OF THE MODEL GUIDANCE TAKES IVO SLOWLY TO
 THE NORTHEAST OVER THE NEXT COUPLE OF DAYS WITHIN THE SOUTHWESTERLY
 FLOW AND TRACK A WEAKENING SYSTEM ACROSS THE SOUTHERN BAJA
 PENINSULA.  IN CONTRAST THE GFS...ECMWF...AND GFDN STALL THE
 CYCLONE...OR ITS REMNANTS...SOUTH OF THE BAJA PENINSULA.  THE
 OFFICIAL TRACK FORECAST IS ESSENTIALLY AN UPDATE OF THE PREVIOUS
 ADVISORY PACKAGE.
 
 WITH THE SOUTHWESTERLY SHEAR EXPECTED TO PERSIST FOR THE NEXT COUPLE
 OF DAYS...GRADUAL WEAKENING IS ANTICIPATED.  THE OFFICIAL INTENSITY
 FORECAST FOLLOWS CLOSELY WITH THE PREVIOUS FORECAST AS WELL AS THE
 INTENSITY MODEL CONSENSUS OF THE GFDL...HWRF...AND SHIPS.  HOWEVER
 IF THE CURRENT BURST OF CONVECTION WEAKENS SIGNIFICANTLY BY THIS
 AFTERNOON...THE INTENSITY FORECAST WOULD BE ADJUSTED DOWNWARD AND
 IVO COULD WEAKEN EVEN FASTER. 
 
 ALTHOUGH IVO IS EXPECTED TO WEAKEN AS IT APPROACHES SOUTHERN BAJA
 CALIFORNIA...TROPICAL STORM WATCHES MAY BE REQUIRED LATER TODAY.
  
  
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      22/1500Z 21.3N 112.7W    50 KT
  12HR VT     23/0000Z 21.9N 112.4W    45 KT
  24HR VT     23/1200Z 22.4N 111.8W    40 KT
  36HR VT     24/0000Z 23.0N 111.2W    35 KT
  48HR VT     24/1200Z 23.5N 110.6W    30 KT
  72HR VT     25/1200Z 24.2N 109.8W    25 KT...INLAND...DISSIPATING
  96HR VT     26/1200Z 25.0N 109.5W    20 KT...OVER WATER REMNANT LOW
 120HR VT     27/1200Z 26.0N 109.5W    20 KT...REMNANT LOW
  
 $$
 FORECASTER MAINELLI