000
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