000
WTPZ42 KNHC 222029
TCDEP2
TROPICAL STORM IVO DISCUSSION NUMBER  18
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP122007
200 PM PDT SAT SEP 22 2007

THE INTENSITY AND EXTENT OF DEEP CONVECTION HAS DIMINISHED OVER THE
PAST SEVERAL HOURS...AND THERE IS LITTLE EVIDENCE OF BANDING
FEATURES.  LATEST DVORAK CLASSIFICATIONS FROM TAFB AND SAB ARE AT
T3.0 OR 45 KT.  HOWEVER...AN EARLIER QUIKSCAT PASS SUGGESTS THAT IVO
COULD STILL HAVE A FEW SPOTS OF 50 KT WINDS SO THE INTENSITY IS HELD
AT 50 KT FOR THIS ADVISORY.  GRADUAL WEAKENING IS LIKELY AS
SOUTHWESTERLY SHEARING INCREASES OVER THE CYCLONE.  IVO COULD
WEAKEN BELOW TROPICAL STORM STRENGTH BEFORE REACHING THE BAJA
CALIFORNIA PENINSULA.  IN FACT...THE GFS...THE U.K. MET. OFFICE 
AND ECMWF GLOBAL MODELS PREDICT DISSIPATION JUST TO THE SOUTH OR
SOUTHWEST OF THE SOUTHERN TIP OF BAJA.

VISIBLE IMAGES MAKE IT EASIER TO ESTIMATE THE CENTER LOCATION AND
THE INITIAL MOTION IS A SLOW 030/4.  THE MID- TO UPPER-LEVEL CYCLONE
NEAR SOUTHERN CALIFORNIA IS GRADUALLY LIFTING NORTHEASTWARD...BUT A
LINGERING TROUGH TO THE SOUTHWEST SHOULD PROVIDE ENOUGH STEERING
FLOW TO CARRY THE TROPICAL CYCLONE SLOWLY NORTH-NORTHEASTWARD TO
NORTHEASTWARD OVER THE NEXT COUPLE OF DAYS.  THE OFFICIAL TRACK
FORECAST IS QUITE SIMILAR TO THAT OF THE PREVIOUS ADVISORY.  THIS
IS ALSO IN CLOSE AGREEMENT WITH A CONSENSUS OF THE LATEST GFDL AND
HWRF PREDICTIONS.

OWING TO THE UNCERTAINTY IN INTENSITY FORECASTS...A TROPICAL STORM
WATCH HAS BEEN ISSUED FOR A PORTION OF THE WEST COAST OF THE BAJA
CALIFORNIA PENINSULA...SOUTH OF 24.5N.

 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      22/2100Z 21.8N 112.5W    50 KT
 12HR VT     23/0600Z 22.2N 112.2W    45 KT
 24HR VT     23/1800Z 22.9N 111.6W    40 KT
 36HR VT     24/0600Z 23.6N 110.9W    35 KT
 48HR VT     24/1800Z 24.2N 110.4W    30 KT
 72HR VT     25/1800Z 25.0N 110.0W    25 KT
 96HR VT     26/1800Z 26.0N 110.0W    20 KT...REMNANT LOW
120HR VT     27/1800Z 27.0N 110.0W    20 KT...REMNANT LOW
 
$$
FORECASTER MAINELLI/PASCH