Tropical Storm IVO

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TROPICAL STORM IVO DISCUSSION NUMBER  19
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP122007
800 PM PDT SAT SEP 22 2007

SOUTHWESTERLY SHEAR AND STABLE AIR HAS TAKEN A TOLL ON IVO. 
SATELLITE IMAGES SHOW THAT THE STORM IS WEAKENING AS THE MID-LEVEL
CENTER OF THE CYCLONE HAS BECOME DETACHED AND IS LOCATED WELL TO THE
NORTH OF THE LOW-LEVEL CENTER.  IN ADDITION...CONVECTION IS RATHER
WEAK AND REMOVED FROM THE SURFACE CENTER.  SATELLITE INTENSITY
ESTIMATES ARE DROPPING FROM ALL AGENCIES...AND THE INITIAL WINDS
ARE LOWERED TO 40 KT.  

VISIBLE AND MICROWAVE IMAGES SUGGEST THAT IVO HAS TURNED TOWARD THE
NORTHEAST AND IS MOVING 045/5.  THIS GENERAL TRACK AND SPEED IS
EXPECTED TO CONTINUE UNTIL LANDFALL.  GENERALLY THE MODELS THAT
SHOW A MORE VERTICALLY STACKED SYSTEM...SUCH AS THE UKMET/NOGAPS/
GFDL/HWRF MODELS...ARE ON THE LEFT SIDE OF THE GUIDANCE ENVELOPE. 
THOSE MODELS ARE WEIGHED LESS IN THE FORECAST THAN THE GFDN/GFS/
ECMWF MODELS...WHICH SHOW A WEAKER SYSTEM MOVING MORE TO THE
EAST.  THE OFFICIAL TRACK IS SHIFTED EASTWARD FAVORING THE WEAKER
SOLUTION.

IT APPEARS THAT THE EARLIER MODEL SCENARIOS OF A FAST DISSIPATION
MAY BE CORRECT GIVEN THE CURRENT STRUCTURE OF IVO.  HOWEVER... THE
GFDL/HWRF/SHIPS MODELS KEEP THE SYSTEM AS A TROPICAL STORM UNTIL
LANDFALL.  THE INTENSITY FORECAST SHOWS IVO AS A WEAK TROPICAL STORM
IMPACTING BAJA CALIFORNIA.  DISSIPATION IS LIKELY IN THE GULF OF
CALIFORNIA...IF NOT SOONER.  GIVEN THE FRAGILE INITIAL STATE OF THE
SYSTEM...IT WOULD NOT SURPRISING TO SEE THE STORM WEAKEN FASTER
THAN FORECAST AND...IF CURRENT TRENDS CONTINUED...THE TROPICAL
STORM WATCH COULD BE DISCONTINUED OVERNIGHT.

 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      23/0300Z 22.1N 111.8W    40 KT
 12HR VT     23/1200Z 22.6N 111.3W    35 KT
 24HR VT     24/0000Z 23.1N 110.7W    35 KT
 36HR VT     24/1200Z 23.7N 110.0W    30 KT
 48HR VT     25/0000Z 24.0N 109.7W    25 KT
 72HR VT     26/0000Z 24.5N 109.5W    20 KT...REMNANT LOW
 96HR VT     27/0000Z 25.5N 109.5W    20 KT...REMNANT LOW
120HR VT     28/0000Z...DISSIPATED
 
$$
FORECASTER BLAKE/AVILA
 
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