354 
 WTPZ42 KNHC 230234
 TCDEP2
 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