000 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