000 WTPZ43 KNHC 291445 TCDEP3 HURRICANE JIMENA DISCUSSION NUMBER 4 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP132009 800 AM PDT SAT AUG 29 2009 JIMENA HAS BEEN UNDERGOING RAPID INTENSIFICATION OVERNIGHT AND RECENTLY A SMALL EYE SURROUNDED BY VERY STRONG THUNDERSTORMS HAS BECOME APPARENT ON VISIBLE SATELLITE IMAGERY. A SPECIAL DVORAK CLASSIFICATION AT 1345 UTC FROM TAFB INDICATED THAT THE SYSTEM WAS NEAR 65 KT...AND THE LATEST OBJECTIVE T-NUMBERS ARE SUGGESTING 70 TO 75 KT. THE INITIAL INTENSITY IS RAISED TO 70 KT FOR THIS ADVISORY. THE LARGE-SCALE ENVIRONMENT APPEARS EXTREMELY FAVORABLE FOR CONTINUED RAPID STRENGTHENING...WITH VERY WARM SSTS OVER 30C...VERY HIGH MID-LEVEL HUMIDITY AND LOW SHEAR. THE SHIPS RAPID INTENSIFICATION INDEX IS FORECASTING A 95 PERCENT CHANCE OF A 35 KT INCREASE DURING THE NEXT 24 HOURS...THE HIGHEST VALUE I HAVE EVER SEEN. IN ADDITION...ALL GUIDANCE SHOWS THIS SYSTEM BECOMING EITHER A CATEGORY THREE OR FOUR HURRICANE. THUS...THE OFFICIAL FORECAST WILL SHOW CONTINUED RAPID STRENGTHENING...SHOWING A 35-KT INCREASE FROM THE 1200 UTC SYNOPTIC INTENSITY OF 60 KT. SSTS DECREASE IN THE LONG-RANGE...AND WEAKENING IS SHOWN AFTER DAY 3. THE INITIAL MOTION IS 285/08. WEAK MID-LEVEL RIDGING OVER MEXICO SHOULD PROVIDE THE STEERING CURRENTS OVER THE NEXT SEVERAL DAYS FOR JIMENA...WITH THE HURRICANE LIKELY MAKING A NORTHWESTWARD TURN IN A DAY OR TWO AS IT ROUNDS THE SOUTHWESTERN PERIPHERY OF THE RIDGE. HOWEVER...THERE ARE SOME BIG DISCREPANCIES IN HOW MUCH THAT RIDGE WEAKENS DUE TO A MID- TO UPPER-LEVEL TROUGH OVER BAJA CALIFORNIA. THE GFDL/HWRF SHOW ENOUGH OF A WEAKNESS IN THE RIDGE TO TURN JIMENA NORTHWEST AND NORTH-NORTHWEST BY TOMORROW...POISING A SIGNIFICANT THREAT TO BAJA CALIFORNIA OR WESTERN MEXICO. ALL OF THE OTHER GUIDANCE MAINTAIN ENOUGH OF A RIDGE BETWEEN THAT TROUGH AND JIMENA TO CONTINUE A WEST-NORTHWEST TO NORTHWESTWARD MOTION OF THE HURRICANE FOR SEVERAL DAYS. IN PREVIOUS YEARS...THE HWRF/GFDL HAVE HAD AN EASTWARD BIAS FOR THESE TYPES OF SYSTEMS...AND THEIR CURRENT FORECASTS HAVE BEEN GRADUALLY SHIFTING WESTWARD WITH TIME. THE NHC FORECAST IS SHIFTED WESTWARD...BUT IS NOT AS FAR WEST AS THE MODEL CONSENSUS. IT WOULD NOT BE SURPRISING TO SEE FURTHER WESTWARD ADJUSTMENTS LATER ON...ESPECIALLY IF THE REGIONAL HURRICANE MODELS COME INTO BETTER AGREEMENT WITH THE GLOBAL MODELS. FORECAST POSITIONS AND MAX WINDS INITIAL 29/1500Z 14.3N 103.2W 70 KT 12HR VT 30/0000Z 14.6N 104.4W 85 KT 24HR VT 30/1200Z 15.0N 105.7W 95 KT 36HR VT 31/0000Z 15.6N 106.9W 105 KT 48HR VT 31/1200Z 16.7N 108.2W 115 KT 72HR VT 01/1200Z 19.5N 111.0W 115 KT 96HR VT 02/1200Z 22.5N 114.0W 90 KT 120HR VT 03/1200Z 25.0N 117.0W 55 KT $$ FORECASTER BLAKE