000 WTPZ43 KNHC 311435 TCDEP3 HURRICANE JIMENA DISCUSSION NUMBER 12 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP132009 800 AM PDT MON AUG 31 2009 THE EYE HAS BEEN COMING AND GOING ON INFRARED IMAGERY AND...BASED ON MICROWAVE IMAGERY...APPEARS TO BE A LITTLE LARGER THAN IT WAS YESTERDAY. THE MICROWAVE IMAGES EARLIER THIS MORNING ALSO SUGGESTED THAT JIMENA MAY HAVE UNDERGONE AN EYEWALL REPLACEMENT. DVORAK SUBJECTIVE AND OBJECTIVE DATA T-NUMBERS HAVE DECREASED A LITTLE OVER THE PAST 12 HOURS...SO JIMENA MAY HAVE WEAKENED SLIGHTLY. HOWEVER...I WILL HOLD THE CURRENT INTENSITY AT 125 KT UNTIL AIR FORCE RECONNAISSANCE INVESTIGATES THE HURRICANE A LITTLE LATER TODAY AND GIVES US SOME IN SITU MEASUREMENTS. THE WATERS ARE WARM ALONG THE PROJECTED TRACK...BUT NOT QUITE AS WARM AFTER ABOUT 24 HOURS AND WITH REDUCED OCEANIC HEAT CONTENT. ALSO...THE GLOBAL MODELS INDICATE SOME INCREASE IN SOUTHWESTERLY SHEAR IN 24-48 HOURS. HOWEVER NONE OF THESE FACTOR ARE LIKELY TO PREVENT JIMENA FROM REMAINING A MAJOR HURRICANE UP TO LANDFALL. THE OFFICIAL INTENSITY FORECAST IS A BLEND OF THE SHIPS AND LGEM MODELS...WHICH HISTORICALLY HAVE BEEN OUR BEST INTENSITY GUIDANCE. INITIAL MOTION IS ESTIMATED TO BE 315/7. THE STEERING SCENARIO REMAINS MORE OR LESS THE SAME. JIMENA IS LIKELY TO MOVE BETWEEN A MID-LEVEL RIDGE OVER NORTHWESTERN MEXICO AND A MID- TO UPPER-LEVEL CYCLONE JUST TO THE WEST OF THE BAJA PENINSULA. THE DYNAMICAL TRACK PREDICTION MODELS ARE IN REASONABLY GOOD AGREEMENT OVER THE NEXT 48 HOURS...WITH THE EXCEPTION OF THE U.K. MET. OFFICE GLOBAL AND THE LOW-RESOLUTION GFS ENSEMBLE MEAN WHICH ARE CONSIDERED WESTERN OUTLIERS AT THIS TIME. IN FACT...THE MEAN OF THE HIGHER-RESOLUTION PARALLEL RUN OF THE GFS IS FAIRLY CLOSE TO THE MIDDLE OF THE GUIDANCE ENVELOPE. THE OFFICIAL FORECAST IS FAIRLY SIMILAR TO THE PREVIOUS ONE AND NOT FAR FROM THE MODEL CONSENSUS. BASED ON THE FORECAST...THE GOVERNMENT OF MEXICO HAS ISSUED A HURRICANE WARNING FOR A PORTION OF THE SOUTHERN BAJA CALIFORNIA PENINSULA AND A HURRICANE WATCH FARTHER NORTH ALONG THE BAJA PENINSULA. INTERESTS IN THE WARNING AREA ARE REMINDED...DO NOT FORECAST ON THE EXACT FORECAST TRACK. A HURRICANE IS NOT A POINT AND DANGEROUS IMPACTS EXTEND SOME DISTANCE FROM THE CENTER. MOREOVER...TRACK FORECAST ERRORS CAN EASILY BE 50 TO 75 MILES IN THE 24 TO 36 HOURS TIME FRAME. FORECAST POSITIONS AND MAX WINDS INITIAL 31/1500Z 18.0N 108.3W 125 KT 12HR VT 01/0000Z 19.1N 109.2W 125 KT 24HR VT 01/1200Z 21.0N 110.3W 125 KT 36HR VT 02/0000Z 23.0N 111.2W 115 KT 48HR VT 02/1200Z 25.0N 111.9W 95 KT...INLAND 72HR VT 03/1200Z 27.6N 112.9W 50 KT...INLAND 96HR VT 04/1200Z 29.0N 113.5W 30 KT...INLAND 120HR VT 05/1200Z 30.0N 114.0W 25 KT...OVER WATER $$ FORECASTER PASCH