000 WTPZ43 KNHC 020259 TCDEP3 HURRICANE JIMENA DISCUSSION NUMBER 18 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP132009 800 PM PDT TUE SEP 01 2009 SINCE THE AIR FORCE PLANE LEFT THIS AFTERNOON...VISIBLE AND INFRARED SATELLITE IMAGES INDICATE THAT JIMENA HAS CONTINUED TO WEAKEN. THE EYE HAS BECOME OBSCURED AND THERE HAS BEEN A GRADUAL SHRINKING OF THE CONVECTIVE COVERAGE. FURTHERMORE...THERE HAS BEEN AN APPARENT DETERIORATION TO THE INNER CORE. DVORAK T-NUMBERS HAVE FALLEN TO T4.5 AND T5.0 FROM SAB AND TAFB...RESPECTIVELY. BASED UPON THE DEGRADED SATELLITE APPEARANCE BUT ALSO USING CONTINUITY...THE INITIAL INTENSITY IS LOWERED TO 100 KT. THE INITIAL MOTION ESTIMATE IS 345/11...SLIGHTLY TO THE RIGHT THAN BEFORE. THE TRACK FORECAST PHILOSOPHY IS UNCHANGED. ACCORDING TO THE TRACK MODEL GUIDANCE...JIMENA SHOULD CONTINUE MOVING NORTH- NORTHWESTWARD BETWEEN A MID- TO UPPER-LEVEL LOW WEST OF THE BAJA PENINSULA AND A MID-LEVEL RIDGE OVER NORTHERN MEXICO FOR AT LEAST FOR THE NEXT 24 TO 36 HOURS. INCREASINGLY DIVERGENT MODEL SOLUTIONS SUGGEST A FORECAST OF LOWER CONFIDENCE BEYOND 48 HOURS. A MINORITY OF GLOBAL MODELS TAKES JIMENA NORTHEASTWARD OR EASTWARD INTO NORTHWESTERN MEXICO...WITH ONLY ONE TAKING IT INTO THE SOUTHWESTERN UNITED STATES. A LARGER NUMBER OF MODEL RUNS EITHER STALL JIMENA OVER CENTRAL BAJA CALIFORNIA...LIKE THE GFDL...OR TURN THE CYCLONE NORTHWESTWARD OR EVEN WESTWARD INTO THE EAST PACIFIC IN RESPONSE MID-LEVEL RIDGING BUILDING TO ITS NORTH. THE NEW OFFICIAL FORECAST TRACK IS SIMILAR TO THE PREVIOUS ADVISORY BUT SHIFTED INITIALLY TO THE RIGHT DUE TO THE CURRENT MORE NORTHERLY MOTION. THE FORECAST IS SOMEWHAT SLOWER AND TO THE LEFT OF THE PREVIOUS TRACK BEYOND 72 HOURS AS A RESULT OF THE MODEL CONSENSUS WHICH HAS BEEN TRENDING MORE WESTWARD. THE WEAKENING CAUSED BY AN EARLIER EYEWALL REPLACEMENT CYCLE HAS CONTINUED...LIKELY AS A RESULT OF GRADUALLY COOLER SSTS AND INCREASING WESTERLY SHEAR. UW CIMSS ANALYSES SUGGESTS 10-15 KT OF WESTERLY SHEAR OVER JIMENA...WHICH SEEMS BELIEVABLE GIVEN THE MORE ASYMMETRIC ORGANIZATION OF THE CORE CONVECTION DURING THE LAST FEW HOURS. PRIOR TO LANDFALL IN 12 TO 24 HOURS...THE GUIDANCE AGREES WELL ON A CONTINUED...STEADY WEAKENING. THEREAFTER...STRONGER WESTERLY SHEAR AND THE CENTER TRACKING MOVING OVER LAND SHOULD LEAD TO A MORE RAPID WEAKENING... WITH THE OFFICIAL FORECAST NOW CALLING FOR JIMENA TO BECOME A REMNANT LOW BY 96 HR. THERE REMAINS A CHANCE THAT JIMENA COULD WEAKEN FASTER THAN FORECAST AFTER LANDFALL. INTERESTS IN THE HURRICANE WARNING AREA ARE ADVISED THAT STRONG WINDS WILL PRECEDE THE ARRIVAL OF THE CENTER BY SEVERAL HOURS...SO PREPARATIONS NEED TO BE COMPLETED VERY SOON. REMEMBER NOT TO FOCUS ON THE EXACT FORECAST TRACK SINCE DANGEROUS IMPACTS EXTEND SOME DISTANCE FROM THE CENTER. THE FORECAST TRACK OF JIMENA IS ALMOST PARALLEL TO THE COAST OF BAJA CALIFORNIA...AND SMALL DEVIATIONS LEFT OR RIGHT OF THE TRACK COULD RESULT IN LARGE ERRORS IN BOTH THE LOCATION AND TIMING OF LANDFALL. FORECAST POSITIONS AND MAX WINDS INITIAL 02/0300Z 23.2N 111.3W 100 KT 12HR VT 02/1200Z 24.6N 112.0W 90 KT 24HR VT 03/0000Z 26.2N 112.6W 75 KT 36HR VT 03/1200Z 27.3N 112.9W 60 KT...INLAND 48HR VT 04/0000Z 28.0N 113.2W 40 KT...INLAND 72HR VT 05/0000Z 28.5N 113.5W 30 KT...INLAND 96HR VT 06/0000Z 29.5N 114.0W 20 KT...REMNANT LOW 120HR VT 07/0000Z 30.0N 114.0W 20 KT...REMNANT LOW $$ FORECASTER KIMBERLAIN