000 WTPZ44 KNHC 121456 TCDEP4 TROPICAL STORM PATRICIA DISCUSSION NUMBER 4 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP192009 800 AM PDT MON OCT 12 2009 INFRARED SATELLITE PICTURES INDICATE A LARGE AND EXPANDING MASS OF COLD-TOPPED CONVECTION ASSOCIATED WITH PATRICIA DURING THE PAST FEW HOURS. HOWEVER...THE CENTER OF THE CYCLONE...WHICH HAS BEEN DIFFICULT TO LOCATE...APPEARS SLOPPY AND NOT PARTICULARLY WELL DEFINED IN A RECENT AMSR-E PASS. DVORAK T-NUMBERS HAVE INCREASED TO 3.0 AND 3.5 FROM SAB AND TAFB...RESPECTIVELY. IN SPITE OF THE SATELLITE APPEARANCE OF PATRICIA...THE INTENSITY IS BEING HELD AT 40 KT BASED ON THE LACK OF INCREASED ORGANIZATION IN MICROWAVE SATELLITE IMAGERY...AND AN ASCAT PASS AT 04Z. A QUIKSCAT PASS IS EXPECTED MOMENTARILY THAT SHOULD HELP DETERMINE THE LOCATION AND STRENGTH OF PATRICIA. RECENT CONVENTIONAL AND MICROWAVE FIXES YIELD A SOMEWHAT UNCERTAIN LONGER-TERM MOTION OF 325/07. EMBEDDED IN A DEEP SOUTHERLY FLOW... PATRICIA HAS BEEN MOVING NORTHWESTWARD TO NORTH-NORTHWESTWARD ON THE WESTERN PERIPHERY OF A DEEP-LAYER ANTICYCLONE EXTENDING WEST-SOUTHWESTWARD FROM THE GULF OF MEXICO. GLOBAL MODELS AGREE THAT THIS MOTION SHOULD CONTINUE DURING THE NEXT 24-48 HOURS... FOLLOWED BY A SHARP TURN TOWARD THE WEST AS THE RIDGE FROM THE GULF OF MEXICO REBUILDS NORTH OF THE CYCLONE. THE ECMWF SUGGESTS THAT THE RIDGE COULD BUILD IN SOONER AND STRONGER...RESULTING IN A TURN FARTHER SOUTH. ON THE OTHER HAND...THE GFS SPEEDS THE STORM NORTHWARD BEFORE RIDGING CAN BUILD IN AND ALLOWS PATRICIA TO BE PICKED UP BY WESTERLY FLOW TO THE NORTH. ULTIMATELY...HOW CLOSE PATRICIA TRACKS TO THE BAJA PENINSULA DEPENDS VERY MUCH ON HOW MUCH NORTHWARD PROGRESS IT MAKES DURING THE NEXT 24-36 HOURS...JUST PRIOR TO THE INFLUENCE OF RIDGING TO THE NORTH. THE OFFICIAL TRACK FORECAST IS ADJUSTED SLIGHTLY TO THE LEFT OF THE PREVIOUS FORECAST BUT NOT AS FAR SOUTH AS THE LATEST MODEL CONSENSUS...GIVEN THE CURRENT UNCERTAINTY REGARDING THE INITIAL POSITION AND MOTION OF THE CYCLONE. PATRICIA REMAINS IN A LIGHT SHEAR ENVIRONMENT OVER WARM SSTS. THESE TWO FACTORS ALONE SUGGEST THAT STRENGTHENING SHOULD OCCUR. HOWEVER...SHIPS MODEL OUTPUT CONTINUES TO INDICATE THAT A RELATIVELY DRY AND STABLE AIR MASS IN THE NEAR-STORM ENVIRONMENT SHOULD LIMIT INTENSIFICATION. IN FACT...SATELLITE IMAGERY SUGGESTS THAT THIS MAY ALREADY BE OCCURRING...AS PATRICIA INGESTS A STRATOCUMULUS DECK OF CLOUDS TO THE WEST. THE OFFICIAL INTENSITY FORECAST IS IN LINE WITH THE MODEL INTENSITY CONSENSUS...CALLING FOR MODEST INTENSIFICATION THROUGH 48 HOURS. THEREAFTER...SHARPLY COOLER SSTS ALONG THE FORECAST TRACK SHOULD INDUCE WEAKENING...AND PATRICIA IS FORECAST TO BECOME A REMNANT LOW BY THE END OF THE FORECAST PERIOD. FORECAST POSITIONS AND MAX WINDS INITIAL 12/1500Z 19.1N 109.6W 40 KT 12HR VT 13/0000Z 20.3N 109.7W 45 KT 24HR VT 13/1200Z 21.6N 109.8W 50 KT 36HR VT 14/0000Z 22.4N 110.0W 55 KT 48HR VT 14/1200Z 22.9N 110.3W 55 KT 72HR VT 15/1200Z 23.0N 112.5W 50 KT 96HR VT 16/1200Z 23.0N 115.5W 35 KT 120HR VT 17/1200Z 23.0N 118.5W 25 KT...REMNANT LOW $$ FORECASTER KIMBERLAIN