Tropical Storm PATRICIA

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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
 
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