Tropical Storm PATRICIA

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TROPICAL STORM PATRICIA DISCUSSION NUMBER   7
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP192009
200 AM PDT TUE OCT 13 2009
 
SSMIS...TRMM...AND QUIKSCAT DATA THAT ARRIVED JUST AFTER THE
ISSUANCE OF THE PREVIOUS ADVISORY INDICATE THAT PATRICIA MOVED
UNEXPECTEDLY NORTH-NORTHEASTWARD EARLY THIS EVENING.  THE
SCATTEROMETER AND TRMM DATA AS WELL AS A RECENT SHIP OBSERVATION
SUGGEST THAT THE PREVAILING NORTHWESTERLY LOW-LEVEL FLOW ALONG THE
SOUTHERN BAJA PENINSULA HAS DISRUPTED THE NORTHERN PORTION OF THE
CIRCULATION...RESULTING IN A SOUTH-SOUTHEAST TO NORTH-NORTHWEST
ELONGATION OF THE SYSTEM.  PATRICIA CONTINUES TO LACK BANDING
FEATURES.  CLOUD TOPS ASSOCIATED WITH THE LARGE MASS OF DEEP
CONVECTION WARMED DURING THE PAST SEVERAL HOURS...BUT MORE RECENTLY
A NEW BURST OF CONVECTION HAS DEVELOPED NEAR THE ESTIMATED CENTER. 
THE QUIKSCAT DATA SHOWED SOME BELIEVABLE 45-50 KT WIND VECTORS AND
THIS IS THE BASIS FOR MAINTAINING AN INITIAL INTENSITY OF 50 KT.
 
A 12-HOUR MOTION ESTIMATE YIELDS AN INITIAL HEADING OF 360/5. 
PATRICIA HAS BEEN MOVING AROUND THE WESTERN PERIPHERY OF A
MID-LEVEL RIDGE TO ITS EAST.  THIS RIDGE IS FORECAST TO BUILD
WESTWARD AS A MID-LEVEL TROUGH CURRENTLY TO THE NORTHWEST OF THE
CYCLONE LIFTS OUT TODAY.  THIS SHOULD RESULT IN THE CYCLONE TURNING
NORTHWESTWARD...THEN WESTWARD TO THE SOUTH OF THE BUILDING RIDGE. 
THE TRACK GUIDANCE GENERALLY AGREES WITH THIS SCENARIO...HOWEVER
THERE ARE LARGE DIFFERENCES IN THE GUIDANCE AS TO HOW SOON THE
RIDGE BUILDS...AND WHEN PATRICIA TURNS WESTWARD.  THE ECMWF AND GFS
MODELS ARE ON THE NORTHERN EDGE OF THE MODEL ENVELOPE AND TAKE
PATRICIA OVER OR VERY CLOSE TO THE COAST OF THE SOUTHERN BAJA
PENINSULA IN ABOUT 24 HOURS.  THE UKMET AND NOGAPS ARE ON THE
SOUTHERN EDGE AND PREDICT AN ALMOST IMMEDIATE WESTWARD TURN.  THE
OFFICIAL TRACK FORECAST HAS BEEN ADJUSTED A LITTLE NORTH OF THE
PREVIOUS TRACK...DUE TO THE RECENT MOTION AND MORE EASTWARD INITIAL
POSITION.  THIS TRACK IS BETWEEN THE MODEL CONSENSUS AND THE ECMWF
AND GFS SOLUTIONS.

PATRICIA IS FORECAST TO REMAIN OVER WARM WATERS AND IN A LOW SHEAR
ENVIRONMENT DURING THE NEXT DAY OR TWO.  WHILE THESE FACTORS FAVOR
STRENGTHENING...DRY AND STABLE AIR TO THE WEST OF THE CYCLONE WILL
LIKELY INHIBIT SIGNIFICANT STRENGTHENING.  THE OFFICIAL FORECAST
SHOWS SLIGHT INTENSIFICATION TODAY...BUT IS LOWER THAN THE PREVIOUS
FORECAST.  THE NEW FORECAST IS IN GOOD AGREEMENT WITH A BLEND OF
THE SHIPS...LGEM...AND GFDL MODELS.  THE HWRF IS CONSIDERABLY
STRONGER AND IS CONSIDERED AN OUTLIER AT THIS TIME.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      13/0900Z 20.7N 109.3W    50 KT
 12HR VT     13/1800Z 21.5N 109.5W    55 KT
 24HR VT     14/0600Z 22.1N 110.1W    55 KT
 36HR VT     14/1800Z 22.4N 111.1W    50 KT
 48HR VT     15/0600Z 22.5N 112.5W    45 KT
 72HR VT     16/0600Z 22.5N 115.5W    35 KT
 96HR VT     17/0600Z 22.5N 118.5W    25 KT...REMNANT LOW
120HR VT     18/0600Z...DISSIPATED
 
$$
FORECASTER BROWN/ROBERTS
 
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