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Tropical Storm PATRICIA


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TROPICAL STORM PATRICIA DISCUSSION NUMBER   6
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP192009
800 PM PDT MON OCT 12 2009
 
THE CLOUD PATTERN OF THE TROPICAL CYCLONE CONTINUES TO LACK BANDING
FEATURES AND IS CHARACTERIZED PRIMARILY BY A CENTRAL DENSE OVERCAST
WITH VERY COLD-TOPPED CONVECTION.  DVORAK CURRENT INTENSITY
ESTIMATES HAVE NOT CHANGED SINCE EARLIER TODAY SO THE INITIAL WIND
SPEED IS KEPT AT 50 KT FOR THIS ADVISORY.  PATRICIA IS EXHIBITING
WELL-DEFINED UPPER-LEVEL OUTFLOW AND SHOULD REMAIN OVER WARM WATERS
FOR THE NEXT COUPLE OF DAYS.  THE SHIPS MODEL SHOWS WEAK SHEAR OVER
THE SYSTEM FOR THE NEXT 36 HOURS...BUT ALSO INDICATES THAT STABLE
AND RELATIVE DRY AIR AT MID-TROPOSPHERIC LEVELS WILL BE INHIBITING
FACTORS FOR STRENGTHENING.  THE OFFICIAL INTENSITY FORECAST...LIKE
THE PREVIOUS ONE...SHOWS ONLY A MODEST INCREASE IN STRENGTH AND IS
CLOSE TO THE STATISTICAL-DYNAMICAL LGEM GUIDANCE.  GIVEN THE
LIMITATIONS IN FORECASTING INTENSITY CHANGE...IT IS CERTAINLY
POSSIBLE FOR PATRICIA TO BECOME STRONGER THAN INDICATED HERE.  IN
FACT...BASED ON HISTORICAL NHC INTENSITY FORECAST ERRORS...THERE IS
ABOUT A 20 PERCENT CHANCE OF PATRICIA BECOMING A HURRICANE IN THE
NEXT 24 HOURS OR SO.

THE CENTER REMAINS HARD TO PINPOINT BUT BASED ON RECENT
GEOSTATIONARY SATELLITE FIXES THE TRACK HAS BEEN SHIFTED SLIGHTLY
EASTWARD.  THE BEST ESTIMATE OF INITIAL MOTION IS SLOWLY NORTHWARD
OR 350/5.  PATRICIA HAS BEEN MOVING ON THE SOUTHWEST PERIPHERY OF A
MID-LEVEL ANTICYCLONE CENTERED OVER THE GULF OF MEXICO.  GLOBAL
MODEL GUIDANCE SHOWS THE ASSOCIATED RIDGE BUILDING WESTWARD...AND
TO THE NORTH OF THE TROPICAL CYCLONE...OVER THE NEXT DAY OR SO. 
THIS EVOLUTION SHOULD CAUSE THE MOTION TO BEND TOWARD THE NORTHWEST
WITHIN 36 HOURS OR SO.  A LITTLE LATER IN THE FORECAST PERIOD...THE
MODELS SHOW THE ANTICYCLONE SHIFTING WESTWARD WHICH WOULD LIKELY
RESULT IN PATRICIA TURNING TOWARD THE WEST.  THE MAIN CONCERN IS
HOW FAR NORTH THE TROPICAL CYCLONE WILL MOVE DURING THE NEXT 24
HOURS...AS THIS WILL LARGELY DETERMINE HOW MUCH IMPACT PATRICIA
WILL HAVE ON SOUTHERN BAJA CALIFORNIA.  EVEN THOUGH THE OFFICIAL
FORECAST DOES NOT BRING THE TROPICAL CYCLONE ANY CLOSER TO THE BAJA
PENINSULA THAN THE PREVIOUS ONE...IT IS IMPORTANT NOT TO FOCUS ON
THE EXACT PREDICTED TRACK DUE TO UNCERTAINTIES.  AT THIS TIME...NO
CHANGES TO THE TROPICAL STORM WATCH ARE NECESSARY. 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      13/0300Z 20.0N 109.9W    50 KT
 12HR VT     13/1200Z 20.7N 110.0W    55 KT
 24HR VT     14/0000Z 21.6N 110.4W    60 KT
 36HR VT     14/1200Z 22.1N 111.2W    60 KT
 48HR VT     15/0000Z 22.3N 112.3W    60 KT
 72HR VT     16/0000Z 22.5N 115.0W    50 KT
 96HR VT     17/0000Z 22.5N 118.0W    35 KT
120HR VT     18/0000Z 22.5N 121.0W    25 KT...REMNANT LOW
 
$$
FORECASTER PASCH/LANDSEA
 
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