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Tropical Storm PATRICIA


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TROPICAL STORM PATRICIA DISCUSSION NUMBER   9
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP192009
200 PM PDT TUE OCT 13 2009

QUIKSCAT DATA NEAR 13Z SHOWED A 45-50 KT WIND VECTOR ABOUT 45 N MI
SOUTH OF THE CENTER OF PATRICIA.  SINCE THAT TIME...THE ASSOCIATED
CONVECTION HAS DISSIPATED...LEAVING A SWIRL OF LOW CLOUDS PARTLY
OBSCURED BY CIRRUS DEBRIS.  THE INITIAL INTENSITY IS REDUCED TO
45 KT BASED ON A SLOW DECAY FROM THE TIME OF THE QUIKSCAT DATA...AND
THIS INTENSITY COULD BE GENEROUS.  WHY THE CONVECTION HAS DECREASED
IS NOT CLEAR...BUT UPPER-LEVEL CONFLUENCE AND ENTRAINMENT OF DRY
AND STABLE AIR INTO THE CYCLONE FROM THE WEST COULD BE REASONS.
 
THE INITIAL MOTION REMAINS JUST EAST OF NORTH AT 010/6.  ALL OF THE
DYNAMICAL MODELS NOW FORECAST ENOUGH MID-LEVEL RIDGING DEVELOPING
NORTH OF PATRICIA TO TURN THE CYCLONE WESTWARD IN THE NEXT 12-24
HRS...AND THERE IS SOME INDICATION OF THE RIDGE BUILDING IN WATER
VAPOR IMAGERY.  THE CANADIAN AND ECMWF MODELS BRING THE CENTER OVER
THE SOUTHERN END OF BAJA CALIFORNIA BEFORE THE TURN OCCURS...AND
WITH THE CURRENT MOTION THIS CANNOT BE RULED OUT.  THE NEW FORECAST
TRACK IS NUDGED A LITTLE TO THE NORTH OF THE PREVIOUS TRACK BASED
ON THE CURRENT POSITION AND MOTION...CALLING FOR THE CENTER TO TURN
NORTHWESTWARD AND PASS JUST SOUTH OF THE CABO SAN LUCAS AREA IN
ABOUT 12 HRS.  AFTER THAT...THE SYSTEM SHOULD MOVE GENERALLY
WESTWARD UNTIL IT DISSIPATES.  THE NEW TRACK IS JUST NORTH OF THE
CENTER OF THE GUIDANCE ENVELOPE.
 
PATRICIA REMAINS IN A LIGHT VERTICAL WIND SHEAR ENVIRONMENT OVER
WARM WATER.  THUS...THERE IS STILL THE POSSIBILITY OF A CONVECTIVE
FLARE-UP LATER TONIGHT THAT COULD MAINTAIN THE INTENSITY OF THE
STORM.  AFTER 12-24 HRS...THE SYSTEM WILL BE MOVING OVER COOLER SEA
SURFACE TEMPERATURES AND INTO THE DRY AIR MASS WEST OF BAJA
CALIFORNIA.  THIS COMBINATION SHOULD CAUSE PATRICIA TO WEAKEN.  
THE NEW INTENSITY FORECAST IS A SIGNIFICANT CHANGE FROM THE
PREVIOUS FORECAST BASED ON CURRENT TRENDS AND THE STATISTICAL
GUIDANCE...CALLING FOR PATRICIA TO SLOWLY WEAKEN THROUGH THE
FORECAST PERIOD.  THE GLOBAL MODELS ALL SHOW PATRICIA DISSIPATING
IN 60 HRS OR LESS...SO IF THE CONVECTION DOES NOT COME BACK THE
CYCLONE COULD DISSIPATE EARLIER THAN CURRENTLY FORECAST.

THE WIND RADII HAVE BEEN REVISED BASED ON THE QUIKSCAT DATA.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      13/2100Z 22.1N 108.9W    45 KT
 12HR VT     14/0600Z 22.7N 109.4W    40 KT
 24HR VT     14/1800Z 22.7N 110.6W    35 KT
 36HR VT     15/0600Z 22.8N 112.2W    30 KT
 48HR VT     15/1800Z 22.9N 114.0W    30 KT
 72HR VT     16/1800Z 23.0N 117.5W    25 KT...REMNANT LOW
 96HR VT     17/1800Z 23.0N 121.0W    20 KT...REMNANT LOW
120HR VT     18/1800Z...DISSIPATED
 
$$
FORECASTER BEVEN
 
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