Hurricane PATRICIA

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HURRICANE PATRICIA DISCUSSION NUMBER   7
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
8 PM PDT TUE OCT 21 2003
 
DVORAK T-NUMBERS ARE UP TO 4.5 FROM TAFB...BUT REMAIN AT 4.0 FROM
SAB AND AFWA.  AS A COMPROMISE...INITIAL INTENSITY ESTIMATE IS SET
AT 70 KT.  THERE IS SOME RESTRICTION OF THE UPPER-LEVEL OUTFLOW
OVER THE SOUTHWEST QUADRANT AT THIS TIME.  I HAVE BACKED OFF A BIT
FROM THE PREVIOUS INTENSITY FORECAST BECAUSE OF THE LIKELIHOOD OF
INCREASING SHEAR.  HOWEVER IT SHOULD BE NOTED THAT THE GFDL
MODEL...WHICH HAS NOT BEEN KNOWN TO OVER-INTENSIFY TROPICAL
CYCLONES MUCH THIS SEASON...PREDICTS PATRICIA TO BECOME A VERY
STRONG HURRICANE OVER THE NEXT SEVERAL DAYS.

THE HURRICANE CONTINUES WNW...290/9.  THERE IS LESS AGREEMENT AMONG
THE DYNAMICAL TRACK GUIDANCE THAN I WOULD LIKE TO SEE.  ALTHOUGH
THE GFS AND NOGAPS PREDICTONS SHOW VERY LITTLE MID-TROPOSPHERIC
RIDGING TO THE NORTH OF PATRICIA...THEY TAKE THE TROPICAL CYCLONE
ON A MAINLY WEST-NORTHWESTWARD TRACK THROUGHOUT THE FORECAST
PERIOD.  THIS IS PRESUMABLY BECAUSE THESE MODELS WEAKEN PATRICIA TO
A SHALLOW SYSTEM THAT WILL BE STEERED BY THE LOW-LEVEL FLOW.  THE
GFDL TURNS PATRICIA NORTHWARD AND THEN NORTHEASTWARD LATE IN THE
PERIOD...AS IT DEPICTS A VERY DEEP HURRICANE THAT WOULD RESPOND TO
THE STEERING PROVIDED BY THE MID- TO UPPER-LEVEL LOW NEAR SOUTHERN
BAJA.  THE OFFICIAL FORECAST LIES BETWEEN THESE TWO SCENARIOS...AND
IS SIMILAR TO THE U.K. MET TRACK EXCEPT LATE IN THE PERIOD WHERE
THAT MODEL TURNS PATRICIA SHARPLY TO THE LEFT.  THE SLOW FORWARD
SPEED SHOWN IN THE OFFICIAL FORECAST TRACK AT DAYS 4 AND 5 IS AT
LEAST IN PART DUE TO SIGNIFICANT UNCERTAINTIES AT THESE TIME
RANGES.
 
FORECASTER PASCH
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      22/0300Z 12.0N 105.5W    70 KT
 12HR VT     22/1200Z 12.5N 106.6W    75 KT
 24HR VT     23/0000Z 13.3N 107.8W    80 KT
 36HR VT     23/1200Z 14.0N 109.0W    85 KT
 48HR VT     24/0000Z 15.0N 110.0W    90 KT
 72HR VT     25/0000Z 16.5N 111.0W    80 KT
 96HR VT     26/0000Z 18.0N 111.0W    70 KT
120HR VT     27/0000Z 19.5N 111.0W    60 KT
 
 
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