ZCZC MIATCDEP1 ALL TTAA00 KNHC DDHHMM 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 NNNN
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Page last modified: Monday, 07-Feb-2005 16:50:01 UTC