ZCZC MIATCDEP2 ALL TTAA00 KNHC DDHHMM HURRICANE PAUL DISCUSSION NUMBER 9 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP172006 200 AM PDT MON OCT 23 2006 OBJECTIVE AND SUBJECTIVE DVORAK NUMBERS ARE RUNNING BETWEEN T4.5 AND T5.0...AND THE INTENSITY ESTIMATE IS INCREASED TO 85 KT. THE EYE HAS BEEN FAIRLY WELL DEFINED IN INFRARED IMAGERY AND IS SURROUNDED BY A NARROW RING OF -70C OR COLDER CLOUD TOPS. OUTFLOW IS STRONG TO THE NORTH AND SOUTH...BUT LIMITED ZONALLY. THE TRACK AND INTENSITY FORECASTS ARE UNUSUALLY PROBLEMATIC. PAUL WILL VERY SOON BEGIN TO INTERACT WITH A LARGE MID- TO UPPER-LEVEL LOW SOUTHWEST OF SOUTHERN CALIFORNIA...AND INDEED THE INITIAL MOTION IS NOW WEST-NORTHWESTWARD...285/4. WATER VAPOR IMAGERY SHOWS VERY STRONG UPPER-LEVEL WESTERLIES TO THE SOUTH OF THIS LOW HEADED FOR PAUL...AND THESE COULD REACH THE TROPICAL CYCLONE IN ANOTHER 24 HOURS OR SO. AS PAUL BEGINS TO RECURVE IN THE SOUTHWESTERLY FLOW AHEAD OF THE UPPER LOW...GLOBAL MODEL GUIDANCE SUGGESTS THAT THE CYCLONE WILL BE RIDING ALONG A VERY SHARP GRADIENT OF VERTICAL SHEAR...AND IT IS ENTIRELY UNCLEAR HOW MUCH EFFECT THIS SHEAR WILL HAVE ON THE STRUCTURE AND HENCE THE TRACK OF PAUL. EVERY GLOBAL MODEL...THE GFS...UKMET...NOGAPS...ECMWF...AND CANADIAN...SHEARS OFF THE TOP OF PAUL AND LEAVES A WEAK LOW-LEVEL REMNANT TO LINGER BEHIND. AND I CAN'T BLAME THIS ON THE INITIALIZATION...BECAUSE THE UKMET AND NOGAPS EACH HAVE A VERY WELL-DEFINED INITIAL VORTEX. ON THE OTHER HAND WE HAVE THE GFDL...WHICH KEEPS PAUL AS A STRONG AND DEEP HURRICANE AND RACES IT OFF TO THE NORTHEAST. AT THE MOMENT...THE COURSE OF LEAST REGRET IS TO FAVOR THE GFDL SOLUTION. INTERESTINGLY...THE FSU SUPERENSEMBLE...WHICH IS DESIGNED TO SORT OUT MODEL BIASES...ALSO FAVORS THE GFDL SCENARIO. THE OFFICIAL FORECAST IS CLOSE TO THE SUPERENSEMBLE FORECAST...WHICH IS CONSIDERABLY FASTER THAN THE TRADITIONAL MODEL CONSENSUS. THE SHEAR WILL BE LIGHT FOR THE NEXT 12 TO 24 HOURS...AND SO SOME ADDITIONAL STRENGTHENING IS LIKELY. AFTER THAT...SOME WEAKENING IS EXPECTED AS SOUTHWESTERLY SHEAR OVERTAKES THE CYCLONE. THE GFDL STILL WANTS TO MAKE PAUL A MAJOR HURRICANE AT LANDFALL BUT IF THE GLOBAL MODELS HAVE THE SHEAR RIGHT THIS SEEMS OVERDONE. THE OFFICIAL FORECAST IS CLOSER TO THE SHIPS GUIDANCE. BECAUSE OF THE SHARP SHEAR GRADIENT...A TRACK TO THE RIGHT OF THE OFFICIAL FORECAST WOULD KEEP PAUL IN A LIGHTER SHEAR ENVIRONMENT WHERE IT COULD MAINTAIN ITS STRENGTH LONGER. A 72 HOUR POINT IS BEING GIVEN ONLY SO AS NOT TO SHOW THE TRACK ENDING ABRUPTLY OFFSHORE. I DON'T REALLY EXPECT THE CIRCULATION TO SURVIVE A PASSAGE OVER THE MOUNTAINS OF SOUTHWESTERN MEXICO. FORECAST POSITIONS AND MAX WINDS INITIAL 23/0900Z 16.2N 111.5W 85 KT 12HR VT 23/1800Z 17.2N 111.9W 90 KT 24HR VT 24/0600Z 19.1N 111.3W 95 KT 36HR VT 24/1800Z 21.4N 110.3W 85 KT 48HR VT 25/0600Z 23.6N 108.2W 65 KT 72HR VT 26/0600Z 27.0N 104.5W 20 KT...DISSIPATING INLAND 96HR VT 27/0600Z...DISSIPATED $$ FORECASTER FRANKLIN NNNN
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Page last modified: Monday, 23-Oct-2006 08:55:04 UTC