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Hurricane PAUL


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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
 
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