Hurricane FRANCES

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HURRICANE FRANCES DISCUSSION NUMBER  26
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 AM EDT TUE AUG 31 2004
 
SATELLITE AND AIRCRAFT DATA INDICATE THAT FRANCES IS COMPLETING A
CONCENTRIC EYEWALL CYCLE.  THE AIR FORCE RESERVE HURRICANE HUNTER
REPORTS A 30-40 NM DIAMETER OUTER EYEWALL WITH MAXIMUM FLIGHT-LEVEL
WINDS OF 121 KT AT 700 MB...ALONG WITH A CENTRAL PRESSURE OF 949
MB.  SATELLITE IMAGERY SHOWS THE REMAINS OF THE EARLIER INNER
EYEWALL ARE STILL PRESENT.  BASED ON THE AIRCRAFT DATA...THE
MAXIMUM INTENSITY REMAINS 110 KT.  THE AIRCRAFT ALSO SHOWS A WIND
MAXIMA OUTSIDE OF THE OUTER EYEWALL.

THE INITIAL MOTION IS NOW 280/13.  FRANCES REMAINS ON THE SOUTH SIDE
OF A STRONG RIDGE OVER THE WESTERN ATLANTIC.  LARGE-SCALE MODELS
ALL FORECAST THE RIDGE TO WEAKEN DURING THE FORECAST PERIOD...BUT
THERE ARE SIGNIFICANT DIFFERENCES IN THE DETAILS WHICH HAVE MAJOR
IMPLICATIONS FOR WHERE FRANCES WILL END UP.  DATA FROM THE RECENT
SYNOPTIC SURVEILLANCE MISSION HAD SOME INTERESTING EFFECTS ON THE
DYNAMICAL MODELS.  THE GFS...WHICH HAS BEEN A LEFT OUTLIER MOST OF
THE TIME...HAS SHIFTED WELL TO THE RIGHT AND IS NOW A RIGHT
OUTLIER...MOVING FRANCES NORTHWARD ALONG 77-78W AFTER 72 HR.  THE
NOGAPS...WHICH HAS BEEN A RIGHT OUTLIER...IS NOW A LEFT OUTLIER
CALLING FOR LANDFALL IN SOUTHEASTERN FLORIDA.  THE GFDL AND UKMET
HAVE BOTH SHIFTED THEIR TRACKS TO THE RIGHT AFTER 72 HR.  GIVEN THE
LARGE CHANGES IN JUST ONE CYCLE...THE OFFICIAL FORECAST WILL NOT
CHANGE MUCH AT ALL...BASICALLY BEING AN UPDATE OF THE PREVIOUS
PACKAGE.  IT IS DOWN THE CENTER OF THE MODEL GUIDANCE UP TO 72 HR
AND ALONG THE LEFT SIDE THEREAFTER.
 
WHEN THE CONCENTRIC EYEWALL CYCLE IS FINALLY DONE...FRANCES SHOULD
STRENGTHEN AS INDICATED BY THE SHIPS AND GFDL MODELS.  IT WOULD NOT
BE A SURPRISE TO SEE MORE STRENGTHENING THAN CURRENTLY FORECAST. 
ALTHOUGH NOT CURRENTLY REFLECTED IN THE INTENSITY FORECAST DUE TO
THE UNCERTAINTY IN THE UPPER-LEVEL WIND PATTERNS...THE SHIPS...
GFDL...AND GFS MODELS SUGGEST CONDITIONS MAY BECOME LESS FAVORABLE
AFTER ABOUT 48 HR.  ALSO...THERE REMAINS THE POSSIBILITY OF OTHER
CONCENTRIC EYEWALL CYCLES THAT CANNOT CURRENTLY BE FORECAST.
 
FORECASTER BEVEN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      31/0900Z 19.9N  62.8W   110 KT
 12HR VT     31/1800Z 20.4N  65.0W   115 KT
 24HR VT     01/0600Z 21.3N  67.7W   120 KT
 36HR VT     01/1800Z 22.2N  70.2W   120 KT
 48HR VT     02/0600Z 23.2N  72.3W   120 KT
 72HR VT     03/0600Z 25.0N  75.5W   120 KT
 96HR VT     04/0600Z 26.5N  78.5W   120 KT
120HR VT     05/0600Z 28.5N  81.5W    85 KT...INLAND
 
 
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