[Tropical] Tropical Cyclone Discussion

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WTNT44 KNHC 070259
TCDAT4
HURRICANE DENNIS DISCUSSION NUMBER  10
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 PM EDT WED JUL 06 2005

DENNIS HAS FINALLY MIXED OUT THE DRY AIR THAT HAD WRAPPED INTO THE
CENTER DURING THE DAY. AIR FORCE RESERVE AND NOAA HURRICANE HUNTER
AIRCRAFT HAVE BEEN FLYING INTO DENNIS THIS AFTERNOON AND EVENING...
AND REPORTS INDICATE SURFACE WINDS HAVE LIKELY INCREASED TO AT LEAST
75 KT AND THE PRESSURE HAS DECREASED TO AT LEAST 980 MB...A
PRESSURE DROP OF 7 MB IN THE PAST 5 HOURS. A CDO FEATURE HAS ALSO
DEVELOPED OVER THE CENTER IN SATELLITE IMAGERY...AND A WARM
SPOT/PRE-EYE FEATURE HAS BEEN TRYING TO DEVELOP THE PAST COUPLE OF
HOURS. HOWEVER...AN EARLIER SSMI MICROWAVE OVERPASS INDICATED A
CLOSED EYE HAD ALREADY DEVELOPED IN THE MID-LEVELS.

THE INITIAL MOTION ESTIMATE IS 300/13.  THERE ARE NO CHANGES TO
PREVIOUS TRACK FORECAST OR REASONING. THE MODELS REMAIN IN STRONG
AGREEMENT THAT THE SUBTROPICAL RIDGE CURRENTLY EXTENDING EAST-WEST
ACROSS THE FLORIDA PENINSULA WILL REMAIN INTACT THROUGH 60-72
HOURS. THIS SHOULD KEEP DENNIS MOVING WEST-NORTHWESTWARD THROUGH 72
HOURS. AFTER THAT...HOWEVER... THE MODELS VARY SIGNIFICANTLY ON HOW
THE MID-LATITUDE FLOW PATTERN EVOLVES ACROSS THE CENTRAL AND
WESTERN U.S....WHICH ULTIMATELY HAS AN IMPACT ON THE STEERING FLOW
OVER THE GULF OF MEXICO. HALF OF THE MODELS BUILD A HIGH AMPLITUDE
RIDGE OVER THE GREAT LAKES AND SOUTHWESTWARD INTO THE SOUTHERN
PLAINS...WHILE THE OTHER MODELS LIKE THE NAM...CANADIAN...GFDL...
AND NOGAPS HAVE LESS RIDGING AND MORE TROUGHING OVER THE WESTERN
AND CENTRAL GULF. OVERALL...THE MODEL GUIDANCE HAS SHIFTED SLIGHTLY
TO THE RIGHT. GIVEN THIS UNCERTAINTY IN THE LONGER RANGE...THE
OFFICIAL FORECAST TRACK IS JUST AN EXTENSION OF THE PREVIOUS TRACK.

NOW THAT A CDO AND EYE HAVE DEVELOPED...THE ONLY INHIBITING FACTOR
WOULD BE INTERACTION WITH LAND. IN THE ABSENCE OF THAT...THE LOW
SHEAR AND 29C SSTS FAVOR SIGNIFICANT INTENSIFICATION FOR AT LEAST
THE NEXT 48 HOURS. THE LATEST GFDL MODEL RUN BRINGS DENNIS TO 127
KT IN 36 HOURS...WHILE THE SHIPS MODEL IS FAIRLY ROBUST IN TAKING
DENNIS UP TO 107 KT IN 60 HOURS. ALL OF THE MODELS AGREE THAT SOME
SOUTHWESTERLY SHEAR COULD AFFECT THE HURRICANE JUST PRIOR TO MAKING
LANDFALL...SO SLIGHT WEAKENING IS INDICATED AT 96 HOURS.

FORECASTER STEWART

FORECAST POSITIONS AND MAX WINDS

INITIAL      07/0300Z 16.5N  73.4W    75 KT
 12HR VT     07/1200Z 17.6N  75.4W    85 KT
 24HR VT     08/0000Z 19.2N  77.8W    95 KT
 36HR VT     08/1200Z 20.7N  80.1W   105 KT
 48HR VT     09/0000Z 22.2N  82.1W   105 KT
 72HR VT     10/0000Z 25.0N  85.0W   105 KT
 96HR VT     11/0000Z 28.5N  87.0W   100 KT
120HR VT     12/0000Z 32.0N  88.5W    80 KT...INLAND

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