[Tropical] Tropical Cyclone Discussion

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WTNT41 KNHC 270904
TCDAT1
TROPICAL STORM JEANNE DISCUSSION NUMBER  55
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 AM EDT MON SEP 27 2004

DOPPLER VELOCITY DATA ARE SHOWING SOME SPIN DOWN OF THE WIND FIELD
ALOFT...BUT SURFACE OBSERVATIONS SUGGEST THAT THERE MAY STILL BE A
FEW SPOTS OF 45 KT WINDS AROUND IN RAINBANDS OVER THE GULF OF
MEXICO AND OVER THE ATLANTIC.  THE OFFICIAL FORECAST CALLS FOR A
SLIGHTLY SLOWER DECAY OF THE WIND FIELD...WHICH SEEMS TO HAVE
EXPANDED SOMEWHAT OVER THE PAST SEVERAL HOURS.  THIS REQUIRES AN
EXTENSION OF THE TROPICAL STORM WARNING NORTHWARD.

THE INITIAL MOTION IS 335/10...A BIT TO THE LEFT OF THE PREVIOUS
TRACK.  MID-LEVEL HIGH PRESSURE TO THE NORTHEAST OF THE CYCLONE
WILL CONTINUE TO EDGE SOUTHEASTWARD AND ALLOW JEANNE TO RECURVE
AROUND ITS PERIPHERY FOR THE NEXT 36 HOURS OR SO.  AFTER THAT...A
SHORTWAVE TROUGH IN THE WESTERLIES WILL BEGIN TO ACCELERATE JEANNE
EASTWARD.  HOWEVER...THE GFS...NOGAPS...AND UKMET ARE ALL NOW
SUGGESTING A DECAPITATION SIMILAR TO WHAT OCCURRED WITH IVAN...IN
WHICH THE LOWER LEVEL CIRCULATION IS LEFT BEHIND WHILE THE UPPER
PORTION CONTINUES RAPIDLY EASTWARD.  THE DISPOSITION OF ANY
ABANDONED REMNANT MAY DEPEND ON WHERE LISA IS IN FOUR OR FIVE DAYS.
IN FACT...THE NOGAPS HAS THE SOUTHERN REMNANT OF JEANNE BECOMING
ABSORBED INTO LISA.  THE OFFICIAL FORECAST IS SIGNIFICANTLY SLOWER
THAN THE PREVIOUS ADVISORY AFTER 48 HOURS AND CALLS FOR A SLOW
MOTION AFTER 72 HOURS FOLLOWED BY DISSIPATION.  THIS FORECAST IS IN
BEST AGREEMENT WITH THE GFS SOLUTION.

AS JEANNE BEGINS TO INTERACT WITH THE MID-LATITUDE SHORT WAVE
TROUGH AFTER 48 HOURS...SOME BRIEF EXTRATROPICAL/FRONTAL
RESTRENGTHENING IS POSSIBLE.

FORECASTER FRANKLIN

FORECAST POSITIONS AND MAX WINDS

INITIAL      27/0900Z 30.5N  83.6W    45 KT
 12HR VT     27/1800Z 31.9N  83.8W    40 KT...INLAND
 24HR VT     28/0600Z 33.7N  82.9W    30 KT...INLAND
 36HR VT     28/1800Z 35.5N  80.0W    30 KT...INLAND
 48HR VT     29/0600Z 36.5N  76.0W    30 KT...INLAND
 72HR VT     30/0600Z 37.5N  68.0W    35 KT...EXTRATROPICAL
 96HR VT     01/0600Z 37.0N  64.0W    25 KT...EXTRATROPICAL
120HR VT     02/0600Z...DISSIPATED


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