Tropical Storm BONNIE

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TROPICAL STORM BONNIE DISCUSSION NUMBER  16
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 PM EDT WED AUG 11 2004
 
BONNIE HAS UNDERGONE SIGNIFICANT STRUCTURAL CHANGES DURING THE PAST
6-9 HR.  THE TIGHT INNER CORE THAT HAD BEEN PRESENT FOR THE LAST
THREE DAYS COLLAPSED DURING THE AFTERNOON...LEAVING THE MAXIMUM
WINDS IN A BAND OF CONVECTION AWAY FROM THE CENTER.  SO FAR...THE
EVENING RECONNAISSANCE FLIGHT HAS REPORTED A CENTRAL PRESSURE OF
1007-1008 MB AND MAXIMUM 850 MB FLIGHT LEVEL WINDS OF 39 KT.  ON
THE OTHER HAND...SATELLITE INTENSITY ESTIMATES ARE 55 KT FROM TAFB
AND 45 KT FROM SAB AND AFWA...SUGGESTING THE AIRCRAFT MIGHT NOT
HAVE SAMPLED THE STRONGEST WINDS.  THE INITIAL INTENSITY IS
DECREASED TO 50 KT...AND THIS MAY BE GENEROUS.

THE INITIAL MOTION IS 045/10.  THE TRACK FORECAST IS VERY STRAIGHT
FORWARD.  BONNIE IS BECOMING EMBEDDED IN SOUTHWESTELY FLOW
ASSOCIATED WITH AN UNSEASONABLY STRONG DEEP LAYER TROUGH OVER THE
CENTRAL UNITED STATES.  THE CYCLONE SHOULD ACCELERATE NORTHEASTWARD
ON THE EAST SIDE OF THE TROUGH...MAKING LANDFALL OVER THE FLORIDA
PANHANDLE THURSDAY MORNING AND THEN MOVING THROUGH THE EASTERN
UNITED STATES.  ALL TRACK GUIDANCE AGREES WITH THIS SCENARIO...AND
THE TRACK FORECAST IS AN UPDATE OF THE PREVIOUS PACKAGE.
 
THE COLLAPSE OF THE CENTRAL CORE AND STEADILY INCREASING VERTICAL
SHEAR SUGGESTS THAT THE WINDOW OF OPPORTUNITY FOR STRENGTHENING IS
CLOSING.  HOWEVER...THE CYCLONE HAS JUST GENERATED A BURST OF
CONVECTION NORTHEAST OF THE CENTER...AND A REPEAT OF LAST NIGHTS
FLARE-UP COULD REGENERATE A TIGHT CENTER AND BRING BONNIE TO
HURRICANE STRENGTH.  ON THE OTHER HAND...IT MIGHT NOT STRENGTHEN AT
ALL BEFORE LANDFALL.  THE INTENSITY FORECAST WILL COMPROMISE
BETWEEN THESE EXTREMES AND CALL FOR GRADUAL STRENGTHENING PRIOR TO
LANDFALL.  AFTER LANDFALL... BONNIE SHOULD WEAKEN AND BECOME
EXTRATROPICAL.  ONE CHANGE TO THE PREVIOUS FORECAST IS TO KEEP THE
WINDS AT 35 KT DURING THE EXTRATROPICAL STAGE DUE TO THE NEAR 35 KT
MOTION.
 
SINCE BONNIE COULD STILL REACH HURRICANE STRENGTH DURING THE DIURNAL
CONVECTIVE MAXIMUM...THE HURRICANE WARNING WILL REMAIN IN EFFECT. 
THIS WARNING COULD BE DISCONTINUED IF LATER DATA SHOWS THAT BONNIE
IS NOT RE-INTENSIFYING.
 
FORECASTER BEVEN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      12/0300Z 27.4N  88.4W    50 KT
 12HR VT     12/1200Z 28.9N  86.8W    60 KT
 24HR VT     13/0000Z 31.9N  83.6W    45 KT...INLAND
 36HR VT     13/1200Z 36.5N  78.5W    35 KT...INLAND EXTRATROPICAL
 48HR VT     14/0000Z 42.0N  73.5W    35 KT...INLAND EXTRATROPICAL
 72HR VT     15/0000Z 53.5N  62.0W    35 KT...INLAND EXTRATROPICAL
 96HR VT     16/0000Z...ABSORBED BY FRONTAL ZONE
 
 
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