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