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TROPICAL STORM DEBBY DISCUSSION NUMBER 7
NATIONAL WEATHER SERVICE MIAMI FL
5 AM EDT MON AUG 21 2000
THE CENTER OF DEBBY IS STILL HARD TO LOCATE. RECENT SATELLITE FIXES
NUDGE THE SYSTEM A LITTLE FURTHER WEST THAN THE PREVIOUS PACKAGE...
AND NIGHTTIME MULTISPECTRAL IMAGERY HINTS THAT IT MIGHT EVEN BE
SOUTH OF 15N. IN VIEW OF THIS UNCERTAINTY...THIS PACKAGE CONTAINS A
LOT OF CONTINUITY AND EXTRAPOLATION. SOME RE-LOCATION MAY BE
NECESSARY IN THE NEXT PACKAGE.
THE INITIAL MOTION IS ESTIMATED TO BE 285/16. A STRONG LOW/MID
LEVEL RIDGE NORTH OF DEBBY SHOULD KEEP IT ON A GENERAL WEST-
NORTHWEST TRACK THROUGH THE FORECAST PERIOD. BY 72 HR...THE RIDGE
MAY WEAKEN AS THE PERSISTENT DEEP LAYER TROUGH OVER THE EASTERN U.S.
RE-INTENSIFIES. HOWEVER...ANY MAJOR CHANGE THIS MIGHT CAUSE IN THE
TRACK OF DEBBY WILL LIKELY OCCUR AFTER THIS FORECAST PERIOD. NHC
TRACK GUIDANCE AGREES ON THE WEST-NORTHWEST TRACK...AND THE ONLY
CHANGE IN THE OFFICIAL FORECAST IS A SLIGHT SOUTHWARD NUDGING.
WHILE SATELLITE INTENSITY ESTIMATES ARE 55 KT...55 KT...AND 45 KT
FROM TAFB...SAB...AND AFWA...THE INITIAL INTENSITY REMAINS AT 45 KT
DUE TO THE UNCERTAINTY IN WHERE THE CENTER IS. DEBBY HAS THE
SATELLITE SIGNATURE OF A SHEARED SYSTEM...AND THE SATELLITE WIND
SHEAR PRODUCT FROM CIMSS AT THE UNIVERSITY OF WISCONSIN INDICATES
ABOUT 10 KT SOUTHWESTERLY SHEAR OVER THE SYSTEM. THE SHIPS MODEL
AND SOME LARGE-SCALE GUIDANCE SUGGEST THAT SOME AMOUNT OF SHEAR
COULD CONTINUE...WHICH WOULD KEEP THE RATE OF INTENSIFICATION DOWN.
THE INTENSITY FORECAST FOLLOWS THE PREVIOUS PACKAGE. NOTE THAT SOME
ADJUSTMENT OF THE INITIAL INTENSITY IS POSSIBLE AFTER AN AIR FORCE
RESERVE HURRICANE HUNTER ARRIVES AT 12Z.
FORECASTER BEVEN
FORECAST POSITIONS AND MAX WINDS
INITIAL 21/0900Z 15.6N 54.7W 45 KTS
12HR VT 21/1800Z 16.1N 57.1W 50 KTS
24HR VT 22/0600Z 16.9N 60.4W 60 KTS
36HR VT 22/1800Z 17.7N 63.6W 65 KTS
48HR VT 23/0600Z 18.5N 66.5W 70 KTS
72HR VT 24/0600Z 20.5N 72.0W 80 KTS
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