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TROPICAL STORM KEITH DISCUSSION NUMBER   6
NATIONAL WEATHER SERVICE MIAMI FL
11 PM EDT FRI SEP 29 2000
 
KEITH CONTINUES TO BECOME BETTER ORGANIZED...WITH A STRONG
CONVECTIVE BAND WRAPPING ROUGHLY THREE-FOURTHS OF THE WAY AROUND THE
CENTER.  SATELLITE INTENSITY ESTIMATES ARE 45 KT...45 KT...AND 35 KT
FROM TAFB...SAB...AND AFWA.  THE MAXIMUM WINDS WILL REMAIN 45 KT FOR
THIS ADVISORY.  THE NEXT AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT
WILL ARRIVE AT KEITH BETWEEN 05Z-06Z.

THE BEST ESTIMATE OF THE INITIAL MOTION IS 320/4.  KEITH REMAINS CUT
OFF FROM STRONG STEERING INFLUENCES AT THE MOMENT.  A SURFACE RIDGE
IS OVER THE GULF OF MEXICO...WHILE PRESSURES ARE LOWER OVER THE
CENTRAL CARIBBEAN AND THE BAHAMAS.  WATER VAPOR IMAGERY INDICATES AN
UPPER LEVEL TROUGH DIGGING INTO THE NORTHEASTERN AND CENTRAL GULF OF
MEXICO...WITH AN ASSOCIATED NON-TROPICAL SURFACE LOW FORMING JUST
SOUTHEAST OF MIAMI.  MOST NHC TRACK GUIDANCE...INCLUDING THE
UKMET...RESPONDS TO THIS PATTERN BY CLUSTERING BY CONTINUING THE
CURRENT MOTION.  HOWEVER...THERE ARE SIGNIFICANT OUTLIERS.  THE
NOGAPS TAKES KEITH WESTWARD INTO THE BAY OF CAMPECHE...WHICH IS
POSSIBLE IF THE TROUGH TO THE NORTH BY-PASSES THE STORM.  THE GFDN
MEANDERS IT WESTWARD TOWARD BELIZE.  THE LBAR AND VICBAR TAKE KEITH
MORE QUICKLY TO THE NORTH AND NORTHEAST...WITH VICBAR SHOWING
LANDFALL NEAR TAMPA IN 72 HR.  THESE POSITIONS WOULD LIKELY BE WEST
OF THE UPPER LEVEL TROUGH...WHICH CASTS DOUBT ON IF THEY WOULD
VERIFY AND HOW MUCH OF KEITH WOULD REMAIN IF THEY DID.  THE GFDL IS
AN EXTREME OUTLIER...FORECASTING A LOOP AND THEN MOVING KEITH
NORTHWARD TOWARD SOUTH FLORIDA.  WHILE THIS COULD HAPPEN IF KEITH
AND THE TROUGH TO THE NORTH INTERACT...THE GFDL HAS LACKED
RUN-TO-RUN CONSISTENCY.  SINCE THERE ARE NO CURRENT SIGNS THAT THE
OUTLIERS ARE COMING TRUE...THE OFFICIAL FORECAST IS AN UPDATE OF THE
PREVIOUS PACKAGE...DOWN THE MIDDLE OF THE MAIN GUIDANCE CLUSTER AND
A LITTLE SLOWER.

KEITH SHOWS GOOD OUTFLOW...AND A SMALL UPPER LEVEL TROUGH BETWEEN IT
AND YUCATAN HAS PROBABLY HELPED IT MORE THAN HURT IT.  LARGE-SCALE
GUIDANCE SUGGESTS AN UPPER-LEVEL RIDGE OR ANTICYCLONE WILL REMAIN
OVER THE NORTHWEST CARIBBEAN THROUGH 72 HR...AND KEITH SHOULD
STRENGTHEN AS LONG AS IT REMAINS UNDER THAT FEATURE.  THE GFDU
BRINGS KEITH TO OVER 100 KT BY 72 HR AND SHIPS BRINGS IT TO 89 KT. 
THE INTENSITY FORECAST WILL BE SOMEWHAT MORE CONSERVATIVE IN CASE
KEITH MOVES OVER YUCATAN...OR MORE QUICKLY INTO A LESS FAVORABLE
ENVIRONMENT OVER THE GULF OF MEXICO.
 
THIS LARGE SYSTEM IS BRINGING MOIST LOW-LEVEL SOUTHWESTERLY FLOW
FROM THE EASTERN PACIFIC TO CENTRAL AMERICA.  NORMALLY...THIS
PATTERN IS RESPONSIBLE FOR TORRENTIAL RAINS OVER CENTRAL AMERICA AND
PREVENTIVE ACTIONS SHOULD BE TAKEN.
 
DUE TO THE SLOW MOTION AND UNCERTAINTIES IN THE FORECAST...ALL
INTERESTS IN THE NORTHWESTERN CARIBBEAN SHOULD MONITOR THE
PROGRESS OF KEITH.
 
FORECASTER BEVEN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     30/0300Z 17.9N  85.3W    45 KTS
12HR VT     30/1200Z 18.3N  85.4W    55 KTS
24HR VT     01/0000Z 18.9N  85.7W    65 KTS
36HR VT     01/1200Z 19.6N  86.1W    70 KTS
48HR VT     02/0000Z 20.5N  86.5W    75 KTS
72HR VT     03/0000Z 22.0N  87.0W    80 KTS
 
 
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