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HURRICANE HUMBERTO DISCUSSION NUMBER 10
NATIONAL WEATHER SERVICE MIAMI FL
5 PM EDT SUN SEP 23 2001
AN AIR FORCE RECON RECENTLY FOUND A 984 MB CENTRAL PRESSURE AND 86
KT AT 700 MB TO THE NORTHEAST OF THE CENTER. A GPS DROP NEAR THE
EYEWALL MEASURED ONLY 56 KNOTS AT THE SURFACE BUT IT IS ASSUMED THAT
THERE IS MORE VERTICAL MIXING NEARBY AND THE INITIAL WIND SPEED
IS INCREASED TO 70 KT. A 90 PERCENT REDUCTION OF THE 700 MB WIND
SPEED WOULD GIVE 75 KNOTS. THE MEAN BOUNDARY LAYER WIND SPEED IN
THE DROP WAS 79 KT. SOME OF MY COLLEAGUES PREFER 75 KNOTS FOR
THEINITIAL WIND SPEED BUT I AM MORE CONSERVATIVE. A LITTLE MORE
STRENGTHENING IS FORECAST FOR 24 HOURS FOLLOWED BY SLOW WEAKENING
UNDER INCREASING VERTICAL SHEAR.
THE INITIAL MOTION IS 360/09. THE FORECAST SCENARIO IS UNCHANGED
FROM EARLIER. HUMBERTO IS MOVING AROUND THE WESTERN PERIPHERY OF A
MID LEVEL SUBTROPICAL HIGH PRESSURE RIDGE. THE NEW TRACK IS
ADJUSTED SLIGHTLY TO THE RIGHT OF THE PREVIOUS FORECAST AND SLIGHTLY
SLOWER. THIS FOLLOWS A CONSENSUS OF THE GUIDANCE AND IS CLOSE TO
THE AVIATION MODEL EXCEPT AT 72 HOURS WHEN THE AVIATION MODEL TURNS
THE MOTION MORE TO THE RIGHT OR EAST-NORTHEASTWARD. THE NOGAPS IS
LEFT AND FASTER AND BRINGS THE CENTER ACROSS THE CANADIAN MARITIMES.
THE GFDL IS FARTHEST TO THE RIGHT AND SLOWER.
THE CENTER IS NEAR ITS POINT OF CLOSEST APPROACH TO BERMUDA.
INTERESTS IN BERMUDA SHOULD MONITOR THE PROGRESS OF HUMBERTO UNTIL
IT MOVES AWAY.
FORECASTER LAWRENCE
FORECAST POSITIONS AND MAX WINDS
INITIAL 23/2100Z 32.3N 67.4W 70 KTS
12HR VT 24/0600Z 33.4N 67.5W 80 KTS
24HR VT 24/1800Z 35.2N 67.4W 80 KTS
36HR VT 25/0600Z 37.6N 66.5W 75 KTS
48HR VT 25/1800Z 40.0N 65.0W 70 KTS
72HR VT 26/1800Z 44.0N 58.9W 60 KTS
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