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HURRICANE FELIX DISCUSSION NUMBER 27
NATIONAL WEATHER SERVICE MIAMI FL
11 AM EDT SAT SEP 15 2001
FELIX HAS TURNED MORE EASTWARD DURING THE PAST 6 HOURS AND HAS BEGUN
TO SHOW SOME SIGNS OF WEAKENING. THE INITIAL INTENSITY OF 90 KT IS
BASED ON A DVORAK INTENSITY ESTIMATE OF 90 KT...T5.0...FROM TAFB.
HOWEVER... VISIBLE IMAGERY DURING THE PAST 2 HOURS SUGGESTS THAT
MID- TO UPPER-LEVEL WINDS MAY BE UNDERCUTTING THE IMPRESSIVE OUTFLOW
CIRRUS LAYER AND INDUCING MID-LEVEL SHEAR ON THE CYCLONE.
THEREFORE... FELIX MAY BE A LITTLE WEAKER THAN THE ADVISORY IS
INDICATING...BUT THE OVERALL CONVECTIVE STRUCTURE REMAINS INTACT SO
I HAVE OPTED TO KEEP THE INTENSITY ON THE HIGH SIDE UNTIL A DEFINITE
EROSION OF THE INNER CORE CONVECTION BECOMES MORE APPARENT.
THE INITIAL MOTION IS 080/15. FELIX HAS ACCELERATED EASTWARD DUE TO
THE INCREASING MID-LEVEL FLOW. HOWEVER...THE MID-LEVEL FLOW
IMPINGING ON THE CYCLONE IS BEING INDUCED BY THE HORIZONTALLY LARGE
AND VERTICALLY DEEP TROPOSPHERIC LOW PRESSURE SYSTEM LOCATED ABOUT
300 NM NORTHWEST OF THE AZORES...OR ABOUT 600 NM NORTH-NORTHEAST OF
FELIX. THE RESULTING BINARY INTERACTION SHOULD KEEP FELIX ON A MORE
EASTWARD TRACK THROUGH 12 TO 24 HOURS UNTIL THE DEEP LOW TO THE
NORTH GRADUALLY SHEARS OUT NORTHWARD IN ABOUT 24 HOURS. A DEEP
TROUGH OVER THE NORTH SEA IS FORECAST BY ALL THE GLOBAL MODELS TO
DIG SRONGLY SOUTHEASTWARD OVER EUROPE...WHICH SHOULD AMPLIFY THE
MID- TO UPPER-LEVEL RIDGE BETWEEN THE AZORES AND THE IBERIAN
PENINSULA. WITH THE RIDGE FORECAST TO BECOME MORE
MERIDIONAL...FELIX SHOULD GRADUALLY SLOW DOWN AFTER 36 HOURS AND
TURN MORE TOWARD THE NORTHEAST...OR EVEN NORTH-NORTHEAST...BY 48
HOURS. THE STRONG TROUGH CURRENTLY ALONG THE NORTHEAST U.S. COAST
IS FORECAST TO MOVE RAPIDLY EASTWARD AND...BY 48 TO 72 HOURS...
SHOULD BEGIN TO TURN FELIX MORE TOWARD THE EAST AS THE SYSTEM
APPROACHES OR MOVES THROUGH THE AZORES ISLANDS.
THE UPPER-LEVEL SHEAR PATTERN AFFECTING FELIX IS FORECAST TO REMAIN
AROUND 15-20 KT THROUGH THE PERIOD...AND THE EASTWARD MOTION WILL
KEEP THE CYCLONE OVER 26-27C SSTS FOR ANOTHER 24 HOURS. THEREFORE...
ONLY SLOW WEAKENING IS FORECAST THROUGH THE PERIOD...AND THE
OFFICIAL FORECAST IS CLOSE TO THE SHIPS INTENSITY FORECAST MODEL
WHICH BRINGS FELIX DOWN TO 58 KT IN 72 HOURS. NOTE...THE 12 FT SEAS
RADII WERE INCREASED IN THE SOUTHEAST AND SOUTHWEST QUADRANTS BASED
ON 15/06Z AND 15/09Z SHIP REPORTS.
FORECASTER STEWART
FORECAST POSITIONS AND MAX WINDS
INITIAL 15/1500Z 31.8N 38.7W 90 KTS
12HR VT 16/0000Z 31.9N 36.2W 85 KTS
24HR VT 16/1200Z 32.9N 33.3W 80 KTS
36HR VT 17/0000Z 34.7N 31.3W 75 KTS
48HR VT 17/1200Z 36.0N 30.0W 70 KTS
72HR VT 18/1200Z 37.5N 27.5W 60 KTS
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