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HURRICANE ERIN DISCUSSION NUMBER  35
NATIONAL WEATHER SERVICE MIAMI FL
11 PM EDT MON SEP 10 2001
 
AIRBORNE RADAR IMAGERY FROM A NOAA HURRICANE RESEARCH DIVISION P-3
FLIGHT VERY LATE THIS AFTERNOON SHOWED THAT ERIN HAS A CONCENTRIC
EYEWALL STRUCTURE.  THIS WAS CONFIRMED BY DOUBLE PEAKS IN BOTH THE
FLIGHT-LEVEL WINDS AND SURFACE WINDS REPORTED BY THE STEPPED-
FREQUENCY MICROWAVE RADIOMETER...SFMR...INSTRUMENT ONBOARD THE P-3.
THE HIGHEST WINDS FROM THE SFMR WERE JUST UNDER 80 KT.  THE AIRCRAFT
ALSO RELEASED A HANDFUL OF GPS DROPWINDSONDES...ONE OF WHICH GAVE A
WIND OF 89 KT FOR ITS LAST REPORT AT AN ELEVATION OF 17 M.
COLLECTIVELY...THE DROPSONDES ALSO WOULD ARGUE FOR A PEAK WIND ON
THE ORDER OF 80 KT.  OVER THE PAST SEVERAL HOURS...CLOUD TOP
TEMPERATURES HAVE WARMED A LITTLE.  DVORAK INTENSITY ESTIMATES ARE
AT 90 KT.  THE INITIAL INTENSITY HAS BEEN LOWERED TO 85 KT.

GIVEN THE CONCENTRIC EYEWALL STRUCTURE...THERE MAY BE SOME 
FLUCTUATIONS IN INTENSITY OVER THE NEXT 24-36 HOURS...AS THE INNER 
EYEWALL COLLAPSES AND THE OUTER ONE TAKES OVER.  GLOBAL MODELS 
SUGGEST THAT ERIN COULD BECOME A VERY VIGOROUS EXTRATROPICAL SYSTEM 
AROUND THE END OF THE FORECAST PERIOD...AND THE OFFICIAL FORECAST 
DOES NOT SHOW AS MUCH WEAKENING AS INDICATED BY THE SHIPS GUIDANCE.
 
THE INITIAL MOTION IS 350/8...A LITTLE TO THE RIGHT OF THE PREVIOUS
MOTION.  THERE HAS BEEN LITTLE CHANGE TO THE FORECAST PHILOSOPHY.  A
SERIES OF MID-LATITUDE TROUGHS MOVING OFF THE NORTHEAST U.S.  COAST
SHOULD BREAK DOWN THE RIDGE AND EVENTUALLY MOVE ERIN TO THE
NORTHEAST.  IT REMAINS TO BE SEEN WHETHER ERIN WILL SIGNIFICANTLY
AFFECT THE CANADIAN MARITIMES.  THE CURRENT OFFICIAL TRACK KEEPS THE
CYCLONE OFFSHORE...BUT THAT COULD CHANGE.

LARGE SWELLS GENERATED BY ERIN WILL LIKELY BE A HAZARD ALONG THE
NORTHEAST U.S. COAST DURING THE NEXT COUPLE OF DAYS.
 
FORECASTER FRANKLIN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     11/0300Z 36.7N  65.7W    85 KTS
12HR VT     11/1200Z 37.8N  65.5W    80 KTS
24HR VT     12/0000Z 38.4N  64.0W    80 KTS
36HR VT     12/1200Z 39.0N  62.0W    75 KTS
48HR VT     13/0000Z 39.5N  59.5W    75 KTS
72HR VT     14/0000Z 43.0N  54.5W    70 KTS
 
 
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