[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 301450
TCDAT2
HURRICANE EARL DISCUSSION NUMBER  21
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL072010
1100 AM AST MON AUG 30 2010

THE EYE OF EARL HAS BECOME BETTER DEFINED IN VISIBLE SATELLITE
IMAGERY THIS MORNING AND IS WELL-DEFINED IN RADAR IMAGERY FROM BOTH
SAN JUAN AND ST. MAARTEN. AN AIR FORCE HURRICANE HUNTER AIRCRAFT
MEASURED 700 MB FLIGHT-LEVEL WINDS OF 111 KT IN THE NORTHEAST
EYEWALL AROUND 1200 UTC. THE AIRCRAFT HAS NOT SAMPLED THE
NORTHEASTERN QUADRANT AGAIN...BUT FOUND 90 KT SFMR WINDS IN THE
NORTHWEST EYEWALL AND A MINIMUM PRESSURE OF 960 MB. THIS SUPPORTS
INCREASING THE INITIAL INTENSITY TO 105 KT...CATEGORY THREE ON THE
SAFFIR-SIMPSON HURRICANE WIND SCALE. THE LOW SHEAR AND WARM WATER
ENVIRONMENT AHEAD OF EARL APPEARS CONDUCIVE FOR ADDITIONAL
STRENGTHENING DURING THE NEXT FEW DAYS.  THIS SUPPORTS KEEPING EARL
AT MAJOR HURRICANE STRENGTH DURING THAT TIME...ALTHOUGH EYEWALL
CYCLES COULD INDUCE SOME FLUCTUATIONS IN INTENSITY.  THE OFFICIAL
FORECAST IS AT THE UPPER END OF THE INTENSITY GUIDANCE. LATE IN THE
FORECAST PERIOD INCREASING SHEAR AND COOLER SSTS SHOULD INDUCE
WEAKENING.

THE INITIAL MOTION REMAINS 285/13.  EARL IS EXPECTED TO TURN TOWARD
THE NORTHWEST WITHIN THE NEXT DAY OR SO AS IT MOVES AROUND THE
WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE DURING THE NEXT COUPLE OF
DAYS. AFTER THAT TIME...EARL IS FORECAST TO TURN NORTHWARD...THEN
NORTHEASTWARD AHEAD OF A MID-LATITUDE TROUGH THAT MOVES ACROSS THE
GREAT LAKES AND INTO THE NORTHEAST UNITED STATES IN 4-5 DAYS.  THE
TRACK GUIDANCE HAS SHIFTED WESTWARD AGAIN AND THE OFFICIAL FORECAST
HAS BEEN ADJUSTED IN THAT DIRECTION.  THE UPDATED TRACK FORECAST IS
NEAR THE MIDDLE OF THE TIGHTLY CLUSTERED GUIDANCE.

THIS IS A GOOD TIME TO REMIND EVERYONE THAT NHC AVERAGE TRACK
FORECAST ERRORS ARE 200 TO 300 MILES AT DAYS 4 AND 5.  GIVEN THIS
UNCERTAINTY...IT IS TOO SOON TO DETERMINE WHAT PORTION OF THE U.S.
EAST COAST MIGHT SEE DIRECT IMPACTS FROM EARL.


FORECAST POSITIONS AND MAX WINDS

INITIAL      30/1500Z 18.7N  63.6W   105 KT
 12HR VT     31/0000Z 19.5N  65.1W   115 KT
 24HR VT     31/1200Z 21.0N  67.0W   125 KT
 36HR VT     01/0000Z 22.8N  68.7W   125 KT
 48HR VT     01/1200Z 25.2N  70.6W   120 KT
 72HR VT     02/1200Z 31.0N  73.5W   110 KT
 96HR VT     03/1200Z 37.5N  71.5W   100 KT
120HR VT     04/1200Z 45.5N  63.0W    75 KT...INLAND

$$
FORECASTER BROWN/BERG



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