[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 300845
TCDAT2
HURRICANE EARL DISCUSSION NUMBER  20
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL072010
500 AM AST MON AUG 30 2010

SINCE THE AIRCRAFT DEPARTED JUST PRIOR TO 0600 UTC...AN EYE HAS BEEN
OCCASIONALLY APPARENT IN INFRARED IMAGERY...AND HAS BECOME
BETTER DEFINED WITH A DIAMETER OF ABOUT 25 NM ON THE ST. MAARTEN
RADAR.  THE AIRCRAFT MEASURED A FLIGHT LEVEL MAXIMUM WIND OF 97 KT
AT 0510 UTC...AND 0600 UTC DVORAK INTENSITY ESTIMATES WERE 90 KT
FROM TAFB AND SAB.  BASED ON THESE DATA...THE INITIAL INTENSITY IS
SET TO 90 KT FOR THIS ADVISORY.  THE OUTFLOW IS IMPROVING IN THE
NORTHEASTERN QUADRANT AND IS GOOD ELSEWHERE...AND THE OVERALL
ENVIRONMENT SHOULD SUPPORT STEADY INTENSIFICATION THROUGH THE NEXT
36 TO 48 HOURS.  THE OFFICIAL FORECAST IS SIMILAR TO THE PREVIOUS
ONE...AND SHOWS EARL REACHING MAJOR HURRICANE STATUS IN THE NEXT 12
TO 24 HOURS...FOLLOWED BY A BROAD PEAK IN INTENSITY BETWEEN 36 AND
72 HOURS.  AFTER THAT TIME...EARL SHOULD BEGIN TO WEAKEN AS IT
MOVES OVER COOLER WATERS AND ENCOUNTERS HIGHER VERTICAL WIND SHEAR.
THE OFFICIAL FORECAST IS A BLEND OF THE SHIPS MODEL AND THE GFDL.

BASED ON AIRCRAFT AND SATELLITE FIXES...THE INITIAL MOTION ESTIMATE
REMAINS 285/13.  EARL WILL GRADUALLY TURN TOWARD THE NORTHWEST IN
THE NEXT DAY OR SO AS IT MOVES AROUND THE SOUTHWESTERN EDGE OF THE
SUBTROPICAL RIDGE CENTERED ALONG 25N.  THE TRACK MODEL GUIDANCE IS
IN GOOD AGREEMENT ON THIS SCENARIO AND THE OFFICIAL FORECAST IS
NEAR THE MIDDLE OF THE TIGHTLY CLUSTERED GUIDANCE ENVELOPE THROUGH
24 HOURS.  AFTER THAT TIME MOST OF THE TRACK GUIDANCE HAS SHIFTED
FARTHER WEST...ESPECIALLY AT 72 HOURS AND BEYOND...AS EARL TURNS
NORTH-NORTHWESTWARD AND INTERACTS WITH A MID-LATITUDE TROUGH MOVING
FROM THE GREAT LAKES INTO THE NORTHEASTERN U.S.  GIVEN THE LARGE
SHIFT IN THE MODELS...THE OFFICIAL FORECAST HAS BEEN ADJUSTED TO
THE LEFT...OR WEST...BUT STILL LIES ON THE EASTERN EDGE OF THE
GUIDANCE SUITE.

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...IF ANY...PARTS OF
THE U.S. EAST COAST MIGHT SEE DIRECT IMPACTS FROM EARL LATER THIS
WEEK.

FORECAST POSITIONS AND MAX WINDS

INITIAL      30/0900Z 18.3N  62.4W    90 KT
 12HR VT     30/1800Z 19.1N  64.0W    95 KT
 24HR VT     31/0600Z 20.3N  66.0W   105 KT
 36HR VT     31/1800Z 21.9N  67.8W   115 KT
 48HR VT     01/0600Z 24.0N  69.6W   115 KT
 72HR VT     02/0600Z 29.5N  73.0W   115 KT
 96HR VT     03/0600Z 35.5N  72.5W   100 KT
120HR VT     04/0600Z 42.0N  65.5W    85 KT

$$
FORECASTER BRENNAN


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