000
WTNT42 KNHC 280255
TCDAT2
TROPICAL STORM EARL DISCUSSION NUMBER  11
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL072010
1100 PM AST FRI AUG 27 2010
 
SATELLITE IMAGES INDICATE THAT CONVECTION HAS INCREASED IN THE
WESTERN SEMICIRCLE OF EARL.  BANDING FEATURES ARE BECOMING BETTER
DEFINED...AND A THUNDERSTORM CLUSTER IS LOCATED NEAR OR JUST
SOUTHWEST OF THE CENTER.  SATELLITE ESTIMATES ARE A CONSENSUS 45 KT
FROM TAFB/SAB...AND THAT WILL BE THE INITIAL INTENSITY.  THE CLOUD
PATTERN SUGGESTS THAT NORTHEASTERLY SHEAR HAS INCREASED DURING THE
PAST SEVERAL HOURS...AND GLOBAL MODELS SUGGEST THIS SHEAR WILL
CONTINUE FOR THE NEXT DAY OR SO.  THERE IS ALSO EVIDENCE THAT SOME
DRIER AIR IS LURKING NEAR THE CYCLONE.  THUS THE INTENSITY FORECAST
WILL BE A BIT BELOW MOST OF THE MODEL GUIDANCE FOR THE FIRST 36
HOURS.  THEREAFTER...EARL WILL BE MOVING CLOSER TO THE CENTER OF A
LARGE UPPER-LEVEL ANTICYCLONE NORTHEAST OF THE LESSER ANTILLES. 
THIS PATTERN IS QUITE FAVORABLE FOR INTENSIFICATION...ESPECIALLY
CONSIDERING THE 29C PLUS SSTS IN THE PATH OF THE HURRICANE.  THE
GFDL/GFDN RESPOND TO THESE CONDITIONS BY FORECASTING EARL TO BECOME
A CATEGORY 4 HURRICANE IN THE LONG-RANGE.  WHILE THE NEW NHC
FORECAST WILL NOT BE THAT AGGRESSIVE...IT IS INCREASED FROM THE
PREVIOUS ONE AND IS CLOSE TO A BLEND OF THE ABOVE DYNAMICAL
GUIDANCE AND THE LGEM MODEL.

A SERIES OF MICROWAVE PASSES SUGGESTS THE CENTER REMAINS A BIT
ELONGATED...THUS CONFIDENCE IN MY INITIAL MOTION OF 275/18 IS LOWER
THAN AVERAGE.  A STRONG RIDGE BETWEEN EARL AND DANIELLE IS EXPECTED
TO KEEP THE TROPICAL STORM MOVING GENERALLY WESTWARD FOR THE NEXT
DAY OR SO.  AFTER THAT TIME...EARL WILL REACH THE WESTERN PERIPHERY
OF THE RIDGE AND IS EXPECTED TO TURN TOWARD THE WEST-NORTHWEST. 
ALTHOUGH ALL OF THE GUIDANCE SHOWS THE CENTER NORTHEAST OF THE
LEEWARD ISLANDS...THERE REMAINS SOME UNCERTAINTY ON HOW CLOSE EARL
WILL COME.  THE GFS HAS THE STRONGEST RIDGE IN THE GLOBAL MODELS
AND MOVES THE CYCLONE CLOSER TO THE LEEWARD ISLANDS THAN MOST OF
THE OTHER GUIDANCE.  AT THIS POINT...IT IS PRUDENT NOT TO MAKE ANY
CHANGES IN THE TRACK FORECAST IN THE FIRST COUPLE OF DAYS...
ESPECIALLY SINCE THE CYCLONE HAS MOVED FASTER TOWARDS THE WEST THAN
PREVIOUSLY FORECAST.  THE NHC FORECAST REMAINS ON THE LEFT EDGE OF
THE GUIDANCE ENVELOPE THROUGH THE FIRST THREE DAYS...THEN IS JUST
LEFT OF THE MODEL CONSENSUS AT THE END.  
 
RESIDENTS IN THE LESSER ANTILLES SHOULD CLOSELY MONITOR THE PROGRESS
OF EARL THROUGHOUT THE WEEKEND.  WATCHES MAY BE REQUIRED AS EARLY
AS SATURDAY MORNING.  
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      28/0300Z 16.0N  47.9W    45 KT
 12HR VT     28/1200Z 16.2N  50.7W    50 KT
 24HR VT     29/0000Z 16.6N  54.0W    55 KT
 36HR VT     29/1200Z 17.3N  56.8W    65 KT
 48HR VT     30/0000Z 18.1N  59.1W    80 KT
 72HR VT     31/0000Z 20.5N  63.0W   100 KT
 96HR VT     01/0000Z 24.5N  66.0W   110 KT
120HR VT     02/0000Z 29.0N  68.5W   105 KT
 
$$
FORECASTER BLAKE