[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 260848
TCDAT2
TROPICAL STORM EARL DISCUSSION NUMBER   4
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL072010
500 AM AST THU AUG 26 2010

CONVENTIONAL SATELLITE IMAGERY INDICATES THAT THE SPIRAL BANDS
AROUND EARL HAVE BECOME BETTER ORGANIZED THIS MORNING...
PARTICULARLY OVER THE WESTERN PORTION OF THE CYCLONE. THE CYCLONE
STRUCTURE...HOWEVER...IS STILL A BIT ELONGATED ALONG A SOUTHWEST TO
NORTHEAST AXIS. DVORAK SATELLITE CURRENT INTENSITY ESTIMATES FROM
TAFB AND SAB ARE 45 AND 35 KT..RESPECTIVELY.  USING A BLEND OF THE
TWO...THE INITIAL INTENSITY IS INCREASED TO 40 KT. THE OCEAN IS
WARM AND THE SHEAR IS LOW...CREATING AN ENVIRONMENT CONDUCIVE FOR
STRENGTHENING DURING THE ENTIRE FORECAST PERIOD. IN FACT...THE
LGEM...HWRF...AND SHIPS MODELS ALL SHOW THE CYCLONE BECOMING A
HURRICANE IN 2 DAYS. THE OFFICIAL FORECAST FOLLOWS SUIT AND ALSO
BRINGS EARL TO CATEGORY TWO INTENSITY BY DAY 5.

THE CENTER OF EARL HAS BEEN RATHER DIFFICULT TO LOCATE THIS MORNING.
A 2315 UTC ASCAT OVERPASS INDICATED AN ELONGATED CENTER NEAR THE
CONVECTION OVER THE SOUTHERN PORTION OF THE SYSTEM...WELL TO
THE SOUTH OF THE PREVIOUS ADVISORY POSITION.  HOWEVER...A SUBSEQUENT
AMSU-B MICROWAVE PASS AT 2318 UTC AND A RECENT 0430 UTC TRMM IMAGE
SUGGESTED THE CENTER IS LOCATED TO THE NORTHEAST OF THE
AFOREMENTIONED ASCAT PASS...MUCH CLOSER TO THE PREVIOUS BEST TRACK.
FOR THIS ADVISORY...AND BASED ON THESE DATA...CONTINUITY WILL BE
MAINTAINED AND THE INITIAL POSITION IS BE NEAR THE NORTHERN
CLUSTER OF DEEP CONVECTION AND CLOSE TO THE TRMM FIX.  IF THE
CIRCULATION CENTER DOES REFORM FARTHER SOUTH...THE FORECAST TRACK
WILL HAVE TO BE ADJUSTED SOUTH...OR TO THE LEFT OF THIS ADVISORY
PACKAGE.

EARL IS MOVING TOWARD THE WEST-NORTHWEST...AN ESTIMATED 285 DEGREES
AT 13 KT. THE TROPICAL STORM IS EMBEDDED WITHIN THE DEEP TROPICAL
ATLANTIC TRADE WIND FLOW AND SHOULD CONTINUE ON THIS GENERAL TRACK
OVER THE NEXT 48 TO 72 HOURS. AFTERWARD...A TURN TOWARD THE
WEST-NORTHWEST IS EXPECTED AS THE CYCLONE BEGINS TO MOVE TOWARD A
BREAK IN THE SUBTROPICAL RIDGE. WITH THE EXCEPTION OF NOGAPS AND
THE NAVY GFDN...WHICH ARE BOTH INDICATING AN EARLIER TURN TOWARD
THE NORTHWEST...THE DYNAMICAL MODELS ARE TIGHTLY CLUSTERED THROUGH
DAY 5. THE NHC FORECAST TRACK IS BASED ON THE TVCN MODEL CONSENSUS
AND IS CLOSE TO THE ECMWF AND GFS.

FORECAST POSITIONS AND MAX WINDS

INITIAL      26/0900Z 15.2N  34.8W    40 KT
 12HR VT     26/1800Z 15.7N  37.2W    45 KT
 24HR VT     27/0600Z 16.4N  40.3W    50 KT
 36HR VT     27/1800Z 16.6N  43.7W    60 KT
 48HR VT     28/0600Z 16.7N  47.0W    70 KT
 72HR VT     29/0600Z 17.9N  52.3W    80 KT
 96HR VT     30/0600Z 20.0N  57.0W    90 KT
120HR VT     31/0600Z 22.5N  60.0W    95 KT

$$
FORECASTER ROBERTS/BRENNAN


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