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Tropical Storm ARLENE (Text)

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TROPICAL STORM ARLENE SPECIAL DISCUSSION NUMBER   1
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL012011
700 PM CDT TUE JUN 28 2011
 
DURING THE PAST FEW HOURS...THERE HAS BEEN AN INCREASE IN THE
COVERAGE AND ORGANIZATION OF THE DEEP CONVECTION IN ASSOCIATION
WITH THE LOW PRESSURE AREA IN THE SOUTHWESTERN GULF OF MEXICO. 
DATA T-NUMBERS FROM SPECIAL DVORAK CLASSIFICATIONS AT 2245 UTC FROM
SAB AND TAFB WERE 2.5 AND 2.0...RESPECTIVELY.  THE HURRICANE HUNTER
AIRCRAFT INVESTIGATING THE SYSTEM THIS AFTERNOON ALREADY FOUND AN
AREA OF 30 TO 35 KT SURFACE WINDS TO THE NORTHEAST OF THE 
CENTER.  BASED ON THE EARLIER AIRCRAFT OBSERVATIONS AND RECENT
SATELLITE TRENDS...THE SYSTEM IS UPGRADED TO A TROPICAL STORM...
THE FIRST OF THE 2011 ATLANTIC HURRICANE SEASON.        
 
THE INITIAL MOTION ESTIMATE IS 290/6.  A MID- TO UPPER-LEVEL
WEAKNESS NORTH OF THE TROPICAL CYCLONE IS FORECAST TO LIFT
NORTHEASTWARD DURING THE NEXT 24 HOURS AS A RIDGE OVER THE 
CENTRAL UNTIED STATES BUILDS EASTWARD.  THIS SHOULD CAUSE THE
TRACK OF ARLENE TO BEND TOWARD THE WEST OR WEST-SOUTHWEST.  THE
TRACK GUIDANCE IS IN GOOD AGREEMENT ON THIS SCENARIO AND THE NHC
FORECAST IS NEAR THE MIDDLE OF THE GUIDANCE ENVELOPE.

ENVIRONMENTAL CONDITIONS APPEAR FAVORABLE FOR STRENGTHENING. THE
SHEARING AFFECTS OF THE RETREATING UPPER-LEVEL TROUGH ARE LESSENING
AND THE SHEAR IS EXPECTED TO DECREASE DURING THE NEXT 24 HOURS.
PERHAPS THE ONE LIMITING FACTOR FOR SIGNIFICANT INTENSIFICATION
COULD BE THE BROAD NATURE OF THE CYCLONE CIRCULATION. THE OFFICIAL
INTENSITY FORECAST IS CLOSE TO THE STATISTICAL MODEL OUTPUT.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  29/0000Z 21.2N  93.7W   35 KT  40 MPH
 12H  29/0600Z 21.7N  94.6W   40 KT  45 MPH
 24H  29/1800Z 22.0N  95.9W   45 KT  50 MPH
 36H  30/0600Z 22.0N  96.9W   50 KT  60 MPH
 48H  30/1800Z 22.0N  97.9W   50 KT  60 MPH
 72H  01/1800Z 21.5N 100.0W   25 KT  30 MPH...INLAND
 96H  02/1800Z...INLAND
 
$$
FORECASTER BROWN/KIMBERLAIN
 
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