[StBernard] Atlantic Tropical Storm ARLENE Special Discussion Number 1

[Westley Annis]

Atlantic Tropical Storm ARLENE Special Discussion Number 1
<http://www.nhc.noaa.gov/text/MIATCMAT1.shtml> 
06/28/2011 08:14 PM EDT


000
WTNT41 KNHC 290014
TCDAT1

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