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Tropical Storm ARLENE


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TROPICAL STORM ARLENE DISCUSSION NUMBER   8
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 AM EDT FRI JUN 10 2005
 
ARLENE HAS A RAGGED APPEARANCE IN SATELLITE IMAGERY THIS MORNING...
WITH MOST OF THE ASSOCIATED CONVECTION IN A POORLY-DEFINED BAND
NORTHEAST OF THE EXPOSED LOW-LEVEL CENTER.  AN AIR FORCE RESERVE
HURRICANE HUNTER AIRCRAFT FOUND A BROAD AND POORLY-DEFINED WIND
CENTER...A 1000 MB CENTRAL PRESSURE...AND FLIGHT-LEVEL WINDS OF 56
KT AT 850 MB NEAR THE ISLE OF YOUTH.  HOW MUCH OF THIS WIND IS
REACHING THE SURFACE IS QUESTIONABLE...AS THE CONVECTION IN THE
AREA IS SOMEWHAT ISOLATED AND THE ISLE OF YOUTH REPORTED 20 KT
WINDS AT 06Z.  HOWEVER...THESE FLIGHT-LEVEL ARE STRONG ENOUGH TO
JUSTIFY INCREASING THE INITIAL INTENSITY TO 40 KT.

ARLENE HAS TURNED TO THE LEFT OVER THE PAST 6 HR AND THE INITIAL
MOTION IS NOW 340/7.  WATER VAPOR IMAGERY SHOWS A LARGE
MID/UPPER-LEVEL TROUGH OVER THE GULF OF MEXICO...WITH A BUILDING
RIDGE OVER THE WESTERN ATLANTIC AND THE EASTERN UNITED STATES. THIS
COMBINATION SHOULD STEER ARLENE GENERALLY NORTH-NORTHWESTWARD UNTIL
IT REACHES THE NORTHERN GULF COAST IN 36-48 HR.  DYNAMICAL MODELS
GENERALLY AGREE WITH THIS SCENARIO...WITH SOME SPREAD IN BOTH THE
TRACK AND SPEED.  THE OFFICIAL FORECAST IS DOWN THE MIDDLE OF THE
GUIDANCE ENVELOPE...CALLING FOR ACCELERATION TOWARD THE
NORTH-NORTHWEST DURING THE NEXT 24 HR FOLLOWED BY SOME SLOWING AS
ARLENE APPROACHES THE COAST.  THE NEW TRACK IS IN BEST AGREEMENT
WITH THE UKMET AND IS SHIFTED A LITTLE TO THE LEFT OF THE PREVIOUS
FORECAST.

THE INTENSITY FORECAST REMAINS PROBLEMATIC.  ON THE STRENGTHENING
SIDE...LARGE-SCALE MODELS SUGGEST THE VERTICAL SHEAR SHOULD
DECREASE SOMEWHAT DURING THE NEXT 24 HR AS ARLENE MOVES OVER THE
FAIRLY WARM WATERS OF THE LOOP CURRENT.  ON THE OTHER HAND...THE
BROAD WIND STRUCTURE AND LARGE AMOUNTS OF DRY AIR SEEN IN WATER
VAPOR IMAGERY NEAR ARLENE BOTH ARGUE AGAINST STRENGTHENING.  THE
SHIPS MODEL CALLS FOR THE STORM TO REACH 45-50 KT INTENSITY BEFORE
LANDFALL... WHILE THE GFDL CALLS FOR A 64 KT INTENSITY AT LANDFALL. 
THE INTENSITY FORECAST WILL COMPROMISE BETWEEN THE TWO MODELS...
CALLING FOR ARLENE TO REACH 55 KT BEFORE LANDFALL.
 
THE FORECAST TRACK AND WIND RADII REQUIRE A TROPICAL STORM WATCH FOR
THE NORTHERN GULF COAST AT THIS TIME.
 
FORECASTER BEVEN
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      10/0900Z 21.6N  84.8W    40 KT
 12HR VT     10/1800Z 23.4N  85.7W    40 KT
 24HR VT     11/0600Z 26.2N  87.2W    45 KT
 36HR VT     11/1800Z 28.5N  88.3W    50 KT
 48HR VT     12/0600Z 31.0N  88.8W    55 KT
 72HR VT     13/0600Z 37.0N  87.0W    30 KT...INLAND
 96HR VT     14/0600Z 42.0N  82.0W    25 KT...INLAND DISSIPATING
120HR VT     15/0600Z...DISSIPATED
 
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