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TROPICAL STORM ARLENE DISCUSSION NUMBER   9
NATIONAL WEATHER SERVICE MIAMI FL
5 PM EDT SUN JUN 13 1999

THERE HAS BEEN NO SIGNIFICANT CHANGE IN THE OBSERVED STRUCTURE OR
ESTIMATED INTENSITY OF THE TROPICAL STORM.  THE LOW-LEVEL
CIRCULATION CENTER REMAINS NEARLY EXPOSED NEAR THE WESTERN EDGE OF
THE DENSE OVERCAST.  DEEP CONVECTION WITHIN A SMALL CDO-LIKE FEATURE
HAS BEEN PULSATING DURING THE DAY.  AGAIN...THERE IS A SLIGHT
POSSIBILITY THAT THE WEST-NORTHWESTERLY VERTICAL SHEAR OVER THE AREA
MAY RELAX.  THUS THE OFFICIAL FORECAST ALLOWS FOR A SLIGHT INCREASE
IN INTENSITY DURING THE NEXT DAY OR TWO.  THIS IS ALSO VERY SIMILAR
THE LATEST STATISTICAL HURRICANE INTENSITY PREDICTION SCHEME...
SHIPS...OUTPUT. 

ARLENE HAS MOVED SLOWLY WESTWARD DURING THE LAST SIX HOURS OR SO. 
THE STORM HAS BEEN EMBEDDED WITHIN THE MID-TROPOSPHERIC SUBTROPICAL
RIDGE AND UNABLE TO MOVE MUCH TOWARD THE NORTH.  HOWEVER...GUIDANCE
MODELS SUGGEST THAT ENOUGH OF A WEAKNESS IN THE RIDGE WILL DEVELOP
SO AS TO ALLOW A TURN TO THE NORTHWEST DURING THE FORECAST PERIOD. 
IN FACT...THE LATEST GFDL MODEL RUN IS QUITE DIFFERENT FROM ITS
PREDECESSOR AND TURNS ARLENE NORTHWEST AND NORTH IN TWO TO THREE
DAYS.  THE U.K. MET. OFFICE MODEL TURNS THE CYCLONE NORTHWARD EVEN
SOONER.  THE CURRENT NHC FORECAST SHOWS A TURN TO THE NORTHWEST AND
IS IN BETWEEN THE LATEST MEDIUM BAM AND AVN MODEL TRACKS.
 
PASCH
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     13/2100Z 29.1N  59.1W    50 KTS
12HR VT     14/0600Z 29.3N  59.6W    50 KTS
24HR VT     14/1800Z 29.6N  60.1W    55 KTS
36HR VT     15/0600Z 30.0N  60.7W    60 KTS
48HR VT     15/1800Z 30.4N  61.2W    60 KTS
72HR VT     16/1800Z 31.5N  62.0W    60 KTS
 
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