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Tropical Storm ROSA (Text)

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TROPICAL STORM ROSA DISCUSSION NUMBER   7
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP192006
100 PM PST THU NOV 09 2006
 
AFTER LOOKING SURPRISINGLY IMPRESSIVE THIS MORNING IN SATELLITE
IMAGERY...ROSA NOW APPEARS INCREASINGLY LESS ORGANIZED.  THE
LOW-LEVEL CIRCULATION IS NO LONGER AS WELL-DEFINED...CONVECTION IS
BECOMING INCREASINGLY DISPLACED EAST OF THE ESTIMATED CENTER OF
CIRCULATION...AND THE PRESENCE OF ARC CLOUDS IMPLIES THAT DRY AIR
IS NOW AFFECTING THE CYCLONE. STILL...SHEARED CYCLONES SUCH AS ROSA
OFTEN DISPLAY FREQUENT FLUCTUATIONS IN THE CONVECTIVE CLOUD PATTERN. 
ACCORDINGLY...THE INITIAL INTENSITY IS HELD AT 35 KT IN LINE WITH
DVORAK ESTIMATES FROM BOTH SAB AND TAFB.  IT IS DIFFICULT
TO ANTICIPATE WHETHER THE CURRENT CONVECTIVE ORGANIZATION...OR LACK
THEREOF...IS THE BEGINNING OF A LONGER-TERM WEAKENING TREND OR IS
JUST A SHORTER-TERM FLUCTUATION.  THE OFFICIAL FORECAST ASSUMES THE
LATTER AND SHOWS LITTLE CHANGE IN STRENGTH DURING THE NEXT 12
HOURS.  THEREAFTER...THE GLOBAL MODELS FORECAST GRADUALLY
INCREASING SHEAR...WHICH SHOULD BRING ABOUT STEADY WEAKENING...WITH
THE CYCLONE EXPECTED TO BECOME A REMNANT LOW IN THREE DAYS OR LESS.
 
THE LOW-LEVEL CIRCULATION ASSOCIATED WITH ROSA HAS BEEN OBSCURED BY
HIGH CLOUDS DURING THE LAST SEVERAL HOURS...AND THE INITIAL MOTION
ESTIMATE IS AN UNCERTAIN 350/04.  TRACK GUIDANCE CONTINUES TO BE
HIGHLY DIVERGENT...ALTHOUGH NONE OF THE MODELS SHOW ROSA MOVING VERY
FAR IN ANY DIRECTION.  THE GFS AND ITS ENSEMBLE MEAN SHOW A TURN
TOWARD THE WEST...WHILE THE GFDN SHOWS A TURN TOWARD THE NORTHEAST.
THESE DIFFERING SOLUTIONS ARE LIKELY DUE IN PART TO VARIATIONS IN
THE DEPTH OF THE MODEL CYCLONES.  THE GFS SHOWS A WEAKER AND
SHALLOWER CYCLONE MOVING MORE TOWARD THE WEST WHILE THE GFDN SHOWS
A STRONG AND DEEPER CYCLONE MOVING TOWARD THE NORTHEAST.  THE
OFFICIAL FORECAST LIES IN BETWEEN...BUT LEANS MORE TOWARD THE
WEAKER AND SHALLOWER GFS SOLUTION.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      09/2100Z 15.8N 105.4W    35 KT
 12HR VT     10/0600Z 16.2N 105.5W    35 KT
 24HR VT     10/1800Z 16.6N 105.7W    30 KT
 36HR VT     11/0600Z 17.0N 106.0W    30 KT
 48HR VT     11/1800Z 17.5N 106.5W    25 KT...DISSIPATING
 72HR VT     12/1800Z 18.5N 107.5W    25 KT...REMNANT LOW
 96HR VT     13/1800Z 19.0N 108.5W    20 KT...REMNANT LOW
120HR VT     14/1800Z...DISSIPATED
 
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