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Tropical Storm ALETTA Forecast Discussion Number 7

Issued at 800 PM PDT TUE MAY 15 2012

000
WTPZ41 KNHC 160232
TCDEP1
 
TROPICAL STORM ALETTA DISCUSSION NUMBER   7
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP012012
800 PM PDT TUE MAY 15 2012
 
AFTER BECOMING A LITTLE BETTER ORGANIZED EARLIER TODAY...ALETTA HAS
RECENTLY BECOME RATHER RAGGED-LOOKING.  BANDING FEATURES HAVE
BECOME ILL-DEFINED...AND ARC CLOUDS HAVE BEEN EMANATING FROM THE
CYCLONE OVER THE WESTERN SEMICIRCLE...WHICH IS USUALLY INDICATIVE
OF DRIER MID-LEVEL AIR ENTERING THE CIRCULATION.  THE CURRENT
INTENSITY IS HELD AT 40 KT...AND THIS MAY BE GENEROUS GIVEN THE
CURRENT APPEARANCE OF THE SYSTEM.  THE LACK OF CONVECTIVE CLOUDS TO
THE WEST AND NORTHWEST OF ALETTA IMPLIES A MORE STABLE AND DRIER
ENVIRONMENT.  THIS...ALONG WITH INCREASING VERTICAL SHEAR...SHOULD
CAUSE A WEAKENING TREND TO COMMENCE WITHIN THE NEXT DAY OR SO.  THE
OFFICIAL INTENSITY FORECAST IS IDENTICAL TO THE PREVIOUS ONE AND
CLOSE TO THE LGEM GUIDANCE.

THE CENTER HAS BECOME DIFFICULT TO LOCATE IN GEOSTATIONARY AND
MICROWAVE IMAGERY...SO THE INITIAL MOTION IS A RATHER UNCERTAIN
285/9.  ALL OF THE RECENT DYNAMICAL TRACK GUIDANCE NOW SHOW A TURN
TOWARD THE NORTH AND NORTHEAST OVER THE NEXT FEW DAYS AS THE
TROPICAL CYCLONE BECOMES EMBEDDED IN A BROAD LOW- TO MID-LEVEL
SOUTHWESTERLY FLOW THAT DEVELOPS TO THE SOUTHWEST OF MAINLAND
MEXICO.  THE OFFICIAL TRACK FORECAST HAS BEEN SHIFTED TO THE RIGHT
OF THE PREVIOUS ONE...BUT NOT NEARLY AS FAR TO THE EAST AS SOME OF
THE MODELS AND THE MODEL CONSENSUS.  THE NEW NHC FORECAST IS FAIRLY
CLOSE TO THE LATEST GFS ENSEMBLE MEAN.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  16/0300Z 11.7N 110.9W   40 KT  45 MPH
 12H  16/1200Z 12.0N 112.2W   40 KT  45 MPH
 24H  17/0000Z 12.4N 114.0W   40 KT  45 MPH
 36H  17/1200Z 12.7N 115.0W   35 KT  40 MPH
 48H  18/0000Z 13.0N 115.5W   30 KT  35 MPH
 72H  19/0000Z 13.5N 116.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  20/0000Z 14.5N 115.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  21/0000Z...DISSIPATED
 
$$
FORECASTER PASCH
 

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