Tropical Storm ALETTA

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TROPICAL STORM ALETTA DISCUSSION NUMBER   6
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP012006
800 AM PDT SUN MAY 28 2006
 
AN AQUA MICROWAVE PASS AT 0820Z AND A TRMM PASS AT 1111Z INDICATE
THAT THE CENTER OF ALETTA DRIFTED WESTWARD OR SOUTHWESTWARD
OVERNIGHT AWAY FROM THE DEEP CONVECTION...ALTHOUGH A NEW BURST HAS
DEVELOPED JUST TO THE EAST OF THE CIRCULATION CENTER.  DVORAK
INTENSITY ESTIMATES FROM TAFB AND SAB AT 12Z WERE 45 AND 35
KT...RESPECTIVELY...AND THE INITIAL INTENSITY WILL BE HELD AT 40 KT
FOR THIS ADVISORY.
 
THE INITIAL MOTION IS STATIONARY.  STEERING CURRENTS ARE WEAK AND
MODEL GUIDANCE IS DIVERGENT.  A WEAK MID-LEVEL RIDGE OF HIGH
PRESSURE OVER MEXICO IS CURRENTLY IMPEDING ALETTA'S PROGRESS TOWARD
THE COAST...BUT SOME OF THE GLOBAL MODELS...INCLUDING THE NOGAPS AND
ECMWF...SUGGEST THAT THIS RIDGE WILL WEAKEN AS A SHORT-WAVE TROUGH
OFF THE BAJA PENINSULA MOVES EASTWARD.  THIS COULD ALLOW ALETTA TO
MOVE CLOSER TO THE COAST OVER THE NEXT DAY OR SO.  ALTHOUGH THE GFDL
TRACKER KEEPS ALETTA OFFSHORE...THE MODEL'S 850 MB VORTICITY CENTER
CLEARLY MOVES INLAND EAST OF ACAPULCO IN ABOUT 30 HOURS.  GIVEN THE
UNCERTAINTIES...THERE ARE NO CHANGES TO THE WATCHES OR WARNINGS AT
THIS TIME.  AFTER 24-48 HOURS...MOST OF THE GLOBAL MODELS
RESTRENGTHEN THE SUBTROPICAL RIDGE...AND SO THE OFFICIAL FORECAST
SHOWS A SLOW WESTWARD MOTION THROUGH THE LATTER PORTION OF THE
FORECAST PERIOD.
 
ALETTA IS STILL EXPERIENCING MID- TO UPPER-LEVEL WESTERLY FLOW THAT
HAS BEEN LIMITING DEVELOPMENT.  SHOULD ALETTA REMAIN OFFSHORE AS
FORECAST...THE GLOBAL MODELS SUGGEST A MORE FAVORABLE ANTICYCLONIC
UPPER-LEVEL FLOW WITH LOWER SHEAR SHOULD EVOLVE OVER THE NEXT DAY OR
TWO.  CONSEQUENTLY...THE OFFICIAL FORECAST INDICATES SOME
STRENGTHENING THAT IS IN GOOD AGREEMENT WITH THE SHIPS MODEL
GUIDANCE.  AS NOTED IN THE PREVIOUS DISCUSSION HOWEVER...DRY AIR
JUST TO THE WEST OF ALETTA WOULD BE AN INHIBITING FACTOR.
 
 
FORECASTER FRANKLIN
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      28/1500Z 15.5N 101.3W    40 KT
 12HR VT     29/0000Z 15.6N 101.3W    40 KT
 24HR VT     29/1200Z 15.9N 101.2W    45 KT
 36HR VT     30/0000Z 16.2N 101.2W    50 KT
 48HR VT     30/1200Z 16.5N 101.5W    55 KT
 72HR VT     31/1200Z 16.5N 102.5W    55 KT
 96HR VT     01/1200Z 16.5N 103.5W    55 KT
120HR VT     02/1200Z 16.0N 104.5W    55 KT
 
 
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