000
WTPZ41 KNHC 300239
TCDEP1
TROPICAL STORM ALVIN DISCUSSION NUMBER  13
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP012007
800 PM PDT TUE MAY 29 2007

THE CENTER OF ALVIN CONTINUES TO BE DIFFICULT TO LOCATE IN
CONVENTIONAL SATELLITE IMAGERY.  HOWEVER...A COUPLE OF MICROWAVE
PASSES DURING THE LATE AFTERNOON AIDED IN LOCATING THE CENTER.   
THE SATELLITE APPEARANCE OF ALVIN HAS BECOME RATHER POOR THIS
EVENING WITH THE CYCLONE CONSISTING OF A SMALL CONVECTIVE CLUSTER 
OVER THE EASTERN PORTION OF THE CIRCULATION.  DVORAK CURRENT
INTENSITY ESTIMATES REMAIN UNCHANGED AND THE INITIAL ESTIMATE WILL
BE KEPT AT 35 KT.  

THE ENVIRONMENTAL CONDITIONS AHEAD OF ALVIN APPEAR LESS THAN IDEAL
FOR SIGNIFICANT STRENGTHENING.  THE CYCLONE'S MAIN INHIBITING
FACTOR CONTINUES TO BE A STABLE ENVIRONMENT.  GIVEN THE CURRENT
SATELLITE APPEARANCE...IT IS TEMPTING TO BACK OFF ON THE PREVIOUS
INTENSITY FORECAST.  HOWEVER...THE SHIPS AND GFDL MODELS CONTINUE
TO FORECAST A LITTLE INTENSIFICATION AND THE OFFICIAL INTENSITY
FORECAST WILL CONTINUE THIS TREND FOR NOW. 

THE INITIAL MOTION IS 270/3.  THE SUBTROPICAL RIDGE TO THE NORTH OF
ALVIN IS FORECAST BY THE DYNAMICAL MODEL GUIDANCE TO SHIFT EASTWARD
DURING THE NEXT FEW DAYS.  THIS SHOULD ALLOW ALVIN TO MOVE A LITTLE
FASTER IN A GENERAL WESTWARD DIRECTION DURING THE FORECAST PERIOD. 
THE OFFICIAL TRACK FORECAST WAS VIRTUALLY UNCHANGED...EXCEPT FOR A
SLIGHTLY NORTHWARD ADJUSTMENT DUE TO A MORE NORTHERN INITIAL
LOCATION.  THE TRACK FORECAST IS CLOSE TO THE NOGAPS AND 12Z ECMWF
MODELS.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      30/0300Z 12.8N 114.3W    35 KT
 12HR VT     30/1200Z 12.9N 114.8W    35 KT
 24HR VT     31/0000Z 13.1N 115.8W    40 KT
 36HR VT     31/1200Z 13.2N 116.8W    45 KT
 48HR VT     01/0000Z 13.2N 117.8W    45 KT
 72HR VT     02/0000Z 13.0N 119.3W    40 KT
 96HR VT     03/0000Z 12.7N 120.5W    40 KT
120HR VT     04/0000Z 12.2N 122.0W    35 KT
 
$$
FORECASTER BROWN