000
WTPZ41 KNHC 292048
TCDEP1
TROPICAL STORM ALVIN DISCUSSION NUMBER  12
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP012007
200 PM PDT TUE MAY 29 2007
 
IT HAS BEEN DIFFICULT TO LOCATE THE CENTER OF ALVIN USING
CONVENTIONAL SATELLITE IMAGERY TODAY...HOWEVER A MICROWAVE PASS
FROM SSMI-S HELPED TO RE-POSITION THE CENTER BACK TOWARD THE EAST A
BIT.  AFTER A FLARE UP OF CONVECTION EARLY THIS MORNING... THE
CONVECTIVE TOPS HAVE WARMED AND DECREASED IN AREAL EXTENT DURING
THE LAST SIX HOURS OR SO.  AT 1338Z...A QUIKSCAT PASS INDICATED A
COUPLE OF RELIABLE 35 KT VECTORS ONLY OVER THE SOUTHEAST
QUADRANT...AS WELL AS A COUPLE OF 40 KT VECTORS.  BASED ON THE
DETERIORATION OF THE CONVECTIVE PATTERN AND DVORAK INTENSITY
ESTIMATES OF 35 KT FROM BOTH TAFB AND SAB...THE INITIAL INTENSITY
WILL BE HELD AT 35 KT.  DESPITE RELATIVELY LOW SHEAR AND WARM
WATERS...THE ENVIRONMENT APPEARS TO STILL BE TOO STABLE FOR
SIGNIFICANT INTENSIFICATION.  THE OFFICIAL INTENSITY FORECAST IS
CLOSE TO THE SHIPS AND GFDL GUIDANCE. 

THE INITIAL MOTION IS 260/2.  ALVIN IS CURRENTLY IN AN AREA OF
RELATIVELY WEAK STEERING CURRENTS.  HOWEVER MOST OF THE DYNAMICAL
MODEL GUIDANCE FORECAST THE MID-LEVEL SUBTROPICAL RIDGE CURRENTLY
TO THE NORTHWEST OF ALVIN TO MIGRATE TO THE EAST...ALLOWING THE
CYCLONE TO MOVE A LITTLE FASTER TO THE WEST THROUGH THE FORECAST
PERIOD. THE OFFICIAL TRACK FORECAST IS VIRTUALLY AN UPDATE OF THE
PREVIOUS ADVISORY AND IS CLOSE TO THE NOGAPS AND ECMWF SOLUTIONS. 

FORECAST POSITIONS AND MAX WINDS
 
INITIAL      29/2100Z 12.6N 114.0W    35 KT
 12HR VT     30/0600Z 12.6N 114.5W    35 KT
 24HR VT     30/1800Z 12.6N 115.6W    40 KT
 36HR VT     31/0600Z 12.6N 116.7W    45 KT
 48HR VT     31/1800Z 12.6N 117.5W    45 KT
 72HR VT     01/1800Z 12.5N 119.0W    40 KT
 96HR VT     02/1800Z 12.3N 120.5W    40 KT
120HR VT     03/1800Z 12.0N 122.0W    35 KT
 
$$
FORECASTER MAINELLI