Tropical Depression FOUR

ZCZC MIATCDAT4 ALL
TTAA00 KNHC DDHHMM
TROPICAL DEPRESSION FOUR DISCUSSION NUMBER   1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL042006
500 PM EDT MON AUG 21 2006
 
THE AREA OF LOW PRESSURE SOUTHEAST OF THE CAPE VERDE ISLANDS HAS
BEEN MAINTAINING ENOUGH CONVECTIVE BANDING TODAY TO WARRANT DVORAK
CLASSIFICATIONS OF T1.5 FROM TAFB AND SAB AT 18Z.  SINCE THEN...A
SMALL BURST OF CONVECTION HAS DEVELOPED NEAR THE CIRCULATION
CENTER.  GIVEN THIS...AND THE BROAD CYCLONIC ENVELOPE OF THE
LOW...ADVISORIES ARE INITIATED ON TROPICAL DEPRESSION FOUR.
 
THE INITIAL MOTION IS 285/10.  THE DEPRESSION IS SOUTH OF THE
SUBTROPICAL RIDGE...BUT THIS RIDGE IS FORECAST BY GLOBAL MODELS TO
SLIDE EASTWARD AS A SERIES OF MID-LATITUDE SHORT WAVES MOVE THROUGH
THE CENTRAL ATLANTIC AND ERODE THE RIDGE.  THIS SHOULD ALLOW THE
DEPRESSION TO TAKE A TRACK BETWEEN WEST-NORTHWEST AND NORTHWEST
AROUND THE PERIPHERY OF THE RIDGE THROUGHOUT MUCH OF THE FORECAST
PERIOD.  THE OFFICIAL FORECAST IS IN GOOD AGREEMENT WITH THE GFS
AND GFDL GUIDANCE...AS WELL AS THE BAM SUITE OF MODELS.  NEITHER
THE UKMET NOR NOGAPS HANG ON TO THE CYCLONE AND THESE MODELS TAKE
ITS REMNANTS WESTWARD.
 
OUTER BANDING STRUCTURES ARE WELL DEFINED...BUT OVERALL THE
CONVECTIVE SIGNATURE IS STILL A LITTLE THIN.  WATER TEMPERATURES
SHOULD BE WARM ENOUGH FOR THE NEXT DAY OR SO TO SUPPORT DEVELOPMENT
AND THE SHEAR IS LIGHT.  DURING DAYS 2 AND 3 OF THE FORECAST PERIOD
THE CYCLONE WILL BE MOVING OVER SOMEWHAT COOLER WATERS AND THE
OFFICIAL FORECAST SHOWS ONLY SLOW DEVELOPMENT AFTER THAT.  THE
INTENSITY FORECAST IS CLOSE TO A BLEND OF THE SHIPS AND GFDL
GUIDANCE.
 
PORTIONS OF THE CAPE VERDE ISLANDS ARE WITHIN THE FORECAST TROPICAL
STORM FORCE WIND SWATH...AND THE GOVERNMENT OF THE CAPE VERDE
ISLANDS HAS ISSUED A TROPICAL STORM WARNING.
 

FORECAST POSITIONS AND MAX WINDS
 
INITIAL      21/2100Z 12.5N  21.5W    30 KT
 12HR VT     22/0600Z 13.0N  23.0W    35 KT
 24HR VT     22/1800Z 14.2N  25.2W    45 KT
 36HR VT     23/0600Z 15.5N  27.5W    50 KT
 48HR VT     23/1800Z 17.0N  30.0W    55 KT
 72HR VT     24/1800Z 20.0N  35.5W    55 KT
 96HR VT     25/1800Z 23.5N  41.0W    60 KT
120HR VT     26/1800Z 26.5N  46.5W    60 KT
 
$$
FORECASTER FRANKLIN
 
NNNN