000
WTPZ45 KNHC 272032
TCDEP5
TROPICAL STORM DARBY DISCUSSION NUMBER  20
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP052010
200 PM PDT SUN JUN 27 2010
 
THE LOW-LEVEL CENTER OF DARBY IS PARTIALLY EXPOSED TO THE EAST OF
THE DEEP CONVECTION...CONSISTENT WITH THE 15 KT OR SO OF VERTICAL
WIND SHEAR ANALYZED OVER DARBY BY THE SHIPS MODEL AND UW-CIMSS. 
THE INITIAL INTENSITY IS LOWERED TO 40 KT BASED ON A BLEND OF
DVORAK INTENSITY ESTIMATES FROM TAFB AND SAB AT 1800 UTC...AND DATA
FROM A 1556 UTC ASCAT PASS.  THE SHIPS MODEL SHOWS THE SHEAR
INCREASING TO 25 OR 30 KT OVER THE CYCLONE IN THE NEXT 12 TO 24
HOURS...AND THIS SHOULD LEAD TO CONTINUED WEAKENING.  DARBY IS
EXPECTED TO BECOME A REMNANT LOW IN ABOUT TWO DAYS...WITH
DISSIPATION IN ABOUT THREE DAYS.  THE OFFICIAL FORECAST IS CLOSE TO
A BLEND OF THE SHIPS AND LGEM.  WHATEVER REMAINS OF DARBY IN A
COUPLE OF DAYS SHOULD BE QUITE WEAK AS IT APPROACHES THE SOUTH
COAST OF MEXICO.
 
THE INITIAL MOTION ESTIMATE IS NOW EASTWARD...090 DEGREES...AT 4
KNOTS.  THE DOMINANT STEERING MECHANISM APPEARS TO BE A LARGE AREA
OF SOUTHWESTERLY FLOW OVER SOUTHERN MEXICO AND SOUTHWEST OF ATLANTIC
TROPICAL DEPRESSION ALEX. THE MODEL GUIDANCE IS IN REASONABLE 
AGREEMENT ON THIS SCENARIO...AND THE NEW NHC FORECAST IS A BLEND OF
THE DYNAMICAL MODELS...AND IS ADJUSTED TO THE RIGHT OF AND FASTER
THAN THE PREVIOUS PACKAGE.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      27/2100Z 13.7N 102.2W    40 KT
 12HR VT     28/0600Z 13.8N 101.7W    35 KT
 24HR VT     28/1800Z 14.2N 100.8W    30 KT
 36HR VT     29/0600Z 14.6N  99.6W    25 KT...POST-TROP/REMNT LOW
 48HR VT     29/1800Z 14.9N  98.3W    20 KT...POST-TROP/REMNT LOW
 72HR VT     30/1800Z...DISSIPATED
 
$$
FORECASTER BRENNAN