000
WTPZ44 KNHC 021432
TCDEP4
 
TROPICAL STORM DALILA DISCUSSION NUMBER  11
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP042013
800 AM PDT TUE JUL 02 2013
 
THE CENTER OF DALILA IS HIDDEN BENEATH A CENTRAL DENSE OVERCAST AND
HAS BEEN VERY DIFFICULT TO LOCATE DURING THE PAST 6 HOURS.  A 0319
UTC SSM/I IMAGE SHOWED THAT THE CENTER WAS DISPLACED NEARLY HALF A
DEGREE SOUTH OF THE MAIN AREA OF CONVECTION...HOWEVER NO MICROWAVE
IMAGES OF THE CENTER HAVE BEEN AVAILABLE SINCE THAT TIME.  THE
INITIAL MOTION IS AN UNCERTAIN 270/2.  A SLOW MOTION IS EXPECTED TO
CONTINUE AS DALILA REMAINS EMBEDDED WITHIN WEAK STEERING FLOW.  THE
GFS AND ECMWF FORECASTS SUGGEST THAT A DEEP-LAYER RIDGE LOCATED
OVER THE SOUTHERN UNITED STATES IS BUILDING TOWARD THE NORTHWEST OF
DALILA.  THIS WILL LIKELY CAUSE THE TROPICAL CYCLONE TO TURN SLOWLY
TOWARD THE WEST-SOUTHWEST.  THE SPREAD AMONG THE DYNAMICAL MODELS
REMAINS HIGH AFTER 48 HOURS.  THE ECMWF FORECASTS THAT A LAYER OF
MID- TO UPPER-LEVEL DRY AIR WILL QUICKLY WEAKEN DALILA...AND THE
LOW-LEVEL REMNANTS WILL MOVE ALMOST DUE SOUTH.  ON THE OTHER
HAND...THE GFS FORECASTS THAT THE DRY AIR WILL NOT ENTRAIN INTO THE
CENTER OF DALILA...AND A DEEPER VORTEX WILL TRACK WESTWARD AFTER 48
HOURS.  IT IS POSSIBLE...HOWEVER...THAT CONVECTIVE FEEDBACK
PROCESSES ARE ARTIFICIALLY MOISTENING THE NEAR-STORM ENVIRONMENT IN
THE GFS.  THE NEW OFFICIAL TRACK FORECAST HAS BEEN SHIFTED
SOUTHWARD...A LITTLE CLOSER TO THE ECMWF FORECAST...AND IS ROUGHLY
A CONSENSUS OF THE GFS AND ECMWF SOLUTIONS.
 
THE INITIAL INTENSITY REMAINS 55 KT...BASED ON DVORAK CURRENT
INTENSITY NUMBERS OF 3.5 FROM TAFB AND SAB.  MOST OF THE INTENSITY
GUIDANCE SUGGESTS THAT DALILA WILL GRADUALLY WEAKEN DURING THE NEXT
SEVERAL DAYS DUE TO CONTINUED MODERATE SOUTHEASTERLY WIND SHEAR.
MOST OF THE DYNAMICAL MODELS ALSO SUGGEST THAT THE ENTRAINMENT OF
DRY AIR WILL CONTRIBUTE TO THE WEAKENING.  THE OFFICIAL FORECAST IS
VERY CLOSE TO THE PREVIOUS NHC FORECAST...AND NOW CALLS FOR DALILA
TO BECOME A REMNANT LOW BY 120 HOURS.

FORECAST POSITIONS AND MAX WINDS
 
INIT  02/1500Z 17.7N 106.9W   55 KT  65 MPH
 12H  03/0000Z 17.6N 107.3W   55 KT  65 MPH
 24H  03/1200Z 17.4N 107.7W   50 KT  60 MPH
 36H  04/0000Z 17.2N 108.4W   50 KT  60 MPH
 48H  04/1200Z 17.0N 109.3W   50 KT  60 MPH
 72H  05/1200Z 16.7N 110.8W   40 KT  45 MPH
 96H  06/1200Z 16.5N 112.5W   30 KT  35 MPH
120H  07/1200Z 16.5N 115.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
 
$$
FORECASTER PASCH/ZELINSKY