Tropical Storm DALILA

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TROPICAL STORM DALILA DISCUSSION NUMBER  10
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP042013
200 AM PDT TUE JUL 02 2013

MICROWAVE SATELLITE IMAGERY BETWEEN 0000-0400 UTC INDICATES THAT
DALILA HAS LOST ORGANIZATION...POSSIBLY DUE TO A COMBINATION OF
MODERATE SOUTHEASTERLY VERTICAL WIND SHEAR AND DRY AIR ENTRAINMENT. 
THE CONVECTIVE BANDING AROUND THE CENTER HAS DECREASED...WITH THE
CENTER NOW TO THE SOUTH OF THE MAIN CONVECTIVE MASS.  SATELLITE
INTENSITY ESTIMATES FROM TAFB AND SAB ARE 55 KT...AND USING THIS
ALONG WITH THE DECREASED ORGANIZATION THE INITIAL INTENSITY IS
REDUCED TO 55 KT.

THE MICROWAVE IMAGERY SHOWS THAT THE CENTER IS SOUTHEAST OF THE
PREVIOUS ADVISORY POSITION...WHICH REQUIRES A RE-LOCATION FOR THIS
ADVISORY.  THE INITIAL MOTION IS A RATHER UNCERTAIN 270/4.  DALILA
IS IN AN AREA OF WEAK STEERING CURRENT BETWEEN A MID-LEVEL RIDGE TO
ITS NORTH...AN UPPER-LEVEL ANTICYCLONE TO ITS EAST...AND A LARGE
AREA OF DISTURBED WEATHER TO ITS SOUTHEAST.  THE LATTER DISTURBANCE
IS FORECAST TO MOVE TOWARD DALILA DURING THE NEXT SEVERAL DAYS. 
THE TRACK GUIDANCE MODELS SHOW A SIGNIFICANT SPREAD...MAKING THIS A
LOW-CONFIDENCE FORECAST.  THE NAVGEM...GFDL...AND GFDN FORECAST THE
STORM TO MOVED NORTHWESTWARD WEST OF BAJA CALIFORNIA.  THE ECMWF
AND UKMET FORECAST A SOUTHWESTWARD MOTION DUE TO INTERACTION WITH
THE APPROACHING DISTURBANCE.  THE GFS AND THE HWRF FORECAST A SLOW
WESTWARD TO WEST-SOUTHWESTWARD MOTION...AND THIS IS THE BASIS FOR
THE CURRENT FORECAST.  THE NEW FORECAST TRACK IS SOUTH OF AND
SLOWER THAN THE PREVIOUS TRACK BASED ON THE CURRENT LOCATION AND
MOTION.

THE NEW FORECAST TRACK COMPLICATES THE INTENSITY FORECAST.  ON ONE
SIDE...THE SLOWER AND MORE SOUTHERLY TRACK WOULD KEEP THE CYCLONE
OVER WARMER SEA SURFACE TEMPERATURES THAN PREVIOUSLY FORECAST.  ON
THE OTHER SIDE...THE ECMWF..UKMET...AND CANADIAN MODELS ALL
FORECAST DALILA TO DISSIPATE BEFORE 120 HOURS DUE TO INTERACTION
WITH THE DISTURBANCE.  THE INTENSITY FORECAST COMPROMISES BETWEEN
THESE POSSIBILITIES...SHOWING LITTLE CHANGE IN STRENGTH FOR 36-48
HOURS FOLLWED BY A GRADUAL WEAKENING AS THE NEW DISTURBANCE GETS
CLOSER.  THE NEW INTENSITY FORECAST IS WEAKER THAN THE PREVIOUS
FORECAST AND IS IN BEST AGREEMENT WITH THE INTENSITY CONSENSUS.

 
FORECAST POSITIONS AND MAX WINDS
 
INIT  02/0900Z 17.7N 106.8W   55 KT  65 MPH
 12H  02/1800Z 17.7N 107.2W   55 KT  65 MPH
 24H  03/0600Z 17.7N 107.6W   55 KT  65 MPH
 36H  03/1800Z 17.5N 108.2W   55 KT  65 MPH
 48H  04/0600Z 17.2N 109.0W   50 KT  60 MPH
 72H  05/0600Z 17.0N 110.5W   45 KT  50 MPH
 96H  06/0600Z 17.0N 112.5W   35 KT  40 MPH
120H  07/0600Z 17.0N 115.0W   25 KT  30 MPH
 
$$
FORECASTER BEVEN
 
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