Tropical Storm DALILA

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TROPICAL STORM DALILA DISCUSSION NUMBER  10
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP072007
200 AM PDT TUE JUL 24 2007
 
LATEST CONVENTIONAL SATELLITE IMAGERY INDICATES THAT DALILA IS
BEGINNING TO STRENGTHEN.  THE AREA OF DEEP CONVECTION OVER THE
SOUTHERN SEMICIRCLE IS NOW SITUATED CLOSER TO THE LOW LEVEL
CIRCULATION CENTER AND NEW CONVECTION IS FORMING NORTH OF THE
CENTER.  THE CURRENT INTENSITY IS SET AT 40 KT IN LINE WITH A
CONSENSUS OF THE VARIOUS OBJECTIVE AND SUBJECTIVE SATELLITE
ESTIMATES.
 
DALILA HAS BEEN MOVING ERRATICALLY DURING THE LAST SEVERAL HOURS BUT
A 12 HOUR AVERAGE YIELDS AN INITIAL MOTION ESTIMATE OF 340/6.  THE
OVERALL TRACK FORECAST PHILOSOPHY REMAINS UNCHANGED. WATER VAPOR
IMAGERY SHOWS A WEAK INVERTED MID-LEVEL TROUGH NORTHEAST OF DALILA
NEAR THE WESTERN COAST OF MEXICO.  THIS TROUGH HAS TEMPORARILY
ERODED A LARGER-SCALE RIDGE OVER NORTHERN MEXICO RESULTING IN A
GENERAL NORTH-NORTHWEST MOTION. MOST OF THE GLOBAL MODELS MOVE THE
MID-LEVEL TROUGH WESTWARD...TO THE NORTH OF DALILA...OVER THE NEXT
DAY OR SO ALLOWING THE CYCLONE TO CONTINUE NORTH-NORTHWESTWARD. 
AFTER THAT...THERE IS SOME DIVERGENCE AMONG THE VARIOUS GLOBAL
MODELS WITH THE CMC...ECMWF...AND GFDN INDICATING THE CYCLONE WILL
CONTINUE NORTHWESTWARD WITHIN A WEAKNESS CREATED BY A SECOND
MID-LEVEL TROUGH CURRENTLY ALONG THE SOUTHERN COAST OF CALIFORNIA. 
THESE MODELS ALSO SHOW A SUSPICIOUSLY STRONG CYCLONE AT THAT TIME.
CONVERSELY...THE GFS...UKMET...AND NOGAPS MODELS SHOW A WEAKER
DALILA TURNING WESTWARD UNDER THE INFLUENCE OF DEEP LAYER RIDGING
OVER THE SOUTHWESTERN UNITED STATES.  GIVEN THE ANTICIPATED
WEAKENING BEYOND 48 HOURS...THE SECOND SCENARIO IS PREFERRED
RESULTING IN LITTLE CHANGE TO THE OFFICIAL FORECAST TRACK THROUGH
48 HOURS AND A SLIGHT SOUTHWARD SHIFT THEREAFTER.
 
EVEN THOUGH VERTICAL SHEAR IS EXPECTED TO DECREASE DURING THE NEXT
24-48 HOURS...THE THERMODYNAMIC ENVIRONMENT DOES NOT APPEAR IDEAL.
ADDITIONALLY...DALILA WILL BEGIN TO ENCOUNTER COOLER WATERS IN ABOUT
TWO DAYS.  THESE FACTORS SHOULD LIMIT SIGNIFICANT STRENGTHENING IN
THE SHORT-TERM AND ULTIMATELY RESULT IN WEAKENING BEYOND 48 HOURS.
INTENSITY GUIDANCE MODELS ARE LITTLE CHANGED AND SO IS THE OFFICIAL
FORECAST.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      24/0900Z 16.7N 109.8W    40 KT
 12HR VT     24/1800Z 17.6N 110.2W    40 KT
 24HR VT     25/0600Z 18.7N 110.8W    45 KT
 36HR VT     25/1800Z 19.6N 111.6W    50 KT
 48HR VT     26/0600Z 20.4N 112.6W    50 KT
 72HR VT     27/0600Z 22.0N 115.0W    45 KT
 96HR VT     28/0600Z 23.0N 117.5W    30 KT
120HR VT     29/0600Z 24.0N 120.5W    20 KT...DISSIPATING
 
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FORECASTER RHOME
 
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