000 WTPZ42 KNHC 240842 TCDEP2 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 $$ FORECASTER RHOME