000 WTPZ44 KNHC 020840 TCDEP4 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