000 WTPZ44 KNHC 011435 TCDEP4 TROPICAL STORM DALILA DISCUSSION NUMBER 7 NWS NATIONAL HURRICANE CENTER MIAMI FL EP042013 800 AM PDT MON JUL 01 2013 A 0949 UTC TRMM PASS SHOWED THAT THE INNER CORE OF DALILA HAS BECOME A LITTLE BETTER ORGANIZED...AND A RAINBAND NOW WRAPS MOST OF THE WAY AROUND THE CENTER. DVORAK INTENSITY ESTIMATES FROM ALL AGENCIES HAVE INCREASED...AND SUPPORT INCREASING THE INITIAL INTENSITY TO 50 KT. ALTHOUGH THE CYCLONE IS LOCATED WITHIN A SYNOPTIC ENVIRONMENT THAT SHOULD SUPPORT INTENSIFICATION OVER THE NEXT DAY OR SO...MOST OF THE MODEL GUIDANCE SUGGESTS ONLY SLIGHT INTENSIFICATION WILL OCCUR. THE OFFICIAL FORECAST REMAINS ON THE UPPER END OF THE GUIDANCE ENVELOPE FOR THE FIRST 36 HOURS...AND DALILA IS STILL EXPECTED TO REACH HURRICANE INTENSITY. AFTER THAT...THE GLOBAL MODELS...PARTICULARLY THE ECMWF...SUGGEST THAT DALILA WILL ENCOUNTER A LAYER OF MID- TO UPPER-LEVEL DRY AIR...WHICH SHOULD CAUSE THE CYCLONE TO WEAKEN STEADILY. MICROWAVE AND IR-BASED CENTER FIXES INDICATE THAT DALILA CONTINUES TO MOVE TOWARD THE NORTHWEST WITH AN ESTIMATED MOTION OF 310/8. A TURN TOWARD THE WEST-NORTHWEST WITH A DECREASE IN FORWARD SPEED IS EXPECTED AS THE CYCLONE IS STEERED BY A STRONG DEEP-LAYER RIDGE TO THE NORTH. THERE IS A LARGE AMOUNT OF SPREAD IN THE MODEL GUIDANCE...ESPECIALLY AFTER TWO DAYS...EXEMPLIFIED BY THE GFS AND ECMWF FORECASTS. THE GFS IS FORECASTING A DEEPER VORTEX WHICH MOVES FARTHER NORTH...WHILE THE ECMWF FORECASTS A SHALLOW VORTEX MOVING SLOWLY TOWARD THE SOUTHWEST. THE OFFICIAL FORECAST...IN LINE WITH THE INTENSITY FORECAST...SPLITS THESE TWO SCENARIOS AND CALLS FOR A STEADY WESTWARD MOTION AFTER 48 HOURS. FORECAST POSITIONS AND MAX WINDS INIT 01/1500Z 17.8N 105.8W 50 KT 60 MPH 12H 02/0000Z 18.2N 106.5W 55 KT 65 MPH 24H 02/1200Z 18.6N 107.3W 65 KT 75 MPH 36H 03/0000Z 18.8N 107.9W 60 KT 70 MPH 48H 03/1200Z 18.9N 108.6W 55 KT 65 MPH 72H 04/1200Z 19.0N 109.5W 50 KT 60 MPH 96H 05/1200Z 19.0N 111.5W 45 KT 50 MPH 120H 06/1200Z 19.0N 114.0W 35 KT 40 MPH $$ FORECASTER PASCH/ZELINSKY