ZCZC MIATCDEP4 ALL TTAA00 KNHC DDHHMM TROPICAL STORM DALILA DISCUSSION NUMBER 11 NWS NATIONAL HURRICANE CENTER MIAMI FL EP042013 800 AM PDT TUE JUL 02 2013 THE CENTER OF DALILA IS HIDDEN BENEATH A CENTRAL DENSE OVERCAST AND HAS BEEN VERY DIFFICULT TO LOCATE DURING THE PAST 6 HOURS. A 0319 UTC SSM/I IMAGE SHOWED THAT THE CENTER WAS DISPLACED NEARLY HALF A DEGREE SOUTH OF THE MAIN AREA OF CONVECTION...HOWEVER NO MICROWAVE IMAGES OF THE CENTER HAVE BEEN AVAILABLE SINCE THAT TIME. THE INITIAL MOTION IS AN UNCERTAIN 270/2. A SLOW MOTION IS EXPECTED TO CONTINUE AS DALILA REMAINS EMBEDDED WITHIN WEAK STEERING FLOW. THE GFS AND ECMWF FORECASTS SUGGEST THAT A DEEP-LAYER RIDGE LOCATED OVER THE SOUTHERN UNITED STATES IS BUILDING TOWARD THE NORTHWEST OF DALILA. THIS WILL LIKELY CAUSE THE TROPICAL CYCLONE TO TURN SLOWLY TOWARD THE WEST-SOUTHWEST. THE SPREAD AMONG THE DYNAMICAL MODELS REMAINS HIGH AFTER 48 HOURS. THE ECMWF FORECASTS THAT A LAYER OF MID- TO UPPER-LEVEL DRY AIR WILL QUICKLY WEAKEN DALILA...AND THE LOW-LEVEL REMNANTS WILL MOVE ALMOST DUE SOUTH. ON THE OTHER HAND...THE GFS FORECASTS THAT THE DRY AIR WILL NOT ENTRAIN INTO THE CENTER OF DALILA...AND A DEEPER VORTEX WILL TRACK WESTWARD AFTER 48 HOURS. IT IS POSSIBLE...HOWEVER...THAT CONVECTIVE FEEDBACK PROCESSES ARE ARTIFICIALLY MOISTENING THE NEAR-STORM ENVIRONMENT IN THE GFS. THE NEW OFFICIAL TRACK FORECAST HAS BEEN SHIFTED SOUTHWARD...A LITTLE CLOSER TO THE ECMWF FORECAST...AND IS ROUGHLY A CONSENSUS OF THE GFS AND ECMWF SOLUTIONS. THE INITIAL INTENSITY REMAINS 55 KT...BASED ON DVORAK CURRENT INTENSITY NUMBERS OF 3.5 FROM TAFB AND SAB. MOST OF THE INTENSITY GUIDANCE SUGGESTS THAT DALILA WILL GRADUALLY WEAKEN DURING THE NEXT SEVERAL DAYS DUE TO CONTINUED MODERATE SOUTHEASTERLY WIND SHEAR. MOST OF THE DYNAMICAL MODELS ALSO SUGGEST THAT THE ENTRAINMENT OF DRY AIR WILL CONTRIBUTE TO THE WEAKENING. THE OFFICIAL FORECAST IS VERY CLOSE TO THE PREVIOUS NHC FORECAST...AND NOW CALLS FOR DALILA TO BECOME A REMNANT LOW BY 120 HOURS. FORECAST POSITIONS AND MAX WINDS INIT 02/1500Z 17.7N 106.9W 55 KT 65 MPH 12H 03/0000Z 17.6N 107.3W 55 KT 65 MPH 24H 03/1200Z 17.4N 107.7W 50 KT 60 MPH 36H 04/0000Z 17.2N 108.4W 50 KT 60 MPH 48H 04/1200Z 17.0N 109.3W 50 KT 60 MPH 72H 05/1200Z 16.7N 110.8W 40 KT 45 MPH 96H 06/1200Z 16.5N 112.5W 30 KT 35 MPH 120H 07/1200Z 16.5N 115.0W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ FORECASTER PASCH/ZELINSKY NNNN
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Page last modified: Monday, 07-Apr-2014 23:29:18 UTC