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Tropical Storm DALILA Forecast Discussion Number 9
2013-07-02 04:46:22| National Hurricane Center (East Pacific)
Issued at 800 PM PDT MON JUL 01 2013 000 WTPZ44 KNHC 020245 TCDEP4 TROPICAL STORM DALILA DISCUSSION NUMBER 9 NWS NATIONAL HURRICANE CENTER MIAMI FL EP042013 800 PM PDT MON JUL 01 2013 THE CONVECTIVE BANDING PATTERN ASSOCIATED WITH DALILA HAS GRADUALLY MORPHED INTO A SMALL CDO FEATURE OVER THE PAST 6 HOURS...WITH CLOUD TOPS OF -80C AND COLDER ALMOST COMPLETELY ENCIRCLING THE CENTER. A 01/1801 UTC TRMM OVERPASS THAT CAME IN AFTER THE PREVIOUS ADVISORY ALSO REVEALED A CLOSED 10-15 NMI DIAMETER MID-LEVEL EYE. SATELLITE INTENSITY ESTIMATES FROM TAFB REMAIN AT T3.5/55 KT...BUT THE DATA-T NUMBER FROM TAFB WAS 4.0/65 KT. A RECENT CIRA INTENSITY ESTIMATE OF 62 KT...ALONG WITH THE TRMM MICROWAVE EYE FEATURE...JUSTIFIES INCREASING THE INITIAL INTENSITY TO 60 KT. ALTHOUGH DALILA HAS BEEN INCREASING AT THE RATE OF ONE T-NUMBER PER DAY OR 20 KT EVERY 24 HOURS...THAT INTENSIFICATION TREND IS NOT EXPECTED TO LAST MUCH LONGER. THE VERTICAL SHEAR ACROSS DALILA IS FORECAST TO REMAIN MODEST AT 12-15 KT FOR ANOTHER 24 HOURS...WHICH IS EXPECTED TO OFFSET THE FAVORABLE OCEANIC CONDITIONS OF 27-28C SSTS. NOW THAT DALILA HAS SLOWED DOWN MARKEDLY...COLD UPWELLING BENEATH THE CYCLONE IS ALSO EXPECTED TO BECOME A FACTOR SINCE UPPER-OCEAN HEAT CONTENT VALUES ARE QUITE LOW AT ONLY 3-5 UNITS. EVEN THOUGH THE SHEAR IS FORECAST TO DECREASE TO 5 KT OR SO AFTER 24 HOURS...COOLER WATERS AND DRIER MID-LEVEL AIR ARE EXPECTED TO HINDER THE DEVELOPMENT PROCESS. AS A RESULT...THE OFFICIAL FORECAST IS SIMILAR TO THE PREVIOUS ADVISORY...AND IS A BLEND OF THE SHIPS...LGEM...AND FSSE INTENSITY MODELS. VISIBLE AND MICROWAVE SATELLITE FIXES SUGGEST THAT DALILA HAS SLOWED DOWN CONSIDERABLY AS EXPECTED...AND THE INITIAL MOTION ESTIMATE IS NOW 290/05 KT. THE EXTENSIVE MID-LEVEL RIDGE TO THE NORTH OF DALILA IS EXPECTED TO REMAIN INTACT THROUGH THE 5-DAY FORECAST PERIOD AND KEEP THE CYCLONE MOVING IN A GENERAL WESTWARD DIRECTION. BY 48 HOURS...HOWEVER...THE GFS AND THE ECMWF MODELS INDICATE THAT A SOUTHWESTWARD MOTION COULD OCCUR DUE TO SOME BINARY INTERACTION WITH THE DEVELOPING LARGE DISTURBANCE CURRENTLY LOCATED TO THE EAST OVER THE GULF OF TEHUANTEPEC. GIVEN THE UNCERTAINTY IN THE DEVELOPMENT OF AND INFLUENCE BY THE LATTER FEATURE...BOTH THE REASONING AND THE FORECAST TRACK REMAIN BASICALLY UNCHANGED FROM THE PREVIOUS ADVISORY. FORECAST POSITIONS AND MAX WINDS INIT 02/0300Z 18.2N 106.9W 60 KT 70 MPH 12H 02/1200Z 18.3N 107.4W 65 KT 75 MPH 24H 03/0000Z 18.4N 108.1W 65 KT 75 MPH 36H 03/1200Z 18.4N 108.7W 60 KT 70 MPH 48H 04/0000Z 18.3N 109.3W 55 KT 65 MPH 72H 05/0000Z 18.3N 110.5W 50 KT 60 MPH 96H 06/0000Z 18.4N 112.8W 45 KT 50 MPH 120H 07/0000Z 18.5N 115.8W 35 KT 40 MPH $$ FORECASTER STEWART
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