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| #58364 (Received by flhurricane at: 10:03 PM 24.Nov.2005) TCDAT3 TROPICAL STORM DELTA DISCUSSION NUMBER 6 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 10 PM EST THU NOV 24 2005 DELTA HAS A BAND OF FAIRLY DEEP CONVECTION WITH TOPS COLDER THAN -60C IN THE NORTHEASTERN QUADRANT... BUT THE OVERALL ORGANIZATION OF THE INNER CORE DOES NOT APPEAR TO HAVE CHANGED APPRECIABLY DURING THE PAST FEW HOURS. DVORAK INTENSITY ESTIMATES REMAIN 55 KT... WHILE CIRA AND CIMSS ESTIMATES BASED ON AN AMSU OVERPASS AT 2023Z WERE 60 AND 73 KT RESPECTIVELY. A QUIKSCAT OVERPASS AT ABOUT 21Z PROVIDED SEEMINGLY UNCONTAMINATED WIND SPEED ESTIMATES OF 55 KT JUST OUTSIDE OF THE DEEP CONVECTION... AND THE WINDS ARE LIKELY A LITTLE STRONGER BENEATH THE CONVECTION. THE ADVISORY INTENSITY IS KEPT AT 60 KT USING A BLEND OF THE VARIOUS INTENSITY ESTIMATES. THE QUIKSCAT DATA ALSO REVEAL THAT THE WIND FIELD IS NOT QUITE AS LARGE AS IT WAS PREVIOUSLY... SO THE INITIAL AND FORECAST 34 KT RADII HAVE BEEN DECREASED SOMEWHAT. DELTA HAS BEEN MOVING SLOWLY SOUTHWARD DURING THE PAST SEVERAL HOURS AT ABOUT 5 KT... APPARENTLY INFLUENCED BY THE DEEP-LAYER RIDGE TO ITS WEST. THE DYNAMICAL MODELS... INCLUDING THE GFS AND NOGAPS THAT HAVE INITIALIZED THE POSITION AND MOTION REASONABLY WELL... FORECAST THE RIDGE TO BREAK DOWN ON FRIDAY AND CORRESPONDINGLY FOR DELTA TO EXPERIENCE LITTLE NET MOTION DURING THE NEXT 24 HOURS. WITH A NEW MID- TO UPPER-LEVEL TROUGH FORECAST TO REPLACE THE RIDGE WITHIN A COUPLE OF DAYS... DELTA SHOULD THEN MOVE TO THE NORTH AND EVENTUALLY NORTHEAST AS ANTICIPATED BY ALL OF THE TRACK GUIDANCE. THE NEW OFFICIAL TRACK FORECAST FOLLOWS THIS GENERAL SCENARIO... WHICH IS AN EASTWARD SHIFT COMPARED TO THE PREVIOUS ADVISORY. A POTENTIAL COMPLICATING FACTOR... HOWEVER... IS A SEPARATE SURFACE LOW PRESSURE SYSTEM FORECAST TO DEVELOP WEST OF DELTA IN ASSOCIATION WITH THE NEW MID- TO UPPER-LEVEL TROUGH. THE MODELS GENERALLY AGREE THAT DELTA WILL REMAIN SEPARATED FAR ENOUGH EAST FROM THAT SYSTEM AND NOT BE DRAWN WESTWARD LATE IN THE FORECAST PERIOD... BUT THE EVOLUTION OF THE TWO SYSTEMS IN THE MODELS IS QUITE COMPLEX AND COULD CHANGE. EVEN THOUGH THE OFFICIAL INTENSITY FORECAST AND THE SHIPS GUIDANCE DO NOT ANTICIPATE DELTA BECOMING A HURRICANE... IT COULD STILL DO SO FOR A BRIEF PERIOD DURING THE NEXT 24-36 HOURS WHILE REMAINING SO CLOSE TO THAT INTENSITY. WESTERLY VERTICAL SHEAR SHOULD BEGIN TO INCREASE IN ABOUT 36 HOURS... WHICH SHOULD INDUCE A GRADUAL WEAKENING TREND. THEREAFTER DELTA WILL MOVE NORTHWARD OVER PROGRESSIVELY COOLER WATERS AND EVENTUALLY BECOME EXTRATROPICAL. FORECASTER KNABB FORECAST POSITIONS AND MAX WINDS INITIAL 25/0300Z 23.7N 39.0W 60 KT 12HR VT 25/1200Z 23.4N 39.0W 60 KT 24HR VT 26/0000Z 23.7N 39.0W 60 KT 36HR VT 26/1200Z 24.5N 38.8W 60 KT 48HR VT 27/0000Z 26.1N 38.5W 55 KT 72HR VT 28/0000Z 29.0N 38.0W 50 KT...BECOMING EXTRATROPICAL 96HR VT 29/0000Z 31.5N 37.0W 50 KT...EXTRATROPICAL 120HR VT 30/0000Z 34.0N 34.5W 50 KT...EXTRATROPICAL |
