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Awesome discussion...Kudos Mr Stewart...probably the best of the season! 028 WTNT44 KNHC 130304 TCDAT4 TROPICAL DEPRESSION NINE DISCUSSION NUMBER 5 NATIONAL WEATHER SERVICE MIAMI FL 11 PM EDT THU SEP 12 2002 TROPICAL DEPRESSION NINE HAS CONTINUED TO BECOME BETTER ORGANIZED...AT LEAST IN THE LOW-LEVELS. SURFACE OBSERVATIONS AND SATELLITE MICROWAVE IMAGERY INDICATE THE DEPRESSION HAS A TIGHT INNER CORE WIND FIELD WHILE THE OUTER WIND FIELD HAS ALSO EXPANDED AND STRENGTHENED...MAINLY IN THE EASTERN SEMICIRCLE. A SMALL BURST OF DEEP CONVECTION HAS DEVELOPED JUST SOUTH OF THE WELL-DEFINED SURFACE CENTER AND BANDING HAS IMPROVED TO THE EAST. THE INITIAL INTENSITY OF 30 KT IS BASED ON 2 SHIPS LOCATED WITHIN 30 NMI SOUTHEAST AND SOUTHWEST OF CENTER THAT REPORTED 30 KT AND A PRESSURE OF 1003.6 MB. A RECON AIRCRAFT IS CURRENTLY INVESTIGATING THE SYSTEM. THE DEPRESSION HAS ESSENTIALLY BEEN STATIONARY THE PAST 3 HOURS AFTER LOOPING TO THE SOUTH AT AROUND 6 KT. HOWEVER...A GENERAL SLOW DRIFT TO THE NORTH IS EXPECTED TO RESUME LATER TONIGHT WITH A GRADUAL INCREASE IN FORWARD SPEED. THERE HAS BEEN A MAJOR WESTWARD SHIFT BY ALL OF THE MODEL GUIDANCE FOR THIS ADVISORY PACKAGE...WITH THE GFDL AND GFDN MODELS BEING THE FARTHEST WEST OVER THE SOUTHEAST TIP OF LOUISIANA IN ABOUT 24 HOURS. HOWEVER...INFORMATION FROM A GULFSTREAM-IV AIRCRAFT OVERFLYING THE CYCLONE INDICATES THAT WHILE THE MID- AND UPPER-LEVEL SHEAR HAS WEAKENED...THE FLOW WAS STILL FROM THE WEST ON THE WEST SIDE. 00Z UPPER-AIR DATA SHOWS THAT 500 MB HEIGHTS HAVE RISEN ABOUT 30 TO 40 METERS ACROSS FLORIDA AND CUBA DURING THE PAST 24 HOURS...WHICH INDICATES THAT THE SUBTROPICAL RIDGE IS BUILDING TO THE SOUTH OF THE DEPRESSION. THE INCREASED MID-LEVEL RIDGING TO THE EAST AND SOUTH SHOULD GRADUALLY BEGIN TO NUDGE THE CYCLONE NORTHWARD. WHILE THE NHC MODEL SUITE HAS SHIFTED WESTWARD...IT IS MORE TIGHTLY PACKED THAN ON PREVIOUS ADVISORIES. THE GFDL AND GFDN KEEP THE DEPRESSION SHALLOW AND WEAK...WHICH PROBABLY EXPLAINS THE MORE WESTWARD TRACK AS THE CYCLONE GETS STEERED MORE BY THE LOW-LEVEL EASTERLY FLOW. HOWEVER...THE OFFICIAL FORECAST CALLS FOR A STRONGER AND DEEPER SYSTEM TO BE STEERED MORE NORTHWARD BY THE BUILDING RIDGE TO THE EAST THROUGH 24 HOURS AND THEN TURN TOWARD THE NORTHEAST AFTER THAT AS AN APPROACHING UPPER-LEVEL TROUGH PICKS UP THE CYCLONE. ALSO...WITH SOME WESTWARD UPPER-LEVEL FLOW COMPONENT IMPINGING ON THE CYCLONE THROUGHOUT THE PERIOD...A MORE EASTWARD BIAS IS EXPECTED. THE OFFICIAL FORECAST TRACK IS A LITTLE WEST OF THE PREVIOUS TRACK AND IS BETWEEN THE AVN AND UKMET SOLUTIONS. IMPORTANT NOTE...A MORE WESTWARD TRACK THAN WHAT IS CURRENTLY FORECAST WOULD REQUIRE THE ISSUANCE OF TROPICAL STORM WARNINGS FOR SOUTHEAST LOUISIANA AND THE REMAINDER OF THE MISSISSIPPI GULF COAST BY FRIDAY MORNING. WHILE THE UPPER-LEVEL SHEAR HAS WEAKENED AND IS FORECAST TO WEAKEN EVEN MORE PRIOR TO LANDFALL...THE PRESENCE OF DRY AIR TO THE WEST OF THE CYCLONE SHOULD HINDER THE DEVELOPMENT PROCESS. HOWEVER...BY 24 TO 36 HOURS...THE AVN MODEL IS FORECASTING A WEAK RIDGE TO DEVELOP ABOVE THE CYCLONE WHICH MAY ALLOW FOR A BRIEF PERIOD OF MORE SIGNIFICANT STRENGTHENING TO OCCUR. THE SHIPS INTENSITY MODEL WAS CLOSELY FOLLOWED AND IT BRINGS THE SYSTEM TO 45 KT IN 36 HOURS. FORECASTER STEWART FORECAST POSITIONS AND MAX WINDS INITIAL 13/0300Z 26.6N 87.9W 30 KTS 12HR VT 13/1200Z 27.5N 88.0W 35 KTS 24HR VT 14/0000Z 29.0N 88.0W 45 KTS 36HR VT 14/1200Z 30.9N 86.9W 50 KTS...INLAND 48HR VT 15/0000Z 32.8N 84.8W 30 KTS...REMNANT LOW INLAND 72HR VT 16/0000Z 35.5N 79.5W 25 KTS...INLAND LOW |