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#106010 (Received by flhurricane at: 4:55 AM 25.Aug.2006) TCDAT5 TROPICAL DEPRESSION FIVE DISCUSSION NUMBER 3 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL052006 500 AM EDT FRI AUG 25 2006 DESPITE WESTERLY SHEAR... THE TROPICAL DEPRESSION APPEARS TO BE APPROACHING TROPICAL STORM STRENGTH. DEEP CONVECTION HAS INTENSIFIED NEAR THE CENTER WITH IMPROVING BANDING FEATURES IN THE EASTERN SEMICIRCLE. HOWEVER IT APPEARS THE CENTER IS ON THE WESTERN EDGE OF THE THUNDERSTORMS... AS SUGGESTED BY A NOTCH IN THE DEEP CONVECTION PATTERN ON NIGHT-VIS SATELLITE IMAGES. SATELLITE CLASSIFICATIONS RANGE FROM 35-45 KT BUT ARE A LITTLE CLOSER TO THE CENTER OF THE DEEP CONVECTION. WITH THE UNCERTAINITY IN INITIAL POSITION.. 30 KT WILL BE KEPT UNTIL VISIBLE IMAGES ALLOW US TO GET A BETTER HANDLE ON WHERE THE SYSTEM IS LOCATED. THE TRACK FORECAST SEEMS LIKE THE EASIER PART OF THE FORECAST THIS MORNING. THE DEPRESSION IS SPEEDING WESTWARD AT ABOUT THE SAME RATE... 280/17. MIDDLE-LEVEL RIDGING SHOULD REMAIN STRONG OVER THE WESTERN ATLANTIC OCEAN... KEEPING THE SYSTEM MOVING IN A GENERAL WEST TO WEST-NORTHWESTWARD HEADING FOR THE NEXT COUPLE OF DAYS. THE NOGAPS/UKMET SHOW STRONGER RIDGING AND A WEAKER TROPICAL CYCLONE... LEADING TO A TRACK CLOSER TO YUCATAN IN ABOUT 5 DAYS. THE GFS AND GFDL TEMPORARILY WEAKEN THE RIDGE IN A FEW DAYS... WHICH ALLOW A STRONGER SYSTEM TO MOVE TO THE NORTHWEST CLOSER TO CUBA. I'M INCLINED TO STICK CLOSER TO THE FIRST OPTION ... LEADING TO A SMALL WESTWARD SHIFT OF THE TRACK FORECAST. THE INTENSITY FORECAST IS TRICKY TO SAY THE LEAST. FIRST OF ALL... THE SYSTEM HAS TO SURVIVE THE STRONG WESTERLY SHEAR IT WILL BE EXPERIENCING FOR THE NEXT DAY OR TWO. THIS IS BY NO MEANS CERTAIN AND IT WOULDN'T BE A HUGE SURPRISE FOR THE DEPRESSION TO DISSIPATE IN THE "GRAVEYARD" OF THE EASTERN CARIBBEAN SEA... LIKE SOME OF THE GLOBAL MODELS ARE FORECASTING. HOWEVER...IF THE TROPICAL CYCLONE SURVIVES...AND THIS IS A BIG IF...GLOBAL MODELS REMOVE THE SHEAR BY FRACTURING THE MID-OCEANIC TROUGH IN THE WESTERN CARIBBEAN. THIS PATTERN CHANGE SENDS AN UPPER-LEVEL LOW INTO THE GULF OF MEXICO IN 3 DAYS WHILE BUILDING UPPER RIDGING NEAR THE DEPRESSION. THIS COULD ALLOW THE SYSTEM TO STRENGTHEN ESPECIALLY AS IT ENTERS THE WESTERN CARIBBEAN. ON THE OTHER HAND... GLOBAL MODELS HAVE NOTORIOUSLY WEAKENED UPPER-LEVEL CYCLONES TOO QUICKLY IN THE PAST AND THE MID-OCEANIC TROUGH HAS BEEN QUITE PERSISTENT AND STRONGER-THAN- NORMAL IN THAT AREA THIS SEASON. AFTER SAYING ALL THIS... THE INTENSITY FORECAST WILL BE QUITE SIMILAR TO PREVIOUS. HOWEVER IF THE LOW SHEAR ENVIRONMENT THE GLOBAL MODELS ARE FORECASTING MATERIALIZES IN THE WESTERN CARIBBEAN... TD FIVE COULD BE A LOT STRONGER THAN SHOWN BELOW IN THE LATER PERIODS. FORECAST POSITIONS AND MAX WINDS INITIAL 25/0900Z 13.4N 65.7W 30 KT 12HR VT 25/1800Z 13.9N 67.8W 35 KT 24HR VT 26/0600Z 14.8N 70.4W 40 KT 36HR VT 26/1800Z 15.6N 72.8W 45 KT 48HR VT 27/0600Z 16.5N 75.0W 55 KT 72HR VT 28/0600Z 18.5N 79.5W 65 KT 96HR VT 29/0600Z 21.0N 84.0W 65 KT 120HR VT 30/0600Z 23.5N 87.5W 65 KT |