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| #44181 (Received by flhurricane at: 4:52 PM 05.Sep.2005) TCDAT5 TROPICAL DEPRESSION FIFTEEN DISCUSSION NUMBER 1 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 5 PM EDT MON SEP 05 2005 SATELLITE DATA DURING THE DAY INDICATE THAT THE LOW PRESSURE SYSTEM SOUTH-SOUTHWEST OF BERMUDA HAS NOW ACQUIRED ENOUGH ORGANIZATION TO BE STARTED AS TROPICAL DEPRESSION FIFTEEN. DEEP CONVECTION HAS DEVELOPED NEAR AND TO THE EAST OF THE CENTER WHICH HAS MEANDERED IN A CYCLONIC LOOP FOR MOST OF THE DAY. BANDING FEATURES HAVE ALSO BECOME MORE WELL DEFINED. THE SYSTEM LIES NEAR A MID/UPPER LEVEL RIDGE AXIS WHICH EXTENDS SOUTHWEST FROM THE DEPRESSION TO THE BAHAMAS...WITH GOOD UPPER LEVEL OUTFLOW IN THE SOUTHERN SEMICIRCLE. THE RIDGE AXIS IS EXPECTED TO DRIFT NORTH OVER THE NEXT FEW DAYS...WHICH SHOULD ALLOW FOR CONTINUED SLOW STRENGTHENING OF THE CYCLONE THROUGH ABOUT 72 HOURS UNDER LIGHT SHEAR. BEYOND THIS TIME...THE SYSTEM IS FORECAST TO GET CAUGHT IN THE WESTERLIES ASSOCIATED WITH A LONGWAVE TROUGH MOVING OFF THE EASTERN U.S. COAST. THIS SHOULD INCREASE THE SHEAR AND PUT AN END TO THE INTENSIFICATION. SHIPS MODEL GUIDANCE FOLLOWS THIS TREND...PEAKING THE INTENSITY AT 60 KT BEYOND 72 HOURS. THE OFFICIAL FORECAST IS CLOSE TO SHIPS THROUGH 48 HOURS...THEN CONSERVATIVELY PEAKING AT 50 KT AT 72 HOURS AND BEYOND. THE SYSTEM COULD STRENGTHEN MORE THAN INDICATED...ESPECIALLY DURING THE FIRST 72 HOURS UNDER THE FAVORABLE UPPER LEVEL ENVIRONMENT. AS MENTIONED ABOVE...THE DEPRESSION HAS MEANDERED IN A CYCLONIC LOOP DURING THE PAST 6 HOURS AFTER A SLOW NORTHWEST MOTION LAST NIGHT. BECAUSE OF THIS CHANGE IN THE SHORT TERM MOTION...THE INITIAL INTENSITY IS SET TO STATIONARY. STEERING CURRENTS WILL REMAIN WEAK FOR THE NEXT FEW DAYS AS THE MID/UPPER LEVEL RIDGE HOVERS NEAR THE SYSTEM. BEYOND 72 HOURS...GLOBAL MODELS AGREE ON A LONGWAVE TROUGH MOVING OFF THE EASTERN U.S. COAST. THIS SHOULD WEAKEN THE MID/UPPER LEVEL RIDGE AND START TURNING THE CYCLONE TO THE NORTH AND NORTHEAST BY THE END OF THE FORECAST PERIOD. TRACK GUIDANCE IS QUITE SCATTERED AS CAN BE EXPECTED WITH A SYSTEM UNDER WEAK STEERING CURRENTS...WITH THE GFS AND U.K. MET OFFICE MODELS MOVING THE CYCLONE VERY LITTLE FOR ABOUT 48 HOURS...FOLLOWED BY A MOTION TO THE NORTH AND NORTHEAST IN THE LATTER PORTION OF THE FORECAST. THE NOGAPS MODEL MOVES THE SYSTEM FASTER TO THE WEST-NORTHWEST THROUGH 72 HOURS BEFORE RECURVATURE. THE GFDL MODEL IS SIMILAR...BUT SLOWER...TO THE NOGAPS. THE FORECAST TRACK IS CLOSE TO THAT OF THE GFDL...EXCEPT SOMEWHAT SLOWER DUE TO THE INITIAL STATIONARY MOTION. FORECASTER MOLLEDA/PASCH FORECAST POSITIONS AND MAX WINDS INITIAL 05/2100Z 27.8N 67.5W 25 KT 12HR VT 06/0600Z 27.8N 67.5W 30 KT 24HR VT 06/1800Z 27.9N 68.2W 35 KT 36HR VT 07/0600Z 28.0N 69.0W 40 KT 48HR VT 07/1800Z 28.3N 70.0W 45 KT 72HR VT 08/1800Z 29.5N 72.0W 50 KT 96HR VT 09/1800Z 31.0N 72.5W 50 KT 120HR VT 10/1800Z 32.0N 70.5W 50 KT |
