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Here is the 11pm Discussion: WTNT43 KNHC 270339 TCDAT3 TROPICAL DEPRESSION LILI DISCUSSION NUMBER 22 NATIONAL WEATHER SERVICE MIAMI FL 11 PM EDT THU SEP 26 2002 A 26/2319Z QUIKSCAT OVERPASS INDICATED THAT THE REMNANT LOW PRESSURE SYSTEM ASSOCIATED WITH LILI HAS BECOME MUCH BETTER ORGANIZED AND THAT A WELL-DEFINED CLOSED CIRCULATION IN THE LOW-LEVEL WIND FIELD NOW EXISTS. IN ADDITION...A 26/2309Z SSMI MICROWAVE OVERPASS INDICATED A TIGHT LOW-LEVEL CIRCULATION JUST SOUTHWEST OF THE STRONGEST CONVECTION. CLOUD TOPS HAVE ALSO COOLED TO -80 TO -85C DURING THE PAST 4 HOURS AND THE OVERALL CONVECTIVE PATTERN HAS CONTINUED TO IMPROVED...EVEN THOUGH IT IS STILL SHEARED. BASED ON THIS INFORMATION...ADVISORIES HAVE BEEN RE-INITIATED ON TROPICAL DEPRESSION LILI. THE INITIAL INTENSITY OF 30 KT IS CONSERVATIVELY BASED ON QUIKSCAT WIND DATA. HOWEVER... SATELLITE INTENSITY ESTIMATES FROM TAFB AND SAB ARE 45 KT AND 35 KT...RESPECTIVELY...AND STRONGER WINDS IN GUSTS TO TROPICAL STORM FORCE LIKELY EXIST IN THE DEEPER CONVECTION THAT IS SHEARED TO THE NORTH AND EAST OF THE CENTER. AN AIR FORCE RESERVE RECONNAISSANCE AIRCRAFT WILL INVESTIGATE THE CYCLONE FRIDAY MORNING AND WILL PROVIDE A BETTER ASSESSMENT OF THE LOCATION AND INTENSITY THE INITIAL MOTION ESTIMATE IS 300/05...WITH EMPHASIS ON THE WORD ESTIMATE. THE NHC MODEL GUIDANCE IS IN GOOD AGREEMENT ON LILI MOVING WEST-NORTHWEST TO NORTHWESTWARD NEAR THE EASTERN TIP OF JAMAICA IN ABOUT 36 HOURS...AND THEN TURNING MORE WEST-NORTHWEST OR WESTWARD AFTER 48 HOURS ONCE LILI CLEARS JAMAICA. THE FORWARD SPEED OF LILI IS PROBLEMATIC WITH MODEL SPEEDS RANGING FROM AS LOW 5 KT BY THE AVN/GFS MODEL AND AS HIGH AS 12 KT BY THE NOGAPS MODEL. THE OFFICIAL TRACK WILL USE A MIDDLE-OF-THE-ROAD VALUE OF 7 TO 8 KT UNTIL A GOOD CENTER LOCATION AND INITIAL FORWARD MOTION CAN BE ESTABLISHED BY RECON DATA. THE UPPER-LEVEL SHEAR THAT HAS BEEN HINDERING LILIS DEVELOPMENT THE PAST FEW DAYS HAS SHOWN SIGNS OF LETTING UP SOME DURING THE PAST 12 HOURS. HOWEVER...SIGNIFICANT SHEAR STILL EXISTS AND ALL OF THE GLOBAL MODELS HAVE BEEN TOO QUICK IN FORECASTING THE SHEAR TO LET UP. BY 36 HOURS...THOUGH...ALL OF THE MODELS INDICATE THE ELONGATED UPPER-LEVEL TROUGH TO THE WEST OF LILI WILL WEAKEN AND MOVE RAPIDLY WESTWARD...WHICH WILL PLACE LILI UNDER MORE FAVORABLE EASTERLY UPPER-LEVEL FLOW. HOWEVER...UNTIL THE CENTER CONSOLIDATES WITHIN THE DEEP CONVECTION...THE OFFICIAL INTENSITY FORECAST WILL REMAIN BELOW THE SHIPS INTENSITY MODEL FORECAST...WHICH BRINGS LILI TO 75 KT IN 72 HOURS. FORECASTER STEWART FORECAST POSITIONS AND MAX WINDS INITIAL 27/0300Z 15.7N 73.5W 30 KTS 12HR VT 27/1200Z 16.2N 74.3W 35 KTS 24HR VT 28/0000Z 17.0N 75.3W 40 KTS 36HR VT 28/1200Z 18.0N 76.3W 45 KTS 48HR VT 29/0000Z 18.9N 77.5W 50 KTS 72HR VT 30/0000Z 20.5N 80.5W 60 KTS ED |