Attachments
EXECUTIVE SUMMARY
The 1993 tropical season was a challenging period for the Joint Typhoon Warning Center, Guam (JTWC). Although the North Indian Ocean stayed relatively inactive and the Southern Hemisphere followed climatology; the western North Pacific was very active with 38 tropical cyclones. Overall activity was 15 percent above normal. JTWC issued 1146 warnings distnbuted over 280 days. Multiple-storm scenarios in our 53 million square mile area were frequent, occurring for 91 days with two or more cyclones and 29 days with three or more. Det 1, 633 Operational ‘Support Squadron and the USPACOM Satellite Reconnaissance Network supported us with more than 4800 fixes. The 67 storms in the JTWC area of responsibility represented nearly 80 percent of the world’s tropical cyclones.
The season highlights included Ed and Flo's Fujiwhara confrontation for dominance, Yancy striking southern Japan as a thirty-year typhoon, the preponderance of late season storms bringing a record 20 systems to the Philippines, the multiple-centered 1100 nautical mile circulation of Hattie, and the Next Generation Doppler Weather Radar's (NEXRAD) introduction to_ tropical meteorology.
Depicted on the cover graphic is Tropical Storm Ed seen from the Guam NEXRAD. The highlight of the season for our local community was that Guam enjoyed a respite from the five typhoons of 1992, recording only a single gust of 53 knots.
The JTWC track forecast errors for the western North Pacific were 112, 213, and 325 nautical miles at the 24, 48, and 72-hour points. This amounts to four, six, and seven percent improvements on the fifteen-year averages. The climatology-persistence model, CLIPER, trailed JTWC by 15 percent with errors of 129, 245, and 368 nautical miles. Forecast intensity errors were also better than historical averages with 10.7, 17.4, and 22.9 knots compared to 12.5, 19.1, and 23.5. Track forecast errors for the North Indian Ocean and Southern Hemisphere were also good. The two "well-behaved" storms in the Northern [.O. resulted in errors of 125, 198, and 231 nautical miles representing four, ten, and 30 percent improvements. Forecast errors on the 27 Southern Hemisphere cyclones were the lowest in JTWC's 12-year history of forecasting in the region at 102 and 199 nautical miles for the 24 and 48-hour forecast points.