Attachments
Executive Summary
This Annual Tropical Cyclone Report (ATCR) was prepared by the staff of the Joint Typhoon Warning Center (JTWC), a jointly manned United States Navy / Air Force organization.
The Joint Typhoon Warning Center was officially established on 1 May 1959 when the Joint Chiefs of Staff directed the Commander-in-Chief, US Pacific Command (USCINCPAC) to provide a single tropical cyclone warning center for the western North Pacific region. USCINCPAC delegated the tropical cyclone forecast and warning mission to Commander, Pacific Fleet (PACFLT), and subsequently tasked Commander, Pacific Air Force (PACAF) to provide tropical cyclone (TC) reconnaissance support. Since 1959, JTWC’s area of responsibility (AOR) for its TC forecast and warning mission has expanded to include the area from the east coast of Africa to the International Dateline in the northern hemisphere, and from the east coast of Africa to the west coast of the Americas in the southern hemisphere. JTWC also monitors TC activity in the eastern and central Pacific Ocean, coordinating with the National Hurricane Center and Central Pacific Hurricane Center to promulgate warnings and provide tailored support to DOD customers. Altogether, this AOR encompasses approximately 80-million square miles of ocean, and includes portions of five geographic combatant commands. Accurate and timely TC warning and decision support products from JTWC protect life and property of U.S. assets, and enable DOD commanders to sustain operations across an area within which over 80% of global tropical cyclone activity occurs annually.
This edition of the ATCR documents the 2018 TC season, and describes operationally or meteorologically significant cyclones that occurred within the JTWC AOR. Details highlight significant challenges and/or shortfalls in the TC warning system and serve as a focal point for future research and development efforts. Also included are TC reconnaissance statistics and a summary of TC research and development efforts, operational tactics, techniques and procedure (TTP) development, and outreach that members of the JTWC conducted or contributed to throughout the year.
Across all forecast basins for the 2018 storm season (Northern Hemisphere 1 January 2018 through 31 December 2018 + Southern Hemisphere 1 July 2017 through 30 June 2018), JTWC produced 1,350 warnings for 66 tropical cyclones (1,476 warnings for 72 TCs for the 2018 calendar year0F 1), eclipsing the 1,193 warnings that JTWC produced during the strong El Niño event of 2015. The 2018 figure is partially attributable to the large number of TCs in the AOR, and the above-average mean duration of these systems (mean best track length was 1,968 miles). Additionally, 2018 was the first year in which JTWC regularly produced six-hourly forecasts in the southern hemisphere. Without a defined break between JTWC’s multi-hemisphere forecasting responsibilities, the high warning frequency limited the time available for Typhoon Duty Officers and JTWC staff to produce the 2018 post-analyzed best tracks and this report. Figure P-1 (below) shows the timeline of tropical activity across the JTWC AOR for calendar year 2018.
In the western North Pacific, the primary TC genesis region was largely consistent with an ENSOneutral environment. The Oceanic Niño Index (ONI) for the Niño 3.4 region began the year with a weak cold anomaly before turning neutral for the summer months, and then ending the year with weak warm anomalies. There were 36 total warned TCs in the basin, which is one standard deviation above the current 25-year climatological mean of 30. Additionally, one TC that formed in the eastern Pacific (Hector) crossed into the Central Pacific, and then briefly into the western Pacific before dissipating.
Note that JTWC began warning on 36W, “Pabuk”, when it consolidated into a tropical depression on the last day of the year. Therefore, WP36 is included in the 2018 JTWC records, as seen in Figure P1. However, the official RSMC began issuing warnings on Pabuk once it reached tropical storm intensity on the following day (January 1, 2019). A commensurate discrepancy between the agency records may be expected. Broken down by category, the above average number of tropical cyclones is largely attributable to an increased number of tropical storms. The number of typhoons (16) is consistent with the long-term mean, although the number of typhoons which reached super-typhoon status was slightly higher than average (seven versus five, respectively). Accumulated Cyclone Energy (ACE) for the basin registered at the third highest value since 2000, thanks in part to 26W (Mangkhut) and 31W (Yutu), which maintained super typhoon status for extended periods. Both of these systems tracked through the Northern Mariana Islands, with Tinian experiencing a direct hit from Yutu as the cyclone passed over the island with sustained core winds of 150 knots. Super typhoon Maria (detailed in a storm review included in this report) made landfall on Guam as a tropical storm. Five tropical cyclones crossed mainland Japan, and two crossed South Korea. Although frequently under the threat of tropical cyclones, Okinawa experienced only one land-falling tropical storm.