Joint Typhoon Warning Center

The origins of the Joint Typhoon Warning Center (JTWC) can be traced back to June 1945, when the Fleet Weather Center/Typhoon Tracking Center was established on the island of Guam, after multiple typhoons, including Typhoon Cobra of December 1944 and Typhoon Connie in June 1945, had caused a significant loss of men and ships. At that time, the center was one of three Navy and two Air Force units responsible for tropical cyclone reconnaissance and warnings in the Pacific. During 1958, the United States Department of Defense weather services and the Weather Bureau formed the Joint Meteorology Committee to the Pacific Command and proposed the formation of a joint Navy and Air Force center for typhoon analysis and forecasting. A committee was subsequently set up to study the issue which issued a report during January 1959, which gave recommendation that the center be set up. It was relocated to Pearl Harbor on January 1, 1999, due to the 1995 Base Realignment and Closure Commission round. During October 2011, the JTWC's name changed from the "Naval Maritime Forecast Center/Joint Typhoon Warning Center" to just the Joint Typhoon Warning Center, as it became a stand-alone command for the first time in its 52-year history. Alternate Joint Typhoon Warning Center In case of debilitation of the agency, the Alternative Joint Typhoon Warning Center (AJTWC) assumes JTWC's functions. The AJTWC was first designated as the Tokyo Weather Central by the Fleet Weather Facility in Yokosuka, Japan, The first time the AJTWC had to activate was after Typhoon Omar passed above Guam in 1992, incapacitating the JTWC for 11 days. The AJTWC was then relocated back to Yokosuka as part of the 1995 Base Realignment and Closure Commission. ==Standards and practices==

The center is staffed by about 61 U.S. Air Force and Navy personnel . and used since 1988. It was adapted for use at the National Hurricane Center (NHC) in 1990. JTWC adheres to the World Meteorological Organization's (WMO) rules for storm names and adheres to acknowledged guidelines for intensity of tropical cyclones and tropical storms, with the exception of using the U.S. standard of measuring sustained winds for 1-min instead of the 10-min span recommended by the WMO (see Saffir-Simpson Hurricane Scale). The JTWC is not one of the WMO designated Regional Specialized Meteorological Centres, nor one of its Tropical cyclone warning centers, as its main mission is to support the United States government agencies. JTWC monitors, analyzes, and forecasts tropical cyclone formation, development, and movement year round. Its area of responsibility covers 89% of the world's tropical cyclone activity. The way the JTWC labels tropical cyclones vary depending on the location and intensity of the cyclone. A scale is used for systems in the Western Pacific based on the wind speed. Elsewhere of the agency's responsibility area, all systems with a wind speed of at least 34 knots (63 km/h) are labeled as "Tropical Cyclone", regardless of the estimated intensity. The numbers are rotated for each time a disturbance forms within a basin, meaning the next invest in the same basin after 99 would be numbered 90. ==Products==

Tropical Cyclone Warnings A tropical cyclone warning is a text message issued on a tropical cyclone by the JTWC. It contains the storm's position and direction, wind speed and the wind distribution, the forecasts of them, and the remarks of the information. Warnings are updated every six hours for the North Pacific and North Indian Ocean (00Z, 06Z, 12Z, 18Z), and are updated every twelve hours for the South Pacific and South Indian Ocean (00Z, 12Z). For a warning to be issued, a storm system must meet one or more of the following criteria: Prior to June 21, 2021, only tropical cyclones in the Western Pacific had their own Prognostic Reasoning Message, and those in the Indian Ocean would have the discussion in the remarks section of warning text messages. Tropical Cyclone Formation Alert A Tropical Cyclone Formation Alert (TCFA) is issued when an area of disturbed weather (designated an invest) has a high chance to develop into a tropical cyclone within the following 24 hours. The necessity of such issuance is based on data gathered on the synoptic scale, and utilizes satellite or other pertinent data. The JTWC follows a checklist to determine whether or not a TCFA should be issued on tropical disturbances. The checklist contains five sections and a miscellaneous section for special cases, covering conditions in the atmosphere starting from the surface to 200 millibar level ( above the surface) as well as sea surface temperatures, while also utilizing the Dvorak technique. If there are a total of at least 35 points, a TCFA shall be issued. Annual Tropical Cyclone Report An Annual Tropical Cyclone Report (ATCR) is prepared by the staff of the JTWC, describing operationally or meteorologically significant cyclones that occurred within the JTWC's responsibility area. Details highlight significant challenges and/or shortfalls in the tropical cyclone warning system and serve as a focal point for future research and development efforts. Also included are tropical cyclone reconnaissance statistics and a summary of research and development efforts, operational tactics, techniques and procedure development, and outreach that members of the JTWC conducted or contributed to throughout the year. . ==See also==