Joint Typhoon Warning Center

The Joint Typhoon Warning Center (JTWC) is a joint United States Navy – United States Air Force task force located in Pearl Harbor, Hawaii. The JTWC is responsible for the issuing of tropical cyclone warnings in the North West Pacific Ocean, South Pacific Ocean and Indian Ocean for United States Department of Defense interests, as well as U.S. and Micronesian civilian interests within the command's area of responsibility (AOR). The JTWC provides support to all branches of the U.S. Department of Defense and other U.S. government agencies. Their products are intended for the protection of primarily military ships and aircraft as well as military installations jointly operated with other countries around the world.

History
The beginning of the formation of a typhoon warning center in the Pacific occurred in the wake of Typhoon Cobra on December 18, 1944. A small but significant typhoon east of the Philippines, Typhoon Cobra led to the largest naval disaster in United States history with 790 lives lost, and was the worst United States military loss from a tropical cyclone impact since 1889. Due to this typhoon, weather stations were established in Caroline Islands, and eventually in Manila, Iwo Jima, and Okinawa. New weather central offices (for coordinating data) were established at Guam and Leyte. JTWC was originally established in 1959 at Nimitz Hill, Guam combined the efforts of the former naval centers located in Guam, Hawaii, and the Philippines with the Air Force center in Japan. In November 1962, Typhoon Karen destroyed the building housing the Fleet Weather Center/Joint Typhoon Warning Center. It relocated in a more typhoon-proof building in 1965. It was relocated to Pearl Harbor on January 1, 1999 due to the 1995 Base Realignment and Closure (BRAC) round. <!-- JTWC Mission: Provide tropical cyclone analysis, forecast and warning support for Department of Defense, and other US Government assets in the Pacific and Indian Oceans as established by Commander, United States Pacific Command Today’s Joint Typhoon Warning Center traces its origins to June 1945, when the Fleet Weather Center (FWC)/Typhoon Tracking Center was established on Guam after the Pacific Fleet experienced significant loss of men and ships in the typhoons of December 1944 and June 1945. The Typhoon Tracking Center was one of three Navy and two Air Force units responsible for tropical cyclone reconnaissance and warnings in the Pacific. In 1950, the Department of the Navy authorized Fleet Weather Central to provide weather services to civil agencies and the general public on Guam, a service that was expanded in 1953 to include all the Trust Territories of the Pacific Islands. To this day, the Department of Defense is responsible for typhoon warnings for the Federated States of Micronesia.

In 1958, the Department of Defense weather services and the U.S. Weather Bureau formed the Joint Meteorology Committee to U.S. Pacific Command, and by June of that year, proposed the formation of a joint Navy and Air Force center for analysis and forecasting of typhoons. After approval by the Joint Chiefs of Staff, the Commander in Chief, U.S. Pacific Command, directed the formation of a Joint Typhoon Warning Center (JTWC) at Nimitz Hill, Guam, under the Commanding Officer of Fleet Weather Central (FWC) with an Air Force Officer designated as the Director. The JTWC was initially chartered to provide warnings on all tropical cyclones west of 180 degrees longitude to affected U.S. government agencies, determine typhoon reconnaissance requirements, prepare annual typhoon summaries, and conduct tropical cyclone forecast and detection research as practicable. Two officers and three enlisted personnel from each Service prepared those first warnings, issued four times daily, forecasting position and intensity through the next 48 hours. Since 1958, the mission has remained largely unchanged, while the area of responsibility has expanded to include the entire Pacific and Indian Ocean basins.

Housing JTWC did not exempt the FWC from the impacts of typhoons, as demonstrated by Typhoon Karen in November 1962 when the storm destroyed the building they occupied, causing the eventual relocation of FWC/JTWC to a more typhoon proof building in 1965. In 1974 the JTWC area of responsibility expanded to include the whole of the Northern Indian Ocean, and in 1980 the Southern Hemisphere was added to the mix.Manned aerial weather reconnaissance began in January 1945 with the arrival of the 655th Bombardment Squadron on Guam. The B-24 aircraft were used to conduct en route and target weather reconnaissance. However it wasn’t until June of that year that the 655th was re-designated the 55th Reconnaissance Squadron, that the first typhoon reconnaissance occurred. In 1945, the 54th Weather Reconnaissance Squadron was established at Andersen AFB, Guam and the 55th rotated back to the United States. At this time, the weather reconnaissance mission transitioned to the WB-29 airframe. Other aircraft used include the Super Constellation, flown by the Airborne Early Warning Squadron One (VW-1) from Naval Air Station, Guam, and the WC-130. Aerial reconnaissance in the western North Pacific continued until 1987, when the Air Force transitioned the mission to weather satellites. The Defense Meteorological Satellite Program (DMSP) polar orbiting satellites were the mainstay along with National Oceanic and Atmospheric Administration (NOAA) polar orbiters and indigenous geostationary satellites. Satellite reconnaissance continues to be the primary means to assess tropical cyclone location and intensity across the entire JTWC area of responsibility.

JTWC moved to its current location in Hawaii in 1999 after the 1995 Base Realignment and Closure (BRAC) committee recommended the closure of the Naval Pacific Meteorology and Oceanography Center, Guam. The Air Force members of JTWC are administratively assigned to the 17 Operational Weather Squadron, Hickam AFB, Hawaii currently under Command of Lieutenant Colonel Kurt Brueske and the Navy members are assigned to the Naval Maritime Forecast Center under Command of Captain Grant Cooper. A small staff support watch standing/shift working members of JTWC who work 12 hour rotating shifts to maintain a 24 hour per day, 7 day a week, 365 days a year watchful eye for tropical cyclone development. This 2-person team is responsible for determining the center position, current intensity, forecast locations and forecast intensity for 89% of the worlds tropical cyclones. To date, JTWC has issuing warnings on more than 2,500 tropical cyclones throughout its area of responsibility. JTWC’s ability to accurately forecast tropical cyclones has improved significantly over the past 50 years. Verification statistics show today’s 5-day forecast accuracy is about equal to the 2-day forecast accuracy 35 years ago.

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Standards and practices
A more modernized method for forecasting tropical cyclones had become apparent by the 1980s. Prior to the development of ATCF, the tools used by the Department of Defense to forecast tropical cyclone track were acetate. grease pencils, and disparate computer programs. The ATCF software was developed by the Naval Research Laboratory for the JTWC beginning in 1986, 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 centres, as its main mission is to support the United States Navy and remainder of the federal government. 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.

Staffing
The Center is manned by 20 U.S. Air Force and Navy personnel. The JTWC uses several satellite systems and sensors, radar, surface and upper level synoptic data as well as atmospheric models to complete its mission.