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The JTWC works closely with NOAA, with which the National Weather Service Pacific in Honolulu and the National Hurricane Center in Miami are essential collaboration partners. Internationally, the JTWC works with the World Meteorological Organization’s designated Regional Specialized Meteorological Centers across the Pacific.
The JTWC’s area of responsibility for typhoon forecasting is west of the international dateline, covering both the northern and southern hemispheres of the Pacific Ocean. While the Atlantic hurricane season extends from June 1 to Nov. 30, the JTWC’s forecasting season is year-round. According to Evans, the JTWC tracks about 80 tropical cyclones each year.
Super Typhoon Haiyan, which ravaged much of the Philippines and other areas of Southeast Asia in November 2013, was typical of the many tropical cyclones the JTWC tracks. “We started tracking Haiyan around Nov. 1, and we knew it was going to get big,” Evans says. “We were tracking it specifically for DoD equities. There were none except for planning of the eventual disaster response.”
While the JTWC was monitoring Haiyan on behalf of DoD, the Japan Meteorological Agency — the World Meteorological Organization’s Regional Specialized Meteorological Center responsible for issuing the official forecasts and warnings for that region — also was keeping an eye on the storm. In addition, the Philippine Atmospheric, Geophysical, and Astronomical Services Administration tracked Haiyan (known as Typhoon Yolanda in the Philippines) on the national level, Evans says.
Because of advances in technology, tracking tropical storms such as Haiyan is much easier today than it was when the JTWC first was stood up, Evans reports. In the 1950s, surface observations were collected to create a surface analysis chart, which provided tropical storm forecasts out to 36 hours. Special typhoon-hunter planes often flew into storms to collect data, which were supplemented with reports from ships and land bases to provide an accurate analysis of storm position and intensity.
Typhoon monitoring capability improved dramatically in the 1960s with the introduction of geostationary and, later, polar-orbiting weather satellites, which greatly enhanced wide-area tropical cyclone surveillance by the JTWC and other organizations monitoring weather across the vast Pacific region. “Satellites were an immediate game changer,” Evans says. “For the first time, we could actually see weather occurring in remote areas of the Pacific Ocean.”
Satellites combined with powerful computers allowed for more accurate weather-prediction forecasting models. In the 1980s, the decision was made to halt the use of typhoon-hunter planes, which the Air Force provided, in the western Pacific. “Today, we do the bulk of our storm position and intensity estimates based on interpretation of satellite images combined with other data,” Evans says. [CONTINUES ON PAGE 76]
Military Officer Ask the Doctor columnist Rear Adm. Joyce Johnson, USPHS (Ret), D.O., deployed to the Philippines as a volunteer with Project HOPE soon after Typhoon Haiyan made landfall. Read about her experience in the February 2014 issue at www.moaa.org/moarchive.