Feature

NASA Marks the Joint Typhoon Warning Center's 50th Anniversary
12.08.09
 
This year, the Joint Typhoon Warning Center (JTWC) turns 50 years old, and NASA is proud to be one of their partners in tropical cyclone forecasting and research.

Screen capture of the JTWC website> View larger image
This is the front Web page for the Joint Typhoon Warning Center. Credit: JTWC
JTWC is a joint U.S. Navy and U.S. Air Force office that includes Navy, Air Force and civilian meteorologists and satellite analysts. The center, located in Pearl Harbor, Hawaii, provides forecasts, advisories and warnings on tropical cyclones (the generic name for a typhoon, cyclone, hurricane, tropical storm or tropical depression).

NASA does not forecast tropical cyclones, but provides satellite data to the JTWC to enable meteorologists there to create forecasts for tropical cyclones in the Western Pacific, Indian Ocean and southern hemisphere. In turn, NASA posts JTWC's forecasts for cyclones that occur in these regions on the NASA Hurricane and Tropical Cyclone page.

JTWC provides tropical cyclone reconnaissance and forecasting to support the safety of military and other government assets in the U.S. Pacific Command and U.S. Central Command areas of responsibility. JTWC forecasters there use NASA, and National Oceanic and Atmospheric Administration (NOAA), Defense Meteorological Satellite Program (DMSP), and foreign satellite sensors, in addition to shore, buoy, ship, and aircraft observations and surface radar imagery. They also utilize the forecasts produced by computer models operated by the United States, Japan, Australia, the United Kingdom, and the European Center for Medium Range Weather Forecasts in the production of tropical cyclone forecasts.

TRMM image of Typhoon Melor> View larger image
JTWC uses TRMM satellite images like this one to assist with their forecasts. Here, TRMM captured Category 4 Typhoon Melor at 14:29 UTC on October 5. Melor had a nearly complete inner eyewall (the innermost bright green ring indicates moderate rain), surrounded by moderate rain (wider ring of bright green). Credit: SSAI/NASA, Hal Pierce
Bill Patzert, climate scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif. said, "For the JTWC, hurricane, cyclone and typhoon forecasting is a year-round job. When the seasons switch hemispheres, the JTWC follows. They are a 24/7, all year center. For the Western Pacific and Indian Oceans (in both hemispheres), the Center is the go-to cyclone forecasting group. For the past 50 years, they have not only insured the safety of America's fighting forces, but also served the many nations of the Western Pacific and Indian Oceans. Also, for all scientists, the JTWC archive is an invaluable scientific resource."

Up until it’s recent failure, the center routinely used NASA QuikSCAT scatterometer-derived ocean surface wind vectors (speed and direction) data to monitor storm genesis (determine when systems reach tropical depression status), storm location, and the radius of gale force winds.

Other NASA satellite data used by JTWC include the Tropical Rainfall Measuring Mission’s (TRMM) Microwave Imager (TMI) and its precipitation radar, Aqua’s Advanced Microwave Scanning Radiometer (AMSR-E), the CloudSat cloud radar, and the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard both NASA's Aqua and Terra satellites.

Non-NASA satellites JTWC uses include microwave imagers onboard the DMSP spacecraft (SSM/I and SSMIS sensors), microwave sounders on NOAA's low earth orbiting (LEO) satellites (AMSU), geostationary data from the United States, Japan, and European Space Agency and several other LEO sensors from foreign sources. JTWC also uses data from the Naval Research Laboratory's Windsat instrument. Windsat is a satellite-based polarimetric microwave radiometer that is part of the risk reduction for the National Polar-orbiting Operational Environmental Satellite System (NPOESS).

AIRS image of Typhoon Melor> View larger image
JTWC also uses Aqua's Atmospheric Infrared Sounder (AIRS) data. Here AIRS captured Typhoon Melor's high thunderstorm cloud temperatures (in purple) that were colder than minus 63 Fahrenheit. This image from October 4 at 12:29 EDT clearly shows Melor's eye. Credit: NASA JPL, Ed Olsen
"Because of its vast area of responsibility, which includes the Northwest Pacific Ocean, South Pacific Ocean and Indian Ocean where there are no routine aircraft reconnaissance missions, JTWC must rely heavily on satellite data to obtain fixes or storm positions to track tropical cyclones over the open ocean," said Stephen E. Lang, a Research Meteorologist on the TRMM mission at SSAI and NASA's Goddard Space Flight Center, Greenbelt, Md.

Lang said "In 2004, the last year that JTWC reported detailed statistics on fixes, TRMM accounted for around 16 percent of all position fixes. TRMM's TMI is especially useful in the early stages of storm development because it can see through the upper-level clouds and has the resolution to detect low-level circulations before an eye has formed. This ability means it can also aid in refining estimates of storm intensity."

JTWC's cyclone forecasts include graphical and text products that include the projected storm track, intensity, and extent of the high wind region of each tropical cyclone.

JTWC was established in 1959 by the U.S. Pacific Command to consolidate and improve the United States military tropical cyclone forecasting effort. Prior to the establishment of the JTWC, the U.S. military had numerous tropical forecast centers throughout the Pacific region. The impetus for the establishment of the JTWC was Typhoon Cobra which struck ships of the Pacific Fleet in 1944, killing 790 sailors and sinking three ships, damaging nine others, and destroying 146 aircraft.

The JTWC, the National Hurricane Center and the Central Pacific Hurricane Center provide forecasts that cover all global tropical cyclones around the world. JTWC covers the western Pacific and Indian Oceans both in the northern and southern hemispheres, while NOAA's National Hurricane Center and Central Pacific Hurricane Centers cover the Atlantic and the Pacific region east of the International Dateline.

"NASA salutes the Joint Typhoon Warning Center on behalf the global scientific community and the many large and small nations of the Pacific and Indian Oceans. Many thanks for your 50 years of service," Patzert said.

 
 
Rob Gutro
Goddard Space Flight Center