Marine Glossary

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NEXRAD

Acronym for "Next Generation Weather Radar", which uses the Doppler effect to enhance the resolution of precipitation echoes and can even detect wind patterns. The actual radar unit used is called the Weather Surveillance Radar 1988 Doppler (WSR-88D), it was developed as a collaboration among the National Weather Service, the Federal Aviation Administration, and the Department of Defense.

A primary motivation for this technology was to predict tornados in the Midwest and microbursts at various airports. NEXRAD data are available from some 50 sites as of mid 1994 with new sites becoming available about once a week. More than 100 sites are planned, although only the coastal installations will have a direct influence on improving marine weather reporting and forecasting. The WSR-88D uses 10-cm radar with a 28-foot radar dish, and 1° beam width. Maximum range is about 250 nautical miles from the unit. Reflected signals must be processed by computer to optimize the information obtained.

NEXRAD maps give up to the minute data on winds and precipitation as well as cloud cover and many other products. It is state of the art information. Unlike other government weather products, however, NEXRAD data are not available directly from the government but rather through any 1 of 4 private companies who have contracted to distribute them — a similar system, by the way, will be used in the near future to distribute the new electronic nautical chart products of the government intended to be used on computers.

NEXRAD products are available via computer modem transfer to individuals, or by home fax machine. These are the typical radar maps shown on TV weather reports. Marine users already have access to this data as the information is incorporated into NOAA Weather Radio reports where applicable. As the system develops, graphics products are also likely to be available via marine radiofacsimile. Waters such as those in Florida and the Gulf Coast subject to frequent squalls especially benefit from this service as these systems can identify local squall winds where earlier technology could not. See Source Book on computer sources of weather information.

Check our web page (http://www.starpath.com) for recent internet references on NEXRAD, including near-live examples from around the country and lists of related articles and terminology, and user's guides.