EMWIN (Emergency Management Weather Information Network) is the name for a datastream that provides free emergency weather information and other related data. In 1995 the National Weather Service recognized the need to provide the emergency management community with access to a set of NWS warnings, watches, forecasts, and other products at no recurring cost. The datastream is distributed through three methods -- Internet, satellite, VHF broadcast.

Funding, volunteer work, and/or technical assistance for EMWIN is provided by the National Weather Service, the Federal Emergency Management Agency, and other public and private organizations.

EMWIN Control Center, National Weather Service

There are three different access methods. Each has its pros and cons, listed in the table below.

Satellite broadcast is one method used to disseminate the datastream. The National Weather Service broadcasts EMWIN on the National Oceanic and Atmospheric Administration's GOES 8 and GOES 10 satellites.

Both satellites are in geostationary orbit 22,000 miles above the equator. GOES 8 is at 75 deg W and GOES 10 is at 135 deg W. The NWS GOES downlink frequency used for the 9600 baud EMWIN datastream is 1690.725 MHz, 275 KHz lower than the standard WEFAX 1691.0 MHz signal.

Coverage of EMWIN signal on GOES satellite

The EMWIN data is also uplinked to a commercial satellite, Telstar 5, as a public service. Telstar 5 is in geostationary orbit at 97 deg W. The EMWIN signal is broadcast on the L-band (12185 MHz), FM-FM, DFSK, 1.065 MHz subcarrier (1435 MHz downconverted).

The signal is received using a 3-foot or larger dish. The signal is then passed through a receiver, low-noise amplifier, and downconverter. It is then converted to a 9600 baud datastream using a demodulator. The data is then extracted by Weathernode software on the user's computer.

Weather Graphics Technologies sells Cyclone, a complete system to receive satellite EMWIN data.

VHF broadcast is one method used mainly by public and private agencies for disseminating parts of the EMWIN datastream in a community and surrounding regions. Some of these rebroadcasts are experimental and could be discontinued at any time.

The broadcasts are usually received on a frequency between 155 and 170 MHz, and are demodulated by special hardware into a 1200 baud signal.

Due to the inherent limitations of the VHF reception method, Weather Graphics Technologies does not market a VHF reception package, however we can provide a price quote on request.

Coverage of EMWIN VHF rebroadcasts

EMWIN Weather data is transmitted by push-pull method to computers equipped with the appropriate software, however this requires a dedicated Internet connection 24 hours a day, and is subject to network degradation and delays during peak Internet load times (during the evening and weekends).