EAS - The Emergency Alert System

The Emergency Alert System (or EAS) uses digital technology to transmit and relay warning messages for weather hazards such as tornadoes, flash floods and hurricanes, as well as emergency warning messages for hazardous materials spills or even a nuclear accident. NOAA Weather Radio is part of EAS through the Weather Radio Specific Area Message Encoder (or WRSAME) technology. All radio, television, AND cable outlets are required to have operating EAS encoders/decoders. The EAS encoders/decoders can then be programmed to broadcast the warning directly, and/or retransmit the received warning to other media outlets for broadcast.

Three pulses of digital information are sent at the beginning of each NOAA Weather Radio warning alert. These pulses are digital codes containing the type of warning, the duration of the warning, the agency issuing the warning, and the cities/counties affected by the warning. The three pulses of data AFTER each NOAA Weather Radio tone alert are end of message codes which deactivate EAS equipment and specially equipped NOAA Weather Radio receivers. Even though they don't utilize WRSAME technology, older NOAA Weather Radio receivers activate via the 1050Hz tone, which proceeds all NWS warning messages.

The figure above shows the Virginia EAS Local Areas overlaid on the NOAA Weather Radio programming areas. Each color represents a different NOAA Weather Radio transmitter. The arrows point to either the NOAA Weather Radio transmitter site or to the counties in Virginia programmed on that transmitter. EAS/WRSAME and WRSAME compatible NOAA Weather Radios are programmed with the FIPS (Federal Information Processing System) codes for each locality. These codes are available on the World Wide Web at the National Institute for Standards and Technology (NIST).

If you have further questions, send an e-mail to Bill Sammler .