NWS Discussion Paper

National Weather Service Discussion Paper
- Emergency Alert System and NOAA Weather Radio -
April 3, 1997

There will soon be almost certain integration of Emergency Alert System (EAS) and NOAA Weather Radio (NWR) Specific Area Message Encoding (SAME)/decoding, and alerting capability into a wide variety of consumer products. In a relatively short time, these devices will find their way into a large percentage of homes and businesses.

This paper provides preliminary information that may be of value in the design, installation, operation, and future features of EAS equipment and NWR receivers. An important issue mentioned later in this paper and the attachment concerns the NWR 1050 Hz Warning Alarm Tone (WAT) and how EAS equipment may effectively notch it out. This paper will be forwarded to the Federal Communications Commission (FCC) for their consideration in further EAS rule making. In addition, the NWS shall submit a formal recommendation to the FCC in the next few weeks providing further details than are outlined in this paper on 1) adjustments to certain event codes, including new non-weather event codes and 2) limiting the record-keeping requirements for logging events to only those which are mandatory or are of specific interest to the individual EAS broadcasters.

The NWRSAME system was primarily designed to append a digital code and the WAT to NWR broadcasts that contain information about existing or potentially dangerous events or conditions and the geographical area affected. This encoding allows selective detection by receivers used by the public, emergency managers, and commercial and other government organizations. In the future, this coding will be put on the initial transmission of virtually all routinely broadcast messages (such as forecasts, weather roundups, etc.), without the WAT, so they can be used by other types of automated distribution services for routine playback. Included are codes that are used mainly for testing and demonstrations. The NWS uses the "DMO" (demonstration code) for routine system testing and training. This code is not intended for use outside the NWS.

The NWS recently learned that the WAT being generated by NWR stations as part of an NWS voice EAS message is causing problems with many radio and television stations.

The NWRSAME system was designed to send the header code block, provide a delay, and then automatically transmit the WAT. This delay was to allow receiver/decoders time to process the received NWRSAME code, determine if there was a match, and begin to perform such tasks as activating a cable television all-channel override before the WAT was sent. The WAT could then serve as an attention signal or perform some other task to further enhance the warning message. It is this delay, that could range from 1 second up to 15 seconds, that appears to be causing the problem since the WAT was being recorded as part of the EAS message on some EAS decoder/recorders.

The NWS is advising that a "window" of at least 15 seconds after transmission of the SAME/EAS header block be provided to listen for and notch out the WAT before beginning to process the verbal message. In addition, equipment must be able to recognize the presence of voice without the WAT where warnings will be broadcast primarily for EAS Local Primary (LP) stations for their listeners outside a NWR service area.

Regarding the WAT, it appears there is some misunderstanding on the part of some EAS equipment manufacturers about the frequencies of the WAT being used and how quickly it follows the transmission of the last EAS header code block.

The WAT frequency sent by the NWS over the NWR system for tone-activated NWR receivers is 1050 Hz and is transmitted for 8 to 10 seconds. The NWS DOES NOT send any other tone for warning purposes and has no plans to do so in the future. Any previous consideration to use other tones has all been superseded by the NWRSAME system. The NWS is fully committed to the exclusive use of NWRSAME digital header codes with the exception of the existing 1050 Hz WAT as further explained in the attachment.

The WAT will accompany any message for a threat that is occurring or expected within a short period, usually with an onset time of less than six hours and on rare occasions up to 12 hours, and within the established service range of a NWR transmitter (about a 40 mile radius over level terrain). There may be locations in the country where a message related to a hazardous event is transmitted with the SAME code but without the WAT. This will occur when the threat is in an area/county covered by an EAS station such as an LP1, but beyond the normal or established service area of a NWR transmitter. This will allow the EAS station to carry the message to the more distant area without causing NWR receivers in the normal range of a NWR transmitter to activate.

Regarding EAS event codes, the current list of such codes is almost exclusively limited to weather- and hydrologic-related events. This was not done intentionally. The NWS has been using these types of codes on all their messages for years and a similar system did not exist for other types of hazards. The NWS, FCC, and the Federal Emergency Management Agency (FEMA) are aggressively working on a set of more detailed non-weather hazard event codes.

The NWS is proposing an idea for standardization of EAS codes. The exact time and form of implementation depends on FCC procedures and industry comment (to be formally submitted to the FCC as mentioned earlier). If adopted, the NWS and the FCC would have all the details worked out in a few months and an amendment issued to the current EAS code set in Part 11.31 of the FCC rules later this year.

The current NWRSAME/EAS codes for all hazardous events, with five exceptions, end in A for watches and W for warnings. The exceptions are SVR (severe thunderstorm warning), TOR (tornado warning), CEM (civil emergency message), EVI (evacuation immediate), and EAN (emergency action notification-national). The NWS is proposing to the FCC that they adopt a standard convention such that all current and future hazardous event codes, with the exception of EAN, would limit the third character of the code to one of three letters. Those letters are A for watches, W for warnings and E for other emergency messages. This convention would make possible a wider range of simpler consumer receivers without changing the system's current capabilities.

A warning (three-letter code ending in W, i.e., --W) is generally defined as an event that poses a risk to people unless they take some immediate action to protect themselves. For EAS purposes, it would also be the type of event that potentially threatens a significant part of the population in the geographic area. A way of deciding whether to call it a warning and whether to make an EAS broadcast is to ask the following two questions: "Do I want to wake up the entire population of the selected area at 2 a.m. and expect them to take some protective action?" and "Would the failure of everyone not receiving this message directly contribute to the loss of life or injury if they did not take some action?" If the answer to either question is no, then it probably is not appropriate to classify it as a warning or activate EAS. Classic examples of warnings are the tornado, hurricane, toxic/nuclear/biological materials release, a law enforcement event such as a riot or prison break, or dam failure, to name a few.

A watch (three-letter code ending in A, i.e., --A) would generally be for the same events as warnings but where there is not an immediate risk. For most events, the watch would not be appropriate for an EAS alert. Watches would probably be confined to NWR broadcasts, many of which would be preceeded by the WAT, or processed through other communications systems as heads-up type information for people with a special need to know.

The other emergency event message category (three-letter code ending in E, i.e., --E) is still not as well defined as the watch and warning. It is primarily being reserved at this time for future uses. The most likely application will be for certain kinds of non-weather threats.

If final agreement on this coding convention can be reached, it will be possible to change the existing four exceptions with little or no impact on the EAS or NWR system. Recommended changes would be TOR to TOW, SVR to STW, CEM to CHW, and EVI to IEW (Immediate Evacuation Warning).

If you have any questions or would like to offer some comments for our consideration, please let us know at the following:

Rod Becker - W/OM11
Dissemination Program Manager
NOAA/National Weather Service
1325 East-West Highway
Silver Spring, MD 20910

e-mail: Rodney.Becker@noaa.gov
ph. 301-713-0090 ext.114

Stan Johnson - W/OSO153
NOAA Weather Radio Program Manager
NOAA/National Weather Service
1325 East-West Highway
Silver Spring, MD 20910

e-mail: Stanley.Johnson@noaa.gov
ph. 301-713-1736 ext. 128

NOAA WEATHER RADIO (NWR) ORDER OF SEQUENCE:
Specific Area Message Encoding (SAME) Code Followed by the 1050 Hertz Warning Alarm Tone (WAT).

For the National Weather Service (NWS) to ensure the greatest possible level of safety to users of NWR receivers, there is no other option but to transmit the WAT AFTER the NWRSAME code. This will not cause any problems with properly designed Emergency Alert System (EAS) receivers/decoders. This attachment provides an explanation for this decision.

The NWR has a large and undefinable listening audience separate and apart from the EAS and the broadcast media. The NWR also has a primary service requirement of being the Federal Government's only broadcast system to deliver warnings directly to the general public -- "The Voice of the NWS."

Experts in the field of human psychology related to communicating emergency information are all in general agreement that it is extremely important to get the attention of the person before the information is actually broadcast. The only way to assure this to NWR listeners with future NWRSAME-activated receivers is by using the WAT after SAME codes. Receivers with NWRSAME decoding capability at "general public level" prices are likely to appear on the market before the end of this year.

The use of the NWRSAME code and the need for an attention signal will not be limited to stand-alone NWR receivers. People will create a multitude of uses for this service that have yet to be defined. For example, some private and public two-way land mobile services are automatically passing warnings on to their units in the field.

For almost the exact same reasons above, the Federal Communications Commission, (FCC) established the EAS rules such that the old Emergency Broadcast System (EBS) tones would not only continue to be transmitted but transmitted after the EAS codes were sent. There are sizeable numbers of EBS tone activated warning receivers in the hands of the public around nuclear power plants and chemical weapons storage facilities to name a few. While these will be phased out in time, they too must be supported for some time. This ensures people monitoring an EAS station are provided an attention signal prior to broadcast of the actual text of the message.

The only place where this coding/attention signal sequence becomes an issue is when EAS devices may be interfaced to a NWR transmitter. However, the NWR WAT tone can be notched out using the same technology to notch the EBS tones coming from an upstream EAS station (so that the downstream devices can regenerate the EBS tones).