Tsunami Warning Centre Products 2
Tsunami Warning Centre Products 2 : Tsunami Warning Centres issue four basic types of messages: (1) information bulletins when a large earthquake has occurred but there is little or no tsunami threat; (2) local, regional, or oceanwide watch and warning bulletins when there is an imminent tsunami threat; (3) cancellation bulletins when destructive tsunami waves are gone; and (4) tsunami communication test messages to regularly exercise the system. Initial or local evaluations and messages are based only on the faster arriving seismic information, specifically earthquake location, magnitude, and depth. If a tsunami threat is large, estimated tsunami wave arrival times, and possibly wave height forecasts, are reported, and sea level records are examined to confirm tsunami generation. Watch and Warning Bulletins are updated regularly, or as needed, or cancelled when the threat is gone. In the Pacific, the types of messages issued by the PTWC include a Pacific-Wide Tsunami Warning Bulletin, Regional Expanding Tsunami Warning and Watch Bulletin, Regional Fixed Tsunami Warning Bulletin, Warning Cancellation Bulletin, Tsunami Information Bulletin, and TsunamI Communication Test Dummy Message. TSUNAMI WATCH: The second highest level of tsunami alert. Watches are issued by the Tsunami Warning Centres (TWCs) based on seismic information without destructive tsunami confirmation. The watch is issued as a means of alerting the affected populations located, for example, one to three hours tsunami travel time beyond the warned area. Subsequent text products are issued at least hourly to expand the watch and warning area, upgrade all areas to a warning, or cancel the watch and warning. A Tsunami Watch may be included in the text of the message that disseminates a Tsunami Warning
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