U.S. TSUNAMI ALERT LEVELS

 

Tsunami Message Definitions

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The U.S. Tsunami Warning Centers issue tsunami messages to notify emergency managers, the public, and other partners about the potential for a tsunami following a possible tsunami-generating event. To provide messages as early as possible, the warning centers use preset criteria based on preliminary earthquake information, before a tsunami is detected, to help them decide when and for where to issue tsunami messages and what alert(s) to include. Subsequent messages and alerts are based on impact estimation resulting from additional seismic analysis, water-level measurements, tsunami forecast model results, and historical tsunami information.

Examples of tsunami messages

Domestic Tsunami Messages *

Domestic tsunami messages are issued for U.S. and Canadian coastlines and the British Virgin Islands. These messages include alerts and also serve to cancel alerts, when appropriate. There are four levels of tsunami alerts: warning, advisory, watch, and information statement. Each has a distinct meaning relating to local emergency response. Recommended protective actions vary within areas under warnings and advisories. Be alert to and follow instructions from local emergency officials because they may have more detailed or specific information.

Alert Level	Potential Hazard(s)	Public Action
Warning	Dangerous coastal flooding and powerful currents	Move to high ground or inland
Advisory	Strong currents and waves dangerous to those in or very near water	Stay out of water, away from beaches and waterways
Watch	Not yet known	Stay tuned for more information Be prepared to act
Information Statement	No threat or very distant event for which hazard has not been determined	No action suggested at this time

Tsunami Warning – A tsunami warning is issued when a tsunami with the potential to generate widespread inundation is imminent, expected, or occurring. Warnings alert the public that dangerous coastal flooding accompanied by powerful currents is possible and may continue for several hours after initial arrival. Warnings alert emergency management officials to take action for the entire tsunami hazard zone. Appropriate actions to be taken by local officials may include the evacuation of low-lying coastal areas, and the repositioning of ships to deep waters when there is time to safely do so. Warnings may be updated, adjusted geographically, downgraded, or canceled based on updated information and analysis.

Tsunami Advisory – A tsunami advisory is issued when a tsunami with the potential to generate strong currents or waves dangerous to those in or very near the water is imminent, expected, or occurring. The threat may continue for several hours after initial arrival, but significant inundation is not expected for areas under an advisory. Appropriate actions to be taken by local officials may include closing beaches, evacuating harbors and marinas, and the repositioning of ships to deep waters when there is time to safely do so. Advisories may be updated, adjusted geographically, upgraded to a warning, or cancelled based on updated information and analysis.

Tsunami Watch – A tsunami watch is issued when a tsunami may later impact the watch area. The watch may be upgraded to a warning or advisory or canceled based on updated information and analysis. Emergency management officials and the public should prepare to take action.

Tsunami Information Statement – A tsunami information statement is issued when an earthquake or tsunami has occurred of interest to the message recipients. In most cases, information statements are issued to indicate there is no threat of a destructive basin-wide tsunami and to prevent unnecessary evacuations. Information statements for distant events requiring evaluation may be upgraded to a warning, advisory, or watch based on updated information and analysis.

A cancellation is issued after an evaluation of water-level data confirms that a destructive tsunami will not impact an area under a warning, advisory, or watch or that a tsunami has diminished to a level where additional damage is not expected.

International Tsunami Messages *

International tsunami messages are issued by the Pacific Tsunami Warning Center (PTWC) to international partners in the Pacific and Caribbean and Adjacent Regions for guidance only in support of the UNESCO/IOC Pacific Tsunami Warning and Mitigation Systemi (PTWS) and the Tsunami and Other Coastal Hazards Warning System for the Caribbean and Adjacent Regionsi (CARIBE EWS). There are two types of international tsunami messages: tsunami threat messages and tsunami information statements. These messages do not include alerts. The primary purpose of these messages is to advise national authorities of the PTWC evaluation of the tsunami threat so they can determine, based on all information available to them, which alerts to issue for their coastlines, if any.

Alert Level	Potential Hazard(s)	Public Action
Threat	Dangerous coastal flooding and/or strong and unusual currents dangerous to those in or very near the water	Seek more information, follow instructions from national and local authorities
Information Statement	Minor waves at most	No action suggested other than normal caution around the sea

Tsunami Threat Message – A tsunami threat message is issued to officially designated national authorities of the PTWS or CARIBE EWS when a potential or confirmed tsunami is forecast to affect some or all coasts within those systems. Estimated arrival times for the first wave are provided for select locations. When sufficient data have been received to forecast tsunami waves, the message is updated to include this information. Messages also emphasize that a tsunami can adversely impact people, structures, and ecosystems on land or in nearshore marine environments. National authorities will determine the appropriate level of alert for each country and may issue additional or more refined information and instructions. Threat messages may be updated based on new information, data and analysis.

A final tsunami threat message is issued when the Pacific Tsunami Warning Center determines there is no further threat or that tsunami waves are now below threat levels in most places and are diminishing.

Tsunami Information Statement – A tsunami information statement is issued to national authorities when an earthquake or tsunami has occurred of interest to the message recipients. In most cases, information statements are issued to indicate there is no threat of a tsunami and to prevent unnecessary evacuations. Information statements may be upgraded to tsunami threats based on updated information and analysis.


* U.S. states and territories in the Pacific and Caribbean (American Samoa, Guam, Hawaii, Northern Mariana Islands, Puerto Rico, U.S. Virgin Islands) should refer ONLY to the Pacific Tsunami Warning Center messages specifically for their regions. International tsunami threat messages from the Pacific Tsunami Warning Center may mention U.S. states and territories, but they do not reflect the additional modeling and analysis conducted to fine tune forecasts and set alert levels for the United States and should not to be relied on by U.S. states and territories.

U.S. Tsunami Warning Centers

NWS Tsunami Products (Effective April 3, 2017) Tsunami messages are National Weather Service (NWS) products. NWS products are described by both a World Meteorological Organization (WMO) Header and an Advanced Weather Interactive Processing System (AWIPS) ID. The following table describes the products issued by the two NWS Tsunami Warning Centers (click on the product for an example). WEPA41 and WEXX20 are segmented Warning, Watch, and Advisory products which contain Universal Geographic Code and NWS Valid Time Event Codes. WEHW40, WEZS40, WEGM40, WEAK51, WECA40 and WEXX30 are Warning, Watch, and Advisory products which are provided in a bulleted format intended for easy reading. WEAK61, WEAK63, WECA50, WECA32, WEXX40 and WEXX42 have the same content as WEAK51, WEAK53, WECA40, WECA42, WEXX30 and WEXX32, but in Spanish. WEPA40 and WECA41 are intended for international authorities and users. While these products do mention U.S. states and territories, they do not reflect additional modeling and analysis conducted by the Pacific Tsunami Warning Center to fine tune the forecasts and alert levels for these coasts. U.S. audiences should refer to the products specific to their region as noted in the table below. Click to download List of Products Region WMO Header NWS AWIPS ID TWC Explanations Alaska, British Columbia, U.S. West Coast Example: WEPA41 PAAQ Example: WEPA41 PAAQ Example: WEPA41 PAAQ TSUWCA NTWC Segmented Tsunami Warnings, Watches, and Advisories Example: WEAK51 PAAQ Example: WEAK51 PAAQ Example: WEAK51 PAAQ TSUAK1 NTWC Tsunami Warnings, Watches, and Advisories Example: WEAK61 PAAQ Example: WEAK61 PAAQ Example: WEAK61 PAAQ TSUSPN NTWC Spanish Tsunami Warnings, Watches, and Advisories Example: WEAK53 PAAQ TIBAK1 NTWC Tsunami Information Statements Example: WEAK63 PAAQ TIBSPN NTWC Spanish Tsunami Information Statements Hawaii Example: WEHW40 PHEB TSUHWX PTWC Tsunami Warnings, Watches, and Advisories Example: WEHW42 PHEB TIBHWX PTWC Tsunami Information Statements American Samoa Example: WEZS40 PHEB TSUPPG PTWC Tsunami Warnings, Watches, and Advisories Example: WEZS42 PHEB TIBPPG PTWC Tsunami Information Statements Guam, CNMI Example: WEGM40 PHEB TSUGUM PTWC Tsunami Warnings, Watches, and Advisories Example: WEGM42 PHEB TIBGUM PTWC Tsunami Information Statements Non U.S. Pacific Example: WEPA40 PHEB TSUPAC PTWC Tsunami Threat Messages Example: WEPA42 PHEB TIBPAC PTWC Tsunami Information Statements U.S. Atlantic, Gulf of Mexico, Canada Example: WEXX20 PAAQ Example: WEXX20 PAAQ Example: WEXX20 PAAQ TSUAT1 NTWC Segmented Tsunami Warnings, Watches, and Advisories Example: WEXX30 PAAQ Example: WEXX30 PAAQ Example: WEXX30 PAAQ TSUATE NTWC Tsunami Warnings, Watches, and Advisories Example: WEXX40 PAAQ Example: WEXX40 PAAQ Example: WEXX40 PAAQ TSUSPA NTWC Spanish Tsunami Warnings, Watches, and Advisories Example: WEXX32 PAAQ TIBATE NTWC Tsunami Information Statements Example: WEXX42 PAAQ TIBSPA NTWC Spanish Tsunami Information Statements Puerto Rico, Virgin Islands Example: WECA40 PHEB Example: WECA40 PHEB Example: WECA40 PHEB TSUCAR PTWC Tsunami Warnings, Watches, and Advisories Example: WECA50 PHEB Example: WECA50 PHEB Example: WECA50 PHEB TSUSP1 PTWC Spanish Tsunami Warnings, Watches, and Advisories Example: WECA60 PHEB Example: WECA60 PHEB Example: WECA60 PHEB TSUCA1 PTWC Segmented Tsunami Warnings, Watches, and Advisories Example: WECA42 PHEB TIBCAR PTWC Tsunami Information Statements Example: WECA52 PHEB TIBSP1 PTWC Spanish Tsunami Information Statements Non U.S. Caribbean Example: WECA41 PHEB TSUCAX PTWC Tsunami Threat Messages Example: WECA43 PHEB TIBCAX PTWC Tsunami Information Statements Test Example: NTXX98 PHEB TSTMSG PTWC Test Messages Example: NTXX98 PAAQ TSTMSG NTWC Test Messages