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Department of Emergency Management



 

Press Release Detail

Sunday, October 26, 2014  00:39

Issued: Tuesday, March 02, 2010  00:00
Version#

Tsunami Alert Messages

 

Here are the 4 levels of Tsunami message definitions that we receive
  
Warning - Inundating wave possible.  Full evacuation suggested
Watch - Danger level not yet known.  Stay alert for more info
Advisory -  Strong currents likely. Stay away from the shore
Information -  Minor waves at most . No action suggested
 
Tsunami Warning – a tsunami warning is issued when a potential tsunami with significant widespread inundation is imminent or expected. Warnings alert the public that widespread, dangerous coastal flooding accompanied by powerful currents is possible and may continue for several hours after arrival of the initial wave.  Warnings also 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. To provide the earliest possible alert, initial warnings are normally based only on seismic information.
 
Tsunami Watch – a tsunami watch is issued to alert emergency management officials and the public of an event which may later impact the watch area.  The watch area may be upgraded to a warning or advisory – or canceled – based on updated information and analysis. Therefore, emergency management officials and the public should prepare to take action.  Watches are normally issued based on seismic information without confirmation that a destructive tsunami is underway.
 
Tsunami Advisory – a tsunami advisory is issued due to the threat of a potential tsunami which may produce strong currents or waves dangerous to those in or near the water.  Coastal regions historically prone to damage due to strong currents induced by tsunamis are at the greatest risk. The threat may continue for several hours after the arrival of the initial wave, but significant widespread 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 are normally updated to continue the advisory, expand/contract affected areas, upgrade to a warning, or cancel the advisory.
 
Tsunami Information Statement – a tsunami information statement is issued to inform emergency management officials and the public that an earthquake has occurred, or that a tsunami warning, watch or advisory has been issued for another section of the ocean.  In most cases, information statements are issued to indicate there is no threat of a destructive tsunami and to prevent unnecessary evacuations as the earthquake may have been felt in coastal areas. An information statement may, in appropriate situations, caution about the possibility of destructive local tsunamis.  Information statements may be re-issued with additional information, though normally these messages are not updated.  However, a watch, advisory or warning may be issued for the area, if necessary, after analysis and/or updated information becomes available.