NOAA's National Weather Service

Colors correspond to the message severity (red=most, green=least).
"WMO" = World Meteorological Organization message header (more information).
"AWIPS" = Advanced Weather Interactive Processing System header (more information).
"NWW" = NOAA Weather Wire header (more information).
For more information, see NOAAPORT.

Pacific Ocean Message Definitions:

• Tsunami Warning
  A tsunami warning is issued by PTWC 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 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 Information
  Tsunami information, issued in a Tsunami Information Bulletin, is to inform that an earthquake has occurred and to advise regarding its potential to generate a tsunami. In most cases there is no threat of a destructive tsunami, and the information is used to prevent unnecessary evacuations as the earthquake may have been strongly felt in coastal areas. The information may, in appropriate situations, caution about the possibility of a destructive local tsunami for coasts located near an earthquake epicenter (usually within 100 km). Because it takes 10-20 minutes for PTWC initial bulletins to be issued, they are typically not effective for a local tsunami that can be onshore in just minutes. In such situations, however, the information can be useful to local authorities so they can at least investigate if a tsunami has occurred and if so quickly initiate recovery procedures. Supplemental tsunami information may be issued if, for example, a sea level reading showing a tsunami signal is received.
  
  
• Tsunami Warning Cancellation
  A cancellation indicates the end of the damaging tsunami threat. A cancellation is usually issued after an evaluation of sea level data confirms that a destructive tsunami will not impact the warned area. A cancellation will also be issued following a destructive tsunami when sea level readings indicate that the tsunami is below destructive levels and subsiding in most locations that can be monitored by PTWC.