NWS issues products targeting both domestic and international
communities. In the case of international products, the information is
intended as advice to designated national authorities and not for the
public. NWS product definitions are summarized below:
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 a may
continue for several hours after the arrival of the initial wave.
Appropriate actions to be taken by local officials may include the
evacuation of low-lying areas. People in the warned areas need to
move to higher ground or inland and stay in a safe area until local
officials give the "all-clear".
A tsunami advisory is issued due to the
threat of a potential tsunami that may produce strong currents or
waves dangerous to those in or near the water. The threat may
continue for several hours after the arrival of the initial wave, but
significant widespread inundation is not expected for areas under the
advisory. Appropriate actions to be taken by local officials may
include the closing of beaches and the evacuation of harbors and
marinas. People in the advisory area should head local official’s
instructions to leave affected areas until given the "all-clear".
A tsunami watch is issued when a
potentially dangerous, distant seismic event has occurred which may
later impact the watch area with a tsunami. Be ready to take action
if a tsunami warning or advisory is later issued.
Tsunami (Seismic) Information
A tsunami information statement is issued
when an earthquake has occurred or a tsunami warning, advisory, or
watch has been issued for another part of the ocean. In most cases,
tsunami information statements are issued to indicate there is no
threat of a destructive tsunami for the area. In international
products, a tsunami information statement is called a tsunami
information bulletin. Tsunami "seismic" information statements may be
issued to share the earthquake information when the earthquake is so
small that it is known that no tsunami threat exists.