Friday, March 11, 2011

Tsunami Warnings and Advisories

While my heart mourns for the people of Japan this morning I thought it might be a good opportunity to educate people on Tsunami’s and for my friends on the West Coast (which includes me in Washington) this will definitely be a good read.

What’s the difference between Tsunami Warning and Advisory?

Tsunami Warning:

Tsunami warnings mean that a tsunami with significant widespread inundation is imminent or expected. Warnings indicate that widespread dangerous coastal flooding accompanied by powerful currents is possible and may continue for several hours after the initial wave arrival.

Tsunami Advisory:

Tsunami advisories mean that a tsunami capable of producing strong currents or waves dangerous to persons in or very near the water is expected. Significant widespread inundation is not expected for areas under an advisory. Currents may be hazardous to swimmers... boats... and coastal structures and may continue for several hours after the initial wave arrival.

Why would some areas be under advisory and others a warning?

As of 2 a.m., all of Oregon, and most of California from roughly Malibu north to the Oregon border were under a tsunami warning, as were parts of Alaska. Meanwhile, all of Washington state, and far southern California, and the other parts of coastal Alaska were under a lesser tsunami advisory.

Why the difference? It's likely related to the geography of the Pacific Coast and the angle at which the tsunami wave was generated. Models indicate the Oregon and North/Central California coastlines are better aligned to the main wave than the Washington coast, and thus the impact is greater there.

What can Washington expect?

A small tsunami wave hit Ventura, California harbor after an 8.8 quake in Chile last March. These are the similar effects we are likely to see around Washington under a tsunami advisory.

This video is from Officer John Higgins who works with the Harbor Patrol in the Ventura, California Port District. The harbor master told him the tide level went up 2 feet around 12:50 p.m. and then dropped 3.5 feet at 1 p.m. and that no one around there could remember any event like that happening before, going back to the 1960s.

This is a pretty good illustration of the expected effects when the quake is far enough away and we are not on a direct line to the quake's epicenter.


Information taken from Meteorologist Scott Sistek- full article can be found at 

The Washington coast was placed under a tsunami advisory, which is more intense than a tsunami watch but not as serious as a warning. Under the advisory, the Washington coast can expect strong currents along the immediate shore. Waves were expected to be between 6 inches to a foot tall, but coastal flooding was not expected.

In southwest Washington's Pacific County, Sheriff Scott Johnson said the county activated its reverse 911 system, phoning residents on the coast and in lowlying areas and asking them to move to higher ground.
An order evacuation was under way before dawn in Long Beach, Ilwaco and Ocean Park, Johnson said.

State spokesman Rob Harper says the highest waves are expected on the central coast around Moclips at about 3 feet. Harper says Grays Harbor County is talking about limited evacuations around Pacific Beach and Iron Beach. Waves are expected to be smaller around the larger cities of Aberdeen and Hoquiam.

He warned that people need to stay off the coastal beaches for 12 hours since the tsunami will arrive in a succession of waves.

Information taken from KOMO Staff & Associated Press article- full article can be found here-

However we will not experience anything near what Japan has suffered this morning- my heart and prayers go out to the people there!


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