Tsunami Warning

[MSmith]

An 8.0 earthquake has occurred off Tonga in the Pacific.

The Pacific Tsunami Warning Center has issued a Tsunami warning at 1542Z today for Fiji and New Zealand.

IF a tsunami exists (no signs yet), it could hit Fiji as early as 1713Z (or 13:13 EDT). New Zealand would be hit between 1821Z and 2154Z. The tsunami largest wave could follow the initial wave as long as 5 minutes to one hour later.

Hawaii is under a Tsunami Watch, with first arrival at midnight HST.

 

[MSmith]

Just got a new bulletin.

They've removed New Zealand from the warning. Hawaii is now under an advisory.

They've also identified that the Samoas are in the warning area.

Fiji could receive a wave as soon as 1704Z (or about 15 minutes from now). If the initial wave exists, Tonga and the Samoas would already have been hit.

 

[MSmith]

There really was a tsunami:

SEA LEVEL READINGS INDICATE A TSUNAMI WAS GENERATED. IT MAY HAVE
BEEN DESTRUCTIVE ALONG COASTS NEAR THE EARTHQUAKE EPICENTER. FOR
THOSE AREAS - WHEN NO MAJOR WAVES ARE OBSERVED FOR TWO HOURS
AFTER THE ESTIMATED TIME OF ARRIVAL OR DAMAGING WAVES HAVE NOT
OCCURRED FOR AT LEAST TWO HOURS THEN LOCAL AUTHORITIES CAN ASSUME THE THREAT IS PASSED. DANGER TO BOATS AND COASTAL STRUCTURES CAN CONTINUE FOR SEVERAL HOURS DUE TO RAPID CURRENTS. AS LOCAL CONDITIONS CAN CAUSE A WIDE VARIATION IN TSUNAMI WAVE ACTION THE ALL CLEAR DETERMINATION MUST BE MADE BY LOCAL AUTHORITIES.

 

[fgcason]

There really was a tsunami:

http://www.prh.noaa.gov/ptwc/bulletins.htm
http://www.prh.noaa.gov/ptwc/wmsg

---------
MEASUREMENTS OR REPORTS OF TSUNAMI WAVE ACTIVITY

GAUGE LOCATION LAT LON TIME AMPL PER
------------------- ----- ------ ----- ------ -----
PAGO PAGO 14.3S 170.7W 1636Z 0.15M 24MIN
NIUE 19.1S 169.9W 1603Z 0.21M 10MIN

TIME - TIME OF THE MEASUREMENT
AMPL - AMPLITUDE IN METERS FROM MIDDLE TO CREST OR MIDDLE
TO TROUGH OR HALF OF THE CREST TO TROUGH
PER - PERIOD OF TIME FROM ONE WAVE CREST TO THE NEXT
---------

tsunami = 6-8 inches. Taking off life jacket now...

 

[MSmith]

Well, I didn't say it was a BIG tsunami

 

[tonycondon]

at least the warning system functioned, right? a good test, methinks.

 

[Richard]

The water depth and bottom contour where the bouys are located is more telling. By definition, all tsunamis are 'shallow water' waves because of their exteremey long period (often measured in hours). Even a 5" crest can cause significant damage and loss of life because it just keeps coming and coming and coming. It may take several hours for even a single wave to pass.

The ocean bottom contour plays an important roll in how the coastline will be impacted by a tsunami. A coast with deep water and narrow or nonexistent sloping beaches will experience less damage that a coastline with long sloping beaches. Bottom line, even a 5" tsunami can create havoc, it depends upon bottom contour.