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Half of Hokkaido has been warned to expect a possible tsunami of 1 metre, the rest of up to 0.5 metres.

Update 3:15pm: warning is still in effect.

[from tenki.jp]

Update 3:30pm: waiting on further details that the tsunami may be stronger than originally thought.

Some tsunami are expected to hit Hokkaido tomorrow between 9:30 and 2pm. Waiting until 4pm now for the first substantial one to hit.

Evacuation recommendations have been made to residents living near the coast in Hokkaido.

Update: warnings in English

Update 3:53pm: If you are in Hokkaido and the Iwate prefecture - stop reading and evacuate NOW to higher ground. Please follow the instructions of your local police.

So far tsunami of 10cms to - 10cms have already hit Hokkaido. However residents are warned to expect further waves.

(- 10cms? This indicates the water has receded due to tsunami activity)

Update: 4pm: ok you know it’s serious when NHK is doing emergency broadcasts in English.

You must evacuate if you are in Hokkaido near the coast in eastern Pacific sea facing the Orkotsk sea, the waves may be up to 2 metres.

Update 4:05pm: An 8.3 magnitude earthquake at 1:24pm off the coast of Hokkaido is responsible for causing the tsunami.

Many of the predicted tsunami have not hit.

The earthquake was located 30 kms under the sea bed.

Update 4:30pm: reports are coming in that tsunami up to 20cms have already hit Hokkaido.

Update 4:45pm: warnings are still in place.

Update 5:00pm: reports are coming in from Aomori ken, 10cm tsunami have hit there along the coast.

At Chichijima a 40cm tsunami has been observed.

Update 5:20pm: In the first wave of the tsunami, waves of up to 40cms were observed. Please note the warning is still in place at this time. Reports from the second wave will be coming in soon.

Update 6:00pm: The tsunami warning has been degraded from Hokkaido to Kyushu to the lowest level. The eastern side of Hokkaido in no longer under a warning.

The second wave has observations of tsunami up to 10 cms.

Update 6:05pm: Flashing tsunami warnings have now been removed from each TV station broadcast.

Update 6:30pm: There is a high probability of small tsunamis expected for the next couple of hours.

Update 7:45pm: All tsunami warnings have now been cancelled.

• How do they even detect a 10 cm tsunami? If you’re not paying close attention, it’s not much different than a wavelet on a windy day, is it?

  Kristen
  07/01/13 02:00 PM

• From: Dept for Planning and Infrastructure - Western Australia:

  “Tsunamis have one remarkable difference to normal ocean surface waves that is responsible for some apparently unusual behaviour. They possess a very long characteristic period, which may be minutes between crests. In the open ocean, this produces wavelengths that may exceed 100 km and determines wave speeds up to 1000 km/h. Due to their very large wavelength, tsunami waves represent large-movements of the ocean water mass and correspondingly have an effect deep in the ocean’s water column. Consequently, the wave is strongly affected by the depth of the water column, travelling faster in deep water and slower in shallow water.”

  MJ
  07/01/15 06:14 AM