Updated 14.18

A SLOW-MOVING tsunami is battering the shoreline of Hawaii’s islands. Rising waters have reached the streets of the town of Wailuku, according to CNN.

The tide began rising along Waikiki Beach in Hawaii not long after 3am local time (1pm here) and a tsunami alert remains in effect. The director of the Pacific Tsunami Warning Centre, Chip McCreary, warned that the tsunami hitting Hawaii could swamp coastal areas of all of Hawaii’s islands.

You can watch the situation on live cam at points around the main island here.

US President Barack Obama, who was born in Hawaii, said that he had instructed the Federal Emergency Management Agency to be ready to give any help that the state needed, Bloomberg reports.

However, Dan Walker, the tsunami adviser at the emergency centre in Hawaii, said that the slow encroachment on Waikiki is not necessarily a sign that the tsunami will not be very damaging. He told local television that Waikiki a relatively sheletered area and that the slow rise there does not mean other areas will be as fortunate. He said it was a “troubling sign” of waves to come and that the situation would have to be monitored for the next two to three hours.

The water has been receding from the shoreline by 150 metres or so, but then returning with a high wash shortly afterwards.

A spokesperson from the Pacific Tsunami Warning Center said that this too constitutes a tsunami:

It’s not like a large surfing wave but people see the water being sucked out and the reef being exposed and thinking – Woah, that’s a lot of reef. But then the water comes in and floods the beach and floods the land.

In 1946, the tsunami lasted all day, with smaller waves washing up every few minutes. This is not as severe as that but in some places… we will see odd behaviour of the ocean all day.

Astonishingly, at around 3.30am local time, news station KGMB reported that a few people were still walking along the shoreline at Waikiki taking photographs of the surging waters.

This message was tweeted by a local real estate agent:

Chip McCreary said:

What these waves look like is an elevation of sea level, where the sea level will rise above its normal level and stay high for 10 or 15 minutes before it starts to recede.

As a result of this, in a tsunami wave, that water can flood the coastline and be a hazard to people and buildings on the coast.

According to the Press Association, a “relatively minor” 4.5 magnitude earthquake has already hit Hawaii but that there are no reports of injuries. Surprisingly, experts say it is unlikely to be related to the Japanese quake.

Tourists had been moved to higher floors of their hotels in the Waikiki district and residents had  been stocking up on petrol, bottled water, canned food and generators as tsunami warning sirens have been sounding all night there (the tsunami is due to hit at 3am local time).

The latest tsunami message issued for Hawaii by the Pacific Tsunami Warning Center at 2.30am local time (12.30pm here), says that a tsunami warning continues to be in effect. It reads:

A tsunami has been generated that could cause damage along coastlines of all islands in the state of Hawaii. Urgent action should be taken to protect lives and property.

The alert also warned that:

The danger can continue for many hours after the initial as subsequent waves arrive. Tsunami wave heights cannot be predicted and the first wave may not be the largest.

Tsunami waves effeciently wrap around islands. All shores are at risk no matter which direction they face.

The trough of a tsunami wave may temporarily expose the seafloor but the area will quickly flood again. Extremely strong and unusual nearshore currents can accompany a tsunami.

Debris picked up and carried by a tsunami amplifies its destructive power. Simultaneous high tides or high surf can significantly increase the tsunami hazard.

The estimated arrival time in Hawaii of the first tsunami wave is 03.46am.

Sky News correspondent Robert Nisbet is currently bunkered down in his hotel in Waikiki. His tweets this morning have been chronicling the state of emergency in Hawaii: