A tsunami warning has been issued for the islands of Tonga and parts of Japan. Tsunami advisories have also been issued for New Zealand's North Island and the west coast of the United States from California to Alaska, as well as Canada's British Columbia. The first waves had already been felt on the US West Coast as of early Saturday morning, Dave Snider, the tsunami warning coordinator at the National Weather Service's National Tsunami Warning Center in Palmer, Alaska, told CNN.
Satellite imagery shows a massive ash cloud and shockwaves spreading from the eruption.
Waves crossed the shoreline of Tonga's capital, Nuku'alofa, on Saturday, flowing onto coastal roads and flooding properties, according to CNN affiliate Radio New Zealand (RNZ).
Tonga's King Tupou VI was evacuated from the Royal Palace after the tsunami flooded the capital, RNZ reported, citing local media reports that a convoy of police and troops rushed the monarch to a villa at Mata Ki Eua.
Residents headed for higher ground, RNZ said, as waves swept the palace grounds, waterfront and main street.
Ash was falling from the sky in Nuku'alofa on Saturday evening and phone connections were down, RNZ said.
The Hunga-Tonga-Hunga-Ha'apai volcano first erupted Friday, sending a plume of ash 12.4 miles into the air, according to RNZ.
A second eruption hit on Saturday at 5:26 p.m. local time, RNZ reported.
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Australia's Bureau of Meteorology said it recorded a tsunami wave of about 4 feet near Nuku'alofa at 5:30 p.m. local time on Saturday.
The Pacific Tsunami Warning Center said tsunami waves of 2.7 feet were observed by gauges at Nuku'alofa and waves of 2 feet at Pago Pago, the capital of American Samoa, Reuters reported.
Jese Tuisinu, a television reporter at Fiji One, posted a video on Twitter showing large waves washing ashore, with people trying to escape the incoming water in their vehicles. "It is literally dark in parts of Tonga and people are rushing to safety following the eruption," he said in another tweet.
The volcano is located about 18.6 miles southeast of Tonga's Fonuafo'ou island, according to RNZ, and about 40 miles north of Nuku'alofa.
In addition to the tsunami warning, Tonga's Meteorological Services issued advisories for heavy rain, flash flooding and strong winds in lands and coastal waters.
The nearby island of Fiji also issued a public advisory asking people living in low lying coastal areas to "move to safety in anticipation of the strong currents and dangerous waves."
A tsunami watch is in effect for all Samoan low-lying coastal areas, the Samoa Meteorological Service said, with residents and visitors advised to stay away from beach areas.
Japan's Meteorological Agency has issued a tsunami warning for the southern Amami island and Tokara island chain in Kagoshima Prefecture and a tsunami advisory for all coastal areas facing the Pacific Ocean, Japanese public broadcaster NHK reported. "A three-meter tsunami is expected to reach Japan following an undersea volcanic eruption off the Pacific nation of Tonga," NHK said.
"The highest tsunami observed so far is about 3.9 feet in the Kominato district of Amami-Oshima Island at 11:55 p.m. on Saturday (9:55 a.m. ET)," NHK reported.
An earlier tsunami advisory for the Pacific island nation of Vanuatu was discontinued, with the nation's National Disaster Management issuing an "all clear." The office had earlier advised residents to move away from the coastline and seek higher ground.
Impacts already seen in the US
The first waves have already begun hitting the US Pacific coast, Snider of the National Tsunami Warning Center told CNN via telephone on Saturday.
A wave as high as 1.2 feet had been observed in Nikolski, Alaska, he said, while waves as tall as one foot were observed in Atka, Adak and King Cove, Alaska.
"This may not be the largest wave as this is coming in yet," Snider told CNN, saying the event was not over.
The waves reaching the US come after a tsunami advisory was issued for the US west coast, including the states of California, Oregon, Washington and Alaska, according to the National Tsunami Warning Center.
The Pacific Tsunami Warning tweeted that no damage was reported thus far from the tsunami observed in the Hawaiian Islands.
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"A tsunami is currently being observed by all Islands' Emergency Management. We are relieved that there is no reported damage and only minor flooding throughout the islands," the agency tweeted.
Adam Weintraub, communications director for the Hawaii Emergency Management Agency, told CNN that while the island had seen some water in low-lying areas, there were no reports of loss of life or any "noteworthy damage" from the tsunami. He did not specify what areas experience the minor flooding.
The impacts were the equivalent of a "high King Tide," Weintraub said. "There is some flooding in parking lots and harbor areas, but it was nuisance flooding," Weintraub said, adding that the EMA was keeping an eye on any developments.
"We have seen the wave moving through the Hawaiian Islands," Dave Snider, tsunami warning coordinator at the center in NWS National Tsunami Warning Center in Palmer, told CNN.
Current observations are that the wave is one-to-two feet high heading toward the US mainland Pacific Coast. The estimated arrival time along the California coast was 7 a.m. to 7:30 a.m. Pacific Time.
Speaking by telephone, Snider noted: "We don't have a really good forecast because this event is based on a volcano rather than earthquake."
Snider notes this is currently an advisory, and not a tsunami warning, in effect for the US west coast.
Nonetheless, the National Weather Service Seattle urged caution along the US Pacific Coast on Saturday. "Move off the beach and out of harbors and marinas in these areas," NWS Seattle tweeted.
"Strong currents and larger waves are possible along these coastal areas. The first wave may not be largest," the agency went on to warn, adding that larger waves may continue to hit the coast for hours after the initial wave.
"Continue to stay out of the water and away from shore along the coastal areas and continue to monitor for updates," the agency said.
Laguna Beach closed all beaches, boardwalks, harbors and piers until further notice in response to the tsunami advisory early Saturday morning, telling residents, "please stay out of the water and away from the shore."
New Zealand on alert
A tsunami advisory was also issued for coastal areas on the north and east coast of New Zealand's North Island and the Chatham Islands, where "strong and unusual currents and unpredictable surges at the shore" were expected, according to New Zealand's National Emergency Management Agency.
New Zealand's official weather service said its weather stations across the country had observed "a pressure surge" on Saturday evening from the eruption.
Scientist Emily Lane, of New Zealand's National Institute of Water and Atmospheric Research, told the New Zealand Science Media Centre that it was a "very significant" eruption.
"The shock wave from it is clearly visible in satellite imagery and there are reports of the eruption being heard at least as far away as New Zealand," she said. "The tsunami from the eruption has reached over 2,500 km being recorded on gauges over all of Aotearoa."
Tsunamis generated by volcanoes are much less common than tsunamis from underwater earthquakes, Lane said.
1.14.2022: (correction on date) Large volcanic eruption near Tonga (Hunga Tonga-Hunga Ha'apai volcano) today as seen from outer space. Shown on visible imagery using the Himawari satellite. #hiwx #tsunami #earthquake pic.twitter.com/Y18W7wvXl9— NWSHonolulu (@NWSHonolulu) January 15, 2022
A smaller eruption in late 2014/early 2015 built up the crater of the volcano to above the surface of the water, Lane added, but it's not yet clear exactly how Hunga-Tonga-Hunga-Ha'apai erupted on this occasion. "When we see what is left of the island after this eruption is over we can start to put together the pieces of what happened," she said.
Professor Shane Cronin, from the School of Environment at University of Auckland, told the New Zealand Science Media Centre that research into historical eruptions by the same volcano suggested that the current eruption episode could last for weeks or months "and that further similar-sized eruptions to the 15 January 2022 event are possible."
"The eruption is likely to result in significant ash fall (cm to ten cm) in Tongatapu as well as the Ha'apai group of islands," he said. "Help will be needed to restore drinking water supplies. People of Tonga must also remain vigilant for further eruptions and especially tsunami with short notice and should avoid low lying areas."
An earlier tsunami warning issued for American Samoa has since been canceled, according to the NWS Pacific Tsunami Warning Center.
There is no tsunami threat to Guam and the Commonwealth of the Northern Mariana Islands from a "distant eruption," according to the Pacific Tsunami Warning Center.
The volcano had been active from December 20, but was declared dormant on January 11, according to RNZ.