Strongest storm in decades to hit Alaska, coastal flooding and high winds

A powerful extratropical cyclone is expected to sweep across Alaska’s west coast starting Friday night — with a storm surge that could bring potential danger from a storm surge of up to 18 feet and gusts of up to 90 mph.

“This is a dangerous storm that will generate widespread coastal flooding south of the Bering Strait, with water levels higher than in nearly 50 years,” the Fairbanks office of the National Weather Service wrote in a forecast discussion Friday morning. level.” The National Weather Service has issued multiple warnings for multiple hurricane-like threats ahead of the dangerous storm.

Threat of high winds and coastal flooding

Roaring southerly to southwesterly winds will sweep across the state’s west coast later Friday as the power plant system approaches Alaska. Large volumes of water blown north by strong winds will wash ashore, raising the ocean by a dozen feet and causing severe erosion in vulnerable coastal communities. The storm is likely to stop off the Seward Peninsula over the weekend, continuing to push the Pacific Ocean toward Alaska’s fragile coastline.

“High water levels last much longer than we often see, so this will lead to longer periods of high-impact surges and waves hitting the shoreline,” said senior service at the National Weather Service’s Fairbanks office. Hydrologist Ed Plumb, told The Washington Post.

A coastal flood warning and a high wind warning have been issued, both of which will remain in place until Saturday night, while a storm warning has been issued offshore to warn seafarers of extremely dangerous conditions.

Wind gusts will reach around 90 mph in some places, and hurricane gusts of up to 80 mph are expected in and around Nome, famous for the finish line of the famous Iditarod Trail Sled Dog Race.

Water levels in coastal towns of 4,000 may peak at 8 to 11 feet above high tide. In nearby Golovan, water levels will be higher, 9 to 13 feet above normal high tide, according to the Bureau of Meteorology.

In Nome and other villages in the northern Bering Sea, Plumb worries that strong southwesterly winds will push water into communities, flooding buildings, washing out major roads and damaging critical infrastructure.

Strong wind gusts of up to 90 mph can also easily bring down power lines and cause other damage.

Huge storm surges and waves that can reach over 50 feet will cause severe beach erosion any time of year, but the fact that the storm hits in September increases the risk of erosion.

Danger of September Storms

When large extratropical storms cross the Bering Sea, it’s usually later in the year — especially into November and December. By then, sea ice had built up along the coast, buffering significant wave action. But with the big storm hitting in September, the coastline has no icy barrier, making it particularly vulnerable.

“This will be the deepest low we’ve ever seen in the northern Bering Sea in September,” Plum said, adding that it would be a powerful storm at any time of the year. “It’s on the perfect textbook track to cause a major storm surge in the northern Bering Sea.”

The September strike is also a concern because September is still hunting season, meaning hundreds of people could be hunting in the remote Alaskan wilderness without receiving an update on the storm.

The road that many hunters and Alaskans use to travel inland, the Nome Council Road, could eventually be swept away by storms, leaving off-grid hunters stranded in the wilderness.

The system resembles a catastrophic storm in November 2011, when a fairly intense non-tropical depression passed through the Russian Far East, just inland in the Bering Strait. The Pacific was also forced inland that month; in Nome, roads and sewer plants were flooded, while some low-lying coastal communities were heavily eroded by high waves.

“In the Nome area, or that part of the southern Seward peninsula, everything is going on as normal and it looks like [this storm] will be as bad or worse than the 2011 superstorm,” Plumb said.

In the Fourth National Climate Assessment, a comprehensive climate change report on U.S. impacts in 2018 — Scientists expressed concern that climate change has laid the groundwork for a larger impact of large nontropical cyclones in Alaska. Summer and ocean warming have resulted in greater-than-normal seasonal loss of sea ice, making the region more vulnerable to ocean inundation.

“For coastal areas, damage from late autumn or winter storms may be exacerbated by a lack of sea ice cover, high tides and sea level rise, which may increase structural damage to oil depots, homes and buildings, and potentially life-threatening flooding losses,” the report reads.

The report added that coastal erosion rates have been accelerating, with parts of the coastline losing as much as 100 feet of land to the sea each year.

“Longer sea ice-free seasons, higher surface temperatures and relative sea level rise are expected to exacerbate flooding and accelerate erosion in many areas, leading to the loss of terrestrial habitats and cultural resources, and requiring entire communities, such as Kivalina in the northwest, Alaska, relocate to safer terrain.”

a perfect storm

A powerful weather system will sweep across Alaska, making it a perfect storm, atmospherically speaking. The remnants of Pacific Typhoon Merbok, once a Category 1, will merge with a pair of non-tropical storms as it turns toward the Bering Strait, a thin band of water between Russia and Alaska.

Typhoons — the western Pacific equivalent of hurricanes — rely on the hot water that is commonly found near the equator for energy in late summer. This is in stark contrast to extratropical cyclones, which run on energy from atmospheric temperature gradients.

When these two types of systems merge, the combination can lead to the formation of powerful storms in a short period of time. The system is expected to intensify explosively as it approaches the Alaskan coastline. The system’s pressure is expected to drop by 24 millibars in 24 hours, meaning the storm will qualify as a so-called weather bomb or “bomb cyclone” due to its intensifying speed.

No need for dodging and cover – it’s a ‘bomb whirlwind’, explains

Such a process greatly strengthened Sandy as it approached the mid-Atlantic in 2012, and as the Pacific storm tilted toward Alaska, it greatly strengthened it.

By Friday night, atmospheric pressure at the center of the storm — which will be over the ocean a few hundred miles southwest of the Russia/Alaska border — was modeled to bottom out at around 940 millibars. The low pressure pulls air in quickly, like a vacuum, and values ​​below 950 mbar are usually only seen in Category 3 or 4 hurricanes.

But since the storm at this point will be a mix of tropical and non-tropical depressions, the wind field won’t mimic a Category 4 hurricane. Instead, all that energy will be spread over a larger area, with lower maximum sustained winds — probably around 90 mph — but with a much larger range.

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