Published: November 6,2014
While the former Super Typhoon Nuri sent meteorological jaws dropping earlier this week, its remnant may have another impressive chapter in store in the Bering Sea and Alaska's Aleutian Islands.
As of late Thursday evening U.S. time, Nuri was undergoing a tropical transition and was centered over 800 miles northeast of Tokyo. Nuri is expected to join up with the polar jet stream and a very strong disturbance in the mid-latitude belt of westerly winds, as highlighted above.
(RECAP: Typhoon Nuri)
Forecasts from both the European (ECMWF) and American (GFS) computer models continue to predict an extremely powerful non-tropical storm to develop from this merger over the Bering Sea, near the western Aleutian Islands of Alaska Friday into Saturday.
In fact, both models have repeatedly suggested the pressure of that post-tropical storm could go as low as 915 to 925 millibars late Friday into Saturday -- almost as low as its estimated pressure was as a super typhoon. If that happens, it would be the strongest low-pressure system ever observed in or near Alaska since October 25, 1977, when a 925 millibar pressure reading was recorded at Dutch Harbor, Alaska. This system may also potentially be one of the lowest sea-level barometric pressures ever observed on Earth outside of tropical cyclones and tornadoes.
(MORE: Alaska's Oct. 1977 Superstorm and Other Extreme Non-Tropical Cyclones)
For reference, the lowest central pressure of Hurricane Andrew (1992) was 922 millibars. Despite the potential of a similar pressure at its peak, wind speeds in extratropical cyclones such as the upcoming storm are much lower than hurricanes, because the pressure gradient is spread out over a much larger area than in a hurricane.
Potential Impacts
The map below shows the European model wind speed forecast for Friday night, with the darkest red colors showing the strongest wind speeds in the western Aleutians and east of Russia's Kamchatka Peninsula.That model is forecasting a large swath of very strong sustained winds, possibly hurricane-force, over the western Aleutian Islands of Alaska.
The National Weather Service in Anchorage has issued a hurricane force wind warning for the waters surrounding the far western Aleutians as well as parts of the southwestern Bering Sea. Sustained winds could reach 80 mph in those areas.
Meanwhile, a high wind warning has been issued for the far western Aleutians themselves Friday into Saturday morning. In addition to the strong sustained winds pictured on the map above, there could be localized gusts of 80 to 90 mph, especially where rugged terrain enhances the winds. The strongest winds will be southerly to southwesterly in origin.
Fortunately, the storm is forecast to lose some of that ferocity later in the weekend, but may remain somewhat stalled over the Bering Sea into Sunday or Monday.
These strong winds, coupled with the potential long duration of this storm, will whip up giant waves over parts of the Bering Sea and north Pacific Ocean.
Wave heights will likely top 45 feet near the western Aleutian Islands Friday night into Saturday, making for very dangerous conditions for all marine vessels not protected.
Swells from 22 to 30 feet may reach the eastern Aleutians and Pribilof Islands, including St. Paul, Alaska, Saturday into Sunday. St. Paul (population: 453) is notorious for intense storms, with a harbor that is susceptible to southwest winds, according to the Alaska Dispatch News.
As these large swells finally reach the coast of western Alaska, some minor coastal flooding and erosion is possible Sunday into Monday.
(MORE: NWS Alaska Weather Alerts)
Areas farther east, including the city of Anchorage will see a band of rain and snow with the cold front Sunday, along with some occasional wind gusts over 40 mph particularly on the southern coast of the Kenai Peninsula, the mouth of Prince William Sound, and Kodiak Island.
(FORECAST: Nome | Anchorage)
November 2011 Deja Vu?
Coincidentally, this upcoming storm is forecast to develop three years to the calendar day after a 2011 storm hammered parts of western Alaska with high winds and coastal flooding.At least 37 Alaskan communities reported at least some form of damage, including storm surge flooding, blown-out windows, roof damage, and debris on roads.
Winds gusted to 84 mph in Wales, Alaska. A storm surge of 10 feet, along with whiteout conditions, hammered Nome, the largest city in northwest Alaska, overtopping a sea wall and covering a sea-front road with large rocks.
As a result, Nome missed its final fuel delivery for the winter. Two months later a Russian tanker, escorted through hundreds of miles of sea ice by a U.S. Coast Guard icebreaker, delivered the 1.3 million gallons of fuel needed to get the town through spring.
Kivalina, a village of 460 residents lying on a narrow spit of land facing the Chukchi Sea, experienced a 5.5 foot storm surge. Most of the town's residents were evacuated to a local school.
No fatalities or injuries were directly related to the storm, a tribute to early warning and good emergency preparedness in this sparsely populated area.
So, what are the potential differences in this upcoming case, compared to the 2011 storm?
- Peak intensity farther west: The central pressure of the 2011 storm dipped to 943 millibars. Of course, it's the gradient in pressure that drives winds. At the same time, a 1031 millibar surface high was centered over Alaska's northeast interior. This intense pressure gradient aligned over the west coast of Alaska drove the high winds.
In this case, the central pressure may be lower (stronger) than 2011, but the storm's position at peak strength, and peak pressure gradient will be farther west in 2011, thus the strongest winds appear most likely over the western and central Bering Sea and western Aleutians, rather than the west coast of Alaska.
- This storm will linger longer: The 2011 storm moved northeast, then north from west of the Aleutian Islands, to the Bering Sea, to the Chukchi Sea in the span of a couple of days. While surge flooding was significant, this lack of duration kept the flooding from being worse.
The current storm may linger in the Bering Sea, though in a weakened state from its late Friday/Saturday peak, into Monday.
Wave heights over the southern and western Bering Sea and adjacent north Pacific Ocean from late Friday into Saturday may exceed those seen in the 2011 storm, however, due not only to the more intense storm, but also the longer duration of high winds.
While the strongest winds may remain well to the west in this case, the duration of southerly winds and the subsequent swells generated may still lead to at least some coastal flooding along the west coast of Alaska.
Stay with The Weather Channel and weather.com for the latest on this upcoming Bering Sea storm.
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