Megastorm for Alaska

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Monster Storm Lashing Outer Reaches of Alaska

Climate Central,

16 January, 2013

An extraordinarily powerful ocean storm, packing hurricane-force winds and waves towering up to 62 feet, has been spinning its way toward Alaska's Aleutian Islands after undergoing a phenomenally rapid intensification process in the Western North Pacific Ocean since Sunday. This satellite image, which captured the storm near its peak intensity on Tuesday, offers a rare glimpse at a storm system of this magnitude.

This visible satellite image shows a massive and intense low pressure system swirling over the Western North Pacific Ocean on Tuesday, Jan. 15.

Click to enlarge the image. Credit: Facebook/Stu Ostro via. University of Dundee, Scotland. 

At its most intense point, the storm had an air pressure reading of about 932 mb, roughly equivalent to a Category 4 hurricane, and more intense than Hurricane Sandy as that storm moved toward the New Jersey coastline in October. (In general, the lower the air pressure, the stronger the storm.) The storm's central pressure plunged by 48 to 49 mb in just 24 hours, making it one of the most rapidly intensifying storms at a mean latitude of 34°N since 1979, according to a data analysis by Ryan Maue of Weatherbell Analytics.

On Tuesday, the storm spanned a staggering 1,440 miles, according to David Snider, a meteorologist at the National Weather Service in Alaska. That's equivalent to the distance between Denver and New York City.

Satellite image with notes provided by NOAA's Ocean Prediction Center, pointing out the center of the storm and its associated features.

Click to enlarge the image. Credit: Facebook/Ocean Prediction Center.

In Alaska, the National Weather Service has issued high wind warnings and hurricane force wind warnings for the sparsely populated, but strategically important central and western Aleutian Islands and surrounding coastal waters starting on Wednesday. “Tonight winds may howl up to 85 miles-per-hour over the western tip of Alaska in the Aleutian Islands,” the NWS said. Sustained winds are expected to be near hurricane force, or 74 mph, and waves of 40 feet or greater are expected to pound the western Aleutian Islands.

As of Wednesday morning, winds were already blowing as high as 72 mph at Eareckson Air Station on the island of Shemya, about 1,500 miles southest of Anchorage. That island is no stranger to extreme weather, considering that it sticks out far into the North Pacific, making it vulnerable to polar storms and storms coming northward from the Western Pacific. (The U.S. Air Force outpost located there isn't exactly the most coveted assignment in the U.S. military.)

The storm was well-forecast by computer models. This image shows the modeled wave heights from a computer model simulation on Jan. 13, valid for Jan. 15. The projection shows a large area of 50-60 foot waves associated with the storm.

Click to enlarge the image. Credit: Facebook/Ocean Prediction Center.

Fortunately for Alaska, the Pacific superstorm is weakening as it moves northeast, and it is not expected to significantly impact the rest of the state. Alaska had a frigid start to the winter, but it has experienced a significant January thaw. An “atmospheric river” event brought tropical moisture to the state during the past week, with warm air turning snow to rain and freezing rain as far inland as Fairbanks. The 0.10 inches of rain that fell in Fairbanks on Monday was the most rain to fall there in a single January storm since 1963, the NWS said.

In the satellite animation above, from NASA's Rob Simmon, the intense storm is seen in the upper left corner as it weakens and approaches Alaska.

As Alaska's temperatures soar, however, Arctic air is getting ready to sneak into the lower 48 states, beginning this weekend and continuing through next week, possibly making for an extremely cold Presidential Inauguration in Washington, D.C. on Monday.