Alaska blizzard pushes 8-foot storm surge into Nome; Sean heads towards Bermuda

The most powerful storm to affect the Bering Sea coast of Alaska since 1974 is slowly winding down today, after pounding Alaska's west coast and Eastern Siberia with hurricane-force winds, a destructive storm surge more than 8 feet high, waves up to 40 feet high, and heavy snow. The highest wind gust recorded during the storm, 89 mph, was at Wales at the western tip of the Seward Peninsula, which forms the U.S. side of the Bering Strait. Hurricane force gusts were observed at seven locations in Alaska:

Cape Lisburne... 81 mph at 7 am Wed
Gambell... ... ... 74 mph at 6 pm Tue
Kotzebue... ... ..74 mph at 6 am Wed
Point Hope... ... 78 mph at 5 am Wed
Savoonga... ... ..76 mph at 7 pm Tue
Tin City... ... ..85 mph at 12 am Wed
Wales... ... ... ..89 mph at 1:42 am Wed

A storm surge of 8.6 feet hit Nome, Alaska near 9 pm EST last night, pushed inland by sustained winds that reached 45 mph, gusting to 61 mph. Large waves on top of the surge encrusted with sea ice battered the coast, causing extensive damage and coastal flooding. Significant wave heights at the Bering Sea buoy north of the Aleutian Islands reached 40 feet during the peak of the storm. The last time Nome, Alaska saw a storm this strong was November 11 - 12 1974, when the city experienced sustained winds of 46 mph with gusts to 69 mph, a pressure that bottomed out at 969 mb, and a storm surge of 13 feet. The center of yesterday's storm moved ashore over eastern Siberia near 12 UTC with a central pressure of 945 mb, and later bottomed out with a pressure of 943 mb. The storm's central pressure had risen to 958 mb this morning, with the center of the storm now located north of Siberia over the Arctic.


Figure 1. MODIS satellite image taken November 8, 2011, of the 943 mb Bering Sea superstorm that affected Alaska and Siberia. Image credit: NASA.


Figure 2. Observed storm surge at Nome, Alaska (green line). MLLW = Mean Lower Low Water, the water level at the lowest tide of the month. The top storm surge of 8.6 feet occurred near 02 GMT this morning (9 pm EST November 9, 2011.) Image credit: NOAA Tides and Currents.

My related blog posts:
Climate change likely to worsen erosion along the Alaska coast
The future of intense winter storms

Tropical Storm Sean
Tropical Storm Sean is on the move towards the northeast, towards a brush with Bermuda. Infrared satellite loops reveal that Sean has not changed much in organization this morning. The storm has a respectable amount of heavy thunderstorm activity near its center that is relatively shallow, and Sean has at times been able to close off an eyewall, and has a ragged-looking eye. Bermuda radar shows one strong rain band from Sean has affected the island, with the bulk of Sean's heavy thunderstorms well to the island's southwest. Sustained winds at the Bermuda airport have been under 30 mph this morning, and Bermuda picked up 0.08" of rain yesterday, and 0.24" as of 9 am EST today. Sustained winds at buoy 41048, about 300 miles west of Bermuda were 40 mph at 7:50 am EST. Strong upper-level winds out of the west are creating about 20 knots of wind shear over Sean, which is low enough to allow some slow development. Ocean temperatures have fallen to 25°C (77°F), which just below the 26°C threshold typically needed for a tropical storm to maintain its strength.


Figure 2. Morning satellite image of Tropical Storm Sean.

Forecast for Sean
The latest SHIPS model forecast predicts wind shear will remain about where it is now through Friday morning. However, ocean temperatures will gradually cool to 24°C during this time, and it is questionable whether Sean will have a favorable enough environment to strengthen into a hurricane. The computer models show little development of Sean, with none of our reliable models predicting it will become a hurricane. Bermuda is the only land area that need concern itself with Sean, as the storm is now caught in a trough of low pressure that will accelerate the storm to the northeast. The center of Sean could pass close enough to Bermuda to bring the island heavy rain squalls and sustained winds of 40 - 45 mph on Friday. NHC is giving a 52% chance that Bermuda will receive tropical storm-force winds of 39 mph. Wind shear will rise to 30 - 50 knots on Friday, which should be able to rip the storm apart by Saturday.

Jeff Masters