Wednesday, September 05, 2012

Anchorage Windstorm Triggers Widespread Tree Damage And Power Outages, Unofficial Max Gust Of 131 MPH Reported At Glen Alps

An intense storm centered in Western Alaska triggered a major windstorm in the Anchorage area during the night of September 4-5, 2012, resulting in widespread tree damage and power outages. Winds gusted to over 50 miles per hour throughout most of Anchorage, with gusts in excess of 100 miles per hour in the Hillside section of east Anchorage and along Turnagain Arm. One resident of Glen Alps reported a gust to 131 mph, while unofficial, the report is credible because the individual is part of the NWS Mesonet. The location, intensity, and duration of the event was successfully forecast in advance by the National Weather Service, although the NWS thought the strong winds would be more restricted to the Hillside and east Anchorage.

The Anchorage Daily News published both an initial story and a later report. Alaska Dispatch also has two reports, HERE and HERE. KTUU Channel 2 published a story, and The National Weather Service has already published an abbreviated report on their Facebook page, and has now published a separate report of maximum wind speeds.

Asterisks indicate station stopped reporting shortly after the wind event began

-- The Anchorage Daily News has a gallery of photos HERE.

-- KTUU Channel 2 has a gallery of photos HERE.

As usual, the Hillside caught it first. Winds steadily increased during the afternoon from 20 to 40 mph to a steady 50 to 60 mph with gusts of 85 mph by 4:30 P.M. A gust to 103 mph was recorded on the Glen Alps wind gauge shortly after 5 P.M., followed sometime later by the 131 mph gust. Hillsiders are accustomed to these wind episodes; they normally occur about 4-8 times per winter, and they build their homes to withstand them. Winds then began to slowly increase throughout the remainder of Anchorage, and the power at my house began flickering occasionally. By around 11:00 P.M., a gust of 56 knots was observed at Merrill Field, just a mile west of my home, and shortly thereafter, I lost power. My power was not restored until around 7:00 A.M.

Power Outages: Widespread throughout the city. During the peak, a majority of Municipal Light & Power's 30,000 customers lost electricity. Falling trees and branches cut power to another 25,000 Chugach Electric customers. ML&P General Manager Jim Posey was personally victimized when he discovered that a 50-foot aspen had fallen on his Ford F-150 in South Anchorage. Numerous intersections lost their traffic signals; police were present at the larger intersections. Efforts to restore power were delayed by the continuing winds and the fact that so many trees had fallen over; had the trees already lost their leaves, they would have withstood the storm better.

The Matanuska Electric Association also reported more widely-scattered outages throughout Eagle River and parts in Wasilla, Houston, Butte, Meadow Lakes, Lazy Mountain and Talkeetna, triggered in part when trees falling on power lines or uprooted resulted in damage to both the high-­voltage transmission and low-­voltage distribution systems.

Other Effects: By 5:30 A.M., the Anchorage School District decided to cancel classes districtwide for the day. All Anchorage state offices were closed for non-essential personnel, and UAA campuses in Anchorage, Eagle River and JBER were also closed. The Anchorage Daily News was forced to delay home delivery of their Wednesday print edition for 24 hours due to the power outage at their plant; subscribers will get both the Wednesday and Thursday editions delivered on Thursday. The winds at Lake Hood were strong enough to reportedly flip over one small floatplane.

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