Monday, March 30, 2009

March 30th Midnight Update On Mount Redoubt: Airport Re-Opens, New Eruption Spreads Ash Northwest, But Threat To Shift Back To Kenai And Anchorage

Click HERE to view all previous posts on the 2009 Mt. Redoubt episode in inverse chronological order, with the most recent post appearing first.

After a period of relative quiet following Saturday's eruptive orgy, Mount Redoubt sounded off again on Sunday night at 11:14 P.M. with a 20,000 ft. eruption which is sending light ash northwestward to Port Alsworth, Sleetmute, and the Kuskokwim Valley. But forecast model guidance suggests the upper level flow pattern will change over the next 24 hours, changing the primary threat of ashfall to the Kenai Peninsula, the western Prince William Sound, and possibly Anchorage.

Stevens International Airport finally began recovering from Saturday's eruptive orgy, getting one runway opened up by mid-afternoon and another by early evening after waiting to ensure there wouldn't be another ashfall in the short term. But many passengers in Seattle are backed up waiting for flights to Alaska, and may have to wait until mid-week. One traveller reported being worried that the oil patch job promised to him up in Alaska may be given to someone else by the time he gets here. Another Anchorage resident has been trying to catch a flight out of Anchorage to close the sale on a home in Fargo, North Dakota. KTUU news video about airport recovery efforts embedded below:

If you're looking for pictures, the Anchorage Daily News has two separate groups. One file of 135 photos is available HERE, and another file of 112 reader-submitted photos is HERE.

One other area of concern is the Drift River oil terminal, located on a flood plain nearly at the foot of Mount Redoubt. Although dikes previously built to protect it have so far withstood everything thrown at it by Redoubt, officials and environmental watchdogs remain concerned about the 6 million gallons of crude still in storage there. Over the weekend, Chevron, the operator of the terminal, and state and federal regulators agreed to set up a joint emergency command to monitor events and also to be able to move quickly in the event of a disaster.

What the Ash Trajectory Forecast shows is a fundamental shift in the upper level wind pattern during the next 24 hours. By Monday night, westerly flow will begin to prevail over South Central Alaska, and as you can see on the map above, the area from Homer northward to Anchorage will become the primary zone for ashfall from any future eruptions. The 500 mb Height/Vorticity charts produced by the National Weather Service (click HERE then select the chart by that name), which show the flow at approximately 18,000 feet, continue this trend through Thursday April 2nd. Consequently, if accurate, this means Kenai and Anchorage will be looking over its shoulder at Mt. Redoubt just about all week. It should be noted that forecast models do not always handle transitions very well, particularly the timing.

On the other hand, although the Alaska Volcano Observatory isn't speculating on this yet, the webicorder output indicates that eruptive activity may be beginning to phase down a bit. Eruptions are becoming fewer and milder, and quiescent periods in between are lengthening. Perhaps Saturday's eruptive orgy may have been sort of a grand mal seizure, and now Redoubt may be slowly returning to hibernation. But the threat is by no means over, and the previous episode 20 years ago lasted four months.

Mind you, we Alaskans aren't complaining...not too much, anyway. We would much rather deal with interrupted flight schedules and 1/8th of an inch of ash than with a river 40 feet over flood stage.

Continue to monitor the following sites for the most current information:

-- National Weather Service Redoubt Page
-- Alaska Volcano Observatory Redoubt Page
-- Latest NOAA Ash Trajectory Forecasts
-- Mt Redoubt Webcam #1 (Hut)
-- Mt Redoubt Webcam #2 (CI)
-- Webicorder Graph Output

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