Saturday, March 28, 2009

March 28th Evening Update On Mount Redoubt: Three Eruptions In Six Hours Spreading Ash From Kenai To Anchorage To Palmer-Wasilla

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

Two afternoon eruptions of Mount Redoubt, at 1:40 P.M. to 25,000 feet, and at 3:29 P.M. to 35,000 feet, combined with a more southwesterly steering flow, have steered volcanic ash over the northern Kenai Peninsula and South Anchorage. Ash has been officially reported on the weather observations from both Stevens International Airport and Merrill Field since 5:53 P.M. local time. I live a mile east of Merrill Field, and there is a trace of ash and a sharp smell of sulfur here as well. Stevens Airport closed at 6:15 P.M. Media stories by the Anchorage Daily News and KTUU Channel 2.

Looking at the webicorder output, it looks like another eruption just started around 7:23 P.M. and is still in progress as I type this post. Now confirmed by AVO, tops to 45,000 feet.

Here's the latest ashfall advisories:

AKZ101-291800-
/X.EXT.PAFC.AF.Y.0010.000000T0000Z-090329T0900Z/
/X.CON.PAFC.HW.W.0013.090329T1300Z-090330T0200Z/
ANCHORAGE-
INCLUDING THE CITIES OF...ANCHORAGE...EAGLE RIVER...INDIAN...EKLUTNA...PALMER...WASILLA...SUTTON...CHICKALOON
851 PM AKDT SAT MAR 28 2009

...ASHFALL ADVISORY NOW IN EFFECT UNTIL 1 AM AKDT SUNDAY...
...HIGH WIND WARNING REMAINS IN EFFECT FROM 5 AM TO 6 PM AKDT
SUNDAY...

THE ASHFALL ADVISORY IS NOW IN EFFECT UNTIL 1 AM AKDT SUNDAY. A
HIGH WIND WARNING REMAINS IN EFFECT FROM 5 AM TO 6 PM AKDT
SUNDAY.

REDOUBT VOLCANO ERUPTED AROUND 723PM THIS EVENING AND THE ASH
CLOUD HAS AGAIN MOVED OVER ANCHORAGE. MINOR ASHFALL WILL CONTINUE
INTO THE LATE EVENING HOURS AS THE CLOUD PASSES OVER THE AREA.

A STRONG WEATHER FRONT WILL MOVE INTO THE NORTHERN GULF LATE
TONIGHT. AHEAD OF THE FRONT THE PRESSURE GRADIENT WILL TIGHTEN
AND CHANNEL STRONG WINDS THROUGH TURNAGAIN ARM AND THE HILLSIDE.
WINDS WILL INCREASE TO 50 TO 65 MPH WITH GUSTS 75 TO 85 MPH
DURING THE DAY ON SUNDAY.




The wind forecast depicted above explains it. You can rule out anything above 40,000 feet; the previous eruptions only went to 35,000 feet maximum. This means the 20,000 to 30,000 ft level is where the ash is falling from. The light blue line and the lime green line are of interest, and they show the trajectory just to the south of Anchorage. This is why the ash is falling here and is heading for Girdwood.

Because of an incoming storm from the southwest, with the passage of time, the Ash Trajectory Forecast shows that lime green lime shifting back towards the west, assuming a more southerly component. This means that any eruptions after midnight are more likely to send ash to the west of Anchorage, up to the Susitna Valley once again, although Wasilla-Big Lake ought to be prepared.

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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