Alaska's Redoubt Volcano erupts; Midwest tornado outbreak possible today

After many months of rumbling, Alaska's Redoubt Volcano finally exploded beginning at 11:38pm last night. Four separate eruptions have sent clouds of ash up to 50,000 feet high into the air. Redoubt is located about 100 miles southwest of Alaska's most populous city, Anchorage. Ash fall advisories were issued for the cities of Talkeetna, Willow, and Cantwell to the north and west of Anchorage until 8am AKDT this morning, and light ash has already been reported at Skwentna. The prevailing southerly winds are expected to carry the ash west of Anchorage today. However, if the volcano has ejected significant ash at a height of 35,000 - 40,000 feet, the southwesterly winds at that altitude would carry the ash over Anchorage (Figure 2). Redoubt last erupted between December 1989 - April 1990, and its ash clouds presented a major hazard to aviation. On December 16, 1989, Redoubt's eruption spewed ash into the air to a height of 14,000 m (45,000 ft) catching KLM Royal Dutch Airlines flight 867, a Boeing 747 aircraft, in the plume. All four engines stalled and the aircraft plummeted 13,000 feet before the pilot was able to restart the engines and land safely in Anchorage. For more information on the Redoubt eruption, check out the Alaksa Volcano Observatory home page.


Figure 1. The summit crater of Alaska's Mt. Redoubt crater showing rapidly melting glacier and enlarged "ice piston" feature on Saturday, March 21, 2009. Image credit: Cyrus Read, Alaska Volcano Observatory/U.S. Geological Survey.


Figure 2. Plot of ash trajectories originating at the Redoubt volcano (black star) at 8 am EDT Monday March 23, 2009. The initial eruption carried ash to a height of 20,000 feet (green line), so ash is expected to move NNE, passing west of Anchorage. Ash has already fallen at Skwentna (SKW) to the north of Anchorage. If the newer blasts were able to carry significant ash to 40,000 feet (pink line), the prevailing southwesterly winds at that altitude would carry the ash over Anchorage (ANC). Image credit: NOAA.

Significant tornado outbreak possible today
NOAA's Storm Prediction Center (SPC) is predicting a "Moderate Risk" of severe weather and tornadoes over eastern Kansas and northern Oklahoma today, as a strong Springtime low pressure system tracks across the Midwest. "Moderate Risk" is SPC's second-highest level of risk, and they expect severe thunderstorms with possible strong (EF2 or EF3) tornadoes will form late this afternoon along the cold front extending south from the low. This severe weather outbreak will be hampered somewhat by a lack of moisture, though. It's been very dry the first three months of 2009, which has made this year's tornado season about 50% less active than usual. Follow the outbreak today on our Interactive Tornado Page and Severe Weather Page.

Jeff Masters