In this aerial photo, clay runoff from streams that surged during Wednesday's storm stains the water in St. Louis Bay orange Wednesday, June 20, 2012 in Duluth, Minn. (Bob King/AP)

The floodwaters submerged two-thirds of the Lake Superior Zoo, drowning 11 animals. MSNBC reported: “All but one of the zoo’s barnyard animals died, zoo spokeswoman Keely Johnson said in a statement earlier. That included the zoo’s donkey, goats and sheep.” The Associated Press said workers safely recovered two seals and a polar bear which had escaped.

Link: Families prepare to face damage after evacuating flooded homes in NE Minnesota

The human toll was also severe as 250 residents were forced to evacuate their homes. The governor declared a state of emergency as scores of homes flooded and roads and bridges were washed out.

Early Thursday morning, the St. Louis river reached record stage outside Duluth (in Scanlon) (NOAA)

What caused the flood?

Rainfall totals in the arrowhead of Minnesota and northwest Wisconsin (National Weather Service)

A cold front approached Minnesota from the High Plains on Sunday, June 17th and this front set off numerous thunderstorms through the evening. Duluth NWS received nearly an inch of rain (0.71”).

The rains that fell on Sunday had indundated the soil, and created more saturated conditions than normal, which primed the Duluth area for runoff in the extreme rain event that we received.

On Tuesday, June 19th another front slowly approached northeastern Minnesota. This front continually formed thunderstorms that developed over east central Minnesota and tracked northeast into the Duluth area, the north shore of Lake Superior and into northwestern Wisconsin. The official rainfall in Duluth on the 19th was 4.14 inches up until 1 am. The thunderstorms finally ended when a strong cold front moved through Wednesday afternoon. The rainfall on the 20th was 3.10”. Total rainfall for the large rainfall event was 7.24”.

The second front was intricately connected to the heat wave in the East. It coincided with the upstream branch of the jet stream which formed the upper level ridge (heat dome) over the Northeast and mid-Atlantic.

Climate change link?

Meteorologist Paul Huttner at the MPR Updraft blog has a reasonable analysis:

What we can credibly say and support with facts is that events like the Great Duluth Flood of 2012 “fit” within the overall pattern of climate changes we’re observing in Minnesota.

With factors such as a warmer atmosphere that can hold (and deliver) more water, and Lake Superior temps warmer than average for June feeding additional moisture into the system we may be able to say climate changes in Minnesota “enhanced” Wednesday dramatic flash flood event. A warmer atmosphere loads the dice in favor of more extreme rainfall.


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A car sits in a giant sinkhole in Duluth, Minn. Wednesday, June 20, 2011. (Brian Peterson/AP)

A car is stranded in floodwaters rushing down a hillside in Duluth, Minn., early Wednesday, June 20, 2012. (Andrew Krueger/AP)

Water flowing from Miller Creek fills the backyards of several homes on West Second Street in Duluth, Minn. (Clint Austin/AP)

In this aerial photo, floodwaters surround the Burning Tree Plaza shopping area in Duluth, Minn., Wednesday afternoon, June 20, 2012. (Bob King/AP)

In this aerial photo, waters from an overflowing nearby creek inundate homes in the Irving Park neighborhood of Duluth, Minn., Wednesday afternoon, June 20, 2012. (Bob King/AP)

Water flows down a damaged street in Duluth, Minn. on Wednesday, June 20, 2012. (Bob King/AP)

More photos: Minnesota Public Radio gallery