From June 17 to 20, the arrowhead of Minnesota and northwest Wisconsin were inundated with 8-10 inches of rain. In Duluth, 7.24” of rain fell Tuesday and Wednesday, the wettest two-day period on record. Massive flooding swept through the region.
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.
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.
The Minnesota Pubic Radio weather blog “Updraft” said the St. Louis River at Scanlon (west-southwest of Duluth) reached 16.6 feet, becoming the new “flood of record” (the previous record was 15.8 feet set in 1950) at that location.
What caused the flood?
The National Weather Service in Duluth has a good overview - essentially two moisture-laden cold fronts generated line after line of heavy thunderstorms, first late Sunday, with the knockout punch coming Tuesday into Wednesday:
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.
Some images obtained from Twitter and Facebook. Allow a few seconds to load...
Photos from the Associated Press
More photos: Minnesota Public Radio gallery