Duluth “Mega Flood” sets new records; Quieter, drier forecast ahead

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10.10" Highest observed rainfall total

(Reported by an NWS employee 4 mi NE of Duluth)

7.24" Preliminary storm total at Duluth NWS office

(Likely the all time greatest 24 hour rainfall total on record for Duluth)

5.79" previous all time 24 hour rainfall record in Duluth (August 22 & 23, 1978)

16.6 feet - new "flood of record" on the St. Louis River at Scanlon

(Reached early Thursday morning)

15.8 feet - Previous flood of record from 1950 (62 years ago)

Photo: Derek Montgomery for MPR

Counting Catastrophes:

Let the record counting begin.

Weather forecasting is what you see out the windshield, current conditions are what's in the sunroof, and climate is what's in the rearview mirror.

Meteorologists had our day Wednesday trying to keep up with frantically changing conditions in and around Duluth and the North Shore. Today, "climatologists" get to pick up the pieces and tell us what it means.

All time greatest 24 hour rainfall for Duluth? Looks like it.

Highest flood ever on the St. Louis River and many other North Shore streams? Likely.

Photo Courtesy of Kelli Latuska

What just happened?

In every disaster there's usually one photo that captures the essence of the event. The photo of the scared looking seal swept away from the Lake Superior Zoo by floodwaters does the trick for me on this one. I'm tempted to call this "The Great Duluth Seal Flood of 2012."

Here's a good preliminary account of the Duluth Mega Flood from the Duluth NWS.

Three day rainfall amounts of 8 to 10 inches were common across the Minnesota Arrowhead and northwestern Wisconsin from June 17th through June 19th. The heavy rain took its toll on the road infrastructure and caused rivers and streams to flood.

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 inundated 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".

Numerous roads were washed out from the deluge of rain from Carlton County through the Duluth metro area and into Douglas County and Bayfield County in Wisconsin.

A state of emergency was declared in Duluth, Hermantown and Superior, WI.

The Fond Du Lac neighborhood of Duluth and the Thomson Township in Carlton County were evacuated due to the quickly rising St. Louis River.

A raging Miller Creek flooded the Lake Superior Zoo, drowning many animals. Two seals were swept from their enclosures, but were returned safely after being found on a local street. The polar bear escaped its exhibit, but was safely returned after being tranquilized by a dart.

An 8-year-old boy was swept into a culvert while playing in the flood waters in Proctor. He was swept through the culvert for 6 or 7 blocks, but besides some scrapes, was unharmed.

This map is a graphical representation of the precipitation reports that we received from off duty weather service employees, cooperative observers, and trained spotters. Both the map and the table of values below are preliminary values as of 6:30 pm Wednesday night, and will be updated as needed.

Source: Duluth NWS

Source: Duluth NWS

Photo: Derek Montgomery for MPR

Fire up the "Dual Pol" Doppler:

The flood gave the Duluth NWS a chance to see how their new Dual Polarization radar worked during this event. The radar calculated a Storm Total Accumulation based on radar returns throughout the event, and when comparing them to precipitation reports received, the radar calculation seems to be reasonably accurate. Click on the image to get a better look at the radar estimates.

Source: Duluth NWS

The Twin Cities NWS in Chanhassen is scheduled to upgrade to Dual Pol in September. We can skip the flood test for that one in my opinion.

Why did this happen?

People wonder why extreme weather events like this happen.

It's easy to point a finger at climate change and say "see, see!" But it may not be that simple.

Extreme weather has always been a feature of Minnesota's landscape. We can't credibly say one event was "caused" by climate change.

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.

Would the event still have occurred without climate change? Probably. How much rainfall "enhancement" can we attribute to climate changes? 10% more rain? 50% more rain?

That may be impossible to quantify.

In early June I gave a talk about "Minnesota's Changing Climate" to a group at The North House Folk School in Grand Marais. One of my tag lines summing up climate changes in Minnesota and along the North Shore was..."Expect The Unprecedented." I'm not sure I expected something so unprecedented so soon!

Merciful Respite: Quieter & drier days ahead

Amazingly, the forecast models look relatively dry the next few days and maybe into much of next week. It looks like other than a few scattered showers, most of Minnesota will get a much needed chance to dry out.

Source: Twin Cities NWS

The forecast models are (thankfully) having a hard time finding significant rainfall in the next week. All models are under .55" in the next 7 days. If that verifies, that would be newsworthy.

Source: Iowa State University

Did somebody just flip the weather switch to the "off" position again? As a storm weary meteorologist I sincerely hope so.

PH