Summary of September 22-24, 2010 Extreme Southern MN Flooding

Overview

Heavy rainfall caused major flooding in southern Minnesota with rainfall totals up to 10 inches in some regions. Near-record water levels were observed for the Minnesota River, Cottonwood River, and Zumbro River. Goodhue, Martin, and Steele Counties experienced the worst damage with evacuations and multiple road closures. In Truman of Martin County, 80% of homes had at least a foot of water, a school was flooded, and there was no electricity.

Photos
Radar
Rainfall
Environment

Photos:


Flooded Highway 58 in Goodhue County (photo courtesy of Howie Strusz)	Flooded house in Owatonna	Flooding in Shakopee	Flooding in Zumbrota

Radar:


Reflectivity (left) and storm relative velocity (right) with flash flood warnings and hail reports on evening of Sept. 22	Reflectivity and surface analysis at 12 Z on Sept. 23	Reflectivity (left) and storm relative velocity (right) with flash flood warning at 16:30 Z on Sept. 23	Reflectivity and surface analysis at 18 Z on Sept. 23

Rain Totals


QPE Accumulation from Sept. 21-24 in southern MN	NEXRAD Storm Total Precipitation at 9:13 AM Sept. 23 in southern MN	MN River Hydrograph	Cottonwood River Hydrograph

Zumbro River Hydrograph

Environment

An exceptionally wet summer and moisture transport from Tropical Storm Georgette and Hurricane Karl increased flood conditions for September 22-24. High-precipitation storms formed over southern Minnesota due to low pressure over northwest Iowa on September 22. Another center of low pressure formed on September 23 and moved northward, transporting even more tropical moisture to a highly saturated area.


Surface analysis map at 0 Z on Sept. 23 showed warm front across northern Iowa	300 mb wind flow showed tropical moisture transport	Water vapor imagery from Sept. 22-23

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