Historic flooding hits Iowa

Truly extraordinary flooding has hit the Cedar River in the town of Cedar Rapids, Iowa. Rainfall amounts in excess of 12 inches have fallen in the past ten days over the Cedar River watershed, which extends to the northwest of Cedar Rapids into southern Minnesota. The rains that fell during the weekend of June 7-8 were fueled in part by moisture from Tropical Storm Alma/Arthur, which affected Central America May 29 - June 2. The Cedar River is expected to crest today at 31.8 feet, which is an amazing 19.8 feet above the flood stage of 12 feet. During the historic 1993 flood, the worst in recent history, the river hit only 19.27 feet, 7 feet above flood stage. Nine rivers in Iowa are at all-time record flood levels, and Iowa Governor Chet Culver has declared 83 of the state's 99 counties state disaster areas. Additional heavy rainfall is not expected over the Cedar River watershed over the next two days, so today should mark the peak of this year's historic flooding.


Figure 1. Total rainfall for the period June 2 - June 12, 2008, as estimated by NASA's TRMM satellite. An additional three inches fell over portions of eastern Iowa in the 24 hours since this image was created.

New way to track river flooding on wunderground
Wunderground has added a way to track local river forecast levels and assess flood risk at www.wunderground.com/wundermap/rivers. Using data from the USGS (the U.S. Geological Survey), the product plots river data and forecasts on top of our interactive "WunderMap". Users can scroll across the country and zoom in and out to view in-depth observations from all major rivers in the U.S. Alternatively, one can click an option to view only the rivers with current flood alerts. Each river observation is color coordinated to reflect its dry/wet percentile and users can click on each observation point to view data and graphs that display Flow Rate, Percentile, Current Stage, Forecast Stage and Flood Stage. Flood Alert symbols will appear on every river icon whenever a river is in danger of flooding.

The WunderMap™ also allows one to choose from a variety of layers including current conditions, animated radar, severe weather and tornado warnings, live webcam images and animated infrared or visible satellite imagery showing cloud coverage. WunderMap™ is available as a link on every U.S. forecast page, just under the small radar image.

Tornado outbreak update
The tornado that stuck the Little Sioux Scout Ranch Boy Scout camp in western Iowa Wednesday night, killing 4 and injuring 48, was rated an EF-3 on the Enhanced Fujita scale. The tornado that hit Manhattan, Kansas the same day, causing major damage at Kansas State University, has been rated an EF-4. This is the tenth violent (EF-4 or EF-5) tornado this year, the most number of violent tornadoes since 13 were observed in 1999.

The Storm Prediction Center is calling for a "Slight" risk of severe weather across the Midwest today, from Michigan to Oklahoma. We can expect a few more tornadoes today in the affected region, although the primary severe weather threat will be damaging thunderstorm winds and large hail. The "Slight" risk of severe weather continues Saturday and Sunday across a large portion of the Midwest.

Tropics
It's quiet in the tropics. There is some disorganized thunderstorm activity in the southern Gulf of Mexico associated with a surface trough of low pressure, but this activity is not likely to develop. None of the models are forecasting tropical storm formation in the next seven days.

Jeff Masters