Tornado kills four Boy Scouts in Iowa

Tragedy struck a Boy Scout camp in western Iowa last night, when a tornado swept through, killing four Boy Scouts and injuring at least 48 people. A tornado warning was issued by the National Weather Service 12 minutes before the tornado hit the camp at 6:35 pm CDT, but it appears the campers never heard the sirens, either because the sirens were too far away from the remote camp, or because the storm caused a power outage in the nearest town of Blencoe, which silenced that town's tornado siren.

Tornadoes also hit southern Minnesota, eastern Kansas, and eastern Nebraska yesterday, and the Storm Prediction Center recorded 52 tornado reports. A tornado caused major damage in Manhattan and Kansas State University, tossing cars and destroying several businesses. A half-mile wide tornado hit the town of Chapman, destroying 60 homes and killing one person. Another person died in a mobile home in the Jackson County town of Soldier. Yesterday's deaths bring this season's tornado death toll up to 118--the most since 1998, when 130 people were killed.



Figure 1. Radar reflectivity (top) and Doppler velocity (bottom) for the June 1, 2008 tornado that hit the Little Sioux Scout Ranch in western Iowa. The tornado was embedded in a line of severe thunderstorms that swept through the state, and did not exhibit the classic hook-shaped echo one commonly sees in tornadoes. The most dangerous tornadoes commonly show a hook echo and tend to be spawned by "discrete supercells"--isolated thunderstorms that are not embedded in a solid line of thunderstorms.

Tornado activity forecast
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 probably not as many twisters as were reported in yesterday's outbreak. The "Slight" risk of severe weather continues Friday across the Midwest, then shifts to the East Coast by Saturday.

Tropics
An area of disturbed weather has developed in the southern Gulf of Mexico between the Florida Keys and Mexico's Yucatan Peninsula this morning. The thunderstorm activity is under about 20 knots of wind shear, and is moving northward into the central Gulf of Mexico. I'm not expecting this to develop, but we should keep an eye on it. None of the computer models are forecasting development of a tropical depression in the Atlantic in the coming seven days.

Jeff Masters