The National Weather Service tries to learn from every severe storm it encounters. That includes the one that spawned the deadly EF-5 tornado in Joplin, May 22.

The Warning Coordination Meteorologist in the Service’s Springifield Office is Steve Runnels. He says one thing learned more about is the phenomenon known as a “debris ball.” It’s what appears on a radar screen when a tornado touches down and begins lifting debris into the atmosphere where the radar signal reflects off of it.

Runnels says a debris ball can be a good indicator that a tornado is in fact on the ground and doing damage, but it is of little help in issuing warnings. That is because the Weather Service wants people to act long before a tornado has touched down. The idea of a debris ball is also not yet widely accepted.

Meteorologists may have also learned something regarding the multiple areas of rotation some storms, such as that in Joplin, produce. Runnels says warnings were issued for several such areas in that storm, but suggests the weather service could do a better job of expressing to the public the increased risk multiple circulations present.

Assessment teams also spent a lot of time talking to Joplin tornado survivors as part of an effort to develop better and more effective warning information. The information from that study is still being evaluated.