Residents survey the destruction after a tornado hit Pratt City, Ala., on April 27. Short-term forecasting of twisters like the ones that swept the South this week has grown increasingly accurate, but long-term forecasting remains highly unreliable. Butch Dill/AP hide caption

itoggle caption Butch Dill/AP

The Linwood neighborhood in Tuscaloosa, Ala., was pulverized by the nation's deadliest tornado outbreak in nearly four decades. Debbie Elliott/NPR hide caption

itoggle caption Debbie Elliott/NPR

Anatoly Kotlyar (left), 59, and Alexander Zenchenko, 58, are two of the thousands of "liquidators," or firefighters, who responded to the 1986 Chernobyl disaster. The Soviet government ordered them to the nuclear facility as first responders. Both men today complain of health problems and say Ukraine's government should be doing more to help with medical bills. David Greene/NPR hide caption

itoggle caption David Greene/NPR

A technician checks a spot with a Geiger counter in a forest that burned in 1992. The wildfire released radioactive particles into the air that were deposited there during the 1986 nuclear accident at Chernobyl. Experts worry nearby forest, which is becoming overgrown, could again be ripe for a blaze. Patrick Landmann/Getty Images hide caption

itoggle caption Patrick Landmann/Getty Images

The brown marmorated stink bug has inundated the mid-Atlantic, taking its toll on crops across the region. Researchers are investigating whether a type of parasitic wasp can bring down stink bug numbers. Jeff Wildonger/USDA Beneficial Insect Research Lab hide caption

itoggle caption Jeff Wildonger/USDA Beneficial Insect Research Lab

An ash plume rises from the Icelandic volcano Eyjafjallajokull on April 14, 2010. Arni Saeberg hide caption

itoggle caption Arni Saeberg