Meteorology: Change in the Weather

Change in the Weather

As the sun rose over Rockford, Ill., last week, residents could not believe their ears. "At 4:35 a.m.," a local radio station reported, "a tornado hit the Rockford, Ill., weather office. The entire town of Rockford has been demolished. If you are in the path, go to a basement shelter." Gazing out their windows, the town's citizens discovered a placid dawn scene. Not even a tree branch was down.

Rockford (pop. 140,000) was the victim not of a lethal twister but of glitches in new computer software used by the National Weather Service. The tornado alert was one of five test...