New Scientist: They are unwelcome at the best of times. But why are tornadoes in the US increasingly popping up at unusual times of the year, and in unusual areas? The question is troubling meteorologists and tornado watchers as citizens in the Midwest count the cost of last weekend's tornado outbreak that killed at least eight people and devastated many towns in 12 states including Illinois, Michigan, Indiana and Kentucky.
The three largest twister outbreaks in the past year have been in November, January and...