The sirens sound when the skies turn black and violent supercell thunderstorms roar through.

The year 2010 brought a difficult and sometimes tragic few months of weather events—first the snowstorms and record cold that battered much of the Northern Hemisphere, then tornadoes and floods in the United States.

After a very unusual tornado caused extensive damage along a 34-mile (55-kilometer) swath of northern Colorado in 2008, a team of scientists from NCAR and Colorado State University undertook a multidisciplinary study integrating meteorology, climatology, and social science.

The collaborative international project, involving scientists from NCAR and other organizations, may ultimately improve tornado forecasting.

Like a cat toying with its prey, an intense area of low pressure took swipes at New England and the mid-Atlantic.