tornado

Tornadoes are notoriously difficult to forecast, with often deadly results: In 2011, tornadoes in the U.S. killed more than 550 people, a higher death toll than in the past 10 years combined. Now a new study of short-term climate trends offers a new approach to tornado forecasting that may give people in tornado-prone regions as much as a month of forewarning that twisters may soon be descending.

On March 14, 2008, at 9:38 p.m., something happened in Atlanta that had never happened in the city’s 171-year history: A tornado ripped through a 10-kilometer-long swath of the city’s downtown. The twister, with winds reaching 210 kilometers per hour, blew out skyscraper windows and stalled a major college basketball conference tournament.

Two hundred years ago, a sea captain was sailing in the Azores, a Portuguese archipelago in the middle of the Atlantic Ocean, when he observed “an immense body of smoke rising from the sea.” As he watched, the smoke, from a volcanic vent offshore of the island of St. Michael’s, began to rotate on the water “like a horizontal wheel,” the captain wrote in his 1811 account of the event. The rotating smoke and ash grew into a dark column and ascended high into the sky, spawning waterspouts and flashes of lightning.

A huge thunderstorm was gathering above central Oklahoma on May 20, 1977. As the storm intensified, a tornado began to form and struck the ground, leaving wreckage in its path. Although the tornado itself is now well-known, the forces behind its formation are still surprisingly sketchy. Using high-resolution modeling, however, a new study reveals how some atmospheric conditions can make tornadoes more — or less — likely to form.