National Geographic : 2010 Oct
MAP SOURCE: MUNICH RE, 2009. PHOTO: JIM REED, CORBIS GEOGRAPHY Where's the Hail? The United States has had some of the largest hailstones, but Kericho, Kenya, may hold the record for most frequent hail. It's not easy to make a hailstone---conditions have to be just right. First come cumulonimbus clouds. What's needed next are powerful updrafts and downdrafts. These winds carry forming precipitation up to the frigid top of the clouds to freeze solid and then down toward the warmer bottom again to collect more moisture, before repeating the cycle. The more times the cycle repeats, the bigger the hailstones can grow (this baseball-size hailstone, left, fell in Kansas in May 2007)---and the more severe the damage down below. Most hail hits in the midlatitudes, on plains downwind of major mountain chains. But intense hail conditions can exist wherever warm, moist air is pushed to great heights, even near the Equator. The high-altitude tea-growing region of Kericho, Kenya, is more than 7,000 feet above sea level and may have more days with hail than any other place in the world. In 2009, 306 destructive hailstorms in 16 states caused more than $500 million in damage to crops and property in the United States. With warmer, wetter summers predicted for the Great Plains, experts fear that number is sure to rise. ---Thomas Hayden U.S. Largest recorded hailstone (8 inches in diameter), found in Vivian, South Dakota, in 2010. Mexico Severe hail here can affect monarch butter- fly colonies. Kenya Hail seeded by dust from farming regularly pelts tea fields in Kericho. Argentina One 2003 hail- storm killed 117 Swainson's hawks on the Pampas. Bangladesh The world's heaviest known hail- stone (2.25 pounds) fell in Gopalganj in 1986. High Low No data Hailstorm frequency and intensity New Atlas This map is from the ninth edition of the Atlas of the World, the most comprehensive and largest format atlas ever published by National Geographic, available this month. Learn more at nationalgeographic .com/atlas.