Thunder, lightning, wind, and rain! All of us in the Chihuahuan Desert are used to these phenomena during the summer rainy season as thunderheads fill the afternoon skies. However, we sometimes forget another common aspect of the thunderstorm until it's brought forcefully, and sometimes painfully, to our attention—hail! Incongruous though it may be, chunks of ice falling from the sky during the heat of August summer, sculpturing a white landscape reminiscent of mid-winter, is not that unusual. How can this be?
Thunderstorms are formed by great rising columns and bubbles of hot air
forcing their way through the cooler air of the higher elevations. Such passage is not
serene, and violent turbulence rules. Hurled upwards by chaotic currents of air into
sub-freezing temperatures, droplets of water turn to ice and then fall, only to be
thrown skyward again as they hit new rising convective currents. Cycling again and
again, the hailstones grow larger and larger as more freezing particles adhere until,
finally growing too heavy to be lifted by the updrafts, they fall to earth.
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.
usatoday, elementary descriptions.
A little more sophisticated from www.weather. com.