Gentle Breezes, Tree Sneezes, and Tornadoes

When I was growing up, my family participated in the Children of Chernobyl program. One hot summer afternoon my dad mentioned how nice the breeze was, and one of the Chernobyl kids then recited an English poem they had learned back in Belarus that mentions breeze. He then asked “what is breeze?” The best answer we came up with was that a breeze was just a small, little wind. But really, what is wind?

Achoo! Source.

Achoo! Source.

Robert Krulwich explains wind in a very simple and beautiful way,

Think of a patch of ground on a sunny day. Sunshine pours down. The air gets warmer. Along comes a cloud, not a big one, but big enough to cast a shadow. The air in that shadow cools a little. Now we’ve got a difference: cool air is sitting next to warm air — and the air that’s warming up is getting lighter. The air that’s cooling down is getting heavier, and as the warmer air rises, the sinking cooler air slips in to take its place. That slipping in? You feel it as a gentle push against your cheek; that’s the beginning of a breeze. Breezes, blustery days, wind — all come from warm and cool air slipping, sliding, tumbling, like kittens at play, across the earth.

This description is quite lovely, but remember that the same temperature differential between warm and cool air that causes that gentle breeze, can turn ugly and cause a deadly tornado.

An eastward advancing cold front is to blame for the recent tornado in Moore, Oklahoma where 24 people were killed, and 377 injured. This pocket of cold air ran into warm air from the Gulf of Mexico. The cold front caused the warm air to rise, since it’s less dense, creating thunderstorms that have in turn spawned tornadoes. The wind/supercell thunderstorms that caused the damage was strikingly visible from space, and the normally serenereal-time wind map looked quite different that day. The Atlantic has an excellent backgrounder on this disastrous tornado.

Tornado tracks over 61 years. Source.

Tornado tracks over 61 years (1950-2011). Source.

Oklahoma falls in the region known as “Tornado Alley“. Interestingly the region of Tornado Alley shifts northward over the course of the year. In December, January, and February, the bulk of tornadoes have been centered on south and south-central states like Mississippi, Texas and Kentucky. In peak tornado season—March, April, and May—the southern states are still affected, but the reach of the tornadoes has extended north and west. By June, July, and August, most of the tornado activity is happening in states like Michigan and Minnesota. Because of its unique location in the alley, Oklahoma gets more tornadoes than any other state.

This recent disaster is yet another reminder of how powerful and destructive nature can be, and that it is important that we continue to study natural disasters, so that we can better mitigate their damage in the future.

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