Air is water’s ghost, flowing, like water, through its seasons. In the spring, as every child in grade school knows, the northern hemisphere of the earth is tipped toward the sun, and the jet stream, that narrowest and swiftest channel of the river moving at speed aloft, drops southward, in a grand lasso, through Canada into the United States. A cold and dry air mass that has been hovering over the polar cap all winter thus barrels across the country. It would drop as far south as Texas and Louisiana, as it sometimes does, but for an epic collision with the only thing on earth that can stop it: the Maritime tropical air mass thrusting north from the Gulf of Mexico. To the ensuing windswirl, and to the water metaphor that helps describe it, a different–and decidedly mixed–metaphor adheres: as air masses advance and clash and retreat like armies, and then advance and clash again across shifting fronts and flanking lines through the months of April, May, and June.
The land that lies beneath these colliding air masses is home to more violent weather than any place else on the planet: on average, 10,000 severe thunderstorms sweep over the continental United States annually, bringing with them 5,000 floods and 1,000 tornadoes. While tornadoes occur everywhere in the world, fully three-quarters of them strike the United States over a region that encompasses all of the mid-west, most of the east coast, and nearly all of the south. Some maps delimit a region of greatest tornado frequency along an area beginning in South Dakota and extending southward to include most of Nebraska, Kansas, and Oklahoma, and much of Texas—the legendary region of Tornado Alley. But there are several Tornado Alleys, perhaps the most significant being the big, right-hand turn at Oklahomathat reaches eastward through Arkansas, Mississippi, and much of Alabama. If these two alleyways were combined, from the Dakotas to Alabama, they would form a giant, listing L, a soaked sock. Distinctions can and will be made among states about their indigenous features, even about tornadoes, a sort of ill wind boosterism that ranks Texas first in the sheer number of tornadoes, Kansas first in the number of that rarest sort of tornado, the F5, from the Fujita scale of magnitude, with 16 such monstrous tornadoes hitting Kansas over the last fifty years. Then there is the matter of the Palm Sunday Super Outbreak of April 3-4, 1974, the biggest outbreak of its kind in recorded history, that unleashed 147 tornadoes across 12 states. So prolific were the storms that at one point there were as many as fifteen different tornadoes on the ground simultaneously. Although most did relatively little damage, the super outbreak produced six F5 category tornadoes, two of which had damage paths in excess of a hundred miles. The F4 tornado that swept through Monticello, Indiana, had the longest damage path at 121 miles. This calamitous event, an historical and statistical anomaly in the extreme, is liable, in the manner of the proverbial five hundred pound movie executive, to draw attention away from a seasonal battle that rages no where else with greater apocalyptic fury than in the prairie state of Oklahoma. “Threat maps,” estimating tornado probability invariably place Oklahoma in the center of an oblate zone of concentric rings with Oklahoma City and its surrounding counties forming a bull’s eye. And indeed, more violent tornadoes of magnitude F4 or higher strike Oklahoma than anywhere else on earth—nearly a hundred in the last fifty years. Oklahoma City has been hit more than any city anywhere–112 times by tornadoes in the last hundred years, 17 of those involving two or more tornadoes striking on the same day.
Yet these statistics, of course, are misleading. Most Oklahoman’s live their lives, growing up, marrying, raising children, growing old, passing through life’s stages, its weeks, months, years, and decades–time lived on the human scale–without ever seeing a tornado first hand. Fewer still are the number of people who are directly affected by the destruction of a tornado. The cycles of tornado occurrence and recurrence are played out on a time scale quite beyond the human frame of reference. For each spot on the Oklahoma prairie, a thousand years might pass between one tornado strike and the next, and yet, statistically—relative to other geographical areas—climatologists who study the matter would consider the rate of one-tornado-per-thousand years a veritable tornadic rush hour. Against the backdrop of statistical recurrence, entire generations come and go between tornado strikes, the memory of their destruction ebbing, receding into the historical vanishing point.
(If you want to understand more about the violent weather the rips across the south, read Big Weather. Written by Mark Svenvold, poet, nonfiction writer, my husband.)
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Tags: Big Weather, Mark Svenvold, Tornadoes