The Kopperl Heat Burst

Forty nine years later, the people of Kopperl, Texas still refer to the meteorological phenomenon that struck their town during the early morning hours of Wednesday, June 15, 1960 as Satan’s Storm.

Newspapers that morning talked about Lyndon Johnson’s landslide victory to be Texas’ candidate for the Democratic Presidential nomination. Texas Republicans were backing Richard Nixon. President Eisenhower was traveling to Japan, where intense riots were underway as leftists protested the pro-Western government. But the people in Kopperl were just glad to see the sun rise.

Kopperl as a town on the edge of Lake Whitney in Bosque County, Texas, about fifty miles southwest of Fort Worth. It was founded in 1881 and named for a banker, Moritz Kopperl.
It was a typical June night in Kopperl. Skies were mostly clear. Some heat lightning was visible on the horizon. One clump of clouds rolled toward the town after midnight. The temperature was about 70F. Suddenly, a tremendous wind arose. It gusted to over 75 mph over a wide area. A store was unroofed. Trees were knocked over. The temperature shot up with an incredible momentum. In just a few minutes, it rose to over 100F. There are reports that thermometers designed to register temperatures up to 140F actually broke as the alcohol expanded so rapidly with the dramatic heat.

People awakened when their air conditioners went out as power failed. Suddenly, their houses were sweltering saunas. They rushed outside, thinking their houses must be on fire. They found that the air outside was scorching. It was hard to breathe. Lightning flashed. They thought the world was coming to an end. Parents wrapped their terrified children in wet sheets to keep them cool.

The next morning, farmers found that their corn that had been green the day before was cooked on the stalk. Ranchers found their young cotton fields burned to a crisp. Leaves on trees, shrubs, and plants were burned as if there had been a freeze.

The event was unexplained in 1960. But today, we know that it was a heatburst. It is a phenomenon that causes extreme winds, a dramatic rise in temperature and a rapid drop in humidity. It happens when air transported high in the atmosphere by a thunderstorm comes crashing back to earth in a downdraft. Most downdrafts are cool in nature, cooled by evaporating rain. But in a heatburst, there is no rain, and the air heats rapidly by compression, rises at 5.5 degrees F as it descends. The air can warm by over 100 degrees F. It rushes outward when it strikes the ground, much as any downburst. Most result in a 20 degree F rise in temperature. The Kopperl downburst was an extreme event, one of the worst heatbursts ever recorded.

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