Natural Wonders: Microbursts » Explorersweb

A microburst is an incredible but very dangerous phenomenon associated with thunderstorms. These localized columns of air suddenly erupt from the bottom of storm clouds. More than just random bouts of rain and high winds, they are close relatives of tornadoes. Their destructive abilities threaten human life and property.

Illustration of microburst. Photo: NASA

Mr. Tornado

Renowned meteorologist Ted Fujita, aka Mr. Tornado, coined the word microburst, also known as downburst. In the 1970s, many people died in multiple plane crashes and the aviation industry was in danger of losing public trust. Many have blamed these disasters on pilot error.

Fujita thought differently. He investigated and discovered that the culprit was an unexpected strong downdraft, or a gust of wind. A column of cool air plunges toward the ground and spreads out in all directions.

Types of microbursts

There are three main types of this phenomenon. The most common is a wet microburst. It occurs during wet spring or summer conditions. Dry air interacts with what is called precipitation load – excessive amounts of moisture. When water droplets or hail meet dry air, they evaporate, cooling the air. This cool air at the base of a thundercloud falls to the ground because it is heavier and denser than warm air. Called entrainment, it forces air and rain or hail to plunge at high speed.

A microburst in a rural area. Photo: Tatu Appeal/Shutterstock

A dry microburst follows the same principle but with little haste. When humidity levels or precipitation are less at the base of the thundercloud, the moisture evaporates. Cool air then descends only as wind.

At last, hybrid microbursts are combinations of the two. They mix specific conditions such as sublimation, high levels of precipitation, entrainment of dry air and cooling air below the cloud base.

Microburst. Photo: Bruce Haffner/Twitter

Tornado-like wind speeds

The microbursts last only 15 minutes and measure less than four kilometers. On rare occasions, there are macrobursts that exceed four kilometers.

Microburst wind speeds can reach a devastating 240 km/h. No wonder some take them for tornadoes. The two can be distinguished by their debris patterns. A microburst flattens trees or infrastructure with a central point of impact. A tornado zigzags across the landscape and leaves behind a cyclonic pattern.

Debris from a microburst. Photo: Stacy Hopke/Burnett County Sheriff’s Department

Scientists can tell if a microburst is likely to occur by monitoring air patterns via radar and DCAPE (Downdraft Convective Available Potential Energy). This model calculates how much energy a downdraft can have in a thunderstorm. But technology can only predict the ideal conditions for an event to occur, rather than when.

About the Author

Kristine De Abreu

Kristine De Abreu

Kristine De Abreu is a writer (and occasional photographer) based in sunny Trinidad and Tobago.

Since graduating with a BA in English and History from the University of Leicester, she has pursued a full-time writing career, exploring several niches before branching out into travel and exploration. While studying for an additional degree in travel journalism with the British College of Journalism, she started writing for ExWeb.

Currently, she works at a travel magazine in Trinidad as an editorial assistant and is also ExWeb’s Weird Wonder Woman, reporting on the natural quirks of the world as well as general stories from the world of exploration.

Though not a rock climber (yet!), she hikes in the bush, has been known to befriend iguanas, and quote the Lord of the Rings trilogy from start to finish.

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