What exactly are microbursts?

It's monsoon season in the American Southwest. Daily thunderstorms pop up over the dry terrain, offering countless chances for observers to capture images and videos of the downpours that bring their annual rainfall to the otherwise arid desert. One of the most eye-catching aspects of these desert storms is the term you frequently encounter online: microbursts. These intense wind events can be alarming to experience firsthand, yet mesmerizing to witness from a distance.

A microburst is a forceful downward burst of wind, rain, and hail that drops suddenly from beneath a thunderstorm. These events typically affect a relatively small area; the range of the strong winds is usually no more than a mile or two across. When viewed from afar, a microburst can resemble a falling water balloon that bursts outward upon hitting the ground, much like a mushroom cloud unfolding in reverse. The image above shows a classic water balloon-style microburst, captured by NOAA scientists around 1980.

Meteorologists largely overlooked this phenomenon until the 1970s, when Dr. Ted Fujita—renowned for his groundbreaking research on tornado intensity that led to the development of the Fujita Scale—began investigating the distinct damage pattern left by these windstorms.

You definitely don’t want to be caught under a microburst. Similar to other violent thunderstorms, some people who experience these powerful winds swear they’ve gone through a tornado. These winds arrive suddenly, quickly transforming from a mild breeze to a terrifying storm, and they can sweep away anything that isn’t secured. Winds in a microburst can easily surpass 60 mph, but the most intense microbursts resemble weak tornadoes, with wind speeds reaching over 100 mph in certain areas.

Various regions across the United States are more prone to certain types of microbursts. A wet microburst is associated with heavy rain or hail and is common in more humid areas like the southeast. Conversely, a dry microburst occurs without any precipitation, often signaled by gusts of dust and debris blowing at the ground. These dry microbursts are typically found in areas with lower humidity, such as deserts or elevated regions.

Microbursts develop due to two primary factors: evaporation and the weight of rain and hail. Evaporation is a cooling process—when liquid water turns into vapor, it absorbs heat and cools the surrounding air. If dry air infiltrates a thunderstorm, it causes the rain to evaporate, leaving behind large pockets of cooler air. This cooler, denser air sinks rapidly, picking up speed until it hits the ground. The weight of rain and hail also accelerates the process. The mass of the water drags cooler air downward, contributing to the creation of a microburst.

The greatest threat of microbursts is how they can form so quickly and unexpectedly. For a long time, microbursts would appear with almost no warning—people often had no idea they were happening until it was too late. This sudden downward burst of wind and the resulting wind shear can pose a serious risk to aircraft during takeoff and landing in stormy conditions. Over the years, microbursts have been responsible for numerous plane crashes, leading to hundreds of fatalities.

We've made significant progress in detecting microbursts. The widespread use of Doppler weather radar across the U.S., including smaller systems placed near major airports, has greatly improved meteorologists' ability to warn both people on the ground and pilots before a microburst strikes. Additionally, wind shear detection systems, both on the ground and onboard aircraft, have played a vital role in helping pilots navigate through severe weather safely.