![]() ![]() While most pilots at this time had been highly trained in wind shear - rapid changes in wind speed or direction - surprisingly little was known about the specific dangers of microbursts. Only 27 people survived this horrific event, and 137 lives were lost. As the aircraft descended toward the runway, an explosive downdraft of wind knocked the plane full of passengers to the ground, sending the aircraft careening onto a highway where it hit and killed an automobile driver and plowed into two large water tanks where it burst into flames. A thunderstorm was hovering over Dallas/Fort Worth International Airport as the pilots of Flight 191 were preparing to land. One terrible disaster in particular - the crash of Delta Airlines Flight 191 - is credited with speeding up microburst research as well as bringing stronger safety measures for all aircraft. And like tornadoes, microburst development can be difficult to detect on radar and seem to come out of nowhere. With winds up to 100 mph, trying to maneuver through a strong microburst is about as difficult as flying through a tornado. Microbursts still pose an incredible danger to aircraft, particularly during a take-off or landing. Many of these had been mistakenly blamed on pilot error. Before the introduction of Doppler radar at airports just a few decades ago, microbursts were responsible for as many as 20 major airline accidents, resulting in over 500 deaths, according to the National Science Foundation (NSF). The study of microbursts is relatively new in the field of atmospheric science. When a tornado hits, it leaves behind a more circular or meandering pattern of destruction and debris, while microburst winds cause straight-line damage that radiates from a center point of impact. The surest way of knowing whether it was a tornado or a microburst, however, is by studying the pattern of damage. In fact, microbursts can cause so much damage that residents often believe they’ve been struck by a tornado. “There has not been a detailed study done to look at how many happen on average each year in different areas, but it is believed a lot of wind damage happening in thunderstorms is likely due to microbursts, so that our climatology of wind damage from storms might give us a good idea ,” Gallus said. ![]() According to the National Weather Service, there are approximately 10 microburst reports for every one tornado, but these numbers are just an estimate. Though less well-known than tornadoes, microbursts are much more common. (Image credit: NWS Birmingham) Microburst or tornado? Some microbursts, known as hybrids, have characteristics of both wet and dry types and are driven by several influences, such as dry air entrainment, precipitation loading, cooling beneath the cloud base and/or sublimation (ice crystals turning directly into vapor), according to NOAA.Īn animated image shows the core of a microburst slamming into the ground. “When this happens, a storm can form from the moisture up high, but as it creates rain, the rain falls into the very dry air near the ground, and it evaporates, which cools the air.” Precipitation that evaporates before it hits the ground is called virga. This kind of situation happens relatively often in places like Denver,” said Gallus. ![]() “For dry microbursts, we know they are more likely when the relative humidity a few thousand feet up in the sky is rather high, but it is much lower (dryer) below that level, especially near the ground. These microbursts are typically driven by both dry air entrainment and water loading.ĭry microbursts usually begin with dry air entrainment due to moisture in the upper levels but eventually turn into wind-driven events with no surface precipitation. Wet microbursts are more common in humid climates where there are plenty of thunderstorms, such as the Southeastern United States. Depending on where you are in the country will determine which type you are more likely to encounter. Microbursts are divided into two basic types: wet and dry. When this cool, dry air is further pulled down by the weight of precipitation, it is called water loading, and this causes the air to drop even faster. ![]() William Gallus, a professor of meteorology and numerical weather prediction in the department of geological and atmospheric sciences at Iowa State University, explains this phenomenon: “Cool air is heavier than warm air, so this blob of cold air can plunge toward the ground, and it spreads out rapidly when it hits the ground, kind of like how water explodes sideways when a water balloon is dropped and hits the ground,” he told Live Science. ![]()
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