What is a microburst? Downbursts and damaging winds

May 12, 2022

Learn all about microbursts, downbursts, and the damaging winds from severe thunderstorms!


A microburst downburst falling from a severe thunderstorm

Of the extreme weather events you might experience during Texas' storm season, microbursts and downbursts are perhaps the most unfamiliar to us, and in the thick of one, you may not even know one is happening. On the low end, they may simply appear as an intensifying storm; heavy downpours become heavier, and the winds grow stronger. But on the high end, they can easily be confused for a tornado - and can often be just as destructive. 

Unlike lightning and tornadoes, microbursts and downbursts are a relatively new discovery in the world of meteorology, but they are a separate form of severe weather unto themselves. Learning about them and the conditions that cause them has helped save thousands of lives in recent decades - and may even help protect you! 

So, what is a microburst? For that matter, what is a downburst? Where do they come from and how are they different from tornadoes and other gusty winds? In the fifth and final part of our spring storm series, we'll tell you everything you need to know about microbursts and downbursts so you and your family can be weather aware and prepared. Read on!

What is a downburst? What is a microburst?


Gusty, straight-line winds are a common part of almost every thunderstorm, severe or otherwise. In most cases, these winds are caused by the downdraft of a thunderstorm, or the rain-cooled air sinking from within the cloud. In standard, non-severe thunderstorms, these winds aren't especially powerful, but may be experienced around and in front of the storm throughout much of the storm's lifecycle. 

But sometimes, a thunderstorm packs an extra punch and produces a sudden, intense downdraft known as a downburst. Downbursts are powerful, rapidly descending winds that sink from within a thunderstorm and spread out in all directions when they come in contact with a ground. In some cases, downbursts can be as powerful and destructive as a low-end tornado with wind speeds up to 100 mph or more. Fortunately, they are relatively short-lived, and only last for five to 10 minutes.

When a downburst is large and covers an area over 2.5 miles wide, they are known as macrobursts, or simply just downbursts. However, most downbursts are smaller than 2.5 miles in diameter - these are called microbursts. Because of their intense winds, destructive capabilities, and relatively small scale, microbursts may often be confused with tornadoes - but they are very different phenomenon.

So, what causes a downburst or a microburst? Why do some storms have standard downdrafts, yet others cause such chaos? Let's take a look!

How are microbursts and downbursts formed?


In our previous severe storm blogs, we've talked a lot about thunderstorms and their updrafts - powerful currents of rising air that form the foundation of a storm. Updrafts are a key ingredient in the formation of hail, lightning, tornadoes, and severe weather generally. 

The updraft is like a conveyor belt of moisture, carrying moist, unstable air up into the atmosphere where it cools into raindrops and hail. As the rain and hail become large and heavy enough, they'll typically fall. However, in some cases the updraft is too strong and the rain and hail are held aloft, suspending in the core of the storm. 

At some point, the updraft begins to weaken and this core of rain and hail begins to rapidly sink towards the ground, dragging air along for the ride. In some cases, the air beneath the storm is an area of low relative humidity, which means that the some of the rain will begin to evaporate in the "dry" air, which further cools it and increases the speed.

The result is like a massive falling water balloon that crashes into the ground beneath it, spreading out in all directions with amazing force - they are often referred to as "rain bombs" for this reason. The winds can break fences, tree limbs, break windows, and hurl all manner of objects out in front of it. The rains within a downburst can be torrential, blinding even, but are often very brief. 

Downbursts and microbursts are phenomenon that usually occur towards the end of a thunderstorm's life cycle, or otherwise are responsible for choking off a thunderstorm. Because a thunderstorm is fueled by an inflow of warm moist air, when a downburst drops tons of cool air, it has a tendency to cut off that supply. 

Microburst discovery and aviation safety


As recently as the 1970s, microbursts were not widely accepted as being a real threat; while meteorology pioneer Ted Fujita hypothesized their existence and danger, it was commonly thought that downbursts could never be strong enough to cause damage. 

Over the years, microbursts have caused a number of tragic plane crashes as they impact aircraft either approaching for landing or taking off. However, they were mostly thought to be tornadoes - not downbursts or microbursts. Then in June 1975, Eastern Airlines Flight 66 crashed as it attempted to land at JFK International Airport. Dr. Fujita suspected that it had been a microburst to blame, not a tornado. 

To test his hypothesis, Dr. Fujita teamed up with the National Center for Atmospheric Research (NCAR) to conduct an experiment called the Northern Illinois Meteorological Research on Downbursts, which used three Doppler radars to scan storms in search of this weather phenomenon. Finally on May 29, the first microburst was officially recorded and observed on radar, confirmed Fujita's long-held hypothesis. 

As a result of this work, the Federal Aviation Administration worked with a number of groups, like the National Oceanic and Atmospheric Administration (NOAA), to develop special radar-warning systems to help avoid deadly microbursts at airports. They developed the Terminal Doppler Weather Radar, which is now installed at most major airports around the country. Additionally, the proof and discovery of microbursts caused the FAA to put in place mandatory microburst training for pilots who operate out of major airports. 

Thanks to the work of Dr. Fujita, there hasn't been a downburst-related plane crash in over 25 years

Tornado vs microburst


Although the damage from a microburst and a tornado may appear similar on the surface, they are two very different weather phenomenon. As discussed earlier, a microburst or downburst is a powerful downdraft that fans out on impact with the earth, causing damaging straight line winds. A tornado is a rapidly spinning, violent vortex of air (simply put). 

Because both weather phenomenon involve destructive winds, damage from tornadoes and microbursts are often confused with one another. In some cases, it may be difficult for the untrained eye to tell the difference. Generally speaking, tornadoes tend to have longer, meandering paths of damage, and sometimes a swirling pattern can be seen on the ground. Microbursts and downbursts tend to leave behind straight-line damage that, when viewed from above, appears to radiate outward from a central point in a starburst-like shape.

As previously mentioned, up until the 1970's it wasn't even clear that microbursts were real, and they were all misattributed to tornadoes. Now, however, the National Weather Service estimates that there are 10 microbursts for every tornado reported. This is only an estimate, but it points to a startling fact - microbursts are a fairly common occurrence. 

How to prepare for a downburst or microburst


So now that we know what downbursts and microbursts are, and we know that they are a fairly common phenomenon, what can we do to plan and prepare for them?

Forecasting possible microbursts and Severe thunderstorm warnings


Despite the many advances in meteorology and doppler radar technology in recent years, forecasting a downburst or microburst is still a difficult task. Unlike general severe thunderstorms and tornadoes, it is difficult to say whether or not microbursts are possible more than 6-12 hours prior to storm initiation. 

Meteorologists can look for high instability, high moisture content, a dry layer of air in the mid level of the atmosphere, and strong winds aloft. These conditions are often present during the most hot and humid days of the summer, especially in the Southeast. 

Severe thunderstorm warnings


Although forecasts can suggest favorable conditions for microburst-producing storms, it's tough to say if a specific storm that is in progress will drop one. This means that the warning time, or lead time, before a microburst or downburst is likely to be short, if there is any advanced warning at all. 

Radar can offer some clues, however, and if the potential for a microburst is there, a storm will receive a severe thunderstorm warning. Unfortunately, many people do not take severe thunderstorm warnings as seriously as tornado warnings. Because severe thunderstorm warnings can indicate the possibility of a microburst or downburst, it is important to treat severe thunderstorm warnings just as seriously as a tornado warning, and take all necessary precautions to protect you and your family.

Preparing your home and your family 


Like tornadoes, microbursts and downbursts can come on fast and without much warning. If a severe storm is likely to impact your area, make sure you know where in your home to take shelter. Similar to sheltering from a tornado, you'll want to be in an interior room away from windows on the lowest floor of your home. If you live in a mobile home, manufactured home, or RV, it is essential that you have another place you can go to seek shelter.

If severe weather is in the forecast, make sure that any potential projectiles in your lawn are put away or fastened to the ground. This could be patio furniture, lawn care equipment, children's toys, but could also be branches and limbs. That's why it's always a good idea to make sure trees and shrubs are trimmed away from your roof and windows regularly. 

Driving during severe weather is always a hazardous practice, especially when there is a possibility of downbursts or microbursts. Pay attention to weather forecasts for a given day, and check the radar before going out on the road. If possible, wait until the severe weather passes before you risk the road. 

If you are caught on the road when a downburst hits, you're likely to have major issues controlling your vehicle, and visibility could be next to zero. If it is possible to safely do so, put on your hazard lights and pull off the road as far as possible and bring your vehicle to a stop. Move away from windows and protect yourself from glass with a jacket, blanket, or your arms as a last resort. Do your best to avoid stopping next to or under trees, telephone poles, or any other object that could potentially be blown over and on top of your car. Fortunately, the event should be over soon. 

Downbursts, microbursts, wind damage, and your home insurance


While microbursts and downbursts are intense and powerful, they do not usually result in catastrophic damage to a home. Still, they can tear off shingles, pull up sections of a roof, shatter windows, and destroy garage doors. So will your home insurance policy cover damage if your home is hit by a microburst or downburst? 

Fortunately, wind damage is a common peril that most property and home insurance policies include in their basic coverages. Whether your home is damaged by a tornado, microburst, or other straight-line damaging wind event, your home insurance should provide coverage.

Of course, coverages and specific policy details can differ between carriers and insurance products, so you want to make sure to speak with your insurance agent or insurance carrier to double check your coverages.

Germania's Spring Storm Series


Make sure you're weather aware this spring storm season - check out the rest of our severe weather blogs!

1. Thunderstorms
2. Hail
3. Lightning 
4. Tornadoes 
5. Microbursts and Downbursts (you are here!)


A microburst falling from a severe thunderstorm

Severe storm season in Texas can cause all sorts of damage to your property. Fortunately, Germania Insurance is here to lend a helping hand! For more information about our insurance products, request a free quote online or reach out to your local Germania Authorized Agent today!

by Geoff Ullrich

About the Author

Geoff Ullrich is a writer and Content Marketing Specialist at Germania Insurance.