Debris Clouds Give Visual Cues of a Tornado Touchdown

double tornado
Rui Almeida Fotografia/Moment/Getty Images

One of the most dangerous parts of a tornado can be its debris cloud. The wind speeds of a tornado can pick up very heavy objects and swirl them around in a dense cloud around the base or the funnel cloud itself.

In fact, items such as trucks, tractors, cars, animals, and people can be swirled around in a debris cloud.

Not all tornadoes produce heavy debris clouds and not all tornadoes have enough sustained winds to pull up large objects.

Therefore, the primary component of most debris clouds is dust and small bits of debris.

Debris Formation

A tornado's debris cloud actually starts to form even before the funnel descends from the thunderstorm cloud downward to the ground. As the funnel descends, dust and loose objects on the area directly underneath it at the Earth's surface will begin rotating and may even lift several feet off of the ground and swing out hundreds of yards wide in response to the air movement above. After the funnel touches the ground and becomes a tornado, the debris cloud travels along with the storm. 

As the tornado travels along its path, its winds continue to carry nearby objects airborne. The size of the objects within its debris cloud depend on the strength of the tornado's winds. Usually however, the debris cloud whirls around smaller objects and dirt particles while the funnel cloud carries larger debris pieces.

This is why the debris cloud color is normally gray or black. It can take on other colors depending on what it picks up.

Keeping Safe From Tornado Debris

The majority of tornado injuries and deaths occur not because of storm winds, but because of debris. In fact, the three main tornado safety tips -- get low and cover your head, wear a helmet, wear shoes -- are all meant to reduce your risk of encountering debris.

  • Take the "duck and cover" position: By getting as low to the ground as you can you reduce the chance of being struck by airborne objects and debris. Covering your head with your arms or a blanket provides an extra layer of defense.
  • Wear a helmet: Since 2011, many people have added a bike, motorcycle, or sports helmet to their tornado preparedness kit. As bizarre as it sounds, when you consider that the single largest cause of tornado deaths is head trauma it suddenly makes good sense. 
  • Wear shoes: If a tornado strikes when you're at home, you'll likely be barefoot or wearing socks, which means your feet will be defenseless as you navigate your way over litter and glass after the storm. This is why it's a good idea to always include a pair of lightweight portable footwear in your safety kit.

 

By observing the takeoff and landing points of storm debris, scientists are able to learn how the debris, and therefore, the storm, traveled. Read more about these storm surveys, here.

Updated by Tiffany Means