A large, so-called gustnado was caught on camera in Nebraska yesterday (May 30).
Cousins to tornadoes, gustnadoes are brief, low-to-the-ground swirling clouds. They are generally weak, but they can still pack a punch. Gustnado wind speeds can reach 80 mph (129 kph), capable of knocking over feeble buildings, according to the National Weather Service. That's similar to the damage caused by an EF-0 or EF-1 tornado, the lowest rankings on the tornado damage scale.
Gustnadoes are not considered tornadoes, however, and telling them apart can be tricky. (In the video, tornado expert Greg Forbes calls the gustnado a tornado, before quickly correcting himself).
Gustnadoes may be accompanied by rain, just like tornadoes, but they are usually wispy or only visible as a debris cloud or dust whirl — a far cry from the dense and menacing funnel clouds of tornadoes.
Yet small tornadoes can seem wispy at first; the key is to look at the top of the suspected gustnado. Unlike tornadoes, gustnadoes are not connected to the storm clouds above, sticking closer to the ground.
True tornadoes spin off those huge rotating storm clouds, called mesocyclones, which can tower tens of thousands of feet into the sky. Gustnadoes are more likely to be associated with a shelf cloud, a low, horizontal cloud structure in the front of a thunderstorm.
- The Science Behind This Terrible Tornado Season
- Infographic: Tornado! How, When & Where Twisters Form
- The Tornado Damage Scale in Images