As the region steps into storm season, it seems appropriate to review the whirls of the Northwest, both great and small.

Of course there are tornadoes, known for being terrifying, beautiful forces of destruction in both reality and popular media. Tornadoes are defined as a violently rotating column of air with both debris at the surface and a funnel extending from a cumulonimbus cloud. Though nearly all violent tornadoes come from already spinning thunderstorms called supercells, many of the tornadoes the Northwest experiences are much weaker and are often spawned by non-supercell storms or even just a strong rain shower. Such tornadoes are often named after where they occur with the names “landspout” or “waterspout.”

It may surprise some, but the atmosphere generally has at least a little spin to it everywhere, all the time. This spin can be oriented in the vertical, like a spiraling column, or in the horizontal, like a rolling pin. This invisible spin is several magnitudes weaker than even the weakest tornado. Such spin is called vorticity. Non-supercell tornadoes, unlike their more violent counterparts, generate their spin by aggregating vorticity that exists in the vertical near the surface. This is explained through conservation of angular momentum, often illustrated using the metaphor of a figure skater who brings their outstretched arms closer to their body to gracefully spin faster on the ice.

These concepts help explain the genesis of non-supercell tornadoes: a weak storm or shower collecting and stretching vorticity up into the vertical until the resulting surface winds are strong enough to loft debris. A photogenic landspout occurred in the Tri-Cities on March 31. Dust devils occur in a very similar manner, but are much weaker and do not require the presence of a parent cloud. With a dust devil, a hot pocket of air rather than an associated storm are acting to spin up vorticity, collecting it and stretching it until a visible surface whirl forms.

There are still other forms of whirls that can occur. One form, a cold air funnel, was seen in Pullman, Washington, on May 18. These are similar to landspouts but are spawned in a different weather environment and almost never touch the ground. The last species of whirls is the gustnado, a portmanteau for “gust front tornado.” Though the name implies it is a tornado, gustnadoes are actually short-lived vortices that form on the edge of strong thunderstorm winds. As gustnadoes do not originate from the cloud, they are not considered tornadoes, though they certainly appear ominous.

Your safety is always of paramount concern to meteorologists. Though many of the whirls are significantly weaker than a bonafide tornado, they have caused both damage and injuries in our region. Any whirl, be it a landspout, dust devil, gustnado or a tornado, is an awe-inspiring sight, but make sure you’re in appropriate shelter for the risk before stopping to take in the atmospheric show.