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clbuckle posted a question about dust devils & it brought to mind something ...
Quote from: DoctorBeaver on 12/08/2009 09:19:39clbuckle posted a question about dust devils & it brought to mind something ...Did you see the link I included in that reply? Guess how many people clicked on it, go, guess! The answer is one! One! ONE!!!
Different kinds of small vortexesThe strongest tornadoes come from the kind of long-lasting, especially fierce thunderstorms known as supercells. As the name implies, these are super thunderstorms with more than their share of potential danger. In addition to tornadoes, supercells can produce large hail and downbursts. Some bring heavy rain while others are relatively dry. Supercells are most common on the Plains, in the Southeast and across the Midwest, but do occur elsewhere. Not all tornadoes come from supercells, but the strongest twisters usually have a supercell as a parent. Weaker vortices, such as waterspouts like those common in the Florida Keys, can come from cumulus congestus clouds, also known as "towering cumulus." These are tall, thick cumulus clouds that might be producing rain, but not lightning and thunder. Some researchers are using the term "landspouts" for similar twisters that form over land, not water. At times, waterspouts move ashore and can do the same damage as weak tornadoes."Gustnadoes" are weak vortices that are not connected to the cloud base, and by definition are not tornadoes. They are relatively shallow vortices associated with intense, small-scale shear in a thunderstorm gust front. They are not directly linked with rotation in the thunderstorm itself. Because they can produce whirling dust clouds (sometimes with small debris), they are very often erroneously reported as tornadoes. It takes a very alert and experienced spotter to tell the difference sometimes. Roger Edwards, a meteorologist and mesoscale forecast specialist at the Storm Prediction Center in Norman, Okla., says that, "On several occasions, I've personally witnessed tornadoes and gustnadoes produced by the same storm; but they have no mandatory link."Cold-air funnel clouds - or simply cold-air funnels - form mainly during the late fall and winter months. Like waterspouts, cold-air funnels also form beneath cumulus congestus clouds, rather than thunderstorms. The cold air above the warmer ground creates instability that grows the fair weather cumulus. Small-scale wind shear forms the funnels along narrow boundaries on the edges of the clouds, much like gustnadoes. So, technically, they could be called "gust funnels" because they are like gustnadoes that never reach the ground. Dust devils are swirls that go upward to fizzle out in clear air; they aren't attached to clouds. While they are most commonly found on deserts and form when air at the ground becomes much hotter than the air above. The lighter, hot air begins rising and takes on a whirling motion that carries dust and sand upward. Top wind speeds seem to be around 60 mph. By Jack Williams and Chris Cappella, USA TODAY.com