It’s that time of the year again- strong winds. What is wind? In essence, wind is the movement of air from areas of high pressure to areas of low pressure.
What can influence air pressure? Temperature, certainly. The little whirlwinds I wrote about last fall are heavily influenced by temperature. They start in areas that are hot, such as parking lots, and when warm air rises, cool air rushes in to fill the void. This can result in the spinning motion that becomes the whirlwind.
Dust Devils and Whirlwinds
Strong swirling winds, but over a small area. Spinning dust and debris. Brief, often a handful of minutes. Almost out of nowhere on a warm, clear day. The literature that studies them calls them dust devils, but to the people that live with them they are dust whirls, whirlwinds, sand trumpets,…
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But winds are always a result of air moving from high pressure to low pressure- not just the ones with circular motion. There are many types of winds that come out of thunderstorms, most of which don’t involve spinning.
Straight-line winds – microbursts, (or macrobursts for that matter- the distance is size) are still formed by air moving by convection. Heavy, colder air in the center of a storm sinks downward, and is pushed to the sides.
Straight-line winds are certainly capable of tornado-level damage. The main difference? Direction. With a tornado, debris is scattered. Straight-line wind? Fan-shaped, and, yes, pretty straight.
The brief storm that passed through lower Trego last week was a nice example- if you’re looking, you’ll see that the downed trees are facing approximately the same direction.
Trego's Mountain Ear 