News•August 11, 2014

How Did the Brooklyn Dust Devil Form?

Some denizens of Brooklyn who were out enjoying a warm, sunny summer day in a park in the Williamsburg neighborhood on Sunday got quite a surprise when a dust devil spun across a baseball diamond as park goers lounged on beach towels nearby.

Dust devils — small, rotating columns of air that we can see because of the dust and debris they pick up from the ground — aren’t a common feature of New York City’s weather, and sparked a surge of local media coverage.

“It’s an item of curiosity,” said Bill Goodman, a meteorologist with the National Weather Service’s New York office. “These things don’t happen very often, especially not in the middle of New York.”RELATEDTwisters Past and Present: Interactive Tornado Tracker
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It happened this time because conditions were right: The day was clear, hot and calm, which can set up a situation where one part of the ground — such as the dark asphalt of a parking lot — heats up faster than the surrounding ground. In this case, the dry dirt of the baseball diamond likely heated up faster than the surrounding grass (which contains moisture that absorbs some of the heat) under the clear skies and hot, dry conditions in the city.

“Yesterday was just a good day for something like that to form,” Goodman told Climate Central.

When you get a contrast in heating such as what happened on Sunday, it can overcome the larger weather influences and create a mini weather pattern. The hotter part of the ground heats up the air above it. This air is hotter than the air around and above it and so rises, punching through the cooler air above and creating a vertical column of warm, rising air. Around this cool air that has been knocked out of the way circulates vertically. If a gust comes along, it can blow this arrangement on its side, forming a dust devil.

Dust devils range in width from about 10 feet to 100 feet, according to the American Meteorological Society, with an average height of about 650 feet.

They aren’t the same as tornadoes, which form by slightly different processes, and don’t get nearly as big or as destructive as tornadoes can get. They can do some damage however, up to an EF1 rating on the Enhanced Fujita tornado damage rating scale, the AMS notes.

While they aren’t common in the New York area, they do happen. Goodman said that when he worked at the Mount Holly, N.J., NWS office, they would get a dust devil report “just about every summer.”