Rare Brooklyn dust devil dazzles

Here's something you don't see everyday, at least in New York City.

A rare dust devil spun up over a baseball field Sunday afternoon Brooklyn, New York.

http://www.youtube.com/watch?v=qX8Biep2gKA

Dust devils are whirling columns of air that spin up from the ground up as hot air rises. They are commonplace in the deserts of Arizona, where I observed them many times in my nine years forecasting weather. They tend to form on warm, calm days and develop near landscape boundaries that produce what meteorologists call "differential heating."

Climate Central's Andrea Thompson has a nice explanation.

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.”

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.

I have seen dust devils rip off car ports in Arizona, and topple garbage cans sending debris around neighborhoods. Winds in Arizona's dust devils can reach speeds of 70 mph.

Dust devils occur in various parts of the world, and have some pretty colorful local names.

A dust devil is a strong, well-formed, and relatively long-lived whirlwind, ranging from small (half a meter wide and a few meters tall) to large (more than 10 meters wide and more than 1000 meters tall). The primary vertical motion is upward. Dust devils are usually harmless, but rare ones can grow large enough to threaten both people and property.

They are comparable to tornadoes in that both are a weather phenomenon of a vertically oriented rotating column of air. Most tornadoes are associated with a larger parent circulation, the mesocyclone on the back of a supercell thunderstorm. Dust devils form as a swirling updraft under sunny conditions during fair weather, rarely coming close to the intensity of a tornado.

In the southwestern United States, a dust devil is sometimes called a "dancing devil" or a "sun devil". In Death Valley, California, it may be called a "sand auger" or a "dust whirl".

The Navajo refer to them as chiindii, ghosts or spirits of dead Navajos. If a chindi spins clockwise, it is said to be a good spirit; if it spins counterclockwise, it is said to be a bad spirit.

The Australian English term "willy-willy" or "whirly-whirly" is thought to derive fromYindjibarndi or a neighboring language. In Aboriginal myths, willy willies represent spirit forms. They are often quite scary spirits, and parents may warn their children that if they misbehave, a spirit will emerge from the spinning vortex of dirt and chastise them. There is a story of the origin of the brolga in which a bad spirit descends from the sky and captures the young being and abducts her by taking the form of a willy-willy.

In Saudi Arabia, Kuwait, Iran, Kazakhstan, and Jordan, they often reach hundreds of meters in height[citation needed] and are referred to as djin ("genies" or "devils").

Egypt has its fasset el 'afreet, or "ghost's wind".

Dust devils have even occurred on Mars, as captured by the Mars rover Discovery.