Weather Updates

Wind chill factor not just weather hype

Wind chill is real people need take it inot consideratiwhen venturing outdoors this winter according Illinois State Climatologist Jim Angel.

Wind chill is real, and people need to take it inot consideration when venturing outdoors this winter, according to Illinois State Climatologist Jim Angel. | Sun-Times Media file

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Updated: March 7, 2014 12:47PM

CHAMPAIGN — Wind chill is more than just weather hype, according to Illinois State Climatologist Jim Angel at the Illinois State Water Survey, University of Illinois.

Angel says there are important things to keep in mind about wind chill, which can present a real danger.

A release from the State Water Survey said that when the temperature dips below zero and the wind picks up, the wind chill becomes a concern for anyone venturing outdoors,

The National Weather Service defines the wind chill temperature as how cold people and animals feel when outside. Wind chill is based on the rate of heat loss from exposed skin caused by wind and cold.

The calculations for wind chill are based on temperature and wind speeds that are usually taken at a nearby airport. While the wind speed is adjusted for the difference between the 33-foot high wind instrument and a height of 5 feet, it is still based on winds at the airport in a wide-open area. Areas in town with many mature trees may have significantly lower wind speeds, the release noted.

Conversely, winds between tall buildings in places such as downtown Chicago may be much higher.

Therefore, the wind chill at a particular location may be much different from that reported at the airport, it said.

The wind chill formula is based on bare skin of a healthy adult, and vulnerability to frostbite or hypothermia can be higher for the elderly and small children. On the other hand, covering bare skin and wearing appropriate clothing greatly reduces the effects of the cold and wind.

Sunshine is not included in the formula even though it has the potential to moderate the effects of wind chill during the daylight hours.

An accurate wind chill forecast requires both an accurate temperature forecast and an accurate wind forecast. Anytime you have to predict two separate weather variables, in this case temperature and wind speed, it can be more a more challenging forecast, the release said.

“While the wind chill observations and forecasts have some limitations, the risk of frostbite or hypothermia from severe cold — especially if accompanied by wind — should be taken seriously,” Angel said.

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