Story URL: http://news.medill.northwestern.edu/chicago/news.aspx?id=111099
Story Retrieval Date: 5/24/2013 6:17:56 PM CST
WGN's Tom Skilling and Northern Illinois University’s Gilbert Sebenste break down what happened to the blizzard predicted for Monday night. The “bust” – a blown forecast, in meteorologists’ lingo – was the result of a trio of weather anomalies. “One of these, no problem – the blizzard hits and we’re still right,” Sebenste said. “It was a perfect storm of things going wrong.”
1. Wind: Gusts that clocked in as high as 75 mph in Rapid City, S.D. on Monday morning died down drastically when they moved east. Instead of the 35 mph gusts predicted, Chicago only saw 20- to 25-mph winds. “You know [the wind] is going to slow down, but predicting exactly how much and when is hard,” WGN meteorologist Tom Skilling said.
2. Rain: Snowflakes have to form around something – usually a piece of dust or dirt in the air. But the air over Chicago Monday night was so clean, Sebenste said, that the moisture fell as freezing rain between 8 and 11 p.m. This formed an ice crust on top of the snow, which kept the snow from blowing and drifting. This weather phenomenon, known as “super-cooled water droplets,” is extremely rare.
3. Snow: The storm system came through faster than expected and instead of dropping 3 to 5 inches, most of the northern part of the state saw only 1 to 3. “The storm tracked a little north and it turned out not to be the system we anticipated,” Skilling said.