Newswise — What's the difference between sleet and freezing rain? What's a snow squall? And does the term “polar vortex” mean we’re in for a really deep freeze all season? Paul Roebber, one of the leading forecasting experts in the United States and the world, can help explain weather terms more commonly heard in wintertime. Roebber is a distinguished professor and founder of the Innovative Weather forecasting service at the University of Wisconsin-Milwaukee. He can discuss subjects like the true effects of the polar vortex, a pattern of high-level winds that circles the North Pole year-round, even on the hottest summer day. Roebber can talk about how weather forecasting has improved over the past couple of decades as computer modeling has improved both in speed and accuracy. He’s a leader in bringing new approaches to meteorology, and his research has changed how experts around the world forecast weather.