Posted at 7:01 AM on April 15, 2008
by Paul Huttner
They call Chicago the Windy City, but Chicago has nothin' on the Twin Cities.
The average annual wind speed in Chicago is 10.4 mph. It's 10.6 mph in the metro.
April is our windiest month in the metro with a monthly average wind speed of 12.3 mph. That will seem like a soft breeze when you step outside today.
Wind advisories and high wind warnings are flying today across the state. A high wind warning is in effect for southwest Minnesota for sustained winds of 40 mph with possible gusts over 58 mph. Elsewhere we can expect sustained winds of 25 to 35 mph, with gusts over 45 mph.
High wind warnings are much more common out west, where valleys channel the wind and increase velocity. The Buffalo Ridge in southwest Minnesota acts as a funnel for some locations, and is actually one of the highest wind producing areas in the country.
High winds in spring mean high fire danger. Grasses, pine needles and leaves will burn easily today, and high winds will spread any fires quickly.
It is interesting to note how urban areas affect wind. Overall, cities with tall buildings act as a barrier to wind flow. This can reduce average wind speeds compared to suburbs and surrounding areas by about 20%.
But anyone who's walked between buildings downtown on windy days knows that the wind can really howl. As the wind flow squeezes between buildings it accelerates. The Venturi Effect can produce a 30% increase in wind speeds near the corners of buildings, and a 50% increase in the fastest flow areas between buildings.
Hang onto your hat if you're headed downtown today!