Updraft: April 15, 2008 Archive

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.

Wind warnings and advisories

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.

U.S. Springtime wind energy potential

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.

Air circualtion in cities

Hang onto your hat if you're headed downtown today!

PH

In 1959, Loerner and Lowe composed a song entitled, They Call the Wind Mariah, for the musical Paint Your Wagon. Tropical storms are named, but not the gradient winds that howl through the prairies of the nation's midsection. I've seen stronger winds in Minnesota than those which alarm coastal residents with the potential for 45 mph wind gusts simply because the tropical storm has a name.

Earlier today I spied a report of sustained winds of 38 mph with gusts to 54 mph at Marshall, Minnesota. High Wind Warnings are in effect for southwest Minnesota with a wind advisory posted until this evening for south central Minnesota.

Fire danger from strong winds

Winds ushering in milder air across the Upper Mississippi Valley are a sign of spring, when snow can melt rapidly, frost dissolves in the soil, thawing of the lake ice is accelerated and the landscape quickly gives up the recent moisture.

Today's gusty winds are the result of nature atoning for the chill of last week and gracing us with seasonal temperatures. Surface pressures are falling as a trough of low pressure takes shape in the Dakotas. This change in air masses could induce a few showers on Wednesday as slightly cooler air reaches northwest Minnesota and the winds switch back to the northwest.

We could initiate a process to name blustery winds after meteorologists. Today, I'll call this blast of warmer wind, Craig.
CE
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