Category Archives: Meteorology

Why was there a reddish tint in the snow this month?

On April 11, there were widespread reports and photos of dust residue on vehicles and tan/brown-colored snow in parts of Wisconsin, Minnesota, Iowa and Nebraska.

The origins of these residues can be traced back hundreds of miles to Arizona, Texas and New Mexico. Continue reading

Category: Meteorology, Severe Weather

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When does winter really end?

Last year’s 7 inches of snow on April 18 provided vivid evidence that, though early April often brings the first string of nice spring days to southern Wisconsin, we are not truly out of the woods until the end of the month.

Despite the possibility of such an outlier event, recent research at UW-Madison has considered the variability of the end of winter based purely on temperatures above the surface. Continue reading

Category: Meteorology, Seasons

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What is the Coriolis force?

Newton’s laws of motion mathematically describe how objects move when forces are exerted on them.

Earth is spinning like a top, even though to us who are standing on Earth, it seems that we are not moving. Newton did not account for Earth’s spin in his equations. The Coriolis force appears as an extra term when Newton’s laws are transformed to account for Earth’s spin. Continue reading

Category: Meteorology, Phenomena

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Why are icicles shaped like long skinny carrots?

Icicles typically form on days when the outdoor air temperature is below freezing but sunshine warms and melts snow or ice. Thus, you may notice that more icicles form on the sunny south-facing side of your home than on the … Continue reading

Category: Meteorology, Phenomena

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What is the best weather forecast model?

If you are not a student of meteorology, you should rely on your local weather forecasters for a good weather forecast — and southern Wisconsin has some very good local forecasters. It is their job to interpret the various numerical weather prediction models.

Numerical weather prediction models, or NWP, solve a complex set of mathematical equations that are based on the physics that drives how the air moves and how heat and moisture are exchanged throughout the atmosphere. Continue reading

Category: Climate, Meteorology

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