Category Archives: Phenomena

What causes a double rainbow?

The classic rainbow is a single, bright, colored arc. Red is the outermost color of this arc, and violet is always the innermost color.

On occasion, you may have seen two rainbows at once. The lower rainbow is the primary rainbow and the higher, fainter, colored arc is the secondary rainbow. The color sequence of the secondary rainbow is opposite to the primary; red is on the inside of the arc and violet on the outside. Continue reading

Category: Meteorology, Phenomena

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What is a derecho?

A derecho (pronounced deh-RAY-cho, a Spanish word meaning “straight ahead”) is an hours-long windstorm associated with a line of severe thunderstorms.

It is a result of straight-line winds, not the rotary winds of a tornado — hence its name. Derechos in the United States are most common in the late spring and summer (May through August). Continue reading

Category: Meteorology, Phenomena, Severe Weather

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Why is the grass wet in the morning, when it didn’t rain?

Recent spring mornings have produced wet lawns. To explain this, we start with the fact that air contains water in the gas phase, called water vapor. Dew is made of liquid water that has condensed from some of the water vapor in the air.

Dew occurs when objects cool. A common example of dew formation is when drops of liquid form on the glass of an ice-cold drink. Dew forms when the object, such as the glass, cools down to the dew point temperature. Continue reading

Category: Meteorology, Phenomena

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How is the ice cover on the Great Lakes?

National Oceanic and Atmospheric Administration (NOAA) monitors and reports on the ice coverage of the Great Lakes. The average concentration of ice on Lake Superior is currently 5.7 percent, compared to 4.6 percent last year and 55.5 percent in 2015. … Continue reading

Category: Climate, Meteorology, Phenomena, Seasons

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Why does the morning low temperature sometimes occur after sunrise?

Those who keep a particularly vigilant eye on the weather might have noticed that on certain mornings, in all seasons, the lowest temperature is often recorded just after sunrise.

One of us had a morning paper route as a boy and was puzzled for years about this seemingly counterintuitive phenomena. How could the temperature continue to fall for the few minutes after sunrise on a cold winter morning? Continue reading

Category: Meteorology, Phenomena

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