Category Archives: Phenomena

Are there rivers in the atmosphere?

The term “atmospheric river” has been in the news recently due to the flooding along the West Coast.

An atmospheric river is a narrow band of concentrated moisture in the atmosphere. It is a narrow moisture plume that is a few thousand miles long and only about 250 to 375 miles wide. The term was coined in the early 1990s. Continue reading

Category: Meteorology, Phenomena, Severe Weather

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How remarkable was the recent winter storm?

The recent winter storm that affected large portions of the United States just days before the Christmas holiday was remarkable in a number of dimensions.

It was an example of a “bomb cyclone” which simply means that the rate at which its central pressure dropped — about 2.5% in a single day — was extremely unusual. Even though a 2.5% change in central pressure does not sound like very much, it was responsible for revving up the extreme winds that brought wind chills into the minus 30s and ground blizzard conditions to a large portion of the Great Lakes states on Dec. 23. Continue reading

Category: Meteorology, Phenomena, Seasons, Severe Weather

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Can a snowstorm have lightning?

Yes, and if you were awake late Wednesday night you might have observed lightning and heard thunder with the snowstorm.

It is not a common occurrence, but when lightning and thunder occur during a snowstorm, the event is reported as “thundersnow.” Continue reading

Category: Meteorology, Phenomena, Severe Weather

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What makes the wind blow?

Southern Wisconsin has certainly experienced some windy days this past week. Wind is defined as the horizontal movement of air from one place to another. Wind exists because of differences in air pressure. Any movement requires a force, and in … Continue reading

Category: Meteorology, Phenomena

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Another example of unprecedented weather extremes

Another entry in the category of unprecedented weather extremes comes from the tropical Atlantic basin where, last week, Hurricane Fiona wrought devastation to the Commonwealth of Puerto Rico, still reeling from its assault by Hurricane Maria eerily precisely five years earlier.

Fiona dropped upwards of 30 inches of rain on the south shores of Puerto Rico before heading north into the Atlantic, where it systematically strengthened into a Category 4 hurricane with sustained winds of more than 130 mph. Continue reading

Category: Meteorology, Phenomena, Severe Weather, Tropical

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