Category Archives: History

What is the National Climate Assessment?

The U.S. National Climate Assessment is mandated by the Global Change Research Act of 1990. The assessment is conducted about every four years and is an authoritative scientific analysis of climate change risks, impacts and responses in the U.S.

The nation this month completed the Fifth National Climate Assessment, or NCA5. The National Oceanic and Atmospheric Administration is the administrative agency for NCA5 and certifies that the report meets Information Quality Act and Evidence Act standards. The assessment is an extensive process that includes internal and external review from federal agencies, the general public and external peer review by a panel of experts. Continue reading

Category: Climate, History, Seasons, Severe Weather

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What is the status of sea ice this year?

The surface waters of our polar oceans freeze seasonally, forming a layer of sea ice that varies in thickness from centimeters to meters. The era of polar orbiting satellites has enabled the monitoring of sea ice distribution for more than four decades.

Seasons are reversed between the Northern and Southern hemispheres, so the sea ice maximum and minimum occur at different times of the year. Generally speaking, around mid-September the extent of the sea ice at the south pole is reaching a maximum, while in the Arctic it is approaching a minimum in September as our Northern Hemisphere summer comes to an end. Continue reading

Category: History, Seasons

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Atmospheric and Oceanic Sciences turns 75

On Friday, the Department of Atmospheric and Oceanic Sciences at the University of Wisconsin-Madison celebrated its 75th anniversary.

When the department was founded in June 1948, the modern science of meteorology was arguably just a few years old, and even basic understanding of the nature of the mid-latitude cyclones that batter us from October to May was truly in its infant stages. Continue reading

Category: History, Meteorology

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Higher overnight lows led to warm September

As we enter the month of October and the traditional end of the warm season, it’s interesting to note that the average temperature last month, through Sept. 28, was 4.0 degrees above normal in Madison.

That is by far the biggest deviation among traditional warm-season months — June, July, August and September. All were warmer than average this year: June was 0.8 degrees, July just 0.5 degree and August only 1.2 degree above the respective norm. Continue reading

Category: Climate, History, Seasons

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Do hurricanes affect Wisconsin?

A tropical cyclone is a rotating low-pressure system that has organized thunderstorms but no fronts. When a tropical cyclone’s maximum sustained winds reach 74 mph, it is called a hurricane. Hurricanes have never directly impacted the Upper Midwest region of the U.S.; however, the remnants of a hurricane or tropical storm have impacted the weather in the Midwest, including Wisconsin.

If a hurricane is particularly strong at landfall, it can move far enough northward to cause a significant rain event for areas in the Midwest. For the most part, such storms originally make landfall in Texas, Louisiana or Mississippi. These storms can be tracked by satellites or surface weather observations because they maintain an identifiable circulation pattern along their entire path. Continue reading

Category: History, Meteorology, Severe Weather, Tropical

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