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Category Archives: Seasons
How is this winter stacking up historically?
We are now a couple of days into what is easily the coldest air we have seen this entire winter.
Until a week ago, complaints about the lack of snow were also justified in the southern part of the state. However, two recent snow events have even changed that situation so that, as of Monday, Madison suddenly is 7.3 inches ahead of normal for the snow season, which started July 1. Continue reading
What happens on the winter solstice?
Astronomical winter begins at the winter solstice, which happened this year for the Northern Hemisphere at 9:27 p.m. Central Standard Time on Thursday, Dec. 21. Winter south of the equator begins in June.
The Northern Hemisphere winter solstice occurs at the time the sun is at its southernmost point in the sky. At this time, the sun is overhead at noon on the Tropic of Capricorn, approximately 23.4 degrees south of the equator. Continue reading
What is the probability of a white Christmas in Madison?
Believe it or not, the National Weather Service has criteria for declaring a Christmas white: If there is at least 1 inch of snow on the ground at 6 a.m. on Christmas Day, the year has registered a white Christmas.
As might be expected, the probability of this condition being met varies widely across the state of Wisconsin. In the far north, the probability exceeds 90% and approaches a certainty in some locations, while in the south the historic probability runs at about 40%, which might strike Madisonians as unexpectedly low. Continue reading
Does fall give any hints about the intensity of the coming winter?
Each winter we keep track of the areal extent of air colder than 23 degrees Fahrenheit at the 850 mb pressure level (about 1 mile above sea-level) around the entire Northern Hemisphere. This measure allows us to characterize the intensity of the winter season with respect to the lower tropospheric temperature.
Over the past 75 seasons there has been a systematic decrease in the December-January-February, or DJF, average areal extent of about 4.6%, and this is an unequivocal sign of global warming, measured in the winter season. Continue reading
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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