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Is there a windiest time of year in Madison?
With the pollen season peaking in southern Wisconsin one may wonder if there actually is a windiest time of year in Madison. Of course, a windy day can come along just about any time of year (the record gust of 83 mph in Madison occurred in June 1975) but the climatology suggests that March and April are the windiest months of the year with average wind speeds of 11.3 and 11.4 mph, respectively. November through February are not far behind logging a four-month average of 10.5 mph.
The fact that it’s windier during the cold season is not surprising as that time of year is characterized by the highest frequency of mid-latitude cyclone activity. Mid-latitude cyclones are large in scale, covering several states simultaneously, and are often associated with very large differences in sea-level pressure over small distances. It is these pressure differences that drive the wind. Continue reading
Category: Climate, Seasons, Severe Weather
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Why is May 6 such a special day in weather science history?
Immediately after WW II, it became fashionable to imagine technologies that might allow human beings to control the weather. In fact, one goal advanced by influential scientists was actually to explode nuclear bombs in the right locations and in the right quantity so as to alter the weather in favorable ways. Such an enterprise would require accurate forecasts of the weather thought possible by using the brand new computer technology to make the millions of requisite calculations.
The drive to use computer models for weather forecasting was initiated at a secret meeting at the U.S. Weather Bureau headquarters in Washington D.C. on the rainy morning of January 6, 1946. After a series of successes and setbacks that mostly discouraged the broad meteorological community, the first operational computer generated forecasts were issued on the afternoon of May 6, 1955. Continue reading
When will we have our last spring frost?
The latest frost in spring is important to gardeners as we seek to protect our garden plants from freezing temperatures. For Madison, based on temperature observations between 1940 and 2024, the latest frost occurred on 10 June 1972 and the earliest final frost occurred on 7 April 1955. The last frost date varies from year to year as it is strongly dependent on current weather conditions. To best estimate the last frost is to use statistics over a given time period. The median date for the last frost in Madison is May 5. Giving the median date of last frost means that there is still a 50% chance that a frost will occur after this date.
An analysis of Madison’s last frost date from 1940 – 2024 shows a trend consistent with the scientific expectations of global warming, that the last frost date now occurs earlier in the spring. Our nighttime minimum temperatures have been getting warmer and that too is consistent with the last frost date moving earlier. Continue reading
What causes tornados and do they have a lifecycle?
A tornado is a powerful column of winds that rotate around a center of low pressure. The winds inside a tornado spiral inward and upward, often exceeding speeds of 300 mph. We don’t know if a particular storm will produce a tornado but we do know the necessary conditions needed for tornado formation.
The required conditions for a thunderstorm to produce a tornado are warm humid air near the surface with cold dry air above. These conditions make the atmosphere very unstable, in the sense that once air near the ground is forced upward, it moves upward quickly and forms a storm. Severe thunderstorm conditions also include a layer of hot dry air between the warm humid air near the ground and the cool dry air aloft. This hot layer acts as a lid that allows the sun to further heat the warm humid air, making the atmosphere even more unstable. Continue reading
Category: Meteorology, Phenomena, Severe Weather
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Should we stop climate research?
Scientific evidence for slow, ongoing, systematic warming of Earth’s atmosphere is unequivocal. This conclusion comes from evidence-based science and a physical understanding of that evidence. Regular scientific assessments of global and regional climate began in the 1970s. These assessments, along with a physical understanding of the atmosphere, show that the impact of human activities on this warming has evolved from theory to established fact. This is not a radical political statement; it is a firm conclusion based on the analysis of carefully considered observations.
Burning fossil fuels generates greenhouse gases, which are transparent to solar radiation but absorb large amounts of terrestrial infrared radiation that results in warming the atmosphere. The planet’s average surface temperature has risen about 2 degrees Fahrenheit since the late 1800s. Most of that warming has occurred in the past 40 years. Continue reading
