The Weather Guys

Employing data from the last 70 winter seasons (December, January and February) we have been examining the extent of air colder than 23 degrees over the Northern Hemisphere. This year’s winter season was the 23rd warmest of the last 70. Not particularly impressive considering that just three years ago we had the very warmest winter season in seven decades.

Using the same data, we have recently been attempting to develop a reasonable measure of the duration of the winter over a region encompassing the Great Lakes.

We divided the 70-year data set into two 30-year periods, 1948/49 to 1977/78 and 1980/81 to 2009/10. We then determined, for each 30-year period, the calendar days on which there was, on average, a 90 percent chance that the coldest day of the year was still yet to come. For instance, no winter in all those years recorded its coldest day as early as Dec. 1. Thus, on that day, the chance that a colder day is still to come is 100 percent.

In the older data set, the 90 percent day is Dec. 16 while the 10 percent day is March 3. Thus, one could make an argument that, on average, our winter extended from Dec. 16 to March 3 in that earlier period.

In the more recent period, the 90 percent-10 percent interval extends from Dec. 30 to Feb. 18 — nearly four weeks shorter than the prior period. This preliminary result suggests that as the Earth continues to warm, not only is winter less extreme, but it may also be substantially shorter.

Steve Ackerman and Jonathan Martin, professors in the UW-Madison department of atmospheric and oceanic sciences, are guests on WHA radio (970 AM) at 11:45 a.m. the last Monday of each month.

March 1st GOES-S satellite launch from
Kennedy Space Center. Photo credit: M. Deep

Yes! The U.S. launched a new weather satellite on Thursday March 1st.

This is the second in a series of four next-generation weather satellites now in orbit 22,300 miles above the Earth. It will reach its final orbit location in approximately two weeks, and will be referred to as GOES-17 (Geostationary Operational Environmental Satellite, number 17).

It will orbit above the western part of North America and will provide faster, more accurate observations for tracking wildfires, fog and storm systems and hazards that threaten the western United States, including Hawaii and Alaska.

Satellite data help forecast the weather in two ways: Expert forecasters interpret the images, and numerical weather-prediction models assimilate observations. Image analysis plays an important role in short-term forecasts, those that predict the weather one to three hours into the future. Numerical weather predictions are more useful in 12-hour to three-day forecasts.

While weather forecasters routinely analyze current satellite observations, most data never reaches forecasters’ eyes. Most satellite observations go directly into numerical weather-prediction models. In fact, today’s weather forecast models rely on satellite data more than any other weather observation. These data include the vertical distribution of temperature and humidity, cloud distributions, land and sea surface temperatures, location of volcanic ash and wind speeds and directions.

Today, more than 120 U.S. space-based instruments observe our planet.

Other nations have just as much interest in observing weather from space as does the U.S. International collaborations organized through the World Meteorological Organization offer a powerful way to understand weather on a global scale.

Steve Ackerman and Jonathan Martin, professors in the UW-Madison department of atmospheric and oceanic sciences, are guests on WHA radio (970 AM) at 11:45 a.m. the last Monday of each month.