 Many factors contribute to abnormal winters
By Tony Schumacher
One of the strangest winter events I've witnessed occurred in the Green Bay
area on January 15, 1999. About an inch of snow fell in the suburb of Allouez . You say that's not so unusual? Well, the snow was "factory-effect snow." As steam from factories and paper mills rose into colder air, moisture condensed, producing clouds. This happens almost every day, but what made this cloud deck a snow producer was the fact that the air hit a strong temperature inversion, a layer of warmer air aloft, which trapped the moisture in a narrow layer. This gave the moisture a
chance to coalesce and produce snowflakes. The wind was from the southwest and blew the snow clouds right into Allouez. The rest of the area had clear skies!
There's no denying the winters have been abnormal in the upper Midwest the last several years. Finding consistent snow and cold for skiing, snowshoeing and ice fishing has been a challenge. Wisconsin, Michigan and Minnesota all had their warmest winter on record in the 1997-1998 season, while Illinois had its second
warmest and Iowa its fourth. This was predicted, thanks to one of the strongest El Niño events underway since the previous spring.
New Weather column debuts As we all know, the world of the silent sports is weather-dependent and many of us have become amateur meteorologists as we follow trends and weather patterns. That said, I thought it was time to hear from an expert. From his base in the center of our readership area, Tony Schumacher will enlighten, entertain and educate us about a topic always on our minds – the weather. ED. I've been a meteorologist for the past seven years, although I've had a lifelong passion for the weather. I grew up in north central Wisconsin about 35 miles west of Wausau, near Dorchester, on a dairy farm. Perhaps this is how I became so interested in the weather: Our family literally depended upon the weather for our livelihood. I distinctly remember fields of cut hay ready to bale that got ruined from unexpected downpours, or fields
of corn withering in the drought of 1988. I even recall some of our cows getting killed by lightning.
I earned my bachelor's degree in meteorology in 1993 at the University of Wisconsin-Madison. I immediately entered the broadcast meteorology field at WSAW-TV in Wausau. In my four years at WSAW, I continued farming part time with my parents. I also worked for Great Lakes Weather Service, a forecasting and consulting company, during my first year at WSAW-TV. In March 1997, I moved to
Green Bay to do weather for WFRV-TV. After two enjoyable years, I moved back to Wausau to work as chief meteorologist for WAOW-TV. I also now manage Great Lakes Weather Service. We have about 90 clients in the Midwest including radio stations, construction and paving companies, utility companies, ski resorts, road departments and agricultural companies. I'm a member of the American Meteorological Society as well.
My wife, Kathy, and I live in Rib Mountain, near Wausau, with our
2-year-old son, Douglas. We enjoy many of the same sports you do, including running, biking and skiing. Many of my seven brothers and sisters, along with nephews and nieces, enjoy participating in relay marathons. We've done seven or eight of them and had a blast. We've even managed to win a few awards.
Tony Schumacher |
El Niño is a warming of the equatorial Pacific between Indonesia and
South America. It develops on average between every 2-7 years. El Niño results from a weakening of the east to west trade winds that normally occur in that region. This causes the normal upwelling of cold water off the coast of South America to decrease. Warm water, which is normally piled up closer to Indonesia, sloshes back to the eastern Pacific. Water temperatures were as much as 8° F. above normal in the eastern Pacific during this past event.
This warm water serves as the fuel for intense storms and rainfall over the Pacific Ocean. Tropical rainfall warms the atmosphere through the release of latent heat as water vapor condenses into raindrops. This in turn dictates in part the strength and position of the jet streams crossing the Pacific. During a strong El Niño, the subtropical jet stream becomes stronger in the eastern Pacific and drives more frequent vigorous storms
into the southern U.S. Likewise, the northern jet stream, the polar jet, gets displaced further north, running from west to east mainly through southern Canada. This prevents Arctic air from invading the upper Midwest. We don't get much snow because we're caught too far away from either storm track.
Only strong El Niño events have this pronounced effect on upper Midwest winters, and they don't happen that frequently. The previous intense El Niño before 1997 was in 1982-1983.
El Niño has a counterpart that occasionally develops right behind it, La Niña. We're still in the La Niña phase that began about the summer of 1998. La Niña is a cooling of the equatorial Pacific between Indonesia and South America caused primarily by the strengthening of the east to west trade winds in the Pacific. This causes the upwelling of cold water off the coast of South America to increase.
Again, this has dramatic impacts of where the heaviest tropical storms and
rainfall will occur, shifting it back further west towards Indonesia. This usually causes more north to south undulations in the southern branch of the jet stream causing increased storm activity in parts of the central U.S., including the upper Midwest. Also, a blocking upper level ridge of high pressure that normally develops during La Niña south of Alaska, can often force the polar jet to dive southward into the central U.S. This leads to
increased frequency of cold air outbreaks in the upper Midwest.
If La Niña alone were the only thing affecting our winter in the upper Midwest last year and now, one would have expected above-normal snowfall and frequent cold spells; this hasn't been entirely the case though. In most of our area, significant snow did not arrive until mid- to late-December in both winters. In fact, as I'm writing this column, on
January 2, there still isn't any significant snow on the ground in southeast Wisconsin or northern Illinois.
Furthermore, November and December temperatures averaged about 4 to 6 degrees above normal in both winters. January 1999 did feature much above normal snowfall and near normal temperatures. Green Bay received 21 inches of snow and Minneapolis 33 inches of snow, for example. However, that was where it ended last winter. February 1999
was one of the warmest Februarys on record in most upper Midwest locations, about 10 degrees above normal. Also, only a few inches of snow fell in most areas. Most of what did fall had melted by mid-month. So obviously the atmosphere is controlled by more than just El Niño or La Niña.
Two other factors that may be changing our winters around here are a long-term climate change, i.e., global warming, and the North Atlantic Oscillation.
According to the Climate Prediction Center, the average temperature during the winter months in particular has increased at a rate of .40 to 1.2 degrees per decade in the upper Midwest since 1940. The change is even more striking from North Dakota and Montana into the western half of Canada, where the rate of increase has been from 1.0 to 2.0 degrees per decade. If you add this long-term change to that of El Niño, it's no wonder the El Niño winter of 1997-1998 was extremely warm around
here. Likewise, this long-term winter-warming trend acts to diminish the normal cooling effects of La Niña in the upper Midwest. Perhaps, then, we'll end up with just near-normal winter temperatures during La Niña instead of colder than normal.
The other important link that may be altering our winter weather is a naturally occurring shift in sea surface temperatures and air pressure in the North Atlantic Ocean, called the North Atlantic Oscillation, NAO for
short. Essentially, there is a semipermanent low-pressure system in the atmosphere over the North Atlantic near Iceland, and a semipermanent high-pressure system near the Azores, off the northwest coast of Africa. The NAO is a shift in strength of the high and low pressure, which peaks during the winter season.
Essentially, when the Icelandic low is stronger than normal, it buckles the jet stream over North America into a configuration that supports less
frequent intrusions of cold air into our area. On average, this type of pattern has been in effect since the middle 1970s. Just the reverse was true from around 1930 to the early 1970s. Perhaps this is what caused the good old-fashioned winter our parents and grandparents talk about. Of course, there were years that didn't fit the general trend.
With all this said, the Climate Prediction Center's forecast for February in our part of the country calls for
near-normal temperatures and above-normal precipitation. That would be all right, but we'll have to wait and see, as there are no sure things in weather forecasting. If you have any weather topics you'd like me to write about, feel free to send me suggestions. My e-mail address is tonys@waow.com. Thank you and
enjoy the weather!
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