Chicago, Illinois has been nicknamed the "Windy City," but it isn't the only part of the state that experiences strong fluctuations in winds. Winds across East Central Illinois fluctuate dramatically, depending upon the season and atmospheric setup. Often times wind direction and strength have a major impact on the weather. In order to understand how winds impact East Central Illinois, one must first have a basic understanding of the state's climate and topography. Illinois's climate is continental, i.e. cold, rather dry winters, warm, humid summers, and frequent short duration, but relatively large magnitude changes in temperature, humidity, precipitation and wind direction (1). Weather in this part of the country is greatly influenced by air masses that originate over Canada, the Pacific Ocean and the Gulf of Mexico. Depending on the season, Illinois experiences all types of inclement weather, some of which are greatly influenced by wind direction. In terms of topography, Illinois is relatively flat and composed of mostly prairies and fertile plains. Terrain tends to vary a little more around several of the state's major river valleys (Illinois, Mississippi and Wabash). In the Champaign-Urbana area, land is best described as flat. In comparison to mountainous regions, Illinois experiences a smaller amount of friction between winds and the earth's surface. However, it is important to note that friction causes winds to slow down more over land surfaces than water surfaces. The frictional force causes winds to slow down about 20 percent (6). For the purpose of this paper, I will primarily take a look at how winds from the Northwest impact weather in the Champaign-Urbana. In order to do this we must first take a look at the atmospheric setup in which winds from the northwest occur. In general, winds are created by pressure differences in the atmosphere. Wind is the rough horizontal movement of air caused by an area of low pressure and an area of high pressure near each other and the wind will blow from the high pressure point to the low pressure point (2). More specifically, it is common for areas of low pressure and frontal boundaries to make their way across the state several times a week. The passing of these pressure systems and fronts often determine wind direction. Wind direction can have a major effect on East Central Illinois weather. Wind direction changes often accompany changes in weather (3). Therefore, it is important to note what type of climate is located in every direction from the forecast location. In Champaign for example, toward the west is cooler and drier air over the plains; to the north is cooler air; toward the east conditions are similar; toward the south is warmer and more humid air. People living in the middle latitudes know well that during the winter, northerly winds can chill you to the bone. Conversely, a sudden change to a southerly flow can bring welcome relief from frigid conditions (4). The reason for this is because winds blowing in from the south will bring in warmer and moister air to the region. Often times wind direction will change as a low pressure and high pressure systems move across the forecast area. For instance, when an area of low pressure moves across the state, winds generally come from the northwest. The reason for this is because winds circulate counter-clockwise around areas of low pressure. Wind direction during the winter months can also significantly alter the forecast temperature. For instance, if winds are from the Northwest and there is already snow on the ground, one can expect temperatures to be colder than models anticipate. Conversely, if winds are coming in from the south or southeast, more moisture from the gulf and warmer temperatures will warm the forecast area. Forecasting for this particular event can sometimes be challenging. Wind speed will play a key role on surface temperatures in situations where there is a strong temperature change with height in the boundary layer (5). For instance, if there is a strong temperature lapse rate near the surface, the wind can mix the surface air with cooler air aloft. Thus, temperatures will be cooler when winds are strong. When winds are strong on a clear night, temperatures will be warmer because the air will mix with warmer temperatures aloft. Another challenge occurs when wind direction changes over a short period of time. Inclement weather can occur when a storm system is quickly moving across the region. In certain parts of the country a forecaster must also look at significant water bodies in close proximity and elevation changes. In East Central Illinois there are no significant water bodies or dramatic elevation, so forecasting is a little simpler. Overall, wind direction is an important forecasting tool. Noting wind speed and direction can help forecasters with temperature forecasting. It is important to note the stronger the mid-latitude wind, the greater the probability of having temperature advection (either warm air or cold air advection) (7). Just by noting the wind direction a forecaster can tell what type of air mass is moving toward the forecast area and how it'll impact people in the community. I think it is also important to remember that each individual forecast region is unique. Obviously, things like elevation, mountains, hills, water bodies and skyscrapers must be taken into consideration. Wind direction can be altered when they encounter different types of topography. What is particularly interesting is how vastly different the topography is from one region to the next in the continental United States. In terms of research, there seems to be a decent amount material out there on winds. However, I found it difficult to find specific research on how northwest winds specifically impact East Central Illinois. I think this would be an interesting phenomenon to consider in the future, because I've noticed since living here just how important wind direction has on a forecast. Ultimately, in order for forecasts to improve, technology must continue to evolve. Although models do a decent job with forecasting temperatures, accuracy still seems to be an issue. Computers don't seem to be advanced enough yet to take into consideration things like wind direction and strength fore specific regions of the country. I think one of the best assets a forecaster can have is experience. However, I also realize that broadcast meteorologists sometimes have to move to different regions of the country depending on where a job is. I think it can be both challenging and exciting to learn a new region of a country. Continual education and experience seems to help forecasters come up with the most accurate forecasts in the long run. I think it's fair to say, forecasters should only use models as a general guide and most importantly have a solid understanding of the topography in which they live. References (1) Illinois State Water Survey in Champaign. Illinois Climate. Retrieved on April 2, 2007, from: http://www.nass.usda.gov/il/1998/9816.htm (2) Wikipedia. Wind. (n.d.). Retrieved on March 25, 2007: http://en.wikipedia.org/wiki/wind (3) Haby, Jeff. Wind Direction and Weather Forecasting. (n.d.). Retrieved on March 25, 2007, from the Weather Prediction website: http://www.theweatherprediction.com/habyhints2/432/ (4) Lutgens, F., & Tarbuck, E. (1979). The Atmosphere. (pp. 193). New Jersey: Prentice Hall. (5) Haby, Jeff. Forecast Bust: Wind Speed and Direction. (n.d.). Retrieved on March 25, 2007, from the Weather Prediction website: http://www.theweatherprediction.com/habyhints2/376/ (6) Haby, Jeff. The Importance of Friction. (n.d.) Retrieved on April 2, 2007, from the Weather Prediction website: http://www.theweatherprediction.com/habyhints/10/ (7) Haby, Jeff. Wind as a Forecasting Tool. (n.d) Retrieved on April 2, 2007, from the Weather Prediction website: http://www.theweatherprediction.com/habyhints/17/ |