In many instances the weather model data does not pick up on or include the influence of Lake Michigan on the weather in West Michigan. Sometimes there are differences in the model data. This can create a problem with the accuracy of the forecast if the influence of the lake is not taken into account. One of the ways it can make a particular event difficult to forecast for is in snowfall amounts from a lake effect snow event. The consequences of that is not forecasting enough snow letting the public know so that they can be prepared for what’s coming i.e. city services, snow plows, businesses, schools etc. For the purpose of this paper I will look at West Michigan’s location, aspects of Lake Michigan and the influence the lake has on the area in different seasons and different weather situations with different air masses. West Michigan is located in the Lower Peninsula of Michigan and includes the major cities of Grand Rapids, Kalamazoo, Battle Creek and Muskegon. The land mass is made up of farm land, forests and lakeshore sand dunes. Lake Michigan is the second largest Great Lake by volume with just under 1,180 cubic miles of water. It is the only Great Lake entirely within the United States. It averages 279 feet in depth and reaches 925 feet at its deepest point. The Lake is 118 miles wide and 307 miles long with more than 1,600 miles of shoreline spanning 4 states. Most of the shoreline is along Michigan and Wisconsin with a very small part along Indiana and Illinois. The average temperature in West Michigan is influence by Lake Michigan; for example in the winter with lake effect cloud cover over the region it won’t be as cold as it would be with a clear sky. The average temperatures are not as cold as other regions unless there is an arctic air mass effecting the area or daytime heat loss due to clear skies. In the winter the area can and does experience several days in a row that are cloudy that helps to keep the temperature from falling as low as it could. Air masses from other regions are influence by the lake, warm and humid air from the Gulf of Mexico, cold dry air from the Arctic. Lake Michigan with these different air masses flowing into and across West Michigan affect the region at different times of the year during the four seasons, winter, spring, summer and fall. In the fall and winter when the lake temperature is warmer than the land temperature and there’s more moisture in the air, the temperature at night will not have a significant cool down. Because of this you have warmer than normal average low temperatures during those times of the year when this occurs. In the spring and summer you have the opposite effect with a colder lake temperature and a warmer land temperature. A cool wind coming across the colder lake will keep the average high temperatures below normal. The weather in each season in West Michigan is influence by Lake Michigan. For instance, in the summer a tropical air mass from the Gulf of Mexico can cause a temperature inversion. It occurs when the warm air crosses over the colder Lake Michigan waters warming the top layers of the water while the bottom layers remain cool which occasionally traps the cool layer below trapping moisture and airborne pollutants from rising and being distributed in the air. The result of this is a temperature inversion which affects the weather with humid conditions in the summer. Increased summer sunshine warms the water on the lakes surface making it lighter than the colder water below. The release of the heat stored in the lakes moderates the climate near the shore in the fall and winter months. In the spring and fall with alternating air masses moving through rapidly, variable weather conditions prevail with frequent cloud cover and some thunderstorms. Also the warmer air and the increase in sunshine in the early spring melt the snow and lake ice creating a thermal layering of the lakes. Cool conditions are sometimes prolonged well into April because Lake Michigan is slower to warm than the land keeping the land area cool. If you’re wondering if Lake Michigan completely ices over it rarely does. In an interesting note from the influences of Lake Michigan on West Michigan weather it will remain cool sometimes well into April. In those years, this delays the leafing and blossoming of plants which protects plants such as fruit trees from late frosts. This allows plants from warmer climates to survive in West Michigan and is the reason for the presence of wine and grape vineyards in the area. A special wind system may form along the coastline of Lake Michigan on late spring and summer days when the temperature soars, called a lake breeze. It forms during the daylight because the lake waters do not warm as quickly as the surrounding land surfaces. Air cooled by contact with the cold lake waters is denser than that surrounding the lake and it forms a high pressure cell over the lake. When the sun heats the land, the air above it warms becoming less dense. Solar heating over the land produces lower pressure. The pressure gradient between the two pushes winds inland off the lake, know as lake breeze flow. When the lake breeze forms and brings the colder lake air onto the land a boundary zone forms between the two air masses forms called a lake breeze front. A lake breeze front could cause enough instability to cause convective storms over land, yet another influence of the Lake Michigan on West Michigan weather. In the winter arctic air from the northwest is very cold and dry but as it crosses Lake Michigan is warmed and picks up moisture from the warmer lake and when it reaches land, the moisture condenses as snow creating heavy snowfalls inland. The vastness of Lake Michigan is a big influence on the cold air traveling across the relatively warmer lake waters which evaporates a lot of moisture in the air and with other processes help to produce lake effect snow. How far the snow goes inland is determined by the strength of the wind. Clouds influence the weather greatly and especially in West Michigan with the influence of Lake Michigan. If you don’t forecast the cloud cover right it can throw off your high and low temperature forecast. There is a decrease in cloudiness in the summer because of the cooling and stabilizing effect of the relatively cool water. This decrease can extend 20 or so miles inland along the western shore of Lake Michigan. In the winter however there are significantly more lake effect clouds thus producing a higher average of cloudy days. These cloudy days impact the temperature greatly by producing warmer temperatures at night while being cooler during the day. There have been some studies done on different events and different aspects of Weather on the Great Lakes such as: Mesoscale Vortices Embedded within a Lake Effect Shoreline Band, A Climatology of Cold-Season Nonconvective Wind Events in The Great Lakes Region, Convective structures in a Cold air Outbreak over Lake Michigan during Lake-ICE and Cold front acceleration over Lake Michigan just to name a few. The last study about cold front acceleration looked at the impact of Lake Michigan on a cold Front, which accelerated over the southern part of the Lake. Part of the study concluded that two primary reasons existed for the increase in speed of the front. One was “the change in the frontal temperature gradient directly caused by changes in thermal fluxes compared with those over land.” Secondly, “changes in surface roughness and near surface thermal stratification that alter the effect of friction.” In order to accurately forecast the influence of Lake Michigan on West Michigan weather you must use all the weather tools at your disposal the models ETA, GFS etc., soundings, skew-t, upper air data, take into account the lake temperature and BUFKIT (a forecast profile visualization and analysis tool kit) which is extremely helpful in certain weather situations. Most important is your experience and weather history of the region to spot those intangibles you may not pick up from the forecast models. Lake Michigan has a great influence on West Michigan weather and more studies need to be done on the lakes influence in certain situations. As far as technology is concern, more automated weather observation instruments need to placed in the area and more buoys could be placed in Lake Michigan to pick up these rapid weather changes to help the accuracy of forecasts. The challenge for any forecaster is to put his or her experience, the history of weather in the area, along with the many weather variables and lake influences in perspective to produce an accurate forecast. References Great Lakes Atlas, Environment Canada and U.S. Environmental Protection Agency 1995 http://www.go-michigan.com/Kalamazoo/weather/ http://www.glerl.noaa.gov/res/region/glbasin/glregion.html http://www.glerl.noaa.gov/res/region/glbasin/michigan.html Cold front acceleration over Lake Michigan William A. Gallus Jr. Moti Segal. Weather and Forecasting: Boston: Oct. 199. Vol. 14, Iss, 5; pg 771, 11 pgs. Convective Structures in a Cold Air Outbreak over Lake Michigan during Lake-ICE Suzanne M Aurn-Birkhimer, Ernest M Agee, Zbianiew Sorbian. Journal of the Atmospherice Sciences. Boston: Jul 2005. Vol. 62, Iss. 7; Part 2 pg. 2414, 19pgs A Climatology of Cold-Season Nonconvective Wind Events in the Great Lake Region Matthew C. Lacke, John A. Knox, John D Frye, Alan E. Stewart, et al. Journal of Climate. Boston: Dec 15, 2007 Vol. 20 Iss. 24; pg. 6012, 9 pgs. Mescoscale Vortices Embedded within a Lake-Effect Shoreline Band Joseph A. Grim, Neil F. Laird, David A R. Kristovich, Monthly, Weather Review, Washington: Sep2004. Vol. 132, Iss. 9; pg. 269, 6 pgs |