Fort Wayne isn’t what you would call a typical city on a lake. Fort Wayne is a little over 100 miles from the southern edge of Lake Michigan. Normally, being this far away from one of the Great Lakes, the lake wouldn’t have too much of an effect on the city and its weather. Because of the topography surrounding Fort Wayne, the weather still manages to make its way to this city. During the winter, one of the main things we’ll see in Fort Wayne is a light lake effect flurry. Farther to the north and to the west, but still in our viewing area, they’ll see heavier snows. But those snowfalls will rarely exceed four inches, and that’s still looking much closer to the lake. Immediately following a synoptic low pressure system that has since moved to the east, a high pressure cell will move in from the west, making for some very strong northwesterly winds. These strong winds usually extend up to the 850 mb level, and they’ll pick moisture up from the lake, allowing that moisture to fall in the form of very light snow as far south and east as Lima and St. Marys, Ohio, about 150 to 200 miles from the lake. These lake effect snow events vary from winter to winter, but on average, they only happen about two or three times each year. And with each of those every winter, a larger lake effect snow event is more rare. These events, although relatively rare, can usually be forecasted within a day or so of the actual event occurring. Only very rarely, will it happen much faster that we can get a surprise snowfall. These events can be difficult to forecast, because all of the models don’t pick up on the light precipitation. In order to properly forecast the event, one must go farther than looking into the surface forecast models. It is good to check the 850 mb temperature and wind progs and checking the 500 mb vorticity progs. The winds at the 850 mb level need to be relatively strong, between 10 mph and 45 mph, and from the northwest right across the lake. It also helps if there is at least a small vorticity maximum moving across the lake, but that is not always necessary. Steve Eddy from the National Weather Service office in Northern Indiana agrees. He says that while these lake effect snow events are relatively rare, they do happen at least once every winter, and when they do occur, snowfall is usually minor to moderate. He also mentioned these events are most common immediately following a synoptic snow event, and the strong northwesterly flow either behind the low pressure cell or ahead of the high pressure cell sets the wind profile up just right for some lake effect snow. And lake effect snow is not the only way Lake Michigan affects the weather in Fort Wayne and other areas in northeastern Indiana. Lake Michigan can also create conditions ideal for strong winds and lake breeze type thunderstorms. The strong winds seen in Fort Wayne are usually associated with a low pressure cell from the southwest, coming from the Ohio River Valley, but we also see those strong winds associated with, what this paper is discussing, Lake Michigan. A strong low will move across the lake and the wind has enough room to really speed up across the lake. These strong winds can be in excess of 50 mph. This type of strong wind event normally happens once or twice a year. Forecasting for these stronger winds is not too terribly difficult. As long as one pays attention to how tightly the isobars are packed over the lake, forecasting for these strong wind events can become a little easier. Sometimes other winds, lake breezes, can create thunderstorms over the lake. These thunderstorms then start to move from the northwest to the southeast, and sometimes those storms will move from the north to the south. Most thunderstorms develop and begin to move from the southwest to the northeast. These lake thunderstorms move in an almost completely opposite direction. This type of thunderstorm occurs rarely, but when they do, it is very similar to an ocean breeze front. Cooler air moves away from the lake, and warmer air from the land runs into it, causing convergence. This convergence creates a lake breeze front, which normally occur in the late spring and early summer as the land heats up much faster than the lake. But these occurrences do not happen very often. These storm cells will then move to the south or to the southeast toward Fort Wayne. The models have trouble with these types of storms as the models always have trouble with smaller thunderstorms. I have found the best way to forecast these types of thunderstorms is to look at the 1000 mb temperature progs. Sometimes, I can spot an area of convergence right along the lake. This, combined with a vorticity maximum at the 500 mb level can be a good indication of one of these thunderstorms possibly happening. Of course, like all forecasting, these conditions do not warrant a storm every time. After talking with Steve Eddy from the National Weather Service, he too mentioned that these types of storms are hard to forecast, and a lot of the times, these storms turn into now casting events. Once they pop up over the lake, we can keep an eye on them and track them as to which direction they are moving. The lake effect snow, strong winds, and lake breeze thunderstorms can all be challenging to forecast in Fort Wayne, IN and in the surrounding area. Of all of these events, forecasting strong winds is the easiest, the lake effect snow next, and the most difficult to forecast are the lake breeze thunderstorms that move from the north to the south and southeast. To improve forecasting for these events, technology needs to be improved and more research needs to be done. NOAA at the Great Lakes Environmental Research Laboratory is doing some of that research, and hopefully this research will lead to better technology and better forecasting models for all cities close to one of the Great Lakes. In the meantime, forecasters will need to show patience and take extra care and attention when they are forecasting a potential lake weather event. Sources: 1. http://www.theweatherprediction.com 2. http://www.crh.noaa.gov/iwx/CLI/FWA/history/climatedescription.php 3. Eddy, Steve. National Weather Service, Warning Coordination Meteorologist, Syracuse, IN. 4. http://www.suite101.com/article.cfm/science_sky/93996 5. http://www.glerl.noaa.gov/res/ |