Ryan North, SUNY College at Oswego
Weather-ready Nation
Gino Izzi, National Weather Service, Chicago
Eric Lenning, National Weather Service, Chicago
Robb Kaczmarek, Center Weather Service Unit, Aurora
National Weather Service, Chicago
National Oceanic and Atmospheric Association (NOAA)
Lake breezes pose a significant challenge to forecasters, and can have widespread effects on airports such as Chicago O’Hare International (ORD) and Chicago Midway International Airport (MDW). Since airplane pilots prefer to land and take off into the wind, the sudden change in wind direction that lake breezes induce can pose a problem to this process. As a result, lake breezes often cause ORD to shift its operations from west flow to east flow if they reach or surpass a threshold of 10 knots. West flow is preferred, and refers to the arrival/departure configuration. Under west flow, airplanes land from the east and take off to the west. If the lake breeze is well forecasted, this shift can be made during an off-peak time, allowing for minimal delays. To aide in the forecasting of these events and their impacts to the airports, a climatology of lake breezes was constructed for ORD and MDW over a 20-year period from 1996-2016 during the months of April-October. To identify a lake breeze, a wind shift from offshore to onshore had to occur during the daylight hours. To distinguish a synoptic event from a true lake breeze event, days exhibiting this shift were compared to Rockford International Airport (RFD), located 105km inland. This yielded 791 and 716 lake breeze events at MDW and ORD, respectively. On average, the lake breeze arrived at MDW an hour before ORD with the greatest frequency of arrival time between 18 and 20Z.
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