I’ve had the privilege of attending the 2012 (20th) Great Lakes Operational Meteorology Workshop (GLOMW) in Chicago, Illinois over the past few days — where daily high temperature records have been obliterated by clear, sunny skies and temperatures in the 80s. However, Thursday’s weather (and forecast) included the impacts of the “pneumonia front”, a feature attributed to Lake Michigan that brought significant temperature drops to stations along the lakeshore, reducing afternoon temperatures in southeastern Wisconsin by as much as 30 degrees. The pneumonia front made it to the Chicago area later in the afternoon and produced low visibilities (fog) and a sharp drop in temperatures along the lake front.
During the Great Lakes workshop, a forecaster gave a presentation on forecasting issues related to the pneumonia front and hypothesized that it behaves with characteristics similar to a density current — similar to thunderstorm outflows and similar features that are localized near the surface. Given the clear skies across the region and near-nadir views from MODIS, the resulting true color imagery highlight the structure of the front as it oozed down the length of Lake Michigan, including enhanced appearance to the clouds and fog along the leading edge and turbulent wake. Perhaps these detailed structures will help to confirm the “density current” structure as hypothesized in the GLOMW presentation.