What is a PNEUMONIA FRONT??

A rare, meteorological phenomenon observed on the western Lake Michigan shoreline during the warm season is the pneumonia front. These fronts are defined as lake modified synoptic scale cold fronts that result in one-hour temperature drops of 16 degrees F or greater. Further knowledge of pneumonia fronts is not only important for the efficiency of commerce (aviation and marine), but also essential for sensible weather forecasts for the dense population base along the Lake Michigan coast. Examining surface temperature data from Milwaukee and Madison, Wisconsin resulted in a set of 25 cases from the period 1948 through 2003. Further investigation of these cases resulted in the identification of two main synoptic patterns coincident with pneumonia front events. ysis suggests that these synoptic patterns are necessary but not sufficient in the forecasting of the pneumonia front phenomenon. Mesoscale controls of pneumonia front events were examined through the use of a simple model, and sensitivity simulations of a specific event (17 July 2003) using the PSU-NCAR mesoscale model (MM5). The simple advection model showed the following: reduced roughness over a north-south lake allows for stronger impact in the southern lake and shoreline; zonal and northwest-southeast cold fronts are more conducive for pneumonia front cases; and colder lake temperatures in the north increase the near-shore temperature gradient and frontal propagation. The results of the MM5 sensitivity tests suggested the following in regards to the 17 July 2003 pneumonia front: orography had little influence on pneumonia front generation and maintenance; temperature falls relating to the pneumonia front were strongly dependent upon landm diurnal heating; and Lake Michigan surface water temperatures impacted pneumonia front strength. The insights gained from this research should allow operational forecasters to reliably ess the likelihood of pneumonia front events in the short-range.