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“Pneumonia Front” In Weather Forecast For Monday

March 14, 2015

I love weather phenomena.  I also am curious about things I know nothing about.  Which brings me to the “pneumonia front” that is in the forecast for Monday.

My absolutely favorite meteorologist, Tom Skilling from WGN TV, remains the source for most of my weather information.  Not only do I find out the short and long range forecasts but also information about weather events that then drive dinner conversations with James, and front yard discussions with those who walk by our home.


The term Pneumonia front, first coined by Milwaukee Weather Bureau Office in the 1960s is used to describe a rare meteorological phenomenon observed on the western Lake Michigan, USA, shoreline during the warm season. These fronts are defined as lake-modified synoptic scale cold fronts that result in one-hour temperature drops of 16 °F (8.9 °C) or greater.

This extreme change in temperatures can result in a flash severe thunderstorm and/or a microburst capable of affecting the structural integrity of weak buildings such as barns and sheds. The drop in temperature has also earned this meteorological event the title “pneumonia front.” The cold weather is usually of short duration, and pneumonia does not have a high likelihood of manifesting itself in the lungs of people who experience the event.

The lake modified synoptic scale cold front effect can be observed down wind of the small retention ponds with above average surface temperatures leading to supersaturation of the atmosphere. This supersaturation results in the formation of a rare type of rotating hail. Dispersal of this hail is largely dependent upon the fractus of the skies, the local coriolis of the earth, and hygroscopic particulate. When drafted into the upper atmosphere by convection currents, the hailstones acquire a rapid rotation about their major axes. Retreat from these currents leaves the hail in a gyroscopically stabilized state approximately 15,000 meters and 30,000 meters above the Earth’s surface. As the hail falls, inelastic collisions with rain droplets and general exposure to moist air at lower altitudes causes the hail to grow in diameter ranging from 5 centimeters to 15 centimeters. Such a mass of ice can shatter unfused quartz glass and lesser grades such as those found on the exterior of buildings and vehicles. Additionally, it can damage malleable metals.

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