Regional Outbreaks of Severe Weather Through Early Next Week; Early Season Heat Wave across the South

Active spring pattern across the center of our nation with several episodes of severe weather and heavy rainfall expected into next week. The potential for very large hail, long track tornadoes, severe wind gusts, frequent cloud to ground lightning strikes and flash flooding are in the outlook. Furthermore, dangerous early season heat wave continues for the Gulf Coast states into early next week. Read More >

Unusual Cloud Phenomena Seen in Central Wisconsin

During the afternoon of November 15, 2006, an unusual cloud formation was seen across central Wisconsin. Known as "hole punch clouds," the holes develop as ice crystals above the main cloud layer fall through the clouds, causing the super-cooled water droplets to evaporate. The result is a circular form void of clouds, with a mass of crystals in the center.

The photo below was taken by Samantha Weise in Stevens Point.
Hole punch cloud

The source of the ice crystals was exhaust from jets. Visible satellite imagery on November 15 (below) showed aircraft dissipation trails (distrails) above central and south-central Wisconsin. Particles in the aircraft exhaust acted as ice nuclei, causing the ice crystals to grow and then fall, creating the punch holes and streaks in the main cloud layer.
Visible satellite image

The image below is a high resolution Aqua MODIS true color image centered on Madison, which clearly shows the northwest-southeast oriented distrails. Satellite images courtesy of the SSEC, University of Wisconsin.
MODIS imagery

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Regional Outbreaks of Severe Weather Through Early Next Week; Early Season Heat Wave across the South

November 15, 2006 Hole Punch Clouds

Unusual Cloud Phenomena Seen in Central Wisconsin