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Category Archives: Phenomena
Was 2025 an interesting weather year for Wisconsin?
Wisconsin has interesting weather in EVERY year. 2025 started with extreme cold warnings issued for all Wisconsin counties from Jan. 19 to Jan. 21. Wind chill indices were as low as minus 45. The year also ended with cold temperatures and low wind chills at the end of December.
Severe thunderstorms struck southern Wisconsin during the early morning of April 18, with baseball-size hail falling from New Glarus to Edgerton. Continue reading
Category: History, Phenomena, Severe Weather
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Will shifts in the polar vortex cause extreme day-to-day temperature fluctuations to become more common?
The polar vortex is a large area of low pressure in the lower stratosphere that is bordered on its southern edge by the polar night jet — so-called because it develops as the sun sets at high latitudes after the autumnal equinox, creating large and deep pools of cold air. The characteristics of this stratospheric polar vortex have a substantial influence on wintertime temperatures in the lowest part of the underlying troposphere, which is where we all live.
The nature of the polar vortex changes throughout the winter. When the vortex circulation is largely west-to-east around the pole, it tends to contain the most extreme cold air masses at high latitudes. When it is characterized by high amplitude waves, often associated with a weaker vortex, it can initiate rapid transport of warm air poleward in some locations and frigid air equatorward in others. Such waves, or lobes, of the polar vortex can pinwheel over the Northern Hemisphere, sending cold air southward in association with weather systems tied to the underlying tropospheric jet stream. Continue reading
Category: Meteorology, Phenomena, Seasons
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What is the largest snowflake?
An ice crystal can grow if the air around it has a relative humidity near 100%. The ice particle grows by water vapor deposition. Growth by deposition is generally slow. If you find nicely shaped snowflakes, they likely were produced by vapor deposition. A snowflake can be an individual ice crystal or an aggregate of ice crystals.
There are four basic shapes of ice crystals: the hexagonal plate, the needle, the column and the dendrite. The dendrites are hexagonal with elongated branches, or fingers, of ice; they most closely resemble what we think of as snowflakes. The temperature at which the crystal grows determines the shape. Continue reading
Does lightning travel from the sky downward or ground upward?
Lightning is a huge electrical discharge that results from vigorous motions that occur in thunderstorms.
Lightning can travel from cloud to cloud, within the same cloud, or between the cloud and ground. In-cloud lightning discharges are more common than cloud-to-ground discharges and are not as hazardous. Cloud-to-ground is the best known type of lightning and it poses the greatest risk. Continue reading
Category: Meteorology, Phenomena, Severe Weather
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What is a haboob?
A haboob is dust storm that can be several miles long, several thousand feet high, and can travel hundreds of miles. Haboobs are caused when an intense column of sinking air in a thunderstorm hits the ground and lofts soil particles into the air. These downdrafts, referred to as a microburst, can hit the ground at 50-80 mph and then spread in all directions. The resulting winds stir up dust and dirt from large arid areas which then get blown along in front of the approaching thunderstorm. The lofted particles can reach heights of 5000 ft and can extend up to 100 miles wide.
The name “haboob” is derived from the Arabian word ‘hab’, meaning ‘to blow,’ and was originally the name for a dust storm or sandstorm in the northern part of Sudan. Continue reading
