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Are wall and shelf clouds new phenomena?

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Dear Tom,
I’ve lived in Chicago all my life, and it seems like it’s only been in the last 10 years or so that have I seen things like wall clouds and shelf clouds. Have these phenomena always been happening or are they new to our current weather?
—Dennis Nowak, Chicago
Dear Dennis,
They are not new and have been around as long as thunderstorms. The difference is the proliferation of camera phones and the explosion of storm chasing and social media that have produced an exponential increase in photographs of these events in recent years. Shelf and wall clouds are not easily viewed in urban confines, so the expanding suburban population is another factor in the increased sightings.
For the same reasons, there has also been a large increase in the number of confirmed low-end EF-0 and EF-1 twisters, explaining damage that would have previously been attributed to straight-line thunderstorm winds.
Wall and shelf clouds are not new; they have been around as long as thunderstorms.

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