Severe thunderstorms swept across the Austin area on Memorial Day, prompting several tornado warnings as well as widespread flash flooding.
Austin's creeks and streams quickly overflowed amid the downpours, stranding cars and leading to at least 20 swift-water rescues. Flooding shut down downtown streets and covered a high school football stadium, according to the AP.
clouds above #thedomain after the storm today #atx #texas #austin #clouds #thunderstorms A photo posted by Alicia Pillion (@ampillion92) on May 25, 2015 at 7:43pm PDT
After the storms ended, however, residents of the city were treated to a rare spectacle: a vivid display of mammatus clouds. These clouds, which look like pouches descending from a flat layer of clouds above, form along the edge of thunderstorm cloud tops, where the air is extremely turbulent.
According to the American Meteorological Society's glossary of meteorology, mammatus clouds consist of "hanging protuberances, like pouches, on the undersurface of a cloud."
Here are some photos of the vivid spectacle:
Insane #mammatus in the #Austin area following Monday's storms! Pic by Maria Pena! #TXwx A photo posted by Andrea Butera (@andreabutera) on May 25, 2015 at 7:20pm PDT
Crazy looking mammatus clouds roll through Austin, hopefully taking the flood with them. #atxfloods A photo posted by jay defoore (@jdefoore56789) on May 25, 2015 at 7:06pm PDT
Post-storm mammatus as the water still churns in Town Lake in Austin, Texas. #atxfloods #txwx pic.twitter.com/lBL9pHRkMD— Will Leverett (@312Will) May 26, 2015
Sometimes mammatus clouds and other rare cloud types are triggered by atmospheric waves reverberating outward throughout large complexes of thunderstorms, as occurred on Monday in Texas. This satellite image shows the huge area of storms, and the wave patterns, like ripples in a pond, moving along the tops of the thunderheads. The tops of these storms extended well above 50,000 feet.
Suomi NPP VIIRS 375-meter resolution IR & visible images of the very large MCS in Texas http://t.co/EBNSSYvqjL pic.twitter.com/RWpzPYuucb— Scott Bachmeier (@CIMSS_Satellite) May 26, 2015
If these have you hooked, the Cloud Appreciation Society has a great gallery of more mammatus images from around the world.