A strong and unseasonal cut-off low formed in Northern California and moved south along the California coast, before moving inland across Southern California. This brought unusual summer thunderstorms all the way from the San Diego beaches to the Colorado River on August 20-21. Some of the thunderstorms became strong and produced large hail–including marble-sized at WeatherExtreme headquarters!
Somewhat ironically, the American Meteorological Society was having a meeting in San Diego at the time, and morning thunderstorms forced them to move a lunchtime “luau” that they were going to have indoors, but by the time the luau took place, the thunderstorms had given way to sunshine and 75 degree temperatures.
This photo shows mammatus clouds pendant from a thunderstorm near Descanso, California. At the time this picture was taken, the National Weather Service had issued a Severe Thunderstorm Warning and a Flash Flood Warning for the storm. The photo was taken by Jim Means, one of WeatherExtreme’s meteorologists, who took a break at lunchtime to do a little storm chasing.