Another Spring storm will move in to the San Joaquin Valley Saturday night, bringing light rain to the Valley and a little snow to the high elevations of the Sierra Nevada. And just like last Tuesday, thunderstorms are possible with this storm! However… it’s a weaker storm that’s arriving after sunset. One of the key components for us to get severe thunderstorms is solar energy, and without that going for us Saturday night, we shouldn’t expect anything wild with our weather this time.
Last Tuesday was a day of violent weather in the San Joaquin Valley, with severe thunderstorms spawning 4 tornadoes! That was an extreme example of what thunderstorms can do here in California, as most of our thunderstorms produce locally heavy rain and dangerous lightning – and not much else. Occasionally we’ll see small hail or gusty winds with thunderstorms, but it’s only on rare occasions that we see tornadoes. The meteorological set-up was good for strong storms that day: a vigorous upper low moving overhead, an April day with some sunshine, and decent available moisture. If this would have been the set-up in February, it may have led to thunderstorms, but they likely would not have been severe ones. But we’re into Spring now, and the April sun continues to rise higher in the sky – which is why we keep warming up until Summer. It’s also strong enough to destabilize the atmosphere with some help, and an upper low passing overhead last Tuesday gave it a lot of help.
We don’t see many tornadoes in California, and the ones we do see are fairly weak. The Enhanced Fujita (EF) scale runs from 0 to 5, and is how the strength of a tornado is measured. We’ve never had an EF-4 or 5 tornado in California – only EF-3 or weaker. And there have been only 3 EF-3 tornadoes in California: in August 1973, a tornado described as ‘barely’ an EF-3 struck Blythe, out in the desert. A second EF-3 tornado struck Orange County in March, 1978, causing millions of dollars of damage. But the strongest tornado in California’s history wasn’t spawned by a thunderstorm – it was spawned by fire! On July 26, 2018, the Carr Fire roared into Redding, burning a thousand homes – and spawned a massive EF-3 fire tornado with winds gusting to nearly 150 mph!…