A big, spinning storm has moved over Southern California, and will douse the region in much needed rain.
Seen in the satellite image above, it’s a common winter storm, called a mid-latitude cyclone, rotating counter-clockwise like a whirlpool. It will shower the area through Tuesday night.
“It’s a good ole mid-latitude cyclone,” said Jeff Weber, a research meteorologist at the University Corporation for Atmospheric Research.
A mid-latitude cyclone is basically air and clouds rotating around a region of low atmospheric pressure — and areas of low pressure invite air to pour into a region, bringing clouds and rain.
And this cyclone brought along a big friend. Below, or to the south of the cyclone, is a long line of clouds, known as an atmospheric river. These are formidable bands of moisture that often deluge California with potent rain and snow, sometimes to damaging degrees. Spinning mid-latitude cyclones often drive these long bands of moisture, as they pull the atmospheric river behind the storm, explained Weber.
In this case, the bulk of the atmospheric river, also dubbed a “river in the sky,” has slammed into Baja California, Mexico’s long, wild peninsula.
Even so, areas around Southern California that have had “very much below average” rainfall will still get some much needed precipitation.
Overall, California just had its driest February on record, with the northern parts of the state particularly dry. But this mid-latitude cyclone won’t help Northern California out, this time, anyway.
The Lower 48 states just had their sixth warmest winter on record, with pretty much all of California experiencing above-average temperatures. These temperatures, combined with unusually low rainfall, foreshadow another ominous wildfire season.
