A "roiling" Pacific Ocean being stirred up by a third-in-a-row La Nina cycle as well as climate change and other factors are making for some unstable and dramatic weather on the West Coast and elsewhere around the globe.
What we're experiencing weather-wise today, and what we saw Saturday in the Bay Area, isn't necessarily unusual for wintertime. But some of the extremes of rainfall, wind velocity, and the frequency of storms lining up is being driven at least somewhat by climate change. And we have a collision of multiple things at once bringing the West Coast some much needed — though maybe too-much-all-it-once — rain.
As the Associated Press reports, a couple of those factors include a strong and "wavy" jet stream, an extra-warm Arctic Ocean, a "blob" of very warm water off the Aleutian Islands, and another temporary weather cycle like La Nina called the Madden-Julian Oscillation.
"I'd describe the jet stream and bomb cyclones as a runaway Pacific freight train loaded with moisture," says meteorologist Ryan Maue, a former chief scientist of the National Oceanic and Atmospheric Administration (NOAA), speaking to the AP. "Climate change adds more fuel to the locomotive engine."
The jet stream is unusually intense, and as the Chronicle's Gerry Diaz explains, "it’s such a strong jet stream that weather models struggled to capture the full scale of its ferocity, leading to rainfall totals that surpassed the forecast [totals] for New Year’s Eve by as much as 2.5 inches on the Peninsula."
Some of the "roiling" of the Pacific, and the formation of the current atmospheric river peeling off from the tropical band of moisture closer to the equator, can be seen in the radar gif below.
A textbook type of Atmospheric River (AR) -- commonly called a Pineapple Express thanks to its origins over the Hawai'ian islands -- is slated to impact California's coastline this week. 🌧️🌧️🌧️— Gerry Díaz (@geravitywave) January 3, 2023
Check out the @sfchronicle's latest piece on ARs ⤵️#CaWxhttps://t.co/nO8NgZPLHi pic.twitter.com/BfN47NVL8T
"The standout here is the wind," says Brian Garcia with the National Weather Service, speaking on today's KQED Forum. "We're talking wind gusts of 50 to 60 miles per hour, especially at elevation."
Garcia was the National Weather Service meteorologist who wrote the dramatic forecast overnight on Monday night that called this a "brutal" storm system and predicted likely many downed trees — even "entire groves" — as well as likely loss of life.
"The last time we saw a storm sequence like this was in 2017," says Diaz on Forum, adding that before that we haven't seen this since the intense El Nino season of 1997.
You may recall that the wet winter of 2017 led to that crisis at Oroville Dam.
We are also looking at a pretty dramatic week ahead, too. Meteorologist Daniel Swain tells KQED that we're looking at an ongoing storm sequence with more atmospheric river moisture on the way this weekend and into next week — and that could spell disaster in places we aren't expecting, due to the many burn scars around the Bay Area from the last couple of years of wildfires.
"A lot of those burn areas haven't yet been tested by a storm sequence like this," Swain says, adding that we should expect mudslides across the region as more of these storms saturate the already saturated ground.
🌧Yes, stronger storm Wed.🌧 #flooding chance but *watch* this trend next 7 to 10 days a deluge of #SF #BayArea #rain storms will keep flood danger higher for days if this holds. 🚨Prepare and please don't drive through flood waters! 1-2ft. can carry a car away🚨 @nbcbayarea pic.twitter.com/EioAbRmhzJ— Jeff Ranieri (@JeffRanieri) January 4, 2023
While we're experiencing this extreme end of winter in California, parts of Europe are having the opposite sort of new year, with warmer than usual temperatures. As the AP notes, thanks to La Nina, Switzerland's peaks have been recording extremely mild temps, and this all has a "silver lining" in that Ukraine is not experiencing the extremes of winter cold — at least for now — while so many people are living without heat and electricity.