Wild weather driven by roiling Pacific, nature and warming

At least one highway in drought-mired California looked more like a river because of torrential rain from what is technically called an atmospheric river of moisture. New Year’s brought shirtsleeve weather to the US East and record high temperatures to Europe as the Northern Hemisphere, on Wednesday, was more than 2.6 degrees hotter than the late 20th century average. And this is after frigid air escaped the Arctic to create a Christmas mess for much of the United States.

“All the ingredients are in place for two weeks of wild weather especially in the Western US,” private meteorologist Ryan Maue said in an email.

Maue said the big driver is a three-year La Niña — natural temporary cooling of the equatorial Pacific Ocean that alters world weather patterns — that just won’t quit. It is creating literal waves in the weather systems that ripple across the globe. And on certain parts of the waves are storms where the atmospheric pressure drops low and quickly, called bomb cyclones, that are quite wet, and they travel on atmospheric waves that transport the weather called the jet stream.

The jet stream now is unusually wavy, said Maue and Woodwell Climate Research Center climate scientist Jennifer Francis. The storms dip over the warm subtropics “and create a conveyor belt of moisture to strafe the West Coast of the US,” Maue said.

“I’d describe the jet stream and bomb cyclones as a runaway Pacific freight train loaded with moisture,” said Maue, former chief scientist of the National Oceanic and Atmospheric Administration in the Trump administration. “Climate change adds more fuel to the locomotive engine.”

More than 5 inches of rain fell, on Saturday, in the Sacramento area. As of Wednesday, snowpack was third highest in 40 years, more than 170% of normal.

In addition to La Niña, a different natural temporary weather event called the Madden-Julian Oscillation enhances storms in the western Pacific, Maue said.

Francis points to a “blob” of warm sea water off the Aleutian Islands, a phenomena that is happening more often, and a ‘’crazy warm” Arctic — Wednesday, it was 5.8 degrees warmer than the 1979-2000 average — as part of what’s juicing up the Pacific.

And with a wavier than normal jet stream, extremes of all kinds go up and down and around the planet, Francis said.

“You can think of it like a jump rope. When you start to flick it at one end, that ripple goes through the whole jump rope eventually,” Francis said Wednesday.

“And so it could be that the waving as such, being perhaps driven in the Pacific, could be accentuating it also over Europe.”