AP

EXPLAINER: Stuck jet stream, La Nina causing weird weather

Dec 4, 2021, 8:23 AM | Updated: Dec 5, 2021, 12:31 pm

America’s winter wonderland is starting out this season as anything but traditional.

The calendar says December but for much of the country temperatures beckon for sandals. Umbrellas, if not arks, are needed in the Pacific Northwest, while in the Rockies snow shovels are gathering cobwebs.

Meteorologists attribute the latest batch of record-shattering weather extremes to a stuck jet stream and the effects of a La Nina weather pattern from cooling waters in the equatorial Pacific.

It’s still fall astronomically, but winter starts Dec. 1 for meteorologists. This year, no one told the weather that.

On Thursday, 65 weather stations across the nation set record high temperature marks for Dec. 2, including Springfield, Missouri, hitting 75 degrees Fahrenheit (24 Celsius) and Roanoke, Virginia 72 degrees Fahrenheit (22 Celsius). Cheyenne, Wyoming, and Billings, Montana, broke long-time heat records by 6 degrees.

Parts of Canada and Montana have seen their highest December records in recorded history. On Friday, parts of South Carolina and Georgia hit record highs.

In Washington state, Seattle, Bellingham and Quillayute all set 90-day fall records for rainfall. Bellingham was doused by nearly two feet (60 centimeters) of rain. The Olympic and Cascade mountains got hit harder, with more than 50 inches (127 centimeters) in three months, according to the National Weather Service. Forks, Washington, received more rain in 90 days than Las Vegas gets in 13 years.

On top of that, there is a blizzard warning on Hawaii’s Big Island summits with up to 12 inches (30.5 centimeters) of snow expected and wind gusts of more than 100 miles per hour (161 kilometers per hour).

Meantime, snow’s gone missing in Colorado. Before this year, the latest first measurable snowfall on record in Denver was Nov. 21, way back in 1934. There’s a slight possibility of snow Monday night, according to the weather service. Yet, with no snow since April 22, this is the third longest stretch the city has gone without it.

One big factor: The jet stream — the river of air that moves weather from west to east on a rollercoaster-like path — has just been stuck. That means low pressure on one part of the stream is bringing rain to the Pacific Northwest, while high pressure hovering over about two-thirds of the nation produces dry and warmer weather, said Brian Hurley, a senior meteorologist at the weather service’s Weather Prediction Center in College Park, Maryland.

If the jet stream moves more or bends differently, rain and other extreme weather won’t be as concentrated, Hurley said.

This is a typical weather pattern with a natural La Nina weather oscillation, he said. The flip side of El Nino, a La Nina is a cooling of parts of the central Pacific Ocean that changes weather patterns across the globe. La Ninas tend to bring more rain to the Pacific Northwest and make the South drier and warmer.

These bouts of extreme weather happen more frequently as the world warms, said meteorologist Jeff Masters, founder of Weather Underground who now works at Yale Climate Connections. But scientists haven’t done the required study to attribute these events to human-caused climate change.

In Boulder, Colorado, meteorologist Bob Henson enjoyed a rare December bike ride on Thursday.

Still, “there’s a lot of angst about the lack of snow,” he said. “It puts you in a psychic quandary. You enjoy the warm weather while keeping in mind it’s not good for Earth to be warming.”

___

Follow Seth Borenstein on Twitter at @borenbears.

___

The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Department of Science Education. The AP is solely responsible for all content.

Copyright © The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

AP

American Airlines put an unspecified number of employees on leave for their involvement in an incid...

Associated Press

American Airlines CEO calls removal of Black passengers from Phoenix flight ‘unacceptable’

American Airlines put an unspecified number of employees on leave for their involvement in an incident in which several Black passengers were removed from a flight in Phoenix.

5 days ago

FILE - Crystal Baziel holds the Pan-African flag Monday, June 19, 2023, during Reedy Chapel A.M.E C...

Associated Press

The beginner’s guide to celebrating Juneteenth

For more than one-and-a-half centuries, the Juneteenth holiday has been sacred to many Black communities. It marks the day in 1865 enslaved people in Galveston, Texas found out they had been freed — after the end of the Civil War, and two years after President Abraham Lincoln’s Emancipation Proclamation. Since it was designated a federal […]

6 days ago

A Boeing 737 Max suffered damage to parts of the plane's structure after it went into a “Dutch ro...

Associated Press

Plane that did ‘Dutch roll’ on flight from Phoenix suffered structural damage, investigators say

A Boeing 737 Max suffered damage to parts of the plane's structure after it went into a “Dutch roll” during a flight from Phoenix last month.

11 days ago

This photo provided by Randy Shannon shows Mooney Falls on the Havasupai reservation outside the vi...

Associated Press

Dozens report illness after trips to waterfalls near Grand Canyon

Dozens of hikers say they fell ill during trips to a popular Arizona tourist destination that features towering blue-green waterfalls deep in a gorge neighboring Grand Canyon National Park.

12 days ago

Mugshot of Rudy Giuliani, who was processed Monday, June 10, 2024, in the Arizona fake electors cas...

Associated Press

Rudy Giuliani posts $10K cash bond after being processed in Arizona fake electors case

Rudy Giuliani, a former New York City mayor and Donald Trump attorney, was processed Monday in the Arizona fake electors case.

14 days ago

FILE - White House former chief of staff Mark Meadows speaks with reporters at the White House, Wed...

Associated Press

Former Trump chief of staff Mark Meadows pleads not guilty in Arizona fake elector case

Former Donald Trump presidential chief of staff Mark Meadows and Trump 2020 Election Day operations director Michael Roman pleaded not guilty Friday in Phoenix to nine felony charges for their roles in an effort to overturn Trump's Arizona election loss to Joe Biden.

18 days ago

Sponsored Articles

...

Collins Comfort Masters

Here’s how to be worry-free when your A/C goes out in the middle of summer

PHOENIX -- As Arizona approaches another hot summer, Phoenix residents are likely to spend more time indoors.

...

Condor Airlines

Condor Airlines can get you smoothly from Phoenix to Frankfurt on new A330-900neo airplane

Adventure Awaits! And there's no better way to experience the vacation of your dreams than traveling with Condor Airlines.

...

Collins Comfort Masters

Here’s 1 way to ensure your family is drinking safe water

Water is maybe one of the most important resources in our lives, and especially if you have kids, you want them to have access to safe water.

EXPLAINER: Stuck jet stream, La Nina causing weird weather