Buy the 2015 Old Farmer's Almanac!

Blame the Arctic Oscillation!

January 10, 2011

Your rating: None Average: 4.4 of 5 (11 votes)

The Arctic Oscillation has many aliases. In California, it is the Yukon Express, the cold northern storm that pushed the Pineapple Express floods down to San Diego. In the East, it is the jaunty sounding Alberta Clipper that sailed to Florida and froze the crops. Whatever its nickname, the Arctic Oscillation is cold, stormy and downright miserable. 

Technically, the Arctic Oscillation (AO) is a climate pattern caused by the ring of winds that blow around the North Pole from west to east. When they are strong, they trap the Arctic air mass north of 55°N. That’s north of Edinburgh, Moscow and Ketchikan, Alaska. When they are weak, however, the frozen polar air escapes south and can visit sunny California.

Photo: Power lines sag after a heavy storm like we are experiencing this week. Credit: NOAA/Department of Commerce/National Historic Weather Service

Notice, the climate pattern is an oscillation, meaning it switches from one extreme to another. When the AO is positive, the winds are strong. The Arctic remains cold and southern regions are relatively warm. When the AO is negative, the reverse is true. The polar air mass surges south and the Arctic regions are warmer than normal, with less sea ice. These oscillations can swing from one extreme to another in a matter of weeks.

See image to the right. The top reflects positive AO climate patterns; the bottom reflects negative AO climate patterns.

Over the past few decades the warm positive phase of the Arctic Oscillation has slowly strengthened. Then came last winter and the AO plunged. Last February, the AO index (which measures the air pressure differences that shape the winds) averaged -4.266, the most negative index in over 60 years. “Snowmageddon” slammed the nation and by February 13 every state except Hawaii had snow.

It’s happening again – the AO is negative. California was flooded, Florida was frozen and New York City was flat-out buried in snow. Overseas, Europe was hit with record-breaking cold, causing mayhem for holiday traveling. Beijing was had its heaviest snowfall in nearly 60 years. People died of the cold in India.

The AO is still negative and once again cold and storms will be assaulting the South, the Plains, the Midwest and East Coast. Unfortunately if one looks at NOAA’s Global Forecast System computer models, it looks as if this chilly trend will continue. While these model projections are not always accurate, their outlook is chilling. The 10-day forecast has the oscillation dropping to -3 while the 14-day forecast has it plunge below -5.


This is going to create some exciting weather this week. Please tell us what you are seeing and experiencing!

Related Articles

Evelyn Browning Garriss, historical climatologist, blogger, writer for The Old Farmer's Almanac, and editor of The Browning Newsletter, has advised farmers, businesses, and investors worldwide on upcoming climate events and their economic and social impact for the past 21 years.


Re Arctic Oscillation


Here in Greenville, TX on Feb 3, 2011 11am temp is 21 degrees F. Earlier this am was 16. La Nina pattern suggests warmer and dryer for here. The Arctic Oscillation has sure overpowered THIS forecast. Snow expected for tomorrow-am. Sure hope the "dryer" el nino kicks in soon.

A song phrase "Slip-slidin away!" comes to mind. :-)

Bitter cold

By Halene Overley

Were having bitter cold temperatures and lake effect snows. Were getting the Alberta Clippers.

This Negative Arctic Oscillation

By PecheMelba doubt has been responsible for these freezing (okay, so it's only 37 farenheit) weather trends & high windy dust storms in Baja California Mexico -- BRRR-RRRR!! but thanks for the info!!

Weather In Georgia

By kelleyforrester...

I live in Banks County,which is in Northeast Georgia. We rarely get snow,and when we do,it's usually just a dusting. Last week however,we got 10 inches of snow,and then ice on top of that! There are still roads that are hard to travel. This has been an unusual,but welcome,winter for us.

Weather in Belize -- Central America

By Xaibe

"Ironically, the Arctic Oscillation is so strong that it is pushing the storm track south of your area. The cold and the rain are missing parts of the northern states and most of Canada."

We are getting that effect even to the far South here in Belize.

My worry is that traditionally such chill events from the North as you describe have meant terrible droughts here.

So besides it being chilly -- it is also drier than normal.

I'm originally from Waterloo Quebec -- but have been living here since 1988.

For us -- Agua est Vida!!

Delivered a lot of pulp to Berlin NH in my past life.

Northern Belize -- Xaibe Village

Weather in Rhode Island

By E in Rhode Island

It's just about 11:00 am and the temp has not risen above 19. In my area we received almost 11" of snow Tuesday night/Wednesday afternoon. Hope this weather pattern doesn't continue!

Weather in Watertown, WI

By Julie R

We are having mild temps, for us, for this time of year. We have had below average snowfall this year as well. Again today, we are just getting a light dusting of snow with temps in the low 20's. Some farmers have commented that the fields are "blowing away", because there isn't enough snow cover on them.

The AO and Watertown

By Evelyn Browning...

Ironically, the Arctic Oscillation is so strong that it is pushing the storm track south of your area. The cold and the rain are missing parts of the northern states and most of Canada.

Weather in Charleston, SC

By lendav

Freezing rain over the last couple of days in Charleston, SC has created havoc. Frozen bridges have caused numerous traffic snarls. Schools were on 3-hour delays and many businesses were closed!

Unusually Early Snow!

By Nancy Pullen 2

I'm just fifteen miles east of Nashville, TN and it seems that we have had snow events unusually early. We actually had a white Christmas for the first time in decades! We just survived another big blast that left about 4 inches behind, Our temps are still below freezing and there's no melting in sight. This sure doesn't feel like winter in the south!

Bracing myself

By Catherine Boeckmann

We're expecting to get pounded by a big snowstorm starting tonight in New Hampshire. Of course, this isn't as unusual as what's happening in the South (ice storms, etc.). Thanks for explaining "why" we're having this weather!

Weather in Texas

By Joyce Wiley

I live just east of Dallas Texas. We had almost 4 inches of snow Saturday and temperatures in the low 20's this morning.

Post new comment

Before posting, please review all comments. Due to the volume of questions, Almanac editors can respond only occasionally, as time allows. We also welcome tips from our wonderful Almanac community!

The content of this field is kept private and will not be shown publicly.
By submitting this form, you accept the Mollom privacy policy.

2015 Special Edition Garden GuideCooking Fresh with The Old Farmer's AlmanacThe Almanac Monthly Digital MagazineWhat the heck is a Garden Hod?