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When Is A Snowstorm Like A Sword?

January 13, 2014

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An ancient story tells of Damocles and a sword.

Damocles was a nobleman who exclaimed how fortunate his king was. The annoyed king offered to allow the nobleman to sit on his throne. Damocles scrambled onto the throne and found himself surrounded by luxury. Then he looked up. Gulp!

Overhead was a sword, held by the single hair of a horse's tail! With power came great danger and worry. Damocles left the throne and crept away.

The Sword of Damocles by Richard Westall. 1812

Look north. Hanging over the US is the coldest Arctic air on record. What keeps it from sweeping south is a single wind—the Arctic Oscillation.

This year, the Arctic has been abnormally cold. Last summer, Arctic sea-ice increased by 60%. Less than fifty days had temperatures above freezing, compared to the normal 90. That was summer. Now it is winter and time for Arctic air to move south. We already saw the air form an “Arctic Vortex” over the Midwest and all 50 states experienced below freezing weather on the same day.

LEFT – Positive Arctic Oscillation RIGHT − Negative Arctic Oscillation.

What keeps the air north are the circumpolar winds. Scientists measure these winds and call this the Arctic Oscillation (AO). When the AO is positive, it means the winds are so strong that the cold air is trapped. When the AO is negative, it means the winds are weak and Arctic air can break through and surge south.

Most of November and December the AO was positive. Even when the weather got nippy, it was normal cold. In the beginning of January, the AO was negative and the US was swept by bitter cold.

That’s all it takes. The wind gets a little weaker. Most experts expected the AO to get negative again and it is happening now (week of January 20). Some think it will get positive by the end of the month.

Experts predict the AO will go negative later this month and the Arctic cold will return. Source: NOAA’s Climate Prediction Center

So how is a snowstorm like a sword? When you have a winter like this, those sharp cold temperatures are dangling just to the north and it won’t take much to make them drop south. It’s enough to make one want to creep away like Democles and find a cozy tropical island!

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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.

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Comments

Always interesting posts. I

By georgewilson

Always interesting posts. I enjoyed your ancient analogy and explanation of the AO. I don't mind the cold, though I do really feel for the folks in California. It must be desperate.

Thank you! They are

By Evelyn Browning...

Thank you!

They are desparate, especially the farmers. A Beverly Hills golf club has more chance of getting water than a Central Valley farm or orchard.

It really is. The lack of

By Evelyn Browning...

It really is. The lack of water will cut back hydroelectricity, the cheapest way to make electricity. Electricity costs are expected to go up 40% for everyone. And it's even harder for the farmers who are not getting water for their crops.

What is your take on the

By debrajhenn

What is your take on the abnormally warm weather of Southern California. So far your predictions are way off.

I don't make the predictions

By Evelyn Browning...

I don't make the predictions for the regular almanac.

I really worry that the situation in California, even if it eases slightly, will be too dry to ease the drought this winter.

Talking about the cold in the

By Marcus Clayton

Talking about the cold in the East and all its repercussions. Good and good to know what to do and how it feels...well, then what's going on with the HUGE discrepancy with California and area "16". The predictions of a wet and mostly cold forecast has gone to the other side of the coin! what did occur here that what's happening as we speak that weather forecasts turned totally the opposite since early December except for some cold air, the entire State and parts of the Western US is drier than Iran as we speak. Any relief coming in any way. This could negatively affect many parts of the nation to food supply, water supply to countless millions of people and so much more!.

I blog for the Almanac, not

By Evelyn Browning...

I blog for the Almanac, not write their forecasts. Relief -- not anytime soon.

In my next post, I will be writing about what is causing the California and Western drought.

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