BLOG: Winter arrived, may be here to stay - | WBTV Charlotte

BLOG: Winter arrived, may be here to stay

(Source: State Climate Office of NC) (Source: State Climate Office of NC)

We have heard a lot about El Nino so far this winter, and certainly that phenomenon of the warming of the Eastern Pacific Ocean off the coast of South America has influenced the first part of our winter season as warm and wet air ejected from that region into the southeastern United States.

That contributed to the mild and soggy end to 2015. 

However, El Nino isn’t the only Atmospheric Teleconnection (I love that word) that affects our weather in this part of the world. 

You may have heard of some others called the North Atlantic Oscillation (NAO) and/or the Arctic Oscillation (AO). 

These patterns can also affect our winter weather outcomes in significant ways. The reason why the word ‘Oscillation’ is in their title is because these patterns tend to bounce, or oscillate back and forth from what has been deemed a negative phase, or a positive phase.

The two patterns are closely related, so for simplicity I will only deal with the Arctic Oscillation. 

Notice in Picture 1 and Picture 2, both medium range computer models have the AO diving deeper into a negative phase and staying that way through at least the first half of January. 

So prepare for the cold air to be around for awhile now.  We were strongly positive through the end of 2015. So what is the significance of positive versus negative. 

In a positive phase, we typically see a stronger area of low pressure around the North Pole. 

Like a hurricane the deep low pressure at the center creates strong winds in the Arctic but also sucks all the coldest air toward the center. With all the coldest air bottled up around the north pole, we’re more likely to see a mild pattern in the Carolinas, which we sure did all the way through the New Year. 

See Picture 3 and Picture 4.  Picture 3 shows the strong area of low pressure over the North Pole while picture 4 shows the cold air pooled up there.  Notice the warmer air over the Eastern United States.

In a negative phase the Polar Low weakens, and that allows the cold air to expand away from the center, break loose and spread southward through the Northern Hemisphere. 

See Picture 5 and Picture 6.  Picture 5 shows the weaker polar low.  Picture 6 shows the cold blobs of air that broke loose from the North Pole, came south and are circulating around the lower latitudes in the Northern Hemisphere. 

These are also referred to as Polar Vortex’es (Vortices). This colder air pattern certainly affects the Carolinas and does increase our chances of seeing snow, although none is in the forecast yet. 

If you follow weather on Facebook or Twitter, you might have also heard about the surge of warm air recently over the North Pole.  These last two pictures also show how that happened as it replaced the cold air that drifted away.

So stay tuned to the weather team at WBTV and we’ll let you know if or when this new pattern sends any snow our way!

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