With Winter 3 Months Away – A Refresher is Needed!

While I no longer post anywhere but on my blog and on my facebook group page, I still read posts from individuals that post them and what I am reading lately is some misinformation and I want to basically put out a refresher of certain teleconnections and what they mean during the winter. So lets look at some teleconnections that are getting mistrued and what they actually mean.

First up is the Arctic Oscillation and because this is winter that I am referencing I am only going to reference a Negative AO because , quite simply a positive AO would produce opposite results. So if the negative is posted then the positive will also be known as well.

Essentially when you have a negative NAO ..its effects downstream is to produce colder air in the mid central part of the country into the NE and the Upper Mid Atlantic. A negative AO does not mean that the cold air  is locked up over Canada and just the northern tier. Depending on the strength of the negative AO and cold fronts will determine along with other teleconnections how far south this cold air can achieve. We just seen the winter of 2009-2010 what a negative AO can do..

Just in case one forgot last winter..

Now I pose a question to those who believe a negative AO means the cold air gets locked up across Canada or only the north. How do you explain the coldest of air being in the south? So as one can plainly see the cold air does not just stay locked to the north with a negative AO ..it largely depends on other teleconnections.

The next teleconnection that needs to be addressed is the North Atlantic Oscillation or commonly called the NAO. Again we are going to look at a negative NAO because if you understand that and its effects then  you will know the opposite side of the spectrum as well.

Now the downstream effect of the Negative NAO is to lead to cold conditions along the same areas that are effected by the negative AO but can cause the entire east coast to feel these colder conditions.

So you can pretty much see what happens and occurs if you have a negative NAO and a negative AO combined together. This equals a cold or below normal temperature regime for the Midwest, Northeast, Upper Mid Atlantic and even into the south.

Now what happens if you were to combine those teleconnections with yet another one? So lets look at the Negative EPO

This puts a ridge over alaska and sends a trough down into the east along with the midwest and central US area. Again, depending on how strong this –EPO is will determine how large the ridge is . And you can get some very cold air entering into the above regions.

Now we are going to look at one more teleconnection and this one we are going to look at when its in its positive phase which is the PNA..

When you have a positive PNA you have a ridge in the west and a trough in the east and generally those troughs in winter will create colder weather and potential snowstorms as they can be associated with areas of low pressure.

Some of our biggest snow storms come via a positive PNA as they round the base of the trough and ride up along the coast creating a Nor Easter type event.

So as you go about reading posts on forums around the net keep these definitions in mind because as long as you know what the teleconnections are and what they imply you can generally use them as a forecasting tool for events during the winter.

Do not be misled by some of the misinformation out on the net.

All images are courtesy of Pro Met Stormchaserchuck!