Sunday, November 18, 2012

3-Year NAO Correlation Suggests Exuberant Winter Ahead

I have found that there is a significant connection between observed conditions in the North Atlantic Oscillation index (NAO) and observed winter conditions across North America approximately 3 years later.

DO NOT use the blue line's values for Nov. and Dec. Data
has not been gathered for those months this year yet.
In this article from the AGU website, it is noted that there is a very strong correlation between what the NAO does in a certain year, and the winter observed in North America 3 years later. This would mean that one could find the general idea of the oncoming winter by using this 3 year rule. Above is a chart showing observed NAO values in the year 2009 and the year 2012 (I know it says 2009-2010, but that was put there for the purposes of relating this back to winter).

What we want to focus on in this chart is the purple line of observed NAO conditions in 2009. As you can see, the NAO began the year with pretty neutral values before doing a quick positive run in May and dipping into negative territory as summer approached. The NAO went back to a positive phase in September 2009 before fluctuating and ending up in strong negative territory for winter.

If we do a quick comparison between the two years, we can see that they are actually pretty similar. They both began fairly neutral/slightly positive in the late winter months before dropping into negative territory towards summer. June and July both included very negative values for both years. Both years' NAO went positive into Fall and took a slight dip in October. If we follow the purple line and compare it to what we could see this year, one would think that this winter could have a pretty strong negative NAO.

Now, this is not an EXACT correlation- the chances of two years' NAO values matching up exactly is next to impossible. However, if we get a feel for the winter of 2009-2010 and use the 3 year correlation on the upcoming winter of 2012-2013, I think that the NAO will stay pretty negative, providing a strong base for an active Northeast winter.



William Andreas said...

Could you share a link to the AGU article Andrew?

Andrew said...

I forgot to place it in the first sentence after the image. That has been fixed. Sorry!

Anonymous said...

How active would the Ohio Valley and Midwest be?

john said...

another thing to go with that. If you look at the arctic oscillation monthly causes and look the time frame of August through October they almost have the exact threshold.

Andrew said...

Anonymous: If the Pacific-North American index can get going back into positive territory for the winter, then these regions would be very active. However, if it's solely the negative NAO, the Northeast would probably cash in.

John: Such connections like this are very interesting!