Wednesday, November 14, 2012

What Are The Teleconnections Telling Us?

We Didn't See Much of This Last Winter
I don't want to harp too much about the connections between the oceans and atmosphere and their influence on our long range outlooks. As I mentioned earlier in the week, teleconnections like El Nino or La Nina or the North Atlantic Oscillation, which has received alot of media attention since Hurricane Sandy rarely provide a straight forword, hard-and-fast forecast commandment to follow. If they did, long range outlooks would be as easy as looking out the window and saying whether it was sunny or cloudy.

Last winter gave us a great laboratory environment by which to view the atmosphere, like a fly on a wall, react to several teleconnections abrupt shift to levels that feature a lack of arctic drivers. This was a wake up call for all of us after a few very cold winters in 2009 and 2010. As a scientist, it was nice to see the other end of the spectrum at work in nature. Let's look at the late 2011 teleconnection levels:

The North Atlantic Oscillation, The Arctic Oscillation and the Pacific North American Index (Click on the link here for a detailed description)

Each one is more influential on weather patterns in the winter. The more POSITIVE the NAO and AO; the more NEGATIVE the PNA, the "colder" pattern shuts down. Conversely, the more NEGATIVE the NAO and AO; the more POSITIVE the PNA, the "colder" pattern becomes stronger and stronger.

North Atlantic Oscillation/Arctic Oscillation/Pacific North American Index charts from late 2011. Notice the perpetual POSITIVE levels. The PNA forecast for December 2011 was barely in positive (colder) territory.

 Now compare late 2011 to late 2010 and late 2009. Notice the levels were opposite.

How are the levels currently as we approach Thanksgiving 2012? They are no where as "mild" as last year and not as "cold" as 2010 or 2009. The NAO and AO are showing signs of more frequent negative turns. Yet the PNA still shows the western ridge or warmth hasn't developed into something steady and strong which would ultimately drive a trough/colder pattern more in the east and Ohio.

I still do not think this winter will be a repeat of last winter. The index levels are reflect a pattern that features a higher frequency of colder air episodes. The wild card will be whether or not the WESTERN RIDGE strengthens and STAYS WEST. Keep an eye on the PNA INDEX. If this happens in December coincident with INCREASED SNOW COVER in CANADA along with a few other factors over the arctic and Siberia, expect more cold this winter than last.


jc said...

Nice blog Scott!! Very hard for the average user to understand all the players but this a a great read for anybody who wants to find out about all the players in the winter game.

Cheers, Jim Cantore

Brandon Beck said...

Hey Scott, nice job with this. We're getting ready to do our winter outlook next week for southern MO and northern AR. 2nd part is all the drivers including some of these. Going to have some fun with it...also hoping southern branch cranks a bit on occasion with the "La Nada." It can't be much "worse" (non-winter) than last year! Bottom line is we're thinking a little colder and a little wetter than average.

Brandon Beck said...


We're getting ready to air our winter outlook for southern MO and northern AR next week. Lots going on this year with all of these. Seems like warm AMO favors blocking and negative NAO. Pacific is certainly warmer in the nino regions, but sort of a "La Nada." My thinking is we'll have some pretty wild swings and end up a bit cooler/wetter than average. With our whopping 1.8" snow total for last season, it can't get much worse!