An Intro to Teleconnections: The NAO & AO Explained

January 13, 2023 // Article by: Armando Salvadore

The atmosphere is one chaotic "fluid". It's constantly in motion, shifting due to dips and rises in the jet stream and this can have major influences on weather patterns across the globe. This is most pronounced in winter, where we see the greatest contrasts and clashes in air masses between the the cold air from the Arctic, and the warmer air in the tropics. Sometimes, we see these interactions occur and this can result in notable weather systems and extremes.

One way we can analyze these sensible impacts is by grouping large-scale global pattern shifts and pressure changes. This is done by using indices or "teleconnections". Two main teleconnections that we look at (especially in the winter) are the "NAO" (North Atlantic Oscillation) and the "AO" (Arctic Oscillation).

 

North Atlantic Oscillation (NAO)

 

 

 

 

 

 

 

 

 

 

Image courtesy of Simon H. Lee's Weather Page & Britannica

The first image represents pressure differences between Greenland and the Azores in the far Northern Atlantic. This teleconnection is "boxed" within an index. In other words, there are two main phases - a positive (+NAO) and negative (-NAO) phase. The Images above show the differences between the two phases. Here are some key points of what happens in each phase:

Negative Phase (-NAO):

Positive Phase (+NAO):

Arctic Oscillation (AO)

 

Image courtesy of Just In Weather : +AO (L), -AO (R)

Sometimes, the AO and NAO work together, and can be in the same phase. Other times, they end up in opposite phases. Not one teleconection depends soely on the other. Similar to the NAO, the AO also has two phases; a positive and negative state. You can see how they are represented globally with the images above. Here are some key points of what happens in each phase:

Negative Phase (-AO):

Positive Phase (+AO):

Image Courtesy of NOAA :variability of the NAO since 1950. + NAO (Blue) - NAO (Red)

So in reality, when these two "tag-team" in the negative phase, this not only significantly increases the odds for cold air to spill into the lower 48 and support snow/wintry precipitation; it also boosts the chances for big winter events to develop along the East Coast and in particular, the Northeast.

Did you know? Our Long Range team uses teleconnections like the NAO and AO when updating the extended outlooks in our WinterRisk® Service. We provide weekly and monthly outlooks on the upcoming winter season, breaking down potentials for snow threats and explaing the chances of having saltable/plowable types events. For more information on this service, you can email Sales@weatherworksinc.com or call us at 908-850-8600

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