A fellow meteorologist recently brought up the complexities of forecasting something called the North Atlantic Oscillation, an atmospheric teleconnection often studied by New England forecasters.
The North Atlantic Oscillation, known as the NAO, can be in one of three phases at any given time: positive, neutral, or negative. When the NAO is in its positive or negative phase, New England meteorologists receive a little insight as to what our local weather may entail.
Take the positive NAO phase, for example. In that case, pressure is abnormally low across the North Atlantic (near Greenland) and abnormally high across the central Atlantic. That keeps the jet stream, or river of air about 20,000 feet up, traveling straight from the United States across the Atlantic. With that configuration, disturbances tend to zip quickly away from the United States out to sea. It also prevents cold Canadian air from dropping down into the Northeast.
During the negative NAO phase, however, the Northeast often turns cold and stormy. That’s because pressure is abnormally high near Greenland. That forces the jet stream to buckle, and run from south to north parallel to the East Coast. Since storms tend to travel with the jet stream, New England is right in their path.
So, understanding the phase of the NAO can tell us (generally) if New England can expect mild and less-stormy conditions (positive phase) or cold and stormy conditions (negative phase). This week, the NAO is slightly negative. Unfortunately forecasting the NAO is very tricking, and often can’t be done reliably more than a week or two out.
Do you have a weather or climate related question? Let me know in the comments section, or on twitter (@MichaelPageWx) and I’ll answer it here on Hingham Patch!
In the meantime, remember to check your latest forecast at HinghamWeather.com
-Meteorologist Michael Page