How teleconnections tell us that below normal temperatures are likely for December in North Dakota | Morse Code of Weather
BISMARCK, N.D. (KFYR) - Teleconnections all across the globe are often used for longer-term weather trends to give meteorologists clues as to what could happen locally in the coming weeks and months. They influence how the jet stream moves around the world, which is a steering mechanism for storms and separates colder air farther north from warmer air farther south.
Below is a list of notable teleconnections, and the four highlighted at the top of the list are located in the Pacific Ocean. These teleconnections are particularly influential on our weather in the United States since weather systems often move west to east — from over the Pacific Ocean to North America.
Most of these teleconnections can be in one of two phases, positive or negative. Depending on the phase of the teleconnection the jet stream will be impacted differently and there will be downstream impacts.
Let’s look at the Pacific North American (PNA) teleconnection first. As we start the month of December, we’re in the negative phase, which favors a ridge of high pressure over the northern Pacific Ocean allowing the jet stream to commonly dip south over the western and central United States. Surges of Arctic air are more common in North Dakota when the PNA is negative.
A teleconnection that some of us might be familiar with is El Niño–Southern Oscillation (ENSO), where the two phases are El Niño and La Niña. We look at ocean temperatures in the equatorial Pacific Ocean to determine which phase of ENSO we’re in. As it has been for the past three years, we’re still in the La Niña phase which usually promotes colder than normal temperatures in the Northern Plains during the winter months.
Another teleconnection to look at in the Pacific Ocean for impacts on our longer-term weather patterns in North Dakota is the Eastern Pacific Oscillation (EPO). This is also currently in the negative phase, which places a ridge of high pressure in the northern Pacific Ocean (similar to the negative phase of the PNA) and allows the jet stream to dip south across much of the United States. Surges of Arctic air are more common in North Dakota when the EPO is negative.
A fourth teleconnection in the Pacific Ocean to investigate is the Pacific Decadal Oscillation (PDO), with decadal meaning something that lasts for a decade or a period of 10 consecutive years. This oscillation changes phases much less frequently than the EPO or PNA, for instance. The chart below shows the phase of the PDO since 1854, and for the past several years, the PDO has been negative. Currently, this teleconnection is very negative which promotes a jet stream pattern that favors colder than normal temperatures in the Northern Plains during winter.
A couple of other teleconnections to look at that aren’t over the Pacific Ocean, but can still have impacts on North Dakota’s longer-term weather patterns include the North Atlantic Oscillation (NAO) and Arctic Oscillation (AO). The NAO is currently in the negative phase, which means that a blocking high pressure is present over the northern Atlantic Ocean — near Greenland — which blocks up the jet stream and allows surges of Arctic air to plunge southward into the central and eastern United States. The AO is also currently in the negative phase which means that a weaker, meandering jet stream is present around the North Pole, and that jet stream dips farther south, allowing Arctic air to spill into the United States.
So looking at these teleconnections, ALL are in the negative phase. Teleconnections can work constructively together, meaning that since the negative phase of each of these teleconnections favors colder than normal temperatures in North Dakota, having all of them be in the negative phase gives us greater confidence that this December will be very cold.
How cold? Let’s go back and look at some past Decembers where most or all of these teleconnections were negative. The Decembers of 2008, 2010, and 2016 come up as comparisons. In all three of those Decembers, a La Niña was present (as is the case this year) and the Pacific North American teleconnection was in the negative phase. In the Decembers of 2008 and 2010, the negative phase of the PDO was found and in December 2010 the negative phase of the NAO and AO were present.
What happened during these three Decembers of the past? They were all very cold and very snowy. In fact, the December 2008 snow total of 33.3″ in Bismarck is a record for all Decembers in record-keeping history.
The Climate Prediction Center agrees that this December will be a very cold one, as HIGH confidence is present that December 2022 will feature below normal temperatures in North Dakota. And that prediction is all tied back to global circulations, called teleconnections, such as the PNA, PDO, EPO, ENSO, NAO, and AO.
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