The periodic cooling of the Pacific water near the equator known as La Nina has arrived once again. In a year already defined by unexpected occurrences and strange happenings, the winter of 2020 is shaping up to be equally strange. The Atlantic hurricane season has already broken records and brought destruction to the Eastern and Gulf Coasts. Could major snowstorms be in store for winter?
La Nina is a major atmospheric force, with the cool waters over the Equator affecting the tropical rainfall from Indonesia all the way to the West Coast of South America. This, in turn, has a major impact on weather in this hemisphere. The main conditions can be felt in the winter in the US, when the jet stream is at its highest speed and activity over the US.
The Jet Stream
The impact of the jet stream on weather in the US is hard to overstate. While the jet stream is always a factor, during La Nina periods in the winter it became even more apparent. First, the subtropic jet joins in with the jet stream off the western coast of Canada. Then, the jet stream develops a wave-like pattern during these periods. This causes cool air from further north in Canada to be pulled into the northern regions of the United States.
This, in turn, brings stormier, wetter, and colder conditions across regions from the Northwest through the Northern Plains. Likewise, it also brings warmer, dried conditions to the Southern region of the US, ranging from Southern California across to South Carolina on the East Coast. This, of course, means that the US primarily experiences two major patterns during La Nina winters.
In the northern reaches of the US, La Nina conditions can be the perfect recipe to conjure up winter storms. Driving blizzards, massive snowfalls, and record-setting low temperatures tend to accompany La Nina for people who live in the northern parts of the country. However, the opposite is the case in the southern half of the county.
In the southern portion of the US, La Nina tends to accompany drought conditions. This unusually dry, warm weather can cause issues for regions already experiencing droughts in the hotter summer months.
Likewise, the northern storms can play havoc on crops and irrigation in the northern part of the country. Typically, the extremes that La Nina drives only push the winter into a more extreme and unpleasant direction, spawning storms for some and bringing drought for others.