A Short Winter and a Boy Child
How do "influencers" half a globe away nudge weather in the middle of the United States?
Except for a shot of winter from late December into mid-January, winter has been remarkably absent from Laura-land (that is, the central United States). Shockingly absent.
Ice coverage on the Great Lakes is historically low as of mid-February. Even if the Great Lakes had a cold spell now, the daylight hours are stretching and milder spring weather is approaching. It’s too late to expect significant ice to form this year. A wide swath from the Dakotas to New England is experiencing its mildest winter on record, according to the Accumulated Winter Season Severity Index (or AWSSI, pronounced to rhyme with “bossy”), and the outlook for the next 2 weeks keeps mild weather as the most likely outcome.
Lots of factors around the globe affect our winter weather patterns here in the United States, and even with decades of research behind us, we only understand some of them. The oceans around the globe are also experiencing record warmth, and it’s not clear how long the extreme temperatures will linger before receding back to a warming average. El Niño is paying a visit this year, but it’s hard to pick out the El Niño signal from all of the other warm ocean temperatures around it. After this winter ends, researchers will study it to tease out all the factors they can identify that contributed to the mild winter.
Speaking of The Boy Child, let’s get to know El Niño a little better! This topic gets a bit nerdy, so please don’t be shy about asking questions in the comments below!
El Niño (The Boy Child)
Rainy in the South. Floods in southern California. Warmer than normal in the northern Plains and Midwest. If you keep up with the news, you might have seen reports of these events over the last month or two, and you might have even heard the phrase “El Niño” tossed in the report.
El Niño is one side of a pendulum that swings from warm (El Niño) to cold (La Niña) sea-surface temperatures in the tropical Pacific Ocean. (“Neutral” lies in the middle and is the third category in the swing.) Put together with both ends of the pendulum, the whole cycle is called the El Niño/Southern Oscillation, or ENSO (pronounced EHN-soh). We’ll give La Niña her due another day. For now, we’re focusing on The Boy Child.
Why do I care about temperatures in the Pacific Ocean this far inland in the United States?
Ocean temperatures in the Pacific Ocean near the equator fuel weather patterns around the globe. Tropical thunderstorms like to form over the warmest waters. When the location of that warm pool shifts around, it moves the thunderstorms with it. Those thunderstorms push the jet stream around, shaping where it lands in North America and whether it is fast and straight or wavy. Each El Niño is different, so the location, speed, and shape of the jet stream is not an exact match for each El Niño winter. But over time, they show some tendencies.
With an El Niño, the subtropical jet stream runs fast and straight, dragging stormy weather across the southern U.S. (the part that’s close to but not quite in the tropics - that is, the subtropics). This can mean rainier, stormier, and cooler winter conditions than normal somewhere in or near that swath from southern California to Texas to Florida. Meanwhile, the northern U.S. is left high and dry, with the polar jet stream well north and out of synch with the subtropical jet. The dice are loaded toward warmer-than-normal temperatures across the north.
ENSO is one of several “teleconnection” patterns. Evoking words like “telegraph,” “telephone,” and “telework,” the “tele-” part of the word means “far off” or “over a distance.” The “-connection” part of the word describes the link between two connected parts of a weather puzzle, such as ocean temperatures in one part of the globe and weather patterns on a continent thousands of miles away. The jet streams are the bridge from the tropical oceans to the continental weather patterns.
When does El Niño matter?
The name El Niño, Spanish for “The Boy Child,” reflects on the timing of El Niño, which often ramps up around Christmas. El Niño peaks during the Northern Hemisphere’s winter season, which happens to be when the jet streams are strongest and have the most influence on weather patterns across the United States.
Its influence (and presence) tends to fade in the spring and stay minimal in the summer. The current El Niño, in fact, has peaked and will start to fade. The ocean temperatures are slowly tempering back toward normal, and the atmosphere will lag behind it as the effects spin out. All eyes are on the increasing chance for La Niña to return by fall, which is probably when you’ll hear from me about the Girl Child.
Rolling the dice
Remember, no two El Niños are alike. Over time, we see tendencies in El Niño winters - patterns that become favored. But they are not guarantees. They simply increase the chances in one direction or the other - loading the dice but not to the point where chances move to 100%. Also, El Niño is not the only pattern in play. There are other teleconnection patterns, too, and sometimes they have competing influences.
If you’re interested in El Niño and want to learn more, I recommend the NOAA ENSO Blog. The contributors, all expert ENSO scientists and communicators, take deep dives into a bunch of ENSO-related topics. Go into their back catalog for tasty “flavors of El Niño,” “(S)no(w) pain, (s)no(w) gain,” and other buried treasures! These get a bit deep in the science, so brace yourself for some technical language and graphs!
This Month in Wilder Weather History
February 15-18, 1881: Almanzo Wilder likely makes the infamous “seed wheat” trip on one day within this time window, traveling with a partner (Cap Garland in The Long Winter) via horse-drawn sled to locate a man named Anderson who had harvested seed wheat and convince him to sell the wheat to the town of De Smet. While the veracity and details of this event are still under investigation, it is supported by numerous pieces of evidence, including census and homestead records. Weather and astronomical records help narrow down the possible dates. Want specifics? Stay tuned!
As I wait for the latest "atmospheric river" to hit southern California this week, big thanks for explaining the whole El Nino/La Nina continuum in a way I can finally understand it! You rock, Barb!!