El Niño is officially here, and while it’s still weak at the moment, federal weather forecasters expect this global disruptor to world weather patterns to gradually increase.
It may sound ominous, but El Niño – Spanish for “the little boy” – is neither malicious nor automatically bad.
Here’s what forecasters expect and what that means for the US
What is El Nino?
El Niño is a climate pattern that begins with the accumulation of warm water in the tropical Pacific west of South America. This happens about every three to seven years. It can take a few months or a few years.
Normally, the trade winds there push warm water away from the coast and let cooler water to the surface. But when the trade winds weaken, the water near the equator can warm up, and that can have all sorts of effects through so-called long-distance connections. The ocean is so vast – covering about a third of the planet, or about fifteen times the size of the United States – that these warm water sloshes have repercussions around the globe.
This warming at the equator during El Niño results in warming of the stratosphere that begins about 10 kilometers above the surface. Scientists are still investigating how exactly this long-distance connection comes about.
At the same time, the lower tropical stratosphere is cooling.
This combination can shift the upper winds known as the jet stream, which blow from west to east. A change in the jet stream can affect all kinds of weather variables, from temperatures to storms and winds that can tear apart hurricanes.
Basically, what happens in the Pacific doesn’t stay in the Pacific.
What does all this mean for you and me?
With an apology to Charles Dickens, El Niño tends to tell a tale of two regions: the best of times for some and the worst of times for others.
On average, worldwide El Niño years are warmer than La Niña years—the opposite of El Niño. Globally, a strong El Niño can raise temperatures by about 0.7 degrees Fahrenheit (0.4 degrees Celsius). But in North America there are many local differences.
El Niño years tend to be warmer in the northern part of the United States and Canada, and the Pacific Northwest and Ohio Valley are often drier than usual during winter and fall. In the southwest, on the other hand, it tends to be cooler and wetter than average.
El Niño typically shifts the jet stream farther south, causing it to blow almost due west-east across the southern United States. This shift causes moisture from the Gulf of Mexico to be blocked, reducing fuel for southeastern thunderstorms. La Niña, on the other hand, is associated with a more wavy and north-shifted jet stream that can increase severe weather activity in the south and southeast.
El Niño also affects hurricanes, but in different ways in the Atlantic and Pacific.
Over the Atlantic, El Niño tends to increase wind shear — the change in wind speed with height in the atmosphere — which can disrupt hurricanes. However, El Niño has the opposite effect in the eastern Pacific, where there can be more storms. Ocean heat can also increase the risk of ocean heat waves, which can destroy coral and ecosystems that fish rely on.
In the central US, El Niño is generally associated with warmer and drier conditions that may slightly increase the chances of a bountiful corn crop.
In contrast, El Niño can wreak havoc on crops in southern Africa and Australia, and increase the risk of fire in Australia from dangerously dry conditions. Brazil and northern South America also tend to be drier, while parts of Argentina and Chile tend to be wetter.
Of course, just because it usually happens doesn’t mean it happens every time. Experience California’s record-breaking rainfall from multiple atmospheric flows at the end of the last La Niña, which would normally mean dry conditions.
Every weather event is slightly different, so El Niño’s impact is a matter of probability, not certainty. How El Niño and La Niña will be affected by climate change over time is not yet clear.
The forecasts do not all agree
Will 2023 be a record year? That’s the multi-billion dollar question.
The National Weather Service declares the beginning of El Niño when water temperatures in the so-called Niño3.4 region are at least 0.9 F (0.5 °C) above normal for three months. This is a large imaginary rectangle south of Hawaii along the equator.
For a strong El Niño, the Niño3.4 region needs to warm by 2.7 F (1.5 °C) over three months. It is currently not clear if this El Niño will reach this threshold this year.
The first El Niño report of the year from the National Oceanic and Atmospheric Administration, released June 8, sees an 84 percent chance that El Niño will be more than moderate by winter and a 56 percent chance that that he will be strong.
However, these forecasts are subject to change and different forecasting methods are offered different forecasts of magnitude.
“Dynamic” models, similar to the models used for typical weather forecasting, have predicted a very strong El Niño, while “static” or statistical models are far less optimistic. Personally, I’m a statistical modeler, and my own model doesn’t point to a strong El Niño in 2023. Rather, my model, like other static models, predicts that 2023 will fizzle out, and after a few quiet or neutral years, we’ll see a strong El Niño in 2026. I got the recent unusual “triple dip” La Niña right, but am willing to be proved wrong by observation, as any good scientist should be.
But no computer model of any kind has experience with the extremely high ocean temperatures that are currently occurring around the world. The Atlantic is unusually warm, and that could offset some of the usual El Niño forces.
This article was originally published on The conversation by Bob Leamon in Baltimore County. Read the original article here.