December 11, 2023

By Mary Gilbert | CNN Meteorologist

Because the US gears up for a winter closely influenced by the primary sturdy El Niño in years, scientists on the Nationwide Oceanic and Atmospheric Administration have launched maps that supply perception into the place snow may pile up.

El Niño – a pure ocean and climate sample within the tropical Pacific – is forecast to achieve essentially the most important degree since a really sturdy El Niño in 2015-2016 fostered the warmest winter on file throughout the contiguous US, in line with NOAA.

Whereas no two El Niño winters are the identical, the sample usually brings wetter and cooler climate to the southern US whereas the north turns into drier and hotter. And that’s precisely what’s anticipated this winter.

Nevertheless, wetter climate doesn’t essentially imply extra snow. And when it does snow, quantities can differ wildly from one location to the subsequent.

That is the place the brand new maps are available. They present the place snow is kind of seemingly throughout El Niño winters in comparison with common.

There’s only one caveat: these maps are historic guidebooks, not forecasts, for a way the season’s snow may play out. An precise snowfall forecast would account for a wide range of atmospheric and climatological elements, not simply El Niño.

“El Niño nudges the chances in favor of sure local weather outcomes, however by no means ensures them,” Michelle L’Heureux, one of many two scientists behind the brand new maps, defined in a NOAA weblog publish.

Snowfall throughout all El Niño winters (January-March) in comparison with the 1991-2020 common (after the long-term pattern has been eliminated). Blues point out extra snow than common; browns point out much less snow than common.(NOAA Local 

The map above depicts how a lot snow differs from common throughout all El Niño winters, no matter El Niño’s energy. The drier pattern that’s typical throughout the northern US exhibits up effectively within the tan and brown shading, whereas the wetter, snowier pattern throughout the southern US seems within the blue shading.

This sample comes from the jet stream’s shift south, pushing storms throughout the southern tier of the nation on the expense of the north. And a rise in storms throughout the winter means snow is extra seemingly.

The stronger an El Niño is, the extra amplified its affect turns into. The map beneath exhibits the identical knowledge for stronger El Niño winters. The pronounced darker hues characterize extra excessive shifts in snowfall throughout a robust El Niño in comparison with a mean one.

Snowfall during all stronger El Niño winters (January-March) compared to the 1991-2020 average (after the long-term trend has been removed). Blues indicate more snow than average; browns indicate less snow than average.(NOAA
Snowfall throughout all stronger El Niño winters (January-March) in comparison with the 1991-2020 common (after the long-term pattern has been eliminated). Blues point out extra snow than common; browns point out much less snow than common.(NOAA Local 

The large snow winners are the mid-Atlantic, the excessive elevations of the Southwest and California, and the South, albeit with an necessary caveat.

It nonetheless must be chilly with a view to snow, so possibilities don’t differ as a lot from regular in parts of Texas and the Southeast, which have a tendency to stay too heat for flakes to fly.

El Niño’s jet stream impact is especially noticeable within the highest terrain of the West, the place chilly and snow isn’t normally exhausting to come back by. Mountains within the Southwest and California thrive whereas the Northwest misses out due to fewer storms.

Storms that have an effect on the mid-Atlantic’s snow possibilities usually take a observe alongside the backbone of the Appalachians or push off the coast and turn out to be nor’easters.

These nor’easters can get “juiced up” by ample tropical moisture throughout El Niño and ship “two to a few huge snowstorms” on common, in line with Jon Gottschalck, chief of the Operational Prediction Department of NOAA’s Local weather Prediction Heart.

This might carry above-average snowfall to locations like Washington, DC, and Baltimore, the place lower than an inch fell final winter.

Although the Northeast usually misses out on snow throughout a robust El Niño winter, all it takes is one large storm, like a “juiced up” nor’easter, to skew snow totals for the entire season.

The number of years with below-average snowfall during the 13 moderate-to-strong El Niño winters (January-March average) since 1959. Red shows locations where more than half the years had below-average snowfall; gray shows locations where below-average snowfall happened in less than half the years studied.(NOAA
The variety of years with below-average snowfall throughout the 13 moderate-to-strong El Niño winters (January-March common) since 1959. Purple exhibits areas the place greater than half the years had below-average snowfall; grey exhibits areas the place below-average snowfall occurred in lower than half the years studied.(NOAA Local 

Snow lovers within the Northwest and Midwest can even have to affix their Northeast counterparts in hoping for an enormous storm. Stronger El Niños have precipitated much less snow than common previously.

Eradicating snowfall totals from the map and specializing in the variety of stronger El Niños with below-average snowfall helps suss out outlier storms.

On the map above, darker reds point out areas which have skilled extra years of below-average snowfall throughout moderate-to-strong El Niño winters.

Elements of the usually snowy Midwest and Northeast which additionally undergo from snowfall deficits leap out clearly, an indication that this can be the place El Niño steals essentially the most snow, most frequently.

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