Stormy, possibly snowy, and strong El Niño

After a mild start, the winter of 2023-2024 is likely to be stormy along the U.S. East Coast with an excellent chance to empty grocery shelves of snow concerns, if not actual snow. El Niño, which may occur with intensity once every decade in the tropical Pacific, will be a major player.

That’s the running consensus among winter forecasts issued so far by major outlets, including one released Thursday by the federal government. Government Climate Prediction Centre.

In Philadelphia, it will almost certainly be more eventful than the winter of 2022-23, which competes with the argument that the Diamondbacks won’t clinch the National League pennant in Arizona this year. (until If they beat the Phillies in the next three games in Phoenix, they still have to return to Philly.)

During an El Niño event, “generally, there tends to be one or two very large snowstorms,” ​​John Gottschalk, chief of the Climate Center’s Operational Forecasting Branch, said at a news conference Thursday. “These storms could actually blow off the East Coast.”

“This is not a bad winter,” said Paul Pastelok, a longtime seasonal forecaster at AccuWeather Inc.. These are large, massive cluster storms that can add up to snow, and if you’re in the right area, you’ll get it.

Expectations

The climate center favors above-average temperatures and precipitation In the Philly area from December 1 to February. 29 (will be a leap year). He wouldn’t hazard a guess at snow, but Gottschalk said this pattern would likely favor large coastal storms, especially later in the winter, but it’s uncertain whether that means snow, rain or just a scare.

Weather.com forecasts are quite similar. It also avoids specific snow forecasts.

AccuWeather expects 18 to 24 inches of snow in Philadelphia — the long-term average is 22.2 inches. As Gottschalk and Pastelok said this week, the bulk of that total could fall in just a couple of storms.

WeatherBell Analytics, in an early forecast issued in August, was calling for up to 30 inches of snow in Philadelphia.

All three forecast services say a slowdown period is likely after a mild December.

During an El Niño event, sea surface temperatures over large areas of the tropical Pacific Ocean are abnormally warm. The warmth is disturbed by westerly and eastern winds that carry the weather to the Americas.

No two El Niños behave the same way, said Sarah Kapnick, a senior scientist at the National Oceanic and Atmospheric Administration (NOAA).

But in this case, forecasters see a developing track that will carry storms up the Gulf Coast and then make a sharp left turn when it reaches the Atlantic Ocean.

This path will allow storms to collect abundant moisture, said the Climate Center’s Gottschalk. This does not necessarily mean snow: storms hugging the coast tend to bring rain winds from the warmer ocean; If they drift too far to the east off the coast, they will have no effect here.

This El Niño phenomenon is particularly strong, with water temperatures about 2.5 degrees Fahrenheit above average, and is expected to continue at or near that intensity through the winter.

The strong El Niño phenomenon has only lasted through the winter seven other times, dating back to 1950, according to climate center records. Winters here tend to be extreme in both directions. Snow totals ranged from 0.0 inches, in 1972-1973, to 79 in 2009-2010, when Philadelphia saw huge snowstorms around the solstice and in February.

Gottschalk recalled that winter on Thursday, and was mentioned in the other two outings.

“Current weather conditions resemble the El Niño of 2009-2010,” said Todd Crawford of Weather.com. WeatherBell’s Joe Bastardi said he doesn’t rule out December 2009 being like December, but the gist of the worst part of the winter, compared to averages, should be from mid-January onward.

AccuWeather’s Pastelok doesn’t see snow falling this early in the season. “December doesn’t seem cold enough,” he said.

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The argument against snow is that outbreaks of frigid Arctic air migrating southward tend to occur less frequently, Gottschalk said.

Of course, in keeping with the global warming trend, the Philadelphia area has seen a series of mild winters in recent years.

Three of the five warmest winters on record in Philadelphia dating back to 1874 occurred in the 21st century, including last year, when the city saw 0.3 inch of snow.

It would be hard not to reach the top.