Three winters in a row, La Niña conditions brought everything from a record snowless season to multiple blizzards across the state.
However, El Niño is back for the first since before the COVID-19 pandemic, and will try to influence our temperatures.
El Niño (Spanish for "little boy") is one of three phases of the El Niño Southern Oscillation. There also is La Niña ("little girl"), and then a neutral state, which New Jersey State Climatologist Dave Robinson jokingly refers to as "La Nada."
What phase we're in is based on how Pacific Ocean temperatures off South America near the equator are faring compared to average. Warmer than average means El Niño, cooler than average brings La Niña and near seasonable water temperatures bring the neutral phase.
Around March, we quickly transitioned out of La Niña and into El Niño.
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The state of the El Niño Southern Oscillation is one of if not the main factors seasonal forecasters use to predict the upcoming winter. However, it's influence on New Jersey is limited.
Generally, a La Niña pattern will merge the subtropical, warmer and wetter Pacific jet stream with the colder polar jet stream in the Western United States. From there, they flow as one to around the Great Lakes and then cut through the interior Northeast.
Chicago and Columbus, Ohio, have a strong wet signal. Atlanta, Houston and the southern United States have a strong warmer and drier influence.
New Jersey will skew milder. Storms that do come have a tendency to erase any chilly air. Rain or mixed precipitation events, possibly ending as snow, can occur.
However, look at the past winters, all of which were La Niñas. Winter 2020 into 2021 brought less than a foot of snow from Island Beach State Park down the coast. Meanwhile, the northern half of the state was well above average with snow.
Snow in winter 2021-22 was the complete opposite. Well above average snow fell from Ocean County to Cape May County, staying below average elsewhere. In fact, Galloway Township, at 36 inches, was the snowiest place in the state. South Jersey was snowier than both Central Jersey and North Jersey for just the third time since records started in 1894-95.
Winter 2022-23 barely brought any snow to New Jersey. South Jersey was the least snowiest since New Jersey records were started by the climate office. Two feet or more of snow was only seen in Sussex County and small portions of Morris and Passaic counties.
El Niño brings a new regime. The subtropical and polar jet streams stay apart from each other over the Lower 48 United States. From Los Angeles to Miami, there's a strong wet signal. There's a strong warm signal from Chicago to Seattle.
For New Jersey, the temperature signal is weak.
However, the strength of an El Niño or La Niña can vary. There's a 92% chance we're at least in a moderate El Niño from December to February and a 62% chance we're in a strong El Niño. The most intense El Niño should be earlier in winter.
The phase of El Niño can be important. Looking back at temperature records since 1950 from the National Oceanic and Atmospheric Administration, strong El Niños have a clear warmer than average signal for New Jersey. Meanwhile, weak El Niños have a pronounced cooler than average signal.
For moderate, the one we could have? Mixed results. Five were cooler, three were warmer.
So we have to look elsewhere for more evidence on what to expect temperature-wise this winter.
One such place is the Quasi-biennial Oscillation. Steve DiMartino, owner of NY NJ PA Weather, has been onto this as a factor for temperatures this winter. We'll skip the details, but an easterly state of the QBO usually means a weak polar vortex in the stratosphere. When that happens, its significant cold is more likely to swipe down. It could be along the East Coast of the United States, it could be in Italy, but it's there.
Another factor is one that occurs every winter — the Atlantic Ocean getting colder.
Off the Jersey Shore, average water temperatures fall from the mid-40s in December to the upper 30s in January and February, according to NOAA. When that happens, the land is just naturally going to be colder, especially when nor'easters blow onshore winds our way.
Taking in all of these factors, it looks likely that December and January wind up above average. El Niño will be strongest here, lending to a warmer signal for the state anyway. Tack on water temperatures that will largely be in the 40s, and that helps support this.
There will be below average days. If the polar vortex does visit New Jersey, then a brief, intense cold spell could occur.
The deepest winter chill should come in February, which has the best likelihood of being below average, assuming El Niño weakens. One thing El Niño does is increase the likelihood for coastal storms later in the winter.
Regardless of whether it snows, sleets or rains in New Jersey, it will almost always bring in colder than usual air for a couple of days. Accepting that means accepting cold spells from that storm track, as well as the probability of a polar vortex invasion or two.
March likely will stay on the cooler side. However, note that average high temperatures in March rise from the mid- to upper 40s to the low to mid-50s as the month goes on.
The same logic as February applies to March. Coastal storms would pull down cooler air after it passes, and polar vortex invasions can still occur.
When March 2024 is over and we add up the winter temperatures, we'll likely wind up at or even above average for temperatures. That warm December signal is strong and could wipe out the below average temperatures later in the season.
Of course, temperatures are only part of the winter forecast equation. The other part is precipitation. Or, maybe more specifically, snow.
Look for a national winter weather outlook on the Across the Sky podcast Oct. 30. For a New Jersey specific outlook, Judah Cohen, director of season forecasting at Atmospheric and Environmental Research in Massachusetts, will guest on the Something in the Air podcast around Election Day in November. Listen at PressofAC.com or wherever you get your podcasts.
