What went wrong for Philly’s winter forecasts? ‘The polar vortex stole the show.’

When the preseason outlooks suggested that the winter of 2020-21 would be about as interesting as the average voicemail menu, Pete Altringer, who runs quite a weather-sensitive business, didn’t pay much attention.

“We kind of ignore them,” said Altringer, owner of a regional chain of car washes in Bucks, Chester, and Montgomery Counties. As it turned out, based on what happened during the three-month meteorological winter that ended on Sunday, not a bad call at all.

The atmosphere played an impressive game of dodgeball with the long-term forecasters and their virtual firepower for the second straight winter.

» READ MORE: In January, it looked like February was going to be mild across the nation

A ferocious and deadly freeze in Texas that penetrated all the way to the Gulf of Mexico; heavy snows in the East, with as much as 4 feet total in parts of the Philadelphia region; and a procession of storms across the country belied the consensus of the outlooks.

What happened?

The La Niña cooling of surface waters in the tropical Pacific that was supposed to dominate the winter encountered formidable competition from another part of the planet.

“La Niña got all the attention in the lead-up to the winter,” said Judah Cohen, a scientist with Atmospheric and Environmental Research in Massachusetts. “The polar vortex stole the show.”

“This is not a pattern that supports much snow,” ABC6 meteorologist Cecily Tynan informed her viewers back on Nov. 20. Tynan and colleague Adam Joseph forecast 9 to 12 inches of “nickel-and-dime” snow, with maybe 18 inches in Allentown.

AccuWeather Inc. was on board with 10 to 15 inches, with temperatures two to three degrees above normal.

Fox29′s Kathy Orr went with 18 inches for Philadelphia, with one decent snowfall of 6 inches or more.

The Weather Channel eschewed the snow but had the region with much-above-normal temperatures for the season. The WeatherBell outlook released in late August favored below-normal snowfall around here and above-normal temperatures.

The Climate Prediction Center avoids snow forecasts but also had odds favoring mild conditions across most of the country, including the Philadelphia region.

Some of it even happened.

AccuWeather correctly predicted above-normal temperatures in the Southwest, and cold and wet in the Northwest, noted Paul Pastelok, the company’s long-range forecaster.

But no one foresaw the extreme cold in Texas, which might end up with its sixth-coldest winter ever, John Nielsen-Gammon, the state climatologist, said Friday.

Around here, things did not go so well, either.

» READ MORE: How much snow this winter? Here is what TV meteorologists had to say in December.

Officially, Philadelphia has received 23.9 inches of snow, and props to Kate Bilo at CBS3 for going with 18 to 24 inches for the city.

“What I didn’t see coming was that all this snow would come in February, or that February would end up being the coldest winter month compared to average,” she said.

And some areas in the neighboring Pennsylvania counties have had amounts approaching 4 feet, and Allentown stood at 57.3 inches as of Friday.

Philadelphia’s overall winter temperature, 36.3, is only about a degree above the 30-year “normal” value, and the snowfall would be just 1.5 inches above the seasonal normal.

But has anything normal happened this winter?

One winter storm lasted four days. Another creamed areas north and west of the city so suddenly that it evoked poet Dylan Thomas’ description of snow that “came shawling out of the ground and swam and drifted out of the arms and hands and bodies of the trees.”

In La Niña years, upper-air winds off the Pacific tend to shunt the storm tracks and cold air to the north, said Pastelok. But the polar vortex crashed the party.

In the winter of 2019-20 the vortex was strong and confined cold air to areas around the Arctic Circle. This winter, it weakened and pieces of it were able to break off and chill areas in lower latitude, including parts of the contiguous United States.

“This split changed the whole jet stream pattern,” said Pastelok.

When the cold air oozed all the way to the Gulf of Mexico it interacted with the warm waters to set off winter storms.

Meanwhile, a “blocking pattern” set up over the North Atlantic that supplied the storms with cold air to manufacture snow.

“I know people like to see them,” Bilo said, but “trying to predict anything months in advance is often a bit of a fool’s errand.”

Blocking patterns and cold-air intrusions, she said, can be seen at most a few weeks in advance.

Addressing what went wrong this season, Nat Johnson, a National Oceanic and Atmospheric Administration researcher, cited “an unusual mismatch” between typical La Niña patterns and what unfolded. “Did the forecasters miss something?” he wrote in a post. “Or was the mismatch due to chaotic weather variability that we cannot predict well in advance?”

Looking at the extreme patterns of the last two winters, Bilo suggested that climate changes are making this more difficult.

“Volatile patterns like those we’ve seen in recent years,” she said, “do not lend themselves well to long-range outlooks.”