As the first snaps of cold weather hit parts of the country this month with snowflakes and below-freezing nights, many people are looking toward the upcoming winter with curiosity, eagerness or fear of what’s to come.

As the first models are starting to hint at a big snow year for the Northeast and a cold, dry winter for the Pacific Northwest, experts cautioned that even the most advanced understanding of physics and meteorology can’t produce a truly reliable long-term weather forecast.

NEWS: Forecasting 'Weather Bombs'

There are just so many variables, many of which can change in an instant.

“A three-to-six month weather outlook is still more of a horoscope than an actual scientific prediction -- your horoscope may be a little more accurate, in fact,” said Paul Douglas, senior meteorologist and co-founder of WeatherNation TV, a new 24-hour national weather channel. “To be honest, any forecast beyond two weeks should come with a warning much like on a pack of cigarettes. In the end, some things are inherently unknowable.”

Among the factors that determine whether a winter will be lion-like or lamb-like, perhaps the most well known is the El Niño-Southern Oscillation, also known as ENSO, which describes shifts in the temperature of surface waters in the Pacific Ocean.

Pacific warming is called El Niño. Cooling is called La Niña. And those patterns have far-reaching influence on atmospheric conditions across the country by influencing where the jet stream runs and how much moisture ends up in the air.

This year is shaping up to be ENSO neutral. There is neither an El Niño or a La Niña brewing, meaning basically that anything could happen. Some models are hinting at a mild El Niño by late winter or early spring, which could deliver stormy weather to the West Coast and extra moisture to the southern half of the country.

But ENSO is far from the only factor that might sway weather forecasts over the next few months. Oscillations in the Arctic and North Atlantic also play a role, and those can flip from one week to the next, said Bernadette Woods Placky, a meteorologist at Climate Central, an organization that analyzes and communicates about climate change. Among other dynamics, there’s also the Pacific Decadal Oscillation, which shifts every few decades.

These and other events help explain why two La Niña years can be so different from each other. They also explain why long-term forecasts are so often wrong.

Although meteorologists were predicting lots of hurricanes this year, for example, the season fizzled. Scientists aren’t exactly sure why but one theory, Douglas said, is that extra dust and hot air blowing off the Sahara prevented thunderstorms from building up enough energy to become destructive.


“Forecasting has come so far in the past couple of decades, and it has come to the point where we can take it to a new level, but we’re not fully there yet,” Placky said. “We’ve come a long way in understanding how these patterns link together, but we don’t understand how to connect all of them.”

Climate change seems to be influencing the state of natural oscillations, as well, Douglas said. Siberia and the Arctic are warming twice as quickly as Europe and the United States, and that, he said has “knocked the jet stream off its rails.”

PHOTOS: Wild Winter Weather

A 2012 study found a 14 percent drop in upper atmosphere wind speeds because of this disproportionate warming. As a result, weather systems are more likely to stall, which could explain the recent non-stop rains in Boulder, Colo., as well as floods in Calgary and Chicago earlier this year and persistent summer droughts in the Midwest.

Slower-moving weather patterns suggest that whatever this winter brings will likely stick around for a while.

Most detailed winter forecasts will emerge in November, but the first few predictions are starting to trickle in. The National Oceanic and Atmospheric Administration’s Climate Prediction Center, for example, is calling for warmer and wetter-than-normal conditions through March in the southwest, centered around west Texas and New Mexico, though NOAA offers equal chances that the rest of the country will be warm, cold or about average.

With signs that the North Atlantic Oscillation is trending negative this year, some forecasters are predicting lots of snow for the northeast. And is calling for cold and dry conditions in the upper Northwest through December and January but a wet December for northern California, Oregon and the lower Mississippi and Ohio valleys.

For the Midwest, Douglas predicted “colder with some snow,” he said. “The more vague you can be for a six-month outlook, the better for you.”

His methods, he admitted, are based on questionable research.

“I am telling people only half tongue in cheek that we have done an analysis of the 12 years since 1976 with government shutdowns and the winters that followed those shutdowns, as a rule, were four inches snowier than non-government shutdown years,” he said. “Seeing as we don’t have a strong signal for El Niño or La Niña, I think that’s as good of an indicator as any other.”