CLEVELAND, Ohio -- Get ready for a snowier winter, Cleveland. The National Oceanic and Atmospheric Administration now predicts a 65 to 75 percent chance of weak La Nina conditions to continue at least through the winter.
Typical La Nina winters
Typically, cooling sea-surface temperatures in the equatorial Pacific Ocean lead to cold, snowy winters for most of the northern half of the United States, with the opposite conditions seen in the south.
Typical La Nina winters.
This year
This year is slightly different, and the recent warming trend is expected to dominate. While it's likely precipitation will stay above normal this winter, since Ohio will trend on the warmer side, it's possible some of that precipitation will be shifted toward rain, rather than the normally very heavy snow during La Nina years.
Either way, Northeast Ohioans are looking at a wet winter, and regardless of the chance of warmer temperatures, many predict snow to be slightly above-average in the area this winter.
Winter 2017-2018 Temperatures
Chances of above or below average temperature this winter.
Winter 2017-2018 Precipitation
Chances of above or below average precipitation this winter.
What is La Nina?
El Nino and La Nina are the warm and cool phases of a recurring climate pattern across the tropical Pacific, called the El Nino-Southern Oscillation, or ENSO. ENSO conditions are usually felt heaviest in the fall and winter, which is why snow and chilly temperatures are most talked about with a La Nina event.
With a La Nina, strengthening winds across the Pacific push the warm surface water away, bringing up cooler water below. This cooler water initiates sinking motion in the atmosphere over the Pacific, which dries things out in that region. The cool water can also shift the position of the jet stream, shifting the threat for severe weather and wet conditions in the United States north.
How does La Nina compare to El Nino?
El Nino is essentially the opposite of La Nina. In this phenomenon, weakened surface winds lead to an unusually warm surface temperature in the Pacific Ocean. The increasing heat in the ocean triggers rising motion in the atmosphere above, which intensifies storms and rain over the Pacific.
Warm Pacific Ocean temperatures also shift the jet stream south, making the atmosphere more unstable there. The instability then makes the southern portion of the United States more susceptible to severe storms and tornadoes. So, during El Nino, the southern portion of the United States sees wetter than normal conditions, while the northern half of the states see a drier winter.
Typical El Nino winters.
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Kelly Reardon is cleveland.com's meteorologist. Please follow me on Facebook and Twitter @KellyRWeather.