ROANOKE, Va. – I’ve had questions since June about what this coming winter would be like. While we don’t have a final answer, we do know one key part of that forecast.
The National Oceanic and Atmospheric Administration is forecasting that the La Niña will continue into the winter, with a La Niña Advisory now in effect.
La Niña is here, with a #LaNina Advisory now in effect. The observed La Niña conditions are likely to continue through the Northern Hemisphere winter (~75% chance). https://t.co/5zlzaYJ1Lp pic.twitter.com/jU6lzWOmHj— NWS Climate Prediction Center (@NWSCPC) September 10, 2020
What is a La Niña?
The El Niño Southern Oscillation is a key part of forecasting hurricane season and winter.
The El Niño refers to warmer than average ocean temperatures along the equatorial Pacific Ocean (west of Perú). This typically leads to a more active jet stream across the Southeastern United States, which can kill off hurricanes and can sometimes mean more winter weather.
The La Niña is the complete opposite. This is when the ocean temperatures west of Perú are cooler than average. This typically means that the jet stream retreats farther north, which implies warmer and drier weather across the southern half of the U.S. in the winter.
Upper-level winds are much lighter without the presence of the jet stream, which could prolong an already historic hurricane season.
What could it mean for us this winter?
Previous research that we’ve done shows the impact that La Niña has on our winters in Southwest and Central Virginia. Since 1950, when ENSO records were first kept, 74% of La Niña winters have produced below-average snowfall.
There are still other things that we need to consider in the coming months, so our official winter forecast will not be released for quite some time. This La Niña also doesn’t mean that we see ZERO snow.
We’ll keep you posted on what we learn in the coming days, weeks and months.