Recently, Federal government forecasters announced that La Niña – the opposite of its more well-known sibling, El Niño – has arrived. NOAA’s Climate Prediction Center said that this year’s La Niña (translated from Spanish as “little girl”) is on the weak side, but should persist through the upcoming winter.
This is the second consecutive La Niña winter. Last year’s episode was unusually brief, developing in November and gone by February. El Niño and La Niña are both part of a see-sawing weather pattern known as El Niño-Southern Oscillation (ENSO), which is a term that meteorologists use to describe fluctuations in temperature that oscillate back and forth in the tropical Pacific Ocean.
El Niño can be thought of as the warm phase of the ENSO pattern. La Niña is the periodic cooling of the equatorial eastern and central Pacific Ocean. When sea-surface temperatures are cooler than average by at least a half degree Celsius, along with consistent atmospheric indications, a La Niña is considered to be in place.
So what does this mean for this winter?
Typically in a La Niña year, below-average temperatures are most likely in the Northwest and Upper Midwest, while the South tends to be warmer than average. Portions of the Ohio Valley, Great Lakes, and Northern Rockies usually receive the highest odds of above-average precipitation and depending on how cold it is at any given time, odds increase for snow over rain.
But what about the Northeast?
“Typically La Niña is not a big snow year in the mid-Atlantic,” said Mike Halpert, deputy director of the Climate Prediction Center, adding, “You have a better chance up in New England.”
Across the southern U.S., a La Niña implies a dry winter, leading perhaps to drought and wildfires, particularly in the Southeast. Some might automatically say, “Well, if we had a weak La Niña last winter and another is forecast for this winter, then we should see a replay of last winter.” During last winter’s weak La Niña, the West and Upper Midwest had one of the wettest winters on record, while large swaths of the East, South, and Midwest had one of the warmest winters since record keeping began in the late 19th century.
But so far, the script this year is significantly different than last year. According to WeatherTrends360, nearly 26 percent of the U.S. is already covered in snow, which is a near-record for this early in the season. Last year at this time snow cover was at a record low with only 1 percent (the average for early November is 7.6 percent). The Veterans’ Day/Remembrance Day weekend felt like the heart of winter as an Arctic blast right out of the North Pole invaded Eastern Canada and the Northeast U.S. with the coldest second week of November since 1987.
More snow fell in early November in the nation’s midsection where it’s a wholesale change from this time last year when we had record warmth prevail in November.
This is one of many signs that the weather pattern this year is nothing like last year, so get ready for winter! Much of Canada is already covered in snow so this will allow Arctic air to stay cold as it heads into the U.S. in the weeks and months ahead.
And just to remind one and all, here is a quick summary of our forecast for the winter of 2017-18: Cold, wet and snowy in the East, Milder and drier out West, and everything else in between! Don’t forget to fasten your sleet belts!