December 2, 2022

NOAA Winter Outlook: Cold, stormy in the Northern Tier with dryness in the South

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NOAA forecasters predict a mild and dry winter for the southern tier of the United States, including the already drought-stricken areas of the lower Mississippi River Valley and Southwest, with cooler and wetter conditions expected in the Pacific Northwest and around the Great Lakes.

The forecast is largely driven by the expectation that La Nina — perhaps the global climate system opposite to the better-known El Niño — will last for a third consecutive winter, which has only happened a handful of times in the past 50 years. . La Niña is associated with cooler than normal waters in the tropical Pacific Ocean, but it has ripple effects on weather around the world.

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That’s an encouraging outlook for areas already stressed by prolonged drought, and could increase wildfire risks in parts of South-Central America that don’t normally face such risks. According to the U.S. Drought Monitor, extended and intensifying dry conditions are likely in the Southwest and in states such as Kansas and Oklahoma.

This will mean continued concerns about the low Mississippi River There is difficulty in transporting goods through barges. Climate forecasters predict drought will develop in the lower Mississippi Valley and seasonally dry conditions in the Missouri River Basin, although drought conditions will ease along the Ohio River.

The mega-drought in California and the West will not slow down without relief to the dry Colorado River Basin And southwestern reservoirs like Lake Mead and Lake Powell are dangerously dry.

“That’s part of the reason for continuing [drought] “The forecast is La Niña, but also the long-term nature of the drought,” said Brad Buck, a meteorologist with NOAA’s Climate Prediction Center.

More than 80 percent of the continental United States is experiencing at least abnormally dry conditions, if not drought, the largest rate since reports began in 2000, according to the Drought Monitor’s latest weekly report.

“About 59% of the country is currently experiencing drought, but parts of the western United States and the southern Great Plains will be hit hardest this winter,” said John Gottschalk, chief of the Climate Center’s Operational Prediction Branch. Report. “With the La Nina climate system still in place, drought conditions will likely extend to the Gulf Coast.”

On the other hand, winter precipitation is forecast to be above normal in the Pacific Northwest, and storm systems are also forecast to deliver above-normal precipitation to the Great Lakes region.

Relatively mild and dry conditions are expected along a stretch of the Interstate 95 corridor along the East Coast, meaning cities from Washington to Boston will be closer to the line between rain and snow for any storms moving up the coast, Gottschalk said. .

More than 80 percent of the United States experiences dry weather

Seasonal forecasting can be a challenge for meteorologists because the main weather forecasting models they use are designed for relatively short-term forecasting. Forecast accuracy breaks down about a week in advance, so for forecasts like the one NOAA released Thursday, scientists rely heavily on signals from global climate patterns like La Nina.

In some years, the seasonal forecast can perform worse than a random guess.

In the United States, La Niña is known to produce warmer and drier conditions across the country’s southern tier, with cooler and wetter than normal conditions in its northern tier, including the Pacific Northwest and Midwest. That’s because it tends to shift the jet stream — a group of atmospheric air that guides weather systems across the continent — toward northern states and Canada.

Despite La Niña’s impact, Gottschalck said there is significant uncertainty in weather patterns in the middle of the country, where forecasters predict an equal chance of cold or mild conditions and dry or wet patterns. La Niña will allow for considerable “week-to-week variability,” as shown by the severe cold snap that caused an energy crisis in Texas in February 2021 and spread across the country, he said.

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In the winter of 2020-2021, the current stretch of La Niña has just begun, and the season is still marked by historic cold across the United States. The polar vortex, a column of cold air normally present in the North Pole, swept southward, creating some of the snowiest winters on record in the Deep South.

However, NOAA’s forecast for this winter closely matches the graphics used to depict classic La Niña conditions. While NOAA uses some long-range forecast models to guide its forecasts, typical expectations of La Niña “serve as a first guess,” Gottschalck said.

La Niña impacts around the world include drier conditions in Peru, Chile and the Horn of Africa, and more rainfall in Southeast Asia and Australia. The U.S. Climate Prediction Center expects a 75 percent chance of La Niña continuing through at least the winter.

This year, NOAA’s predictions are consistent with other conventional thinking, including seasonal forecasts published by AquaWeather and The Weather Channel, which call for continued La Niña influence on weather patterns.

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