DISCUSSION: On October 19th, the National Oceanic and Atmospheric Administration released their winter weather outlook for the 2017/2018 winter weather season.
The biggest “wildcard” of these winter weather predictions is a possible La Niña forming for the second year in a row, with a 55% - 65% chance of it setting in before the winter season begins. You may be familiar with the term “El Niño,” which is the opposite of a La Niña. Both are part of the El Niño-Southern Oscillation(ENSO). The ENSO is a naturally occurring phenomenon which results in above or below normal sea surface temperatures, and also varying wet and dry conditions over the course of a few years. La Niña, translating to “the girl” in English, occurs when the water around the equator in the eastern Pacific Ocean is cooler than normal for a number of months. When this happens, the easterly winds along the equator increase. This could be a factor as a result from this past intense hurricane season we just endured. A La Niña typically results in altered weather patterns making the southern half of the United States warmer and drier, with the Northern half of the United Stated seeing cooler and wetter winters. There are other factors to consider when forecasting the winter weather outlook, such as other oscillations in the atmosphere, including the Arctic Oscillation, which can predict how far cold air can be pushed south, and the Madden-Julian Oscillation, which can have an impact on the number of heavy rain events the west coast experiences.
For December through February, NOAA predicts that wetter than average conditions will be favored across the northern part of the United States, from the Northern Rockies to the eastern Great Lakes. For the southern part of the United States, drier than normal conditions are expected to dominate. In terms of temperature, warmer than normal conditions are expected across the southern two-thirds of the country, with parts in eastern Texas/ New Mexico expected to have 50% warmer than normal temperatures. The Northern tip of the country, from Minnesota to the Pacific Northwest are expected to have cooler than normal temperatures. The rest of the country will have an equal chance of above or below normal precipitation and temperatures.
As of right now, NOAA has issued a La Niña watch, meaning conditions through observations and forecast models show those cool temperatures in the eastern Pacific Ocean. Look out for the next update from NOAA on a possible La Niña expected to come out November 9th.
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©2017 Meteorologist Claudia Pukropski