NOAA’s winter outllook was just released. Let’s take a look at this outlook and discuss some key factors shaping our winter temperature and precipitation patterns.
Blue = Colder Than Normal Brown = Warmer Than Normal
Green = Wetter Than Normal Brown = Drier Than Normal
Climatology: Increasingly Active Jet Stream
November marks the start of a more active time of the year, gradually exiting the typically quiet early fall and entering a period of a more active jet stream. There is a secondary several weather season across the southern tier of the nation as more frequent pushes of arctic air clash with lingering warm and moist air.
Let’s discuss a number of factors influencing the 1- and 3-month outlooks. These include:
From a climatological perspective, precipitation is enhanced across the Pacific Northwest (PNW) as well as the Eastern U.S. In the map to the right, areas shaded in blue and green receive a relatively-higher amount of precipitation in November while areas shaded in red receive less.
Hurricane activity peaked in early September and, from a historical perspective, has pretty much ended by the middle of November. However, a late-season tropical system can't be ruled out, especially early in November.
The past weak El Niño (Region Niño 3.4) has faded and should not have any significant impact on fall or winter weather.
However, as a post earlier this week discussed in more detail, areas of unusually-warm water within the Pacific Ocean are likely to influence temperature and precipitation into 2020.
Many long-lead climate models, including NMME, seem to pick up on wet soils across the North Central U.S. This results in a continuation of above-normal precipitation within these areas.
Unusually hot, in some cases setting record highs, has settled across the central and southeast U.S.
On the other hand, (negative) feedback due to dry soils over the Southeast U.S. could lead towards continued below-normal precipitation.
Outlooks, especially later in the forecast period, align closely with long-lead climate models, especially the North American Multi-Model Ensemble (NMME). Almost all climate models indicate above-normal temperatures across much of the nation through the rest of 2019.
The winter outlook also aligns with recent-past winter trends. Note the smaller area of “Equal Chances” over the Northern Plains and Upper Midwest. This represents intrusions of unusually-cold air, especially later in winter, over recent-past winters.