Winter Forecast: The big picture and how El Niño plays in
Saturday, March 19, 2016, 6:00 -
EDITOR'S NOTE: To see what the next two months have in store, click here for our UPDATED winter forecast.
The past two winters were dominated by a particularly resilient weather pattern, which kept the warm influence of the Pacific confined to the West Coast, and left the Eastern US open to persistent outbreaks of brutal Arctic cold. The winter of 2015-2016 finally looks to bring an end to this stubborn setup, but what exactly will that mean for your weather in the months ahead? Get the full details in the Weather Network’s 2016 Winter Forecast.
The major driver of this winter’s weather pattern is the intense El Niño currently occurring in the equatorial Pacific.
Classically El Niño has a reputation for bringing mild winters to the northern states and cool, wet conditions to the south. While the current El Niño rivals some of the strongest ever observed, not all El Niño winters can be painted with the same brush.
The unique configuration of this year’s El Niño means that there will be sodme key differences in the global weather pattern, which will have significant impacts on the forecast as winter progresses.
December looks to be the most classically El Niño-like month of this winter, with very mild temperatures dominating across the East Coast, Ohio Valley, Great Lakes, and Northern Plains. Cooler than normal temperatures are expected across Texas, the Four Corners, and the Great Basin.
However, it is important to keep in mind that a mild month does not eliminate the threat for significant winter weather. Places like Chicago illustrated that potential already this November with above average snowfall despite very mild temperatures for the month as a whole. In a similar fashion, as we head into the latter half of December (including Christmas) there will still be potential for wintry weather in places that have been warmer than normal for the month overall.
As we head deeper into winter, especially during late January and February, we expect that a significant change in the jet stream pattern will bring an end to the mild period, and lead to several weeks of colder weather from the Great Lakes to the Southeastern states. This pattern will be reminiscent of the one we experienced in the last two winters, though thankfully not as persistent or severe. Still, near- to below seasonal temperatures should dominate the Eastern US through the second half of winter.
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Taking a look at winter as a whole, which includes the months of December, January, and February, this is the temperature pattern we expect. Temperatures will be above normal across the Pacific Northwest, the Northern Plains, and the Upper Mississippi Valley. Temperatures will be below normal from the Southwest through the Southern Plains, the Southeast, and the Atlantic Seaboard.
Near normal temperatures for New England will be a welcome change from the past two years, but winter is by no means cancelled for the Northeast. Despite a mild start in December, the pattern is expected to turn cold by February with the threat for significant winter storms.
Nearly all El Niño winters on record have featured an active storm track across the Southern tier and the Atlantic coast. Our forecast shows a similar pattern for Winter 2016, which will bring above average precipitation from Southern California across the entirety of the South and up the Atlantic coast, including the major northeastern Metros.
This storm track brings a heightened threat for snow and ice to the Southern Plains and the Southeast, as well as to Appalachia and New England. However snowfall totals for the Northeast should not rival what we saw during the historic winter of 2014-2015. This pattern also increases the threat for severe weather near the Gulf Coast, including Florida.
The dominant storm track is expected to sag south of the Pacific Northwest, which should result in fewer rainy days across the region overall. However at times the storm track will move north and tap into deep subtropical moisture, bringing intermittent periods of heavy coastal rains and causing places like San Francisco, Portland, and Seattle to end the winter with near-normal precipitation totals.
Below average precipitation and snowfall is expected from the Interior Northwest to the western Great Lakes. The region from the Ohio Valley through the eastern Great Lakes (including Pittsburgh and Syracuse) will be very close to the dividing line between above average and below average precipitation. These areas could readily tip in either direction as a result of the dominant storm track shifting a bit closer or farther away.
How Long Will Winter Last?
El Niño years do not have a reputation for bringing an early spring. However, as we look specifically at years in which El Niño was rapidly fading – as we expect to be the case in 2016 – and taking other global weather patterns into account, we do often find a milder look to the temperature pattern from the Northwest through the region around Lake Superior.
So, while February’s cold weather is expected to linger into early March, we should see spring weather arrive on schedule or possibly even earlier than normal for many, especially in the Pacific Northwest and Northern Plains. A cooler than normal March is expected across much of the South, but keep in mind that “normal” in this region still involves steadily climbing temperatures through the month.
Forecast Rationale - This Is Not Your Typical Strong El Niño
While there are many other variables that were considered in developing our winter forecast, the dominant driver of our weather pattern this winter will be the ongoing strong El Niño event.
El Niño is associated with warmer than normal sea surface temperatures in the Pacific Ocean near the equator. The map above shows the ocean water temperatures relative to normal during the final week of November 2015, with warm water represented in shades of yellow, orange, and red. The circled area highlights the signature warm water pattern associated El Niño, where water temperatures are over 5°F warmer than normal.
This is undoubtedly a strong El Niño signal, however, there is a key difference between this winter and other significant El Niños of the past. During the previous two strongest El Niño events on record, (1982-83 and 1997-98) the warmest water was found farther east, right along the coast of South America. This time the warmest water is displaced towards the Central Pacific, and it is expected to shift even farther west through the winter.
A look back through history shows that when the warmest water relative to normal is found in the Central Pacific rather than along the South American coast, the impact on winter weather across the US is different, especially from the Great Lakes through the Mid-Atlantic States.
These maps show the comparison between Pacific water temperatures in the fall of 1997, and the fall of 2015. The westward shift of the warmest waters in 2015 is apparent, and there are other key differences as well. The 2015 pattern includes a large area of warmer than normal water temperatures throughout the North Pacific that is more pronounced than in 1997. This resembles the pattern that we saw through most of the last two years, which brought frigid winters to much of the East. In addition, the pattern for the North Atlantic is almost the direct opposite in 2015 compared to 1997.
Another key to the upcoming winter forecast is the timing of the El Niño cycle. It appears that the current El Niño is near its peak, and that it will steadily weaken during the winter. In contrast, the 1997-98 event remained strong through the winter. These unique fingerprints are what makes each El Niño event different, and highlight why not all El Niños result in the same weather patterns.
While the strength of the 2015-16 El Niño is comparable to 1997-98, the numerous differences in the global pattern outlined above (and several other factors beyond the scope of this article), are why we do not expect a classic El Niño winter for the Northeast and Mid-Atlantic. The pattern for early to mid-December will be quite mild for much of the country, but we do expect that winter will make an extended visit after the New Year.
WATCH BELOW: In depth look on El Niño's impact this winter