Winter 2015-16 temperature outlook update: Warmer than average in the North, cooler in the South, East Coast
Winter is just a few weeks away, and a new outlook from WSI, a division of The Weather Company, has a few clues as to what you can expect around the country.
Some good news is ahead for those in the northern tier of the contiguous U.S. that are not looking forward to the bitter chill of winter, as warmer than average temperatures may be ahead. A break from the typical cold of the season is expected from the Pacific Northwest into the northern Plains, Midwest and interior Northeast.
However, the situation is the opposite for the South and parts of the East Coast which are expected to see colder than average temperatures during the December through February time period.
One of the biggest factors in this forecast is the strong El Niño that is expected to last through this winter. There is a tendency for temperatures to be cooler in the southern half of the U.S. and warmer in northern sections of the U.S. during El Niño winters.
"The unusual strength and east-based location or "flavor" of the El Niño event suggests that a very warm 1982-83 or 1997-98 winter is quite possible, with highest confidence for a mild winter across the northern Plains and Pacific Northwest and highest confidence for a cooler winter across the south-central U.S.," said Dr. Todd Crawford, WSI chief meteorologist, a division of The Weather Company.
However, there are other factors that could play a pivotal role in temperatures this winter, especially in the East. One of which is what are the risks of strong upper-level atmospheric blocking in the North Atlantic, since this can lead to colder temperatures in the East.
There was unusually strong blocking this past July, which may lead to blocking during this winter and blocking can trump El Niño conditions. However, according to the WSI outlook, "the only winters that have had big North Atlantic blocking since 1970 were within two years of a solar minimum" and the next solar minimum isn't expected for approximately five years.
Another element that can help determine the risks for atmospheric blocking are whether there will be a significant stratospheric warming (SSW) event. However, these SSW events, which increase the odds of colder conditions in parts of the mid-latitudes in the Northern Hemisphere due to the breakdown of the polar vortex, are very difficult to predict.
Crawford points out that "the unusually strong Siberian high in November does increase the chances of having a sudden stratospheric warming event during the winter, but other indicators still suggest otherwise." This strong Siberian high is driven from above-average snow cover in Siberia in October.
One of these contrary indicators is the current value of the solar flux, which currently corresponds to cooler stratospheric temperatures this winter, which would reduce the odds of a SSW event that would drive blocking.
However, another factor to consider is that the European computer forecast model shows a very strong signal for upper-level ridging to develop from western North America north to the pole during late winter, which indicates the chance for colder temperatures to dive into portions of the East late this winter.
Warmer than average temperatures are expected from the East through the Midwest and into the Pacific Northwest in December. The area that is likely to see with the most above-average temperatures is from the Dakotas into the eastern Great Lakes.
If you are looking for a chillier than average December, head to the Southwest and the southern Plains, with the coolest conditions in Arizona, southern New Mexico, as well as southern and western Texas.
As discussed above, the risk of upper-level blocking increases heading into January and February. This will bring a change in overall expected temperatures to the East early in 2016.
Colder temperatures will shift eastward in January stretching from New Mexico and southwestern Arizona through the South and along the East coast into southern New England. The area that will likely see much colder than average conditions will be found from much of Texas into Louisiana and southwestern Mississippi.
The remainder of the contiguous U.S. will likely see a relatively warm January. The Pacific Northwest through the Great Lakes are expected to see warmer than average temperatures, especially in North Dakota and adjacent areas.
Most of the West Coast through the northern and central Plains and into the Upper Midwest will continue to find those less harsh temperatures in February. The northern Plains will once again see temperatures that are well above-average.
Meanwhile, a chillier than average February may be on tap from the Northeast through the South and into parts of the Southwest. Much of the South, from North Carolina to Texas will see the coolest temperatures in comparison to what you would expect for February.
It is important to remember that these forecasts are for the overall month and season. These expected temperatures will be accompanied by periods of both colder and warmer temperatures.