US Winter Weather Outlook!
Outlook for this Winter Season (2015 - 2016)
Each autumn, many of us have been curious about the upcoming winter. In the past, farmers were desperate to know what they needed to be prepared for; a cold winter or an easy winter, a short summer or a long summer? This created a prime market for those Farmer’s Almanacs to cater to, which claim an 80% accuracy even while forecasting weather an entire year out. Nowadays, we know that we can only truly forecast with credibility to the next 7-10 days. But, we do have the advantage of many years of data and trends to examine we might expect this winter.
We know that this year’s El Nino will be one of the strongest influences on this winter season. The Arctic oscillation and the Madden-Julian oscillation will also be influencing some of this winter’s weather.
Concerning the El Nino, we can compare similarly strong El Nino winters from the past to ours this year to paint a better picture of what we can expect. Traditionally, during an El Nino winter, the Pacific jet stream is located across the southern half of the U.S. as shown below. Compared to a La Nina winter where the Pacific jet stream is variable, and often merges with the Polar jet stream. With the Pacific jet stream positioned over the southern states, it directs storms from the Pacific along its track. This is why it is also referred to as an “amplified storm track.”
The Arctic Oscillation (AO) is “a climate pattern characterized by winds circulating counterclockwise around the Arctic at around 55°N latitude” (NCDC). When AO is in a positive phase, strong winds circling the north pole confine the polar air. When the AO is in a negative phase, the winds weaken and allow those polar air masses to migrate to lower latitudes, often causing stormy weather. The most current phase for the AO is currently negative (-0.250) and has been in a negative phase for the past 4 months. The AO will influence the how many arctic air masses will move south and cause nor’easters for the East Coast.
The Madden-Julian Oscillation (MJO) is “an eastward moving disturbance of clouds, rainfall, winds, and pressure that traverses the planet in the tropics and returns to its initial starting point in 30 to 60 days, on average” (Climate). Even though it is a series of disturbances in the tropical region, they still disrupt jet streams which then in turn can create “cold air outbreaks, extreme heat events, and flooding rains all over the U.S. and North America” (Climate).
With these major influences described, some patterns can be deduced. The southern half of the U.S. will have an amplified storm track (due to El Nino) ensuring plenty of moisture, so above average precipitation can be expected in those areas. Since the AO is in a negative phase, it can be expected for some of that counterclockwise-spinning arctic air to migrate south, and create some disturbances in the mid-latitudes (possibly created some nor’easters). From the tropics, the MJO can and will cause disturbances that will affect the southern half of the U.S.
But, most people want to know exactly what we started off with: what kind of winter can we expect? Let’s examine specific regions of the country, and what outcomes are likely for the current patterns expected.
It is likely to be warmer in the Northeast and Mid-Atlantic this winter. It is thought that the arctic air won’t move south until late-winter, meaning that the states around the Great Lakes will experience much less lake-effect snow during that time. It is possible for these areas to have below average precipitation this winter. Multiple reports have stated that truly cold conditions may come later in the season for the East Coast.
The Southeast and the Gulf Coast will be experiencing an above-average amount of precipitation, and with more rain comes higher chances of flooding. Also, the Southeast will have a larger amount of severe storms, as developing systems will travel across the country while growing on the amplified storm track. Florida especially will be at risk for severe storms and tornadoes.
In the Plains, the North can expect wintery weather early, but there will likely be waves of this cold weather as patterns move through. They can expect below-average precipitation. The Southern Plains are subject to the amplified storm track in the south, and can expect some significant precipitation.
The Northwest will have above-average temperatures, and below-average precipitation. Hopefully spring will bring sufficient rain to avoid any major drought conditions from developing.
In the Southwest, you can expect a rainy and snowy winter. Snowy? That’s right - don’t forget about those mountains! The Southwest is positioned perfectly in that southern storm track, so the desert will be watered this winter.
California, there is good news. There will be rain and snow coming your way. Will it be enough to end the drought? Probably not, but the precipitation might tip the balance in the right direction. Unfortunately, the topographic influences in the state often cause incoming weather patterns to repeat. Meaning that much of this rain will fall repeatedly in the same locations, and the same can be expected with the snow. This will then cause mudslides and flooding. Temperatures are expected to be above-average.
In Alaska, it is likely to be a warmer than average winter. Northwest Alaska can expect below-average precipitation, and Southeast Alaska can expect normal to above-average precipitation.
Hawaii will likely have above-average temperatures and below-average precipitation.
Each of the regional forecasts truly fits into the overall theme of an El Nino winter, with the Southern states battered with storms keeping the Northerns states dry. And there is always room for normal systems to develop and surprise. There are many people who surely want more details that what has been provided, but when looking out months ahead, forecasts need to be given in generalities and in terms of averages.
As you read this winter outlook and any others, please remember that “the frequency, number and intensity of these events cannot be predicted on a seasonal timescale” (Mike Halpert, NOAA CPC). Scientists have done their best by examining past and current trends to find what is likely to occur, but we will never be able to know just when to expect them. After all, it is only November.
For more reading, please check out the sources I have used:
NWS CPC: http://www.cpc.ncep.noaa.gov/products/predictions/long_range/seasonal.php?lead=3
Weather Bell Analytics: http://www.weatherbell.com/public-winter-15-16-forecast
The Weather Channel: http://www.weather.com/forecast/national/news/winter-2015-2016-temperature-forecast-december-january-february