Where did summer go? Autumn officially arrives this Wednesday at 4:21 AM, and many of us are already looking ahead at winter. The record breaking cold and snow of January and February 2015 is still fresh in the minds of many. I can say with confidence, this winter’s weather pattern drivers will be much different than last winter’s. Most notably the development of a strong El Nino will play a big role in this upcoming winter. El Nino by definition is just an abnormal warming of the eastern Pacific ocean.
That in turn configures the jet stream in a way that provides more wet weather for the southern part of the United States. Weather in New England however can be more variable during El Nino seasons, and often depends on the strength of the El Nino. During most El Nino seasons the northern half of the US averages warmer than normal for the months of December, January, and February.
It’s worth mentioning this winter’s El Nino is forecast to be one of the strongest on record. Prior to this year, the two strongest El Ninos recorded were during the winters of 1982-83 and 1997-98. A good tool to monitor this feature called El Nino Southern Oscillation index or ENSO index..
You can clearly see the ENSO index is expected to peak this winter and then weaken during the spring. This graph shows several forecast model projections, and some models hint at a record or near record El Nino this winter.
The weather effects of El Nino are often felt most during the winter months. During the strong El Nino winters of 1982/83, Portland’s average temperature was 27.8 degrees, which is 3.6 degrees warmer than normal ( average 24.2 degrees Dec.- Feb. 1941-2011). During the winter of 1997/98 Portland’s average winter temperature was 29.3 degrees which is a whopping 5.1 degrees warmer than normal. Snow statistics for those years stand out as well. During the winter of 1982/83 the Portland Jetport received 42.6 inches of snow which is 8.3 inches below normal ( average 50.9 Dec.-Feb. 1882-2011). During the winter of 1997/98 the Jetport received only 24.3 inches of snow Dec. – Jan.. That’s 26.6 inches below normal which is about half normal snowfall. For these reasons, the winters described above were given some weight in formulating this seasonal forecast.
Many seasonal forecast models are picking up on a trend cooler than normal over the southern half of the US. That same area is forecast to be wetter than normal as well. Northern parts of the United States including New England are forecast to be around normal or slightly warmer than normal. Snowfall is more variable though. A warmer winter does not always mean less snow. In fact that can sometimes be the opposite. This winter however is forecast to be wettest over the southeastern part of the US, and drier farther north. I expect northern New England to receive around normal precipitation for the months of Dec., Jan., and Feb. One good seasonal model is the JAMSTEC which is locked onto this trend I just described. Here is the temperature forecast for Dec- Feb issued per month Sept, Aug, July, June.
NOAA is onto this trend as well. Here’s their Dec- Feb temperature forecast issued in mid September.
Here’s the JAMSTEC precipitation anomaly’s and NOAA’s forecast for the months of Dec, Jan, and Feb.
Based on this forecast, winter 2015-2016 will not be as harsh as the previous two winters in Northern New England. Much like last year, December will likely be the warmest (relative to normal), and then we’ll get into some bouts of real winter weather in Jan. and Feb. The worst of this winter, including cold and snow, will likely be felt late in the winter here in northern New England.
I’ve never been one to rely much on seasonal forecasts, but they can be fun and a real challenge as a forecaster. The science of meteorology has come such a long way in just the past few decades that seasonal forecasts can be made with a certain level of confidence. My intention is to give folks a starting point of what to expect, but we’ll take it one 7 day forecast at a time. Have a great fall and winter!