A strong El Nio continues as indicated by well above-average sea surface temperatures across the central and eastern equatorial Pacific ocean. A typical wind pattern associated with an El-Nino is expected for the start of winter. Tropical moisture will move into the southern states due to an extended and persistent pacific jet stream with the polar jet stream staying farther north, keeping the frigid air in Canada.
Most models indicate that a strong El Nio will continue through winter 2015-16 and the expectation is that this El Nio could rank among the top three strongest episodes since 1950.
However, looking at forecast probabilities of El-Nino, a weakening trend and a transition to ENSO-neutral is expected during the spring into summer.
Some factors considered in determining our winter forecast are the strength of El-Nino and whether is it strengthening or weakening. A weakening trend during the second half of winter could lead to colder intrusions of air from Canada as the polar jet drops further south more often. We need to also take into account shorter term weather patterns which can alter the wind patterns from time to time. And looking back at data from past winter’s with a strong El-Nino sheds light on what we might see this winter.
The overall winter temperature is expected to come in above normal for the northern tier states and cooler for the south. Mid-Missouri will come in slightly above average although there will be a few cold snaps, especially late in the winter.
A wet winter is expected for the south with more rain than usual while the northern states will be drier with Missouri right in between, coming in with slightly more rain than we normally see in the three month period.
As far as snowfall, with less moisture available, the northern states won’t see as much snow this winter but the south will have more than usual as storm systems move in from the southwest, carrying ample moisture, meeting up with colder air from the north. Southern Missouri has a better chance of snow this winter due to this pattern.
Here is the ABC 17 Stormtrack winter forecast for 2015-16:
We will have many mild periods with above average temperatures for the first half of the winter followed by increasing cold snaps for the second half. Rainfall will come in above normal but snow will come in below our 18 inch average. We have a better chance of an ice storm from January through mid-February.
Comparing last winter to what we expect this winter, last year our overall winter temperature came in slightly below average at 31.5 degrees. The forecast for this winter is warmer with 33 degrees.
As far as precipitation, 5 of the past 7 winters with a strong El-Nino came in wet. This winter we expect more precipitation than usual, coming in close to 7 inches. However, snow will be lacking, coming in slightly below average. Last year we picked up 17.8 inches of snow. This year will come in a bit lower, closer to 15 with a better chance of snow in the middle of winter and toward the end.
There is a good possibility of freezing rain during the second half of winter as shallow, cold air masses move in from the north, and warmer, moist air moves in aloft from the persisting El-Nino pattern.