INDIANAPOLIS (WISH) — The winter of 2018-2019 got off to a mild and wet start.
Central Indiana’s average temperature was nearly 5 degrees above average for the month of December and finished just shy of 4 inches of precipitation, mostly in the form or rain.
In January, we flipped the winter switch and turned much colder with a continued wet pattern. The result was nearly a foot of snow for the month, about 3 inches above average. The active pattern continued into February, with slightly above-average temperatures. Central Indiana closed the month out with 4-1/2 inches of snowfall, for a grand total of 16.7 inches for the winter season of December, January and February. That ran just over 5 inches below average. Central Indiana tacked on an additional 2 inches of snowfall, which put us close to 20 inches for the season, just shy of the snow season average.
Last year was considered a La Niña year. La Niña and El Niño are references to the El Niño southern oscillation. It’s in association to placement of warm water along the Equatorial Pacific, and plays a major role on global weather patterns; specifically the winter weather forecasts across the continental United States.
This year, we will likely not be in either an El Niño or La Niña, but will be considered in a “neutral” state. This puts into play a lot of different factors including some other oscillation around the globe. The bottom line: There are a lot more questions than answers when it comes to this year’s winter weather forecast.
You can pick this up in this year’s Climate Predictions Center’s winter outlook. Specifically with temperatures, much of the Midwest is neither in orange or blue, meaning there is an equal chance for being either above or below average in temperatures.
What may be a bit more clear is the precipitation forecast. The center calls for a wetter-than-normal winter season. Whether that is rain or snow depends on how the temperatures play out during the year.
What gives us a hint into this winter is looking at past neutral El Niño-Southern Oscillation (ENSO) events and how those winters played out.
Mike Ryan, a meteorologist from the National Weather Service’s Indianapolis office, said, “I came up with five years. Not all of them are ENSO-neutral years, but they were utilized for other factors where some of the teleconnection patterns seem to match, where the warm September and October patterns with drier conditions seem to match.”
“So what I have is (the winters of) ’64-’65, ’83-’84, which was a cold winter as I’ll show you in a minute. (The winters of) ’04-’05, which interestingly enough is the year we seem to be mimicking closest so far through the fall. (The winters of) ’07-’08, ’08-’09, and, yes, I did include ’13-’14, which was our ice-box winter.
When you break down the years Ryan selected, the average for both produce cooler and wetter conditions. However, when you break it down, you see that a few years haven’t always followed that path. In fact, when you look year to year, things look a lot different, which very much plays into the temperature uncertainty of this season’s forecast.
When you look at the precipitation for the same years, there is a much stronger signal of above-normal precipitation.
So while we are in an ENSO-neutral state, there will be other drivers as well.
“The north Atlantic oscillation and Arctic oscillation (AO) because those are two of our biggest teleconnection drivers in the winter. When the AO is positive, the cold air remains contained; stable polar vortex. But when we get a wavy polar vortex, that’s when the cold air moves south,” Ryan said.
So when you put many of these factors together you can start to piece together the forecast. With there being some many question marks in play this season, it does lead Ryan to a lower confidence in the forecast.
“I think we’re somewhere looking at the 20s (in inches of snow) here locally in Indianapolis maybe 25-30 inches. That’s my thought right now,” Ryan said.
So if Ryan’s forecast pans out, central Indiana would be looking at near-average to above-average snowfall for the season.
This next part maybe the more difficult thing to hear.
“I also think everything we looked at in those years that we looked at suggested March stayed cold. So we may be look at a bit of a delay in getting into spring weather,” Ryan said.