Leaves are falling, the days are getting shorter, and the nights are getting colder. Yes indeed, winter is just around the corner. With that in mind, it is time for me to make my annual stab at a forecast for the upcoming season. I know winter has been on the minds of many even since late summer. That’s understandable, especially since our summer was a wet and relatively cool one. I’ve had MANY a person ask me, “Does this cool summer mean we’re going to have a harsh winter?” My answer to that: “Not necessarily”. While it’s true the winter that followed our last really cool summer (2009) was quite cold and snowy, the winter that followed 2004 (another cool summer) was quite mild, especially after Christmas. I think mid-autumn patterns (October/early November) have more bearing on how the upcoming winter plays out. That’s a big reason why I never bite on these forecasts until November.
I should remind everyone there is SO MUCH to consider when comprising these forecasts. Having them verify when all is said and done is even more difficult. In fact, that part is out of my hands completely! One thing that makes the challenge enormous is that no two winters in South-Central KY are exactly the same. Remember, it was just a few years back when Bowling Green experienced back-to-back double digit snowfall seasons (2009-’10: 15” and 2010-’11: 21”). On the other hand, the last two seasons have been duds for “snow hounds”. The average annual snowfall for BG is 9” (based on 1981-2010 data).
I think it’s also important to keep average monthly temperatures in perspective. January is typically our coldest month, with an average temp of 35.7° (that’s all the highs/lows combined). It’s closely followed by December (38.6°) and February (39.8°). Although the onset of Spring falls in March, not to mention the month is excluded from what is known as “meteorological winter”, it can be chilly (March 2013 was!), with 48.4° being the month’s average reading.
Now, let’s discuss the factors or atmospheric “players” that I took in consideration for this forecast. The language gets a little “weatherese”, so bear with me.
1 *El Nino-Southern Oscillation (ENSO): In a nutshell, this refers to the warming or cooling of the Pacific Ocean waters just north of the equator. If abnormal cooling is taking place, then we have “La Nina”. If warming is happening, it’s “El Nino”. So what about this year? Well, it appears neither condition is likely to be present since water temperatures in the Central Pacific are forecast to remain close to normal. That’s what we call an “ENSO Neutral” condition. There’s some suggestion we could see a weak El Nino try to develop late this winter. That could throw a monkey wrench in my outlook down the road. For now, though, I am of the belief that ENSO will NOT be a big player this season.
* NAO/AO (North Atlantic Oscillation/Arctic Oscillation): These two are the wild cards, especially the NAO. The North Atlantic Oscillation refers to a blocking pattern that exists in the North Atlantic Ocean. A “positive” NAO happens when an upper low situates itself between Greenland and Iceland while a strong upper high is parked near the Azores off the coast of Spain and Portugal. When that low in the North Atlantic breaks down and higher pressure builds there, blocking of the polar jet stream can occur (aka a “negative” NAO). This can send the jet plunging deep into the eastern United States, bringing colder air our way. This is especially true if the AO works in tandem with it. Basically, a “positive” AO means pressures over the Arctic Circle are low, which tends to cause cold air to sit and “well up” near the North Pole. A “negative” AO, on the other hand, means pressures are rising in the arctic, often forcing cold air southward.
In the last several winters, these AO and NAO have arguably been the biggest players in terms of the overall pattern. But trying to predict how these two will interact and behave over the course of a three month period is darn-near impossible! That’s because there is very little skill when it comes to computer model projections with these indices beyond two weeks out. These are highly variable pressure patterns, unlike El Nino or La Nina, which are driven by sea surface temperatures that change more slowly with time. My gut feeling is that we probably won’t see a blocking pattern establish itself over the North Atlantic for too long a period this winter, which leads me to believe this could be a “see-saw season” for us.
3. *Pacific-North American Pattern (PNA): The PNA deals with the relationship between the circulation pattern over the northern Pacific Ocean and the existing pattern over North America. A “positive” phase of the PNA results when high pressure sits close to Hawaii and over the western part of the lower 48, while low pressure resides just south of Alaska and over the southeastern part of the lower 48. When combined with a negative NAO/AO, it can make for very chilly temperatures in the Blue Grass state, sometimes setting us up for big snows IF an active subtropical jet is present.
4. *Snow Cover/Arctic Sea Ice: Not much has been said about it, but there’s actually been an uptick in the amount of real estate near the North Pole covered by sea ice vs. this time last year. In theory, cold begets cold, and the more ice there is over the arctic, the more cold air can develop and sustain itself. It remains to be seen whether or not this increase in sea ice can extend for another couple of years or if the overall decline in it over the long haul continues. I do think it has some bearing on how cold our temperatures get when arctic outbreaks occur, though.
5. *Other Factors (Sunspots, AMO): It’s worth noting the increasing sunspot activity over the past three years. Exactly what impacts these sunspots have on Earth’s overall global temperature is very much up for debate. It is interesting, though, that some of our coldest, snowiest winters coincide with downticks in solar activity (i.e. 1917-1918 and the late 1970s).
On a different yet somewhat related subject, the AMO (Atlantic Multidecadal Oscillation), MAY be one reason – along with sunspot cycles – so many recent winters have been fairly mild. The AMO deals with sea surface temperature trends over the North Atlantic Ocean. The chart below shows how these temperatures have fluctuated over the past 150 years or so. Note the areas in blue (1900-1920s with another in the late 1960s-early 1980s). These coincide with some of the most brutal winters Kentucky has ever seen. Right now, however, we are in a “warm” cycle of the AMO. But the AMO has trended a bit cooler since the mid 2000s.
Will this trend continue? I don’t think anyone has a definitive answer to that question. Some believe the AMO could go into a “cold” cycle within the next decade or so. Should that happen, it may increase the chances for us to experience more of the kind of harsh winters we had back in the 1960s and ‘70s.
ANALOG YEARS: Listed below are winters that had atmospheric patterns and ENSO conditions closest to those expected for this season. These are what we call “analog years”. Total snowfall amounts for those seasons are listed in parentheses.
If you’ve reached this far without your head spinning too much, kudos to you! Now that I have discussed the “players” I took into account when making this forecast, let’s dive into the forecast itself. I will focus on the three months that make up “meteorological winter” (December, January, and February), though I would not be surprised if measurable snow takes place in March once again, as it did this past season.
First, allow me to get the obligatory annual disclaimer out of the way: This is NOT an official First Alert Storm Team forecast!! It is simply my take on how I think the season plays out.
DECEMBER: This is a month that could prove to be a microcosm for how the rest of winter shakes out. There’s a lot of indication in the long range models that November could end very cold with the chill lingering into the first week to ten days of December. We’ve been spoiled with mild days on our first rounds of Christmas parades these past couple of years. It could be a different story this time, though. It does not appear as if the cold will persist through the entire month, though. There are indications that a large ridge of high pressure may anchor itself over the Southeast during the month. If so, a flip to a milder pattern will take place, one that could hold even through Christmas. Our last White Christmas was in 2010. Since history tells us White Christmases seem to come closely together for Bowling Green, the chance at seeing one can’t be ruled completely out. But with the way I see the month unfolding, the late Bing Crosby would probably cry rather than croon. Maybe more of a Jimmy Buffett “Christmas in the Carribean” (you may have known I would go there).
Forecast average temperature: (39°-41°, one to three degrees above normal)
Forecast precip: Slightly below normal
Forecast snowfall: Trace to ½” (Below normal)
JANUARY: In most years, this month is the coldest of the bunch. This one could start fairly mild, however, especially if the Southeast high pressure ridge holds its own. There is some indication that much colder air could return by the second half of the month. This could make for a volatile setup at some point. Kentucky will often be right in the battle zone between frigid air just north and warm, moist air to the south. We had to deal with severe weather during the early morning of January 30th last season, and it would not surprise me if a similar scenario unfolds again this January (always be prepared!). If you’re a fan of the white stuff, some patience may be in order. I don’t think we’ll be shut out completely in the snowfall department in January, but our best chances at a decent snowfall may wait until later in the season.
Forecast temperature: (35°-37°, near to slightly above normal)
Forecast precip: Near normal
Forecast snowfall: 1-2” (below normal)
FEBRUARY: I believe it’s here where winter may finally show its hand. If the Southeast ridge breaks down and more blocking develops over the North Atlantic, then there could be more opportunity for colder air to dive southward into Kentucky. Also, IF a very weak El Nino tries to get going toward season’s end, it could result in a slightly more active subtropical jet. This increases the chances for a wetter pattern, and if colder air is present, some snow. One word of caution: ENSO Neutral winters are infamous for ice storms in South-Central KY. Remember the short-lived but nasty one we had in late January? I think it’s highly likely we could see another significant icing episode this season.
Forecast temperature: (36°-38°, one to three degrees below normal)
Forecast precip: Slightly Above normal
Forecast snowfall: 5-7” (above normal)
Chances for seeing at least one or two significant severe weather outbreaks and/or flooding events: 60% with best chance coming during the first half of winter
Chances for seeing at least one icing event of a quarter inch or more: 40%
Chances for seeing a 4” snowfall from one system: 40%
Chances for seeing a 6” snowfall from one system: 10%
Total snowfall for the season: 7-10” (near to slightly below normal)
Chances for seeing a White Christmas: (historically 10%, this year, I give it 5%)
Coldest temperature: Between 5° and 10°, most likely in February
So there you have it. I think in the end, Winter 2013-2014 does not go down as ranking among our coldest or snowiest of all-time, but I do like our chances of seeing at least a little more snow than in the past two seasons. I think most of the wintry weather comes from two or three systems, with many bringing just plain old rain or a mixed bag of precip quickly changing to rain. There’s a CHANCE for one really decent snowfall (the kind that brings us at least 4”). Otherwise, look for a “see-saw season” with no real dominant pattern. It would not shock me if we hit 70° and 7° within the same week; that’s the kind of season I think it will be. I hope you’ve had your flu shots and have cold medications stocked up and ready!
Remember, as with any forecast, there is ALWAYS bust potential! For example, if the Southeast high pressure ridge builds more strongly than anticipated, then winter could wind up warmer with even less snow. By the same token, if blocking patterns develop and the subtropical jet is active when/if they do, then we could wind up with a little more snow than I think. I’m just calling it as I see it right now.
Thanks for reading! Let the games begin!