Hi folks! We’re into the final weeks of “meteorological Fall”, which runs from September 1st through November 30th. But Mother Nature has already delivered reminders that Winter will soon be upon us. Many of us saw our first snowflakes of the season on Halloween night. Remember last November? Bowling Green picked up an inch of snow three nights before Thanksgiving. We are indeed entering the time of year where ANYTHING goes with our weather. With that in mind, it’s time for me to make my annual predictions on the upcoming season.
Winter forecasting is mighty challenging! Each year brings us a different set of atmospheric setups resulting in variable patterns. Fluctuations in the two jet streams (the subtropical and polar) that steer our storms and control our weather during the cold season have EVERYTHING to do with what we see and what we don’t. Trying to predict exactly how the jet streams will behave and interact is not simple, especially two to three months down the pike. Heck, last season was proof that it’s tough enough just nailing down possible snow/ice accumulations only a few short hours prior to a winter storm’s arrival! But there are clues that provide us forecasters with some ideas on what kind of patterns will try to establish themselves and which pattern may be the most dominant over the course of a winter season.
Before I get into the discussion of this season’s “atmospheric players”, let’s check for a moment to see how I did overall with last Winter’s forecast. Let me first say this about last year: It was the TOUGHEST WINTER I have ever faced in my 14 years of forecasting at WBKO! It seemed Bowling Green was almost always on the rain/snow fence or was on the edge of a main snow band with practically each system that came through.
***LAST YEAR: 2012-2013 Forecast snowfall for the season – 7-10”. Actual seasonal total: 10.4”, although nearly half that amount came with the big snow/sleet storm (more sleet than snow) that hit on March 2nd/3rd.
2012-2013 Forecast temperatures (here’s where I really wound up with egg on my face!):
–Dec. 2013: (1-3 degrees above normal) Actual monthly average: 38.8 (close to normal)
–Jan. 2014: (0-2 degrees above normal) Actual monthly average: 29.4 (6 below normal)
–Feb. 2014: (1-3 degrees below normal) Actual monthly average: 35.2 (4 below normal)
That was last year. Now, let’s talk about this season and the factors that were given considerable weight when I comprised this outlook. Bear with me, as the talk gets technical at times, but I shall do my best to explain as I go.
1.) EL NINO/LA NINA (EL NINO-SOUTHERN OSCILLATION)
Chances are you’ve probably heard about “El Nino” and “La Nina” since these two often steal the headlines. Basically, El Nino refers to an abnormal warming of the sea surface water in the Central Pacific ocean off the South American coast. When those same waters show cooling, it’s “La Nina” that is present. If the water temperature at the sea surface is right at or close to normal, neither El Nino nor La Nina is present. That’s what we call an “ENSO Neutral” condition. Such was the case last season.
*Imagery courtesy of NOAA
Early in the Summer, NOAA issued an El Nino Watch for the good possibility of significant warming in the central Pacific waters. Up to this point, however, that warming has been modest at best. So it’s clear we are NOT looking at a strong El Nino this season. The forecast indices continue to hint at what will likely be a weak El Nino this upcoming season. This DOES have a great deal of bearing on my forecast. Normally, strong El Ninos result in very mild winters with not a lot of snow for us. However, weak El Ninos tend to be much colder and snowier overall for Kentucky.
2.) PDO/AMO (Pacific Decadal Oscillation/Atlantic Multi-decadal Oscillation)
The PDO refers to water temperatures in the North Pacific south of Alaska and off the coasts of western Canada and the U.S. Pacific Northwest. Heading into this season, the waters in these regions have displayed some warming. That’s important to this forecast because often when that warming occurs, we’ll see large ridges of high pressure become established over the Gulf of Alaska, which can often force very cold air to ride up and over and then down into the lower 48. The chart below shows a history of PDO cycles (note the cold PDO though much of the 1960s and ‘70s, many of those years featured harsh winters for South-Central KY):
The AMO refers to the overall water temperature in the Atlantic. The AMO typically runs in 30 year cycles. Throughout much of the late 1950s, 60s, and 70s, the AMO was in a “cold phase”. Some of you may remember the brutal winters we endured during that stretch (1959-’60 and the last three seasons of the ‘70s). The AMO was also in a cold phase back in the 1910s, a decade that featured one of the Ohio Valley’s most severe winters (1917-’18). Since the 1980s, however, the AMO has been in a “warm phase”. It remains in that mode now. Many speculate this could be a major reason why many (though NOT all) recent winters have been relatively mild for our region.
3.) NAO/AO (North Atlantic Oscillation/Arctic Oscillation
These pressure systems are the “wild cards” when it comes to winter forecasting. Unlike the indices mentioned above that deal more directly with sea surface temps, these refer to the movement (a.k.a. oscillations) of semi-permanent pressure systems in the North Atlantic and Arctic, respectively. Those movements can be erratic, and it’s difficult — even for the most experienced meteorologists — to forecast them beyond two to three weeks out.
There are two phases of both the AO and NAO. When each is in a negative phase, the polar jet tends to dip down into the eastern U.S., sometimes sending cold, arctic air into our region. By the same token, a positive phase of each of those indices generally means the eastern U.S. (including our region) is mild to warm. The AO/NAO fluctuated wildly at times last winter, often resulting in repeated shots of bitterly cold air. Long-range climate outlooks hint that high-latitude blocking may set up at times again this season, which could lead to extended stretches of very cold air. Again, one can only speculate.
4.) OTHER MINOR FACTORS
There’s still lots of uncertainty on the role solar flares and their cycles play on winter weather. Some speculate that more solar flares/activity leads to milder conditions. Another factor to consider is snow cover across polar regions and Canada leading into November.
I don’t fly blindly when it comes to comprising seasonal forecasts. There really is a lot to consider. The variability of the AO and the NAO does not make forecasting any easier. But it helps to look back at previous winters to find those that saw atmospheric conditions and ocean temperatures similar to what is expected this go round. Those seasons are referred to as “analog” seasons. Here are the ones I found that seem to most closely resemble the kind of pattern I think shapes up this winter:
Notice most of those seasons I have listed show up here in this composite of temperature departures from normal (courtesy: NOAA)
If you like snow, you’ll be happy to know that many of the winters mentioned above were pretty generous in bringing the white stuff. The season that may raise a few eyebrows might be 1976-’77. That El Nino season featured some brutally cold weather (esp. in January ‘77) with many days of sub-zero cold and over 20” of snow! More recently, 2002-’03 gave Bowling Green around a foot of snow with 16” falling in ‘09-’10. I will say ‘76-’77 is the extreme/worse-case scenario in terms of cold – one that is HIGHLY unlikely to be duplicated this season. But remember…none of this is a guarantee!
THE WINTER FORECAST
With all that said, it’s time for me to cut to the chase to get into what I know you came here to read: The Winter Outlook. My focus will be on the three months that make up “meteorological winter” December, January, and February. I’ll add, too, that this is NOT an official First Alert Storm Team forecast! It’s simply my own take on how things may play out.
DECEMBER: This could be a tale of two halves. I think the November chill could carry over into the first half of this month, with a milder spell to finish it. Probably not what you want to hear if you’re hoping for a White Christmas, although we can never say never to that. In a way, this month could be shades of last December…one that started mighty cold before warmer temperatures won out for awhile late. I do think we’ll have at least a couple of shots for accumulating snow during this month.
DECEMBER TEMPERATURES: 1-2 degrees below normal (Avg. temp for the month is 38.6)
DECEMBER PRECIP: Near normal
DECEMBER SNOWFALL: 1-2” (Above normal)
JANUARY: This is normally the coldest of the winter months, and overall, this one should be quite chilly! We should see the polar jet take more plunges southward this month with at least a couple of extended periods of cold. I don’t look for the entire month to be bitterly cold, though. Past history of years with patterns similar to this one indicate we will see some mild periods (January thaws) from time to time. January 2003 and January 2010 both had their fair share of very cold temps but we did see the cold relax for roughly a 10 day stretch in those months. Snow amounts will greatly depend on how the polar jet interacts with the subtropical jet. In previous weak El Nino winters, South-Central KY usually came close to, or was right in the middle of a major winter storm. A storm in late January 2010 brought 5.5” of snow to Bowling Green…the most from one system since March 1996. However, in January 2003, a similar system took a jog further south and nailed Nashville with 8” of the white stuff while Bowling Green wound up with only three inches. Another winter storm took a track almost like that one in January 1988 (another El Nino season) with parts of Tennessee getting more snow than South-Central KY. History could repeat itself if we see the southern-branch jet stick closer to the Gulf coast this season, but I think our area gets in on at least a couple of decent snows in January 2015.
JANUARY TEMPERATURES: 1-2 degrees below normal (avg. temp for the month is 35.7)
JANUARY PRECIP: Near normal
JANUARY SNOWFALL: 5-7” (Above normal)
FEBRUARY: This is often the toughest month to make a prediction as there is more uncertainty about how the patterns will behave this far out. So again, we must look at past history with our analog seasons. In most of those seasons, we had at least one significant snow event during February with one or two other minor events. Something else we may have to watch for this season is an enhanced risk for an icing episode. February 2003 brought a major ice storm to northern portions of the WBKO viewing area as well as Northern/North-Central KY. I believe February starts cold before some late-month warming takes place as Spring draws closer.
FEBRUARY TEMPS: 0-2 degrees below normal (avg. temp for the month: 39.8)
FEBRUARY PRECIP: Above normal
FEBRUARY SNOWFALL: 5-7” (Above normal)
When it all shakes out, here is the way I envision the season unfolding:
TEMPERATURES: Slightly below normal
PRECIPITATION: Slightly above normal
TOTAL SNOWFALL: (12-16” – 3-7” above normal)
CHANCES OF SEEING AT LEAST ONE ICING EVENT OF A TENTH OF AN INCH OR GREATER: 40% (lower than in “ENSO Neutral” seasons)
CHANCES OF SEEING AT LEAST ONE SIGNIFICANT SEVERE WEATHER EVENT BETWEEN DEC. 1ST AND FEB. 28TH: 30% (lower chance than in La Nina winters but one or two severe episodes are possible)
SEASON’S COLDEST TEMPS: Between 0-5 degrees (should happen in January)
There you have it. Basically, when it’s all said and done, I think this season is snowier overall although probably not as “stretched out” with the snow events as last season, when the first occurred in November and the last in mid-April. In each of the weak El Nino seasons that served as analogs for this one, we did not see significant snowfall after February. That is not to say we won’t see accumulating snow in March (recall our biggest winter storm of last season happened Mar. 2nd/3rd), but I think it’s less likely this time. Once the cold breaks in these weak El Nino seasons, it’s usually “hello Spring” afterward. We shall see if this one follows suit!
I’ll be the first to admit THERE IS BUST POTENTIAL with any forecast, especially one that goes several months out! For example, if the subtropical jet stays suppressed to the south and/or the polar jet stays locked up into Canada more often than expected, than we could wind up with less snow than forecast. But I am leaning quite a bit on past history with weak El Nino seasons that featured similar sea surface temperatures and indices.
I’d like to know what YOU think. Do you agree or disagree with my outlook? Let me know either via my professional Facebook page, my twitter feed (@Main_Event_Wx) or via e-mail at firstname.lastname@example.org. Just keep the comments clean, please.
As always, be ready for no matter what the weather throws our way this winter season. Have a plan of safety should you ever need to use it. Whether an ice storm or a tornado, you should always be prepared. As we like to say around here “Know the weather before it knows you!”
Let the games begin.