We talk about ‘meteorological seasons’ a lot. Instead of just going with the astronomy, like regular humans, that makes up a true season, weatherfolks make things nice and neat beginning and ending them at the start or finish of months. So for meteorological winter we’re talking December 1 to February 28. It’s also technically a couple of days shorter than meteorological summer, but now we digress.
As we’re at January 15 we’re close enough to ‘halftime’ for this winter of 18-19 to take a look at where we stand. It should come as absolutely no surprise that so far this ‘winter’ is warmer and wetter than normal, but by how much? We’ll that’s what we’re here for.
The season turned on December 11. That’s when we emerged from a 2 month regime of much colder than normal weather and flipped things around. This has been discussed in previous posts of our year long plus pattern of 6 week or so weather cycles. Winter seasons are seldom monolithic. With a couple of notable exceptions (hello 78) winters are rarely all cold, or all warm, and usually over time some degree of balance is found with warm and cold periods both happening.
Since we’re at the half way point, here’s where we stand first with temperature.
Overall, this is the 3rd warmest we’ve been at winter’s halftime. It’s easy to see how it’s on the strength of warm morning lows which comes in as the 2nd warmest, not even averaging below freezing. What this tells you is that there is a lot of moisture in the atmosphere. Moist air heats and cools much more slowly than dry air. That moisture is purely the by-product of the wettest year on record and a continued rainy pattern.
Just in case you were thinking that this is the start of some new trend, it’s not. When you look at the recorded weather history in Lexington what is absolutely and truly remarkable is how the warm first half of winters (and many other things) come in bunches. We only took the records back to 1900, so we’ve got 120 years to disperse things fairly evenly around. When you see the numbers, it doesn’t work that way. Of the top 10, 3 came from the 1930s, 2 from back to back winters from 1948-50, 2 from this decade and 1 more from the 21st century, and 2 randoms from the 1970s (they weren’t all brutal winters) and a century ago in 1918-19. By the way, the warmest was 1931-32 by almost 3 degrees over this year and 2 degrees over 1949-50…This year is tied with 1971-72 for 3rd. Whatever upper level pattern sets up to cause this early winter warmth must work on general cycles of over a year.
Now we talked earlier about how cycles over time balance out, winters are rarely homogenous so what starts warm usually finishes cold, or at least has a cold period within and vice versa. We may be about to flip that switch. It may not be the hit and completely hold, but there are many things going on to say at least in the short term winter is about to return…and perhaps in a big way.
Recall from previous blogs about balance (and it’s the same link as earlier which apparently means that was a heckuva blog post) that in the winter when we’re warm then Alaska is usually cold and vice versa. The past several weeks have been brutal in Alaska and northern Canada with 20 to 40 below zero temperatures common..and we’ve been warm.
Well take a looky here boys and girls…
Where it had been ridiculously cold in the 20 below zero range in Alaska is now mainly in the 20s ABOVE zero range. Alaska got warm (relatively-hey it’s still Alaska) and dislodged the motherlode of pure Arctic air into north Central Canada, where it’s in a position to be much more mobile. Roughly the northern half of the US is below freezing, roughly on par with most of Alaska, and the below zero line is at the Canadian border. This weekend, that below zero line will be at least I-70 and maybe even closer to the Ohio depending how the monstrous weather system about to hit the Pacific coast plays out.
The conventional wisdom on that storm from here is that it’s mainly a rainmaker for us, and likely a heavy one with stronger storms possible even here. The modeling is cutting it basically on or even north of us so far. Truthfully that’s a pretty likely scenario with the cold air plunging in behind the system and giving us some snow, a FLASH FREEZE, and a rude reminder of what Wisconsin feels like.
However, an old sage friend of mine, the Great and Powerful Cos, used to tell me that lows love boundaries. Remember prior to last week’s litttle snow and mostly rain here we were telling you to not be surprised when that rain/snow line would creep north. The closest snow field to us was in the northern Great Lakes, so it was easy for that low to drift north. Welll, last weekend’s snow put down a huge snowpack centered more or less on I-70, which is not far from where the current modelling is putting the rain/snow line this weekend. It’s possible, and a scenario we’ll be watching as the low moves ashore into the dense data network, that with that new boundary there, the low may try and push more south. It’s likely not far enough to get it all the way here, but a southward drift of the rain/snow line is certainly plausible and with a pressing full blown Arctic air mass it’s an option that can’t be discounted yet. Old school meteorology worked pretty well last week, let’s see how it does as we’re still several days out with plenty of time to hone in on details.
One other note, we’re coming up on the 25th anniversary of one of THE great Arctic Outbreaks of all time. Several states, including Kentucky, saw their state record low temperatures set this week in 1994 (-37 in Shelbyville). This was the final shot in a weather week that was truly amazing. A round of light snow with a brief break, then heavy freezing rain followed by 10 inches of snow on top and then all time record low temps…It paralyzed much of the Bluegrass for days.
We’re definitely entering a much more active weather pattern, and one that should feature many more shots of true winter in the coming few weeks, since we need to balance out the lack thereof from the previous few weeks.
All the best