Welcome to the long-winded but hopefully useful discussion and forecast that is my outlook for the 2021-2022 winter (December through March). Basically, I combine meteorological winter (December, January, February) and astronomical winter (December 21-March 20) to come up with this, so you can basically think of this forecast as being valid December 1-March 20). Does that mean I’m going to give you a day-by-day detailed 110 day forecast with high temps, low temps, wind speed & direction, exact rainfall & snowfall amounts down to the nearest hundreths and tenths of inches! Sure, I could do that, and it might be a “good” forecast out for the first 3 days, and then basically fiction from there on. You all know that’s not how long range forecasting works, and I’m not going to pretend to know more than I do about it. What I and my colleagues attempt to do when preparing these outlooks is take everything we have learned so far, everything we know now, and link it with our best educated guess about the future weather trends, garnered by a close look at numerous “puzzle pieces” consisting of long term, medium term, and even some shorter term behavior of ocean and atmosphere. You’ve already seen several of these outlooks from various media outlets. What follows here is my own version. Will it be similar to others? Read on…
OVERVIEW
The usual players will be on the field as we assess their potential and observe their performance going into winter. ENSO: We are in a La Nina now, and will likely remain in one at least through February, after which we may see it weaken toward a little more neutral as we get into March. The QBO (Quasi-biennial Oscillation), stratospheric winds in the tropical regions, in their easterly phase at this time with this likely to continue through the winter as well. The PDO (Pacific Decadal Oscillation) is and will likely continue to be in a negative phase (cool water off the US West Coast and warmer water toward the central North Pacific). This index may play a little havoc with the forecast if it goes more neutral later in the winter, which it may do. The MJO (Madden-Julian Oscillation), which is a measure of movement of regions of enhanced and suppressed tropical rainfall, has been an aggravation for long range forecasting the last couple winters due to its almost non-factor but the unknown of when it could “wake up” and be more of a factor. As we approach the end of November, the MJO is currently in a weak phase and not a huge factor (where have we heard that before?), however the ensemble forecasts from our major medium range guidance have indicated at least somewhat of an upswing in the index’s influence on the global pattern as we head into early December, with it being borderline between indicating enhanced snow threats and just a more benign milder regime, so at the moment, the MJO is of not much help in discerning much, and I suspect for another winter it will behave much like it has the last couple winters, like the prankster lurking around the corner, waiting for the right moment to throw a water balloon at you. And don’t forget our good old friends, the AO (Arctic Oscillation), NAO (North Atlantic Oscillation), and perhaps the villain of the story, the PV (Polar Vortex). I’ve often seen too many forecasts go bad in a quick way when too much dependence is placed on the behavior of the PV without taking into account the remaining factors. When the AO is in its positive phase, the PV is generally tighter to the polar regions, and stable, which is generally a milder pattern for the mid latitudes with more zonal flow. This is often a fairly mild and sometimes tranquil weather pattern for the US in winter (though there can be storminess from other factors, like an active southern jet stream, especially during El Nino years, which this is not). When the AO is in its negative phase, the PV is disrupted and usually breaks into several lobes which extend much further southward from the polar regions, resulting in a much less stable weather pattern, but where these lobes go and whether or not they are fairly stable in one area or progressive (moving west to east) or retrogressive (moving east to west) has to be taken into account in determining the finer details of the pattern for any area. First, a PV disruption is often linked directly to cold/snowy weather for the Northeast. This is not always the case. A PV lobe could just as easily take up residence in the central or western US and leave the eastern areas mild. When the QBO is in its easterly phase, this has been linked to the initiation of PV disruption more often, so we look at that as a factor in a potential early-season disruption. Some of the long range (weekly and monthly) forecast models have also hinted at potential PV disruption in the orientation that colder weather would visit the northeastern US earlier in the winter (December to early January) with a then more stable PV following that for later January and February. A fair amount of La Nina winters have featured the coldest core of air, relative to normal, from the upper Midwest to the Northwest, with milder weather a little more dominant in the Northeast with occasional intrusions of colder air. This tends to be more the case with a stable PV, so in that case, we could make an argument for the chance of colder weather, relative to normal, being more likely during the first third of the winter (December – early January), with the trend for milder weather, relative normal from mid January through February, leaving March vulnerable due to the wildcard factors of strength of La Nina by late winter, and the unpredictability of both the AO and MJO that far in advance, and to a lesser degree the magnitude of the expected continued negative PDO. Another factor is somewhat below normal arctic sea ice, which is a factor in initiating PV disruption, a better advance of snowcover in parts of the northern hemisphere than we saw last year, which can help build cold air masses and get them started heading southward in the case of an unstable PV. And lastly, the solar cycle, still climbing away from a recent minimum and toward the next maximum but not nearly there yet. Solar minima are sometimes correlated to colder winters with solar maxima correlated to more mild winters, but this is not necessarily a huge factor, only a contributing one, that can be overshadowed by the many other indices. So based on that, I don’t see the solar cycle playing a huge part in this particular winter’s weather pattern. A bit of amusement and maybe poking fun at myself in the process: So often you hear me on the blog during the year talking about not being a fan of winter forecasts that are issued before a careful observation and analysis of the pattern of October and at least the first half of November, so I put that practice in play as I always do, and I honestly didn’t get much out of it this time. I don’t have a strong feel for the “October/November predicting the winter pattern” thing this time. And lastly, analog winters. I’ve always been so-so on this. Yes, there are definitely clues to what an upcoming season can hold when you can identify similarities to indices leading up to that season in other years. In fact, one of the analogs leading into this winter is that we have a lot of similarities to 2011’s autumn (weather pattern, current and expected indices being similar, including La Nina and negative PDO). Boston only recorded 9.4 inches of snowfall that winter, and for many suburban locations the “biggest snowstorm of the winter” actually occurred in late October. So there may be similarities but definitely no mirror image. This doesn’t mean that Boston’s snowfall will end up that far below normal. Too many other things go into that result. So that is why analogs can be used as a tool but should never sway a forecaster too much… So there are all the edge pieces and a few of the middle pieces of the puzzle we can fit together to form a reasonably adequate educated guess. The pieces we have not fit into place represent the uncertainty that is always present in forecasting, especially long range efforts.But based on what I do know, let’s move on to the month-by-month breakdown followed by a temperature / precipitation / snowfall forecast for the winter as a whole…
DECEMBER
In theory, this should be the easiest portion of the forecast to make, since it is the shortest-range portion. However, a little doubt was cast into this section from the most recent runs of the weekly and monthly model forecasts, previously looking colder than they look now. That said, I’ve also spoken recently of how poorly the guidance has performed, at one point painting a major winter storm for the Northeast just a day before Thanksgiving, and as we know, we’ll be under the influence of high pressure with chilly but dry weather that day (just one example of several). So that’s a good reason not to let any kind of run with a big change in it (regardless of whether its looking out just a couple weeks or several months) influence my overall thinking. For December, we’ll look for La Nina conditions, an easterly QBO helping to lead to a slightly better than 50% chance we see a PV disruption in progress or initiating, one or two periods of negative NAO (high latitude blocking in the North Atlantic), and continued negative PDO. Arctic sea ice will increase but remain below normal, another factor in possibly helping to initiate a PV disruption. A tendency for a little more high latitude blocking in the North Atlantic would bend the air flow southeastward as it gets into the eastern part of North America, and the lack of early-appearance of a Southeast Ridge would help allow more frequent intrusions of cold air into the northeastern US, including New England. Digging disturbances in this pattern would be the shots at snowfall and as we get deeper into the month a determining factor in whether or not places like Boston get a white Christmas. Temperature: Near to below normal. Precipitation: Near normal, most active in the middle 20 days. Snowfall: Near to slightly above normal.
JANUARY
If we are going to have a period of classic winter weather, the first half of the first month of 2022 would be the time to look for it, as the pattern of December helps us build some cold, and the transitional period out of a negative to neutral to eventually positive AO would likely be accompanied by an active Pacific jet stream with disturbances interacting with cold air in place. We’ll continue La Nina, easterly QBO, and negative PDO, with wildcards MJO and NAO helping to determine more detailed outcomes. Temperature: Near to above normal, coldest early followed by a thaw. Precipitation: Near to above normal. Snow: Near to slightly below normal, but may start out snowy with above normal for the first half of the month.
FEBRUARY
La Nina continues, easterly QBO dominates, PV is stronger and AO positive, NAO largely positive (not much if any blocking), PDO continues negative. The La Nina-driven Southeast ridge likely makes its most prominent appearance at this time driving the primary storm track from northwestern US through the Great Lakes into southeastern Canada, with the majority of lows passing north and west of New England. While mountain areas can be cold enough for snow at times in this pattern, the majority of precipitation events tend to be more rain for southern New England. However, with it being just at and barely beyond the coldest time of the year, from a climatology standpoint, a pattern like this can result in some icing events, including southern New England areas, and we will need to watch for this. Temperature: Above normal. Precipitation: Near normal. Snow: Below normal.
MARCH (FIRST 20 DAYS)
Oh March, the month that can bring anything from extreme cold and major snowstorms to the first hints of summer (we have been over 80 several times). What March is most remembered for in New England: Late-season snow and cold, ice, mud, wind, and people asking “will winter ever end?” This particular March outlook is a tough one. It’s hard to believe that a pattern of milder weather (as is expected in February and assuming it verifies) would continue right through March. I mean, something has to go wrong, doesn’t it? Our MJO and PV/AO wildcards will very probably still be in place. We’ll still likely be in negative PDO but maybe not as strongly so, and we also may be seeing the weakening of La Nina heading more toward neutral ENSO by then. An easterly QBO is likely to still be present, remaining a factor in helping to initiate another disruption of the PV. Should this occur, we may be able to expect one more blast of winter’s cold and some snow, before we finally bid it goodbye. As I have stated previously, late season snow, occurring with a steadily climbing sun angle, tends to disappear nearly as fast as it appears, so if you’re tired of winter, at least you won’t have to look at it for all that long. The higher sun angle also counteracts some of the March cold, as we get a more direct sun for more hours than we had back in the low sun / short days of early winter. Temperature: Near to below normal. Precipitation: Near normal. Snow: Near normal.
WINTER SEASON OVERALL
Temperature: Slightly above normal (departure +1F to +2F).
Precipitation: Slightly above normal (departure about +1 inch).
Snow: Below normal.
-Boston 30-40 inches
-Worcester 40-50 inches
-Providence 20-30 inches
-Hartford 30-40 inches