Well here is my attempt to foretell the general weather patterns and as a result the temperature, precipitation, and of course, snowfall outlook for the winter season upcoming. Keep in mind that while winter is defined at least 2 ways, meteorologically December 1 – February 28 (or 29), and astronomically from the winter solstice to the vernal equinox, there is no real hard and solid boundary to the start or end of any season when it comes to the sensible weather we most expect in it. We can have warm rainy winter days that make you think of May, or a mid to late spring blast of cold and snow, a chilly ocean wind and low overcast in summer making you think it’s April. You get the idea. The boundaries are fuzzy, but the overall seasons define themselves in the variety of weather they produce, most of which fits into the “normal” or “expected”, and some that doesn’t. That’s how it goes here in the lower 40s latitude and a longitude that places us next to an ocean. and not far from mountains. While some areas have already seen their first minor measurable snow event of the season, it’s obvious by looking at the calendar that the actual winter still lies ahead, and in that time frame the vast majority of our chances at “winter weather” as generally defined. Isn’t it interesting though that there have been times when our biggest snowfalls of a particular winter season have occurred outside of that time frame we think of as “winter”. Examples: Many areas had their largest snowfall of the season on October 29-30 2011. Many areas also recorded easily their largest snowfall of the season on April 1 1997. It happens outside the frame, sometimes. Most of the time, it does not. But I’m not here to try to predict if that is going to be the case this time, just to give you a general idea of what type of winter we may expect based on what I (and my colleagues) know about what is going on and what is expected, and in some cases what has already gone on (you’ll see what I mean). On to it.
The “players” on the field are many, and vary from winter to winter, but the same basic ideas apply. We look at ENSO (El Nino Southern Oscillation), QBO (Quasi-biennial Oscillation), PDO (Pacific Decadal Oscillation), MJO (Madden-Julian Oscillation), AMO (Atlantic Multidecadal Oscillation), AO (Arctic Oscillation), NAO (North Atlantic Oscillation), among other things. What we do know is this will be the third consecutive winter we enter in the La Nina phase of ENSO – cooler than average water temps in the equatorial Pacific Ocean. “Triple-Dip” La Nina, as they are called, are fairly rare, with only about 3 of them observed during the last century. There are no huge trends that stand out for those we have seen, and with so few to sample from we can’t really draw any conclusions about that, so it’s better to just focus on the fact La Nina starts the winter, and the expected trend is for it to weaken as we move on through winter. One of the larger drivers in how winter trends may be the PNA (Pacific / North America) index and especially EPO (Eastern Pacific Oscillation). A large area of warm water exists in the western North Pacific while Alaska is cooler. If this pattern persists, the influence is to put low pressure troughing and colder weather in Alaska and eastern Pacific which often translates to milder weather in the central and eastern USA, which would be somewhat counteracted by the La Nina tendency to have a cold air often in the Pacific Northwest, northern Plains, Upper Midwest, and sometimes the Great Lakes. Also, if the EPO should shift so that the warmer air to the west moves to the east, this would induce a ridge in Alaska and when that happens it can be easier for cold air in the arctic and Canada to flow into the US Mainland. The Polar Vortex status is going to be a big player this season. It’s prone to interruptions as we head into and through December, which can make for a more volatile pattern and the ability to drive cold air into the USA from Canada, the persistence of it dependent on how quickly the lobes of interrupted PV move. The other indices mentioned above either impact long-term or shorter-term weather and just need to be monitored as we go along. They are always wildcards of sorts and that will be no different this time. However, there is a wildcard we have not mentioned yet, and that is the eruption of the Tonga volcano earlier this year. This eruption was one of the larger scale events we have seen related to volcanic activity, and this being an undersea volcano was able to put more water vapor into the upper atmosphere than we have observed since we were able to measure it. The impact this has can range from more upper atmospheric cloud cover resulting in cooling to a trapping of more of the sun’s heat leading to warming. It’s unknown if one of these will dominate, or if they will tend to balance out, and what the overall impact will be. It’s a potential factor in throwing off the forecast but certainly an opportunity for learning. Based on all this, the knowns, and the unknowns, the best guess I have for our region for the winter of 2022-2023 is one that will feature a fair amount of variability, probably a little colder than last year although not substantially so, and probably a fairly average amount of precipitation and snowfall. Let’s try to break it down a little bit more going month-by-month.
Heading out of November with a pattern that features some up and down temperatures but certainly is colder than how the month started out, it appears that the MJO will help initiate a return to somewhat milder weather with briefer cold shots as we move through the first third of the month. After this, the primary driver is expected to be a polar vortex that becomes unstable resulting in a negative AO. If the EPO stays negative (warmer water west of the Gulf of Alaska), the tendency would be for the coldest air to be in the upper Plains and Midwest, but if we shift that warmer water a bit further east creating a positive EPO, those cold shots would have an easier time getting through the Great Lakes into the Northeast. The latter is my leaning, with help from the MJO after its initial influence of milder weather. This could potentially mean that the colder and snowier face of winter may show up around mid month on through Christmas and toward the New Year. I’m leaning this way at this time. So after a quieter start, it may get a bit more “fun” for the holiday season. La Nina will likely be at its strongest during this portion of winter, so that means another player can become a ridge in the southeastern US, which when strong enough tends to make our region mild, but this time may be less prominent, allowing the cold air to have a more direct impact in the Northeast. We most likely see the greatest influence from this ridge in the first 10 days of the month then become more vulnerable to the colder shots from Canada thereafter. The transition between this and the colder side of the pattern can be slow, and this can also set up ice storm chances, so that will also be something to watch for. Potential bust factors for the forecast are a more persistent ridge and the often negative PNA pattern we’ve been seeing. Temperature: Near to below normal. Precipitation: Near normal. Snowfall: Slightly above normal.
La Nina weakens, PV stays cranky for a while then starts to settle down. Coldest and snowiest weather weighted toward the first half of the month with a relaxation of the pattern later. Aforementioned wildcard factors must be kept track of. There are things in play that could prolong the colder and snowier expectation or cut it off earlier. Temperature: Near normal, starting cold, shifting milder. Precipitation: Near normal. Snow: Near to slightly below normal, but may start out snowy with above normal for the first half of the month.
La Nina weakening trend continues and we head toward neutral ENSO conditions. PV stable – AO positive. Still enough of a Southeast ridge from what remains of La Nina to place milder air in easier reach. That, combined with the expectation of positive AO would lead to a milder, more benign pattern. Temperature: Above normal. Precipitation: Near to below normal. Snow: Below normal.
MARCH (FIRST 20 DAYS)
This is obviously the time period furthest away and lowest confidence forecast. Leaning toward a continuation of February’s pattern of generally mild, but wildcards in play can still initiate shots of strong winter weather, cold and/or later-season snow, so we will want to be on the look-out for that. Temperature: Near to above normal. Precipitation: Near normal. Snow: Near to below normal.
WINTER SEASON OVERALL
Temperature: Slightly above normal (departure +1F to +2F).
Precipitation: Slightly below normal (departure about -1 to -2 inches).
Snow: Near normal (snowiest earlier, less later).
-Boston 45-55 inches
-Worcester 55-65 inches
-Providence 35-45 inches
-Hartford 50-60 inches