Last year I mentioned struggling with the winter forecast, which ended up verifying somewhat but not completely. Temperature patterns are, in general, easier (using that word loosely) to forecast than precipitation patterns. Or are they? I’ve had it go both ways. I guess I could say again there is a struggle coming up with this forecast, but are any long range forecasts easy? No. So this is really just the normal. And speaking of normal, it’s time to discuss how close to, or far away from, normal that I feel our temperatures, precipitation, and snowfall will be during December through March. I include March in the winter outlook basically encompassing all of “meteorological winter” December through February, as well as “astronomical winter” from winter solstice to vernal equinox. We all know here in New England that March is often more weather-related to the winter month of February than it is to the spring month of April, so for most it’s still winter in reality while in your fantasy it’s already spring. Oh well, facts are facts. What do I think is going to happen this season? Read on!

At this time last year we had broken a drought and were still in a noticeable long term precipitation deficit, which, on paper, still exists if you go back through 2013, but is far less apparent if you take into account one of our wettest autumns on record here in 2018 (the wettest in some locations). There have been some suggestions that a wet autumn leads to a snowy winter. Statistics will show this correlation to be about as good as a coin flip, so it’s not a big factor. So we look to a combination of the ongoing weather pattern and how the medium term to long term atmospheric and oceanic indices may or may not have an impact on it. My most recent, very recent, examination of these reveals these main points. ENSO is showing developing weak El Nino which may approach moderate but probably stay weak through most of the winter, maybe morphing to Modoki style which means the warmer water is concentrated more to the west of the South American coast rather than along and just off of it. PDO looks negative for a while which tends to keep El Nino events weaker. QBO coming out of strong negative phase the last few months and looking to go positive during the course of the winter, though weak in magnitude so may not be a major factor. MJO, which is something that favors cold and/or snow in the Northeast while in phases 8, 1, and 2, has been very weak and almost a non-factor for several months. It’s projected to be weak to borderline moderate and move through phases 8, 1, and 2 from late November into December, but it remains to be seen how much of an impact this will have, so not giving it all that much weight right now. AO/NAO trend is negative for both, which tends to trigger colder weather and sometimes storminess in this area, depending on the positions of blocking features and proximity of northern and southern jet streams and their ability to phase. The upcoming pattern favors a strongly negative AO and negative trending toward neutral NAO for the next few weeks, a weak to moderately negative AO and a split on the NAO but with the tendency for it to be negative more often than positive. Ironically if I was making a forecast specifically for the US Southeast there are factors that point to both mild AND cold, so it comes down to which are the overwhelming factors, and that will have an impact on the weather here as well. The PNA looks to me like it wants to be positive early and late winter, and neutral to negative in the middle. A positive PNA tends to induce troughing in the East with colder weather. Again, none of these will singlehandedly determine the winter pattern here, so trying to come up with a result based on the interaction of these is difficult, at best, but here is my best shot at a month by month forecast of the large scale pattern and its resultant impact on temperature and precipitation here in southeastern New England. And as always we can talk more about these indices and what they mean in detail in the blog comments…

DECEMBER
Synopsis: Weak borderline Modoki El Nino establishes. Major drivers will include that combined with AO/NAO tending to be negative. Should be a split flow jet stream with polar jet dominating our weather and subtropical jet staying mostly to the south. Jet stream phase ups may occur but the most likely places for this is the Midwest which would result in a parent low traveling through the Great Lakes, a brief warm-up, and a system being pulled apart producing more rain than snow, with the other phase up location likely offshore, leaving the region drier/colder as main action passes south and east of the region. Most of the snowfall in this pattern would be from polar jet stream disturbances including clippers and polar and arctic cold fronts. Wildcard is MJO passing through favorable cold/snow phases, but maybe too weak to have a major influence. Snowfall forecast is high stakes because we can have very little or the forecast below can verify from just 1 or 2 significant systems.
Temperature: Below normal.
Precipitation: Near to below normal.
Snow: Near to above normal.

JANUARY
Synopsis: Weak to borderline moderate potentially Modoki El Nino with AO negative to neutral and NAO neutral to positive. The NAO’s phase shift would lift the polar jet to the north enough for the temperature to be milder than December, relative to normal, but still close enough so that snowcover-fueled cold shots could still occur. The subtropical jet would remain active with wet weather to the south including rain events for the Southeast and mixed/snow events for the Mid Atlantic, with a lot of these missing New England to the south.
Temperature: Near normal.
Precipitation: Below normal.
Snow: Below normal.

FEBRUARY
Synopsis: El Nino weakens slightly, AO/NAO more strongly negative. Blocking returns and is strong enough so that storm systems from phasing subtropical and polar jet energy pass mostly to the south. However, unlike January, a southward-displaced polar jet stream would keep it colder
Temperature: Below normal.
Precipitation: Below normal.
Snow: Below normal.

MARCH
Synopsis: The first third of the month would see a continuation of the February pattern before relaxing with more separation in the jet streams as AO/NAO trend toward neutral and subtropical jet is suppressed as well as a little weaker as El Nino reaches its weakening stage.
Temperature: Below normal early month, near normal later month.
Precipitation: Below normal.
Snow: Below normal.

WINTER SEASON OVERALL
Temperature: Below normal.
Precipitation: Below normal.
Snow: Near to below normal.
-Boston 30-40 inches
-Worcester 35-45 inches
-Providence 30-40 inches
-Hartford 30-40 inches