40/70 Benchmark

Pattern update. https://easternmassweather.blogspot.com/2025/12/mid-month-warm-up-arrives-on-schedule.html

Mid-Month Warm Up Arrives On Schedule Path to White Christmas Remains Despite Friday Grinch December Forecast Largely On Track Thus far the month of December has behaved largely as expected, primarily owed to the similarity of the anticipated deviation from the predominate Maritime Continent forcing of the past decade, to the analog periods of December-January 2017-2018 and 2024-2025. December 1-13 2025: December 2017-January 2018: December 2024-January 2025: The primary differences being that this month has been more extreme in terms of the magnitude of negative temperature departures, possibly owed to the extreme Bering Sea blocking (-WPO) that has been observed (-3.48 WPO peak on 12/13). The polar vortex disruption that occurred late last month has behaved remarkably similar to the early December 2000 analog event in that it fell just shy of triggering a full 850MB zonal mean wind reversal in the arctic. This has afforded the vortex the opportunity to recover to something that will approach climo levels by the holiday week, as forecast last fall per research conducted Lee et al (2019), which indicates that the arctic high regime is favored for less than 20 days following a weak PV (roughly November 28th). This despite the insistence of initial modeling and social mediaologoists alike that it would remain weak through the new year. This consistent recovery following the lack of a zonal wind reversal has allowed the high latitude blocking to relinquish it's grip by mid-month, as forecast. The increasingly hostile polar domain in conjunction with lowering heights on the west coast as reflected by a descending PNA value will allow the storm track to shift west just in time for the expected "Grinch Storm" this Friday, which will eradicate all of the snowpack throughout southern New England. This is event is similar to periods prior to the Christmas holiday in the referenced analog months of December 2007 and 2008, especially the former. Thereafter, there is going to be a battle waged throughout the holiday period as the MJO remains shallow and variable, while the Pacific Trough regime begins to assert itself. White Christmas Odds Perilous As Pacific Trough Regime Establishes One of the primary assertions made in the Eastern Mass Winter Outlook last fall was that the aforementioned recovery of the polar vortex and persistent RNA pattern would team up to induce a Pacific trough pattern during the second half of the month, as a potential pre-cursor to a January stratospheric reflection event. Current long range guidance now reflects such a pattern. While the forecast for the balance of 2025 would appear rather unchallenging, things are seldom as they appear in weather. In this particular instance, the caveat is an MJO wave that is expected to remain rather meager and variable after having largely dissipated over the course of the past week following its brief flirtation with phase 8 near the outset of the month. Note the tendency for the MJO to stagnate and become incoherent enough in phase 8 as to actually be reflected as having reemerged into the MC phases as byproduct of the continued warmth in the western Pacific that was referenced last fall. The consistent struggle for the MJO to remain a coherent wave in the western Pacific has been a theme over the course of the past decade that any seasoned forecaster should not have neglected to consider. The disjointed signal that results from the continuation of the battle for proxy between the MC and western Pacific will allow for an occasional element of western Pacific expression to assert itself into the pattern as a byproduct of the areas of dual forcing. This will be especially prevalent during the final week of the month, which is when some potentially colder intrusions may periodically infiltrate the northeastern quarter of the country Here is the Christmas Eve 500mb depiction per EURO Weekly product, EURO ensemble package, GFS ensemble and Canadian ensemble. Having a supply of cold near by means that the likelihood of a white Christmas across the southern New England forecast area, while unlikely after the visit from the Grinch on Friday, can not be discounted since there may be some weak northern stream energy passing through in the vicinity of the holiday. There is also some suggestion amongst guidance that Scandinavian blocking could develop by the New Year, which could represent a precursor to an episode of some Greenland Blocking prior to the development of any subsequent refection event later in January. That being said, it would not at all be surprising if this -NAO signal waned at least somewhat in future guidance. Although the pattern is unquestionably turning milder on average, it would be advisable to stay tuned for updates as the all important holiday period approaches because the devil is often in the details.

Yea, I had found it...you're quick! Thanks.

Introduction to Road Rage 101??

Yea, 2022-2023 has some utility as an analog, but it won't be as mild as those seasons in the east.

Ok, enjoy your major snowstorm.

Well, at the end of the day, the kids in Whoville got their gifts back, but we still call him the Grinch-

Oh, well in that case, I guess my two inches of crust will be delivered back under the tree by Santa...phew.

Hmm Yes, it is.

I think it is...it wipes everyone out.

I was just noticing small bodies of water frozen over around Boston on the drive in this AM.

Not a bad list there on the bottom-

Exceedingly rare.

I would take 1996 and run relative to what I have had recently...December was nice, and had an early April event for the ages.

It does suck, I agree. But it could be worse and we have certainly seen worse this time of year.. I wouldn't be surprised if most of us had an inch or two on the ground for xmas. That said, this is not the pattern for a major snow...completely agree.

Yea, that was a few days before my favorite one on 12/16/07.

Spoken from the guy that doesn't have 4 under the age of 7

Oh boy...pope is chiming in; this should be about as refreshing as morning breath.

18 years ago today, the best SWFE that god ever created was upon us.

I mean, it's not hopeless....which in and of itself is all you can ask for.

Gun-to-head...I think a lot of us pull a white xmas out of our rear stocking.

Both GFS and EURO OPs (00z) give many a white Xmas.....non-negligible signal at day 9. Euro more xmas eve and GFS Day.

IDK about the rest of you guys, but in a rudimentary sense...give me volatility, over the single digits on NW flow.