Winter Outlook 2024-2025

[40/70 Benchmark]

https://easternmassweather.blogspot.com/2024/11/using-past-forecasting-difficulty-to.html

[cleetussnow]

Awesome.  I read about 30% scanning for the big picture stuff.  I'm thinking the snow totals you have and +2 to +4 are good and in line with other seasonal forecasts like NOAA/accuweather.  I swagged 14 inches for NYC myself.  I feel like to get to the higher ends of your snow forecast ranges we'll need some money in the bank by the end of December.  Still better than last winter for most. 

You put a lot into this and I'll read some more later.  A lot is above my grade level but I'll learn something.  Good shit.

[J Paul Gordon]

1.5-2.0+ for my location overall. Not devastating by any stretch. Snowfall for Worcester is virtually the same here (-10" to normal) is better than the past few years. So, probably more than our share of cutters, but some real chances for benchmarks, too. I can live with this. I'll make my final 23-25 prediction on April 1st.

High 53 here today, current temperature, 39 is the low. DP 21. Unbelievable stretch of extremely dry weather. 

[512high]

LMAO, am I the only one that caught Tolland CT /Methuen, MA projections lol...oh Ray, lol

[cleetussnow]

2 hours ago, 512high said:

LMAO, am I the only one that caught Tolland CT /Methuen, MA projections lol...oh Ray, lol

Mt. Tolland 

[brooklynwx99]

amazing work. I agree that 2021-22 likely matches the flavor of this year the best

[weathafella]

That's a funny poke to Kevin....lol.

[40/70 Benchmark]

6 minutes ago, 40/70 Benchmark said:

 

 

December Appears Poised To Evolve Colder Than Anticipated

"La Niño"Pattern To Drive Cold Regime Into Mid Month

Recent Corrections Amongst Guidance

There has been a major shift amongst seasonal guidance over the course of the past ten days towards a colder month of December than originally anticipated. Here is the CFS forecast monthly 500mb and temperature departure anomalies for the month of December issued on November 16th.

 

This pattern shown is reflective of a -WPO/-PNA configuration given the warmth over the eastern and southwestern US, as outlined in the Eastern Mass Weather Winter Outlook. 

 

 

However, there have been incremental adjustments over the course of the latter half of November that have culminated in this most recent run of the CFS forecast for the month of December.

 

This new forecast is still indicative of a negative phase of the WPO given the continued warmth over the southwestern third of the US in response to the above average heights in the vicinity of the Bering Sea. However, the marked change towards lower heights and colder temperatures over the east and southeastern third of the nation is representative of a +PNA, which is a significant departure from the previously advertised -PNA (RNA).

 

 

This is obviously both unexpected and uncharacteristic of a burgeoning cool ENSO event, and in fact, it is more representative of the type of regime expected during a warm ENSO event.

Growth of La Nina Interrupted by Hostile Zonal Wind Pattern

The anomaly in region 3.4 as of October 23 was -0.5C and all indications were that at least a modest La Niña was developing. However, as of November 20, the anomaly has warmed to -0.1 This is due to the fact that the zonal wind pattern across the tropical Pacific throughout the month of November has been largely devoid of the easterly trade winds necessary to upwell the subsurface cold pool, and thus sustain the growth of La Niña. Note the stark contrast in the zonal wind anomalies during the month of November to the composite of those preceding the past five cool ENSO events.

 

 

Perhaps the most telling sign of the growing tropical discontinuity is the fact that this past month of November featured one of the most powerful westerly wind bursts on record for the month of November.

 

Note that 5/6 seasons in the above annotation are El Niño, and 4/6 are very powerful warm ENSO events at that. Interestingly enough, the sole cool ENSO season of 1998 also took place on the heels of a potent El Niño and on the cusp of a longer term, multi-decadal shift in the PDO. It is no surprise that the 850mb zonal wind composite of these months of November is much more redolent of November 2024 than the recent cool ENSO composite.

 

Both this growing discontinuity throughout the tropics, as well as last year's potent El Niño within the secondary nadir of a prominent Pacific Cold phase are signs that a major shift in the multi-decadal phase of the PDO maybe imminent. 

 

While this is unlikely to have major ramifications for the coming winter, the ongoing tropical deviation from the cool ENSO regime that has been so prevalent for the past decade most certainly will, for at least the first half of the December, anyway.

December 2024 Preview

Perhaps the purest manifestation of this unexpected and historic westerly wind burst during the month of December is with respect to the Global Angular Atmospheric Momentum, which continues to be positive and more indicative of a warm ENSO event than an incipient La Niña. 

 

This is likely the primary reason why this deviation from the Maritime Continent forcing, which was expected to take place in January per the Eastern Mass Weather Winter Outlook, has taken place earlier than expected and appears rather stable. Note the persistence of this -WPO/-EPO/+PNA paradigm throughout the first half of December.

 

 

 

While the MJO has not been a major influence on the pattern of late due to the overwhelming +atmospheric momentum, it may represent a subtle constructive interference with the ongoing regime early on in December with its passage though phase 5.

 

 

Regardless, the early month pattern is of high confidence with multi-ensemble suite consensus.

 

 

There is also strong agreement that this pattern will remain in place until at least the end of the second week of the December.

 

 

 

However, mid month is when the plot thickens, so to speak, as there are mixed signals abound. The trade winds are forecast to reinvigorate, as the atmosphere makes one final attempt to ignite La Niña.

 

 

This late reinvigoration of a modest La Niña is similar to November 2008, when the region 3.4 anomaly warmed from -0.5C on October 1 to -0.1C on November 5th. Note the similarity in the modest subsurface cold pools below region 3.4.

 

 

Concurrent with the expected resurgence of La Niña mid month is the potential propagation of the MJO into phase 6, which features an Aleutian ridge oriented, RNA pattern that is much more reminiscent of cool ENSO.

 

 

The caveat being the issue of whether the MJO wave will make it into phase 6 with a enough amplitude to over power the residual, waning positive atmospheric momentum, as guidance indicates that the MJO impulse may decay before reaching phase 6. 

 

 

 

The early December 2010 is a prime example of a meager Maritime Continent wave being insufficient to de-constructively interfere with ample antecedent positive global angular momentum.

 

 

However, even the latter portion of December 2010 featured a return to an RNA pattern and the ensuing resurgence of the moribund La Niña should ensure a similar occurrence this month before another potential deviation beyond the new year.

 

 

In the mean time, a few higher terrain locales may experience a sneak preview of winter on Thanksgiving day, with perhaps up to 1-3" in the highest terrain of the Worcester hills and up to 2-5" in the Berkshires for a transition to rain. 

 

 

Thereafter, the region awaits the first potential major and widespread wintry threat along or about December 7th.