My official winter forecast for 2024-2025

[George001]

Although my last winter forecast was a success in that I forecasted AN temps and BN snow for the Boston area, I was right for the wrong reasons. So this year, the goal is to learn from that and continue improving.

Background:

Throughout the summer and fall, there was a lot of talk about the developing La Niña, the structure, strength etc and how it would drive the winter pattern. I was fully bought into that idea myself, but cracks began to show throughout the fall. Guidance kept weakening the La Niña over time, it was supposed to start in September, then October, and now it is November 21st and we are in ENSO neutral. In fact, on the weeklies ENSO 4 and 1.2 are straight up in warm neutral territory, while ENSO 1.2 has recently risen to weak El Niño territory on the dallies. The latest IRI update gives a 50/50 chance of La Niña development, with a peak of around -0.5 ONI for region 3.4 expected. Therefore, ENSO is expected to be very weak and thus not a major pattern driver (reflected by the latest MEI of -0.5). Based on the latest trends, my expectation is for the ENSO state to be cold neutral. Other factors will drive the winter pattern.

Key factors:

fall pattern- warm and dry 

expected ENSO: cold neutral

High solar/geomag: favors a strong PV/+NAO/+AO pattern

-PDO: Has risen significantly from -3 to -2 recently with some guidance indicating further rising, but the PDO should remain moderately to strongly negative throughout the winter. 

EPO: began the month positive leading to warm conditions, but shifting to negative to strongly negative in late November/early december

Hurricane season: late developing but hyperactive- currently 160+ ACE, should be just about done based on climo. Expected ACE is around 165, maybe a bit less. 
 

Analogs: 

great- (2012-2013, 2013-2014, 2001-2002)

good- (2021-2022, 2022-2023, 2016-2017, 2008-2009)

So, we have a mix of great winters, ratters and mediocre winters in the analog package. There isn’t a particularly strong signal for a great or horrible winter, it’s somewhere in the middle with a lot of variance making the forecast difficult and low confidence. That makes sense considering we have a good mix of favorable (weak ENSO, late November -PDO, high ACE in cold ENSO) and unfavorable (-PDO, high solar/geomag in cold ENSO, warm and dry fall, warm November) factors. However, the way I will be evaluating winters is based on the length of the cold vs warm periods, not the total snow. You could luck into an above average snow winter despite an overall unfavorable base state, but that doesn’t mean we should expect that to happen again with a similar set up. On the other hand, we can get skunked with a more favorable base state and should expect better results if we see a similar set up again. Keeping this in mind, this is how I evaluate the above analog winters 

favorable (longer cold periods than warm): 13-14, 08-09

unfavorable (longer warm than cold): 01-02, 16-17, 21-22, 22-23

Middle ground (even split between warm and cold periods: 2012-2013

Analog weights:

#1 analog (2012-2013): 5 points

#2 analog (13-14): 4 points

#3 analog: (01-02): 3 points

All other analogs are worth 2 points. 
 

When the weights are applied we have:

Total points: 20

Unfavorable: 9/20 points, 47% 

favorable: 6/20 points, 30%

middle ground: 5 points, 25%

Final forecast for Boston:

temps: Dec-Mar +2 AN

snowfall: 30-40 inches. Im leaning towards the lower end of this, so below average but not a total ratter. 
 

 

 

 

[George001]

Note: there is extremely high bust potential. The way I see it is both the middle ground and unfavorable path support AN to well AN temps (a 50% cold/ 50% warm split is tilted AN due to climate change). There is a 70% chance we go down one of those 2 camps according to my forecast. However, that means there is a 30% chance of below normal temps. Thats really not all that low, and is higher than I expected before I started the process of making my forecast. Climate change always plays a role no matter which path we go down. Climate change is a double edged sword. The average and unfavorable patterns will be worse. But if we can get a favorable pattern with below normal temps, the clash between that and the warm ocean temps could lead to enhanced cyclogenesis and bigger storms. If we go down the favorable path I would not be shocked to see Boston end up with around 70 inches of snow. However, if we go down the unfavorable path we are looking at +4 to +5 AN temps, in that scenario I would expect to underperform the expected 30-40 inches significantly. I wouldn’t be shocked to see 10-20 inches for the entire season if we go down that path. So this is a low confidence forecast and there is still a wide range of outcomes.