January 2026 OBS and Discussion

[EastonSN+]

1 minute ago, Wannabehippie said:

Any model is going to have a greater degree of error past 5 days than in the short term. So many different pieces need to fall in to place to get a huge snowstorm for the big cities in the Atlantic corridor. The Greenland block needs to be in just the right spot. EPO, NAO, AO, PNAall set up just right. MJO in the right phase. Not too strong of a high coming down from Canada. Anything out of place and that big storm doesn't form or hit. This is why I try not to get excited about anything past 5 days, no matter which model is showing something. 

This 1,000%. So much has to be in place for a KU. 

[Krs4Lfe]

3 minutes ago, TJW014 said:

Rinse, lather, repeat. Same thing will happen with the signal around the 20th.

I still think the only thing going for us is that NYC had a good december, and that tends to correlate well with the rest of winter (when it's a La Nina winter). But even now, we have fallen below average, and it just sees so hard to score something over here. We'll have to wait for a Feb 2015, Feb 2021, or Feb 2013 scenario. In all 3 of those years, most of December and January was a dud until end of the month and then we had a wintry February to bring us up to average or above average. 

[eduggs]

1 minute ago, Krs4Lfe said:

I still think the only thing going for us is that NYC had a good december, and that tends to correlate well with the rest of winter (when it's a La Nina winter). But even now, we have fallen below average, and it just sees so hard to score something over here. We'll have to wait for a Feb 2015, Feb 2021, or Feb 2013 scenario. In all 3 of those years, most of December and January was a dud until end of the month and then we had a wintry February to bring us up to average or above average. 

Snow is good anytime, but February is melt season and often the beginning of mud season. December- and January snow is more emotionally and aesthetically valuable at our latitude. 

[Krs4Lfe]

2 minutes ago, eduggs said:

Snow is good anytime, but February is melt season and often the beginning of mud season. December- and January snow is more emotionally and aesthetically valuable at our latitude. 

Agreed, and I don't know what's up with March this decade but there's only been snow in March 2022. The rest of the years have been snowless in March. March 2020 and 2023 was good for New England but mainly rain for us. 

[EastonSN+]

9 minutes ago, Krs4Lfe said:

I still think the only thing going for us is that NYC had a good december, and that tends to correlate well with the rest of winter (when it's a La Nina winter). But even now, we have fallen below average, and it just sees so hard to score something over here. We'll have to wait for a Feb 2015, Feb 2021, or Feb 2013 scenario. In all 3 of those years, most of December and January was a dud until end of the month and then we had a wintry February to bring us up to average or above average. 

2006 as well.

[donsutherland1]

For those who are not familiar with it, sensitivity analysis incorporates uncertainty into an assessment. It is not deterministic in nature. It is not a point estimate. After the first 11 days of the month, the probability of a colder than normal January was just 55%. That means that there is still a lot of uncertainty. One sees it in the varying ensembles and weeklies and the lack of run-to-run continuity in cases. That's the key takeaway from any sensitivity analysis. It's capturing the large amount of uncertainty quite well, assuming one knows what one is looking at with the probabilities.

For perspective, back in December, the estimated probability of a below normal monthly anomaly was 89% on December 7th. That was about as close to a "slam dunk" as one can get at such a long lead time. The estimated monthly mean temperature then was 34.0° (December finished at 33.8°).

The major weakness is that the analysis assumes a Gaussian curve (normal distribution). Not everything is normally distributed. This assumption is necessary, because the kind of detailed model verification data that would be needed to construct a more robust curve is not publicly available. Thus, the simplifying assumption of a normal distribution is used. 

Finally, I include the estimated monthly mean temperature only because it's nice to have. But one should know what one is looking at. The estimated mean is similar to an ensemble mean, while the probability of an outcome plays the role akin to an ensemble spread (low probability reflects a large spread in outcomes due to high uncertainty). IMO, the probability of an outcome (I just use below or above normal) is really the more useful element of the piece concerning sensitivity analysis, especially at long lead times.

[donsutherland1]

The January 15-16 event was highly unlikely to be a big snowstorm from the onset even if some social media accounts warned of a "big one." Aside from occasional operational GFS runs (unsupported by the other guidance and the various ensembles), no big event was on the table.

Three important reasons apply:

1) The AO-/PNA+ pattern is just getting established. The trough was not likely to be sufficiently sharp for January 15-16.

2) There are numerous areas of vorticity competing with one another. The probability that the various areas of vorticity will develop into a single consolidated low that takes an ideal track for a classic NE snowstorm is low. Large splashes of color on vorticity maps don't always translate into surface potential. Neither do deep 500 mb lows. There's a lot involved for the upper levels and surface to become aligned.

3) The realistic scenarios  of a light impact had been available for some time, even as the exact solution was outside the range of the guidance regarding the ability to resolve synoptic details. During the 1/11 0z EPS cycle, a single ensemble member had 6"+ snow (none had 10"+) and during the 1/11 12z EPS cycle, no ensemble members had 6"+ snowfall in New York City. For Boston, the figures were 6 and 4 members respectively. Bottom line: the probability of a significant NE snowstorm was low; the probability of a major NE snowstorm was extremely low.

Based on the above three reasons, I never incorporated the idea of a significant or major snowstorm into my daily posts regarding the January 15-16 timeframe.

If one is constructing a checklist, one needs both a favorable pattern and favorable synoptic details to get a KU-type snowstorm. If either is lacking, the probability of such an outcome is low. When both are lacking (as is the case regarding January 15-16), the odds are close to zero.

 

[eduggs]

Don, if you go with uncertainty analysis or probabilistic analysis, then I think we're on the same page. But not sensitivity analysis. Early in most months it should be close to a coin flip whether the month will end up above or below normal. Our climatic base state relative to previous decades is warm, so we hedge warm to start. And then Bayesian updating based on long-range modeling.

[donsutherland1]

15 minutes ago, eduggs said:

Sorry Don. You're not a statistician. And what you describe is not sensitivity analysis. 

For those who want a highly simplified but easy-to-understand description of sensitivity analysis, one can reference the following: https://thedecisionlab.com/reference-guide/statistics/sensitivity-analysis. And for those who want insight into the estimated probability, applying multiple variations to the model value, assessing the probability against a benchmark (1991-2020 normal value) using a normal distribution. 

[Krs4Lfe]

ICON wants nothing to do with the 18th threat. As unlikely as it seemed a few days ago, we might have to punt most of January. I remember all the talk about winter cancel and winter over in January 2021 after that month was dry and mild. Similarly, there was evidence of a big pattern change and a shift to colder and stormier across the US by end of January and would last through February. That panned out very well, and it saved winter. But years like 2021, 2013, 2006, 2015 are few and far between. If the 18th doesn't work out either, it's quite possible that winter has shown its cards and it'll be time to pack up. Long range Euro and GFS looks great with ample cold and chances for snow through early Feb and it doesn't seem to be losing the pattern change either. But who's to say the rest of the chances for snow won't go the way the 16th and 18th went?

[eduggs]

8 minutes ago, donsutherland1 said:

1) The AO-/PNA+ pattern is just getting established. The trough was not likely to be sufficiently sharp for January 15-16.

I agree strongly with everything written except this. I believe these features are not causally connected. They are only loosely correlated, and always in hindsight. Besides that, the trof IS clearly sufficiently sharp for a major event. But the synoptic details (which you correctly mention) impede development in a way that would impact us locally. 

[eduggs]

3 minutes ago, donsutherland1 said:

For those who want a highly simplified but easy-to-understand description of sensitivity analysis, one can reference the following: https://thedecisionlab.com/reference-guide/statistics/sensitivity-analysis. And for those who want insight into the estimated probability, applying multiple variations to the model value, assessing the probability against a benchmark (1991-2020 normal value) using a normal distribution. 

Some of us know what a sensitivity analysis is. And for those who do not, your link is helpful. But what you present is not a sensitivity analysis. Or maybe you are withholding most of it, which should include:
- which inputs you used in your analysis
- how they were perturbed
- how the output (mean temp) varied with those perturbations
- ranking of influential variables

The goal of a sensitivity analysis in to determine which variables have the biggest impact on some output... not just what is the most likely output. And if the variables, assumptions, and their tested ranges aren't included, the output is kind of meaningless.
 

[ForestHillWx]

What is happening to this place? The winter melts are starting already? 

[psv88]

2 hours ago, EastonSN+ said:

Most winters have a January thaw. This mild pattern will be 10 to 15 days. 

Colder than average starting the 18th. 

15 day warm up is not a thaw. A thaw is like 3-5 days. 15 days is half the month!

[BxEngine]

Holy christ enough

[eduggs]

Sunday is still on the table for some kind of event. All the ensembles have something. It's workable.

[psv88]

22 minutes ago, eduggs said:

Some of us know what a sensitivity analysis is. And for those who do not, your link is helpful. But what you present is not a sensitivity analysis. Or maybe you are withholding most of it, which should include:
- which inputs you used in your analysis
- how they were perturbed
- how the output (mean temp) varied with those perturbations
- ranking of influential variables

The goal of a sensitivity analysis in to determine which variables have the biggest impact on some output... not just what is the most likely output. And if the variables, assumptions, and their tested ranges aren't included, the output is kind of meaningless.
 

Take this to DMs. If you want this information from Don, I am sure he will give it to you. 

Further, show the man some respect. He contributes alot to this board and for many years. Your attitude towards him is not called for. 

Seriously, nobody cares about your picking apart his statistical analysis. You may think it makes you look smart, but it makes you seem like an asshole. This is not a college course, its a weather board. Give it a rest. 

[Krs4Lfe]

GFS even more disjointed for the 16th. Brings moderate snow inland, some rain showers over here. What a turn of events. What a massive cave

[Krs4Lfe]

GFS won't get it done for the 18th either. Long range looks cold and active though.

[eduggs]

3 minutes ago, psv88 said:

Take this to DMs. If you want this information from Don, I am sure he will give it to you. 

Further, show the man some respect. He contributes alot to this board and for many years. Your attitude towards him is not called for. 

Seriously, nobody cares about your picking apart his statistical analysis. You may think it makes you look smart, but it makes you seem like an asshole. This is not a college course, its a weather board. Give it a rest. 

If he says something incorrect and continues to insist that he is correct, I will challenge it right here. Maybe I'm wrong. Maybe he's wrong. Either way, anybody reading can learn. If I had no respect for him, I would ignore it. People need to know what's true and what's not. 

[psv88]

2 minutes ago, eduggs said:

If he says something incorrect and continues to insist that he is correct, I will challenge it right here. Maybe I'm wrong. Maybe he's wrong. Either way, anybody reading can learn. If I had no respect for him, I would ignore it. People need to know what's true and what's not. 

Again, you are making yourself look foolish. Nobody cares at all. Take it off line. 

The way you challenge comes across as disrespectful. I respect Don immensely, as does everyone else on here. 

Again, take it to DM and move forward. Nobody, and i mean nobody, cares about the equations he uses in his posts. You just come across as a pompous prick. 

Your aggressive and disrespectful posts will drive one of our best posters away from the board. 

[EastonSN+]

17 minutes ago, psv88 said:

15 day warm up is not a thaw. A thaw is like 3-5 days. 15 days is half the month!

If the forecast holds the warm up would have lasted 9 days. The 6th through the 14th. 

[MJO812]

13 minutes ago, Krs4Lfe said:

GFS even more disjointed for the 16th. Brings moderate snow inland, some rain showers over here. What a turn of events. What a massive cave

Cmc likes the 18th. That has some support.

[psv88]

2 minutes ago, EastonSN+ said:

If the forecast holds the warm up would have lasted 9 days. The 6th through the 14th. 

Not at all. 

The warm up started on 1/4. 

From my point and click. 

1/15 - 43

1/16-34

1/17 - 40

1/18 - 36

Highs 36-43 are within the normal range for mid-January. So if we cool down on 1/19 as currently forecasted, the warm up was 1/4 to 1/18

[EastonSN+]

3 minutes ago, psv88 said:

Not at all. 

The warm up started on 1/4. 

From my point and click. 

1/15 - 43

1/16-34

1/17 - 40

1/18 - 36

Highs 36-43 are within the normal range for mid-January. So if we cool down on 1/19 as currently forecasted, the warm up was 1/4 to 1/18

I am using central park which has an average high of just above 39.

[eduggs]

19 minutes ago, psv88 said:

Again, you are making yourself look foolish. Nobody cares at all. Take it off line. 

The way you challenge comes across as disrespectful. I respect Don immensely, as does everyone else on here. 

Again, take it to DM and move forward. Nobody, and i mean nobody, cares about the equations he uses in his posts. You just come across as a pompous prick. 

Your aggressive and disrespectful posts will drive one of our best posters away from the board. 

Look, I don't care how I look on this weather board. And there are certainly many people who know more than I do and whose brains work much faster than mine. I care about truth, facts, evidence, and the scientific method. These are the things that improved human quality of life tremendously over the past few hundred years. When you know what's true and you understand cause and effect, you can make good decisions that benefit people. The opposite is true when you make decisions based on myth, tradition, dogma, voodoo, or a misunderstanding of what's real and true.

That's why I have a problem when people anthropomorphize weather features (surface highs/lows, "kickers") or climate indices, because it misleads people about what's actually happening.

I'm sensitive to a distortion of facts and partial truths... especially when they are presented with an heir of expertise. That's why I challenge these things. If Don performed a sensitivity analysis that as a byproduct generated a mean (output) value for monthly temperature, then he should either say that or call it something else, like a probability analysis. Words matter. Perceptions matter. The reality is that, sensitivity analysis or not, we don't have a robust method to estimate local temperature beyond 10 days. The uncertainty is huge, particularly at our latitude along the coastal plain in January. To imply that we have a statistical handle on the likely outcome is disingenuous. 

[NorthShoreWx]

9 minutes ago, psv88 said:

Not at all. 

The warm up started on 1/4. 

From my point and click. 

1/15 - 43

1/16-34

1/17 - 40

1/18 - 36

Highs 36-43 are within the normal range for mid-January. So if we cool down on 1/19 as currently forecasted, the warm up was 1/4 to 1/18

This reads more like a "normal up", although there were those 50⁰ maxes 1/8-10.

IMBY:

 

 

[EastonSN+]

8 minutes ago, NorthShoreWx said:

This reads more like a "normal up", although there were those 50⁰ maxes 1/8-10.

IMBY:

 

 

Is there an actual definition for how long a January thaw lasts at CPK? 

Just an AI Google search...

 

 

 

 

 

 

A January thaw in Central Park typically lasts about a week, sometimes a little longer, with temperatures rising significantly above average before returning to normal winter conditions, though the exact duration and intensity vary yearly. 

[NorthShoreWx]

1 minute ago, EastonSN+ said:

Is there an actual definition for how long a January thaw lasts at CPK? 

I'm not sure how long it lasts, but it is more typically towards the end of the month.  I've always felt it is one of those things that you can subjectively fit into any January... there's always going to be a few days warmer than all of the others.

[NEG NAO]

6 minutes ago, EastonSN+ said:

Is there an actual definition for how long a January thaw lasts at CPK? 

From folklore to science: The 'January Thaw' is real, as the Northeast and Middle Atlantic states are about to find out | Cornell Chronicle