psuhoffman

I don’t think they put much effort into those maps once outside the DC metro area and immediate surrounding area. This has been more common than actually getting a “typical” blocking response the last few years. It seems blocking the first half of the season has lost its mid latitude impact recently.

Unfortunately what he did was kinda smart. I think many wanted to be optimistic (myself included) and sided with a forecast of a closer to median snowfall winter. But the analogs and stats said there was pretty close to a 45% chance of a god awful single digits season, 45% of a closer to median bad but not horrible season and like 10% or less of a truly snowy season. So why not do what he did and stick out there. Even if we get closer to the better outcome we’re very likely to end below avg so he won’t bust too bad. And if this goes the way of some of the awful analogs he gets to crow and look like a genius. Smart play.

Our disaster scenario would be if we had a Nino ish pattern earlier (not good because it’s hard to overcome the pac puke you get) and then the SSTs couple mid winter and the typical Nina dreg Feb pattern takes over with a central pac ridge of death pumping a SE ridge to Quebec.

I have no idea. Sometimes the SSTs fail to produce the typical effect on the atmosphere. FailIng to couple is the catch phrase lately I think. Obviously it’s more common when the SST anomalies are less pronounced but other then that it’s difficult to predict.

@Jimade a good point yesterday. The reason the stats are so awful regarding Nina’s that start bad like this is that there are two archetypes of Nina and the colder type typically produced some snow by now. The warmer type tends to be a torch straight through. But this year hasn’t been the warmer type so far we just didn’t get snow. So maybe this is an anomaly that won’t fit the past comps. Also, we’ve been in a Nino type north pac pattern a lot. Quite often the best analogs have been ninos. And ninos do tend to flip mid winter and end snowier. The data is the data but perhaps there are reasons to have hope this year doesn’t fit the typical patterns.

Adding to my last thought, I’d also like to see us snow from a domestic airmass with no epo help. Below is the composite of our 6 biggest snowstorms of the last 50 years. One problem we’ve had repeatedly recently is we only get cold enough to sustain snow with epo help. Some have started to excuse our fails with “of course it failed look at the epo, or no cross polar flow” but that ignores the fact that historically 90% of our snow did not occur in an arctic airmass with cross polar flow. That’s actually not a good longwave pattern to get storms to amplify into the box we want. Fact is a lot of our big snows happened in a look many would say is a “hostile” pacific (look above) because that’s actually the best longwave pattern to get a system to dig and amplify along the east coast. That’s why often a big snow was followed by a big warmup. Cold isn’t sustainable in that look. Conversely a lot of our really long truly cold periods didn’t include a big snowstorm or if they did it came at the end. A very negative epo has 2 problems. If it’s west based anything that amplified will cut. If it’s more east it can overwhelm the CONUS and just squash everything to the south. The TLDR version: we’ve been too quick to just dismiss things with “pac puke” when a lot of our past snow came in a pac puke pattern. It’s just pac puke didn’t used to be sooooo warm that it was automatically a shut the blinds pattern.

@CAPE you mentioned our next modoki Nino will be a good test case indicator. This setup coming up could be also. A western Hudson Bay high used to be a classic way to create a bootleg setup to get a snow absent a good setup with the NAO/AO/EPO/PNA. They weren’t typically huge storms. Temps were always an issue and they are mostly progressive but there were a lot of 4-8” type snows from this kind of setup in the “study” I did of all 4”+ events. A western Husdon high in an otherwise crap longwave pattern was actually the second most likely look to snow up behind the classic +pna -NAO for a long time, 1940 through 90s. Then they kinda went extinct. Over the last 5 years after I did the study I’ve noticed several of these setups and I’ve noted they did often produce a storm that took a good track, but each time it was simply too warm and DC got a 35-40* rainstorm. That is anecdotal though. I didn’t scour through every rainstorm of the 40s to 90s to confirm how common a perfect track rain in this setup was. But what’s not anecdotal is we used to get a snow from this kind of look fairly regularly until recently when suddenly we haven’t. I would feel a lot better if one of these Hudson high setups in an otherwise crap longwave pattern worked out to some degree. Just to prove we can in fact still get snow this way.

It was fairly cold leading into 2016, we had a very minor cold snow a couple days before. But your point is true. DC often has had very warm temps just a couple days either side a significant snow. Upper 50s and 60s for sure. 70s also but they usually were reserved for late Feb and March storms but perhaps that will become more common in January too.

past results do not always predict future outcomes... but lets be honest its not how we want the season to start.

@WesternFringe I replied in the "snowfall futility" thread. Lets move our discussion there so as to not further clutter up this thread. Others have been discussing this general topic there also so I agree with terp that this belongs there.

Moving this here so as not to clutter up the main thread any further. Counter points... 1) Using grades might not be the best example since my district enforces a minimum grade of 50 so as not to skew students grades with 0s lol. But lets not get into that please. Thought I would start with some levity. 2) The claim that outliers don't skew the mean is predicated on the mean of the whole dataset. But we are comparing the change in mean over time. To do that you have to chunk the mean into smaller portions. Climo uses a 30 year mean. If we remove just 4 years out of those 30 the current mean for DCA is only 9". Those 4 years are most definitely skewing the mean of the current 30 year period...and by doing that is also skewing the slope of the trendline. 3) This depends what you are trying to tease out of the data. The mean tells you over a period of time how much total snowfall is likely to fall proportional to each year. But it does not tell you how much snow is most likely to fall in any given year. The truth is over the last 30 years that 9" number (what you get if you remove the 4 super outliers) is way closer to what you should expect going into any given year than the 14" mean number with which was only reached 26% of the time. In any given season there was a 74% chance you were getting less snow than that. If you are trying to calculate how much snow you should expect in any given season, the mean is not the best tool. 4) Maybe we are trying to get at different things. What I am getting at are in any given season the odds of getting a specific amount of snow are dropping. The odds of getting 8", 10", 12", 15" and so on...going into any season are going down. And going down a LOT. The odds of getting a 4", 6", 8" storm are all dropping. That is what I am focused on. That going into any specific season the chances of it being crap are going up. The mean does not capture that fact as well. 5) You keep focusing on what the change is per year. Over time very small changes add up to be significant. 6) In a vacuum its correct to say 99% is attributed to random chance because the math you are using doesn't know any corroborating evidence. But we do know some additional facts. The fact that it is getting warmer for instance. If you apply logic to the fact that at the same time the slope of snowfall is decreasing correlates to an increase in temperature the amount we should attribute to "random chance" goes down. 7) Lastly I am not making this about human caused climate change. Maybe this is cyclical. Maybe its not human caused. Maybe at some unknown point in the future the trend reverses. Those are all true. But that is not what I am getting at. I am not living at some random unknown point in the future. I don't care what the chances of snow will be is 2323 I care what the chances of snow are right now in 2022. For the sake of this argument I don't care if the warming is man made or natural it is still impacting my snowfall right now just the same. And since we don't know when or if the trend will reverse I don't even care about that. What my analysis was showing is that our chances of snow in any given season right now are significantly lower than they were during recent recorded history. It's not even a predictive thing. I am not making a statement about what snow probabilities will be 50 years from now. I have no idea. I am making a statement on what they are RIGHT NOW. Your analysis isn't wrong. Everything you say is 100% true. But you are focusing on different metrics that me and teasing different things out of the data. You seem to be more focused on predictive measures of snowfall over any long period of time with statistical certainty. That is a very different concept than trying to calculate what the probability of a given amount of snow in one specific season is right now and how that probability has changed over the last 100 years. We are looking at very very different things.

I left El Niño’s out when I posted the stats because they more commonly start warm then flip snowy. I posted all neutral and Nina years. La Nina’s are more often front loaded so when they start bad it can get really bad. However, we’ve had a bit of a Nino ish pattern so…if this year doesn’t behave like a typical Nina it leaves the door open more. Also as Ji pointed out most of the past Ninas that were snowless were warm early. Nina’s that start very warm tend to stay warm. But it was kinda cold just no snow. There are good reasons to cling to hope. But I wouldn’t use El Niño years since they are notorious for flipping in January.

We have a below average temp month this December ...we had a good pattern. The no snow was a fluke.....its different from other shutout December months I tend to think there is some validity to this. I commented a few days ago that perhaps the warning has made a snowless start more common also making a turn around more likely. Early season seems to be most impacted. But I’m just posting statistics. I’ve always done this. Good or bad. Ironically many years ago I was on the flip side of this and I remember some including Mitch being frustrated at me for being too optimistic! Truth is I bust high way more than low on snowfall. I’m not pessimistic. It’s just been so god awful recently it makes it seem that way when I simply post the objective statistics.

Fringed

We should be discussing snow threats…oh wait

maybe read some before posting

To comfort those on the ledge...its still extremely likely it snows at some point this winter, even if not very much. We aren't at the point yet where its likely we get a complete shut out.

I love snow...and I REALLY hope is snows 100" the next nino winter. But the evil me kinda takes pleasure knowing at least if it is a total fail I get to see the total nuclear meltdown on here.

We just had a raging -AO, about as negative an AO as we can ever get...we just didn't get any snow out of it lol.

I didn't claim my stats proved anything...I simply laid out facts and explained why I disagreed with his analysis of the data. Anyone is welcome to disagree with me. I laid out the data, people can decide for themselves which interpretation they agree with.

I will enjoy any snow we get. If we don't get any I'll take my kids to Blackwater Falls in WV after they get an upslope event to play and go sledding. I will see snow a few times when I go skiing in New England or Colorado. It will be ok. But we were all hopeful maybe this would be a "good for a nina" season...where we get close to median or maybe even closer to avg if we got lucky. But it is becoming increasingly likely this is going to be one of the bad ones...like bad bad not just just kinda bad. But likely doesn't mean definitely. Even if every past comp was awful there aren't enough years to say its a statistical certainty. But we all know this is how the really awful years start. I still do have some hope...these statistics are just data. Not a prediction. But I will lay this out there...if the PV starts to couple with the TPV and we see the AO go extremely positive in January its game over.

this implies we have a peak climo anymore lol

If I make it to January 10 without 1" of snow the numbers get even uglier. It's a VERY small list...but most are years that ended with almost no snow at all around DC.

I will take you at your word that you are not trolling and engage one last time with what I take issue with in your statistical analysis. But first I'll post some data that I will reference in my response below. @Terpeast I have used only DCA data from 1942 onwards. DCA annual snowfall with a linear trendline and 30 year running mean imposed. 18 year running probability of getting at least 10" of snow in any given season 18 yeas was not arbitrary but was chosen because in this discussion yesterday 18 years was agreed upon as a minimum data set to avoid overly skewed results to get a statistically significant result. Some additional facts. The running 30 year mean snowfall at DCA has decreased from 17.8" to 13.9" over the period of record for the airport. This trend is continuing and is getting even worse...the current 15 year mean is only 13.6" The median has decreased from 15.8" to 10.85". This trend is also getting worse. The current 15 year median is 7.8" The chances of getting at least 10" of snow in a given season have gone from 72% to 50% in a given season. This trend also is getting worse...the current 15 year probability is 47% The chances of getting 15" in a season have gone from 53% to 27%. The chances of DC getting 20" have gone from 40% to 17% 1) The words bolded above are all your opinion. The slope is NOT 0, virtually is opinion...yes over any one year the change is insignificant but over a long period of time .03 adds up to 4" of snowfall we have lost annually over the period of record. That is not insignificant when your average is only about 14". That's more than 20% of our annual snowfall we have lost. 2) Single digit snowfall years is not arbitrary, its a way of showing what chance there is of getting a significant amount of snow in any given year in DC. We can use another number if you want...8", 12", 15", 18", 20"...they all show the exact same trend so it doesn't matter. I didn't cherry pick 10 to skew the data, I picked 10 because its a nice simple even number to highlight the issue which is in any given year the odds of getting snow is going down. That is true whether you use the threshold of any amount between about 7 and 20", outside that you get some crazy useless percentages because you're using a number outside a standard deviation. 3)I've repeatedly said that using the probability of snowfall or the median is way more useful to a climate like DC and you repeatedly dismiss that which is your opinion and fine but I will explain what is wrong with a mean. DC snow climo is inflated by anomalously snowy seasons like 1996, 2003, 2010 and 2014. But the snow that happens in those winters doesn't make the years in between any less awful. They do not affect what a typical winter is. Getting a huge amount of snow every 7 years or so affects the mean a lot but isn't indicative of what any given winter is likely to be like...which is probabilistically much more likely to be one of those other 6 years. Median filters out those big years better to give you a better indication of what any given specific season is likely to be like. 4) You've said there is no evidence that the mean is being skewed but the evidence is right on the chart for everyone to see. While the median and probabilities of snowfall are clearly decreasing the range of snowfall in any given year over a period of time is increasing. The standard dev of snowfall is increasing. Even though the baseline for snowfall is lower we have had several of the biggest snowfall seasons recently. This is preventing the mean from dropping as quickly as the probabilities of snow in any given season are. But for our purposes the probabilities are more important. Who cares that it snows a crap ton once every blue moon when the truth is we spend 80% of the time in the total suckage periods in between that are getting worse! 5) You repeatedly try to manipulate the data by using an arbitrary date in the 1980's from which you can say "snowfall has increased since". That is really bad statistically because snowfall does run in cycles. We are no doubt in a down cycle right now. I have never implied DC won't have better snowfall periods ahead. But by cherry picking a date that is a minimum with which to compare the current point in time fails to acknowledge that over a longer period of time its evident that the "snowy" cycles are becoming less snowy and the "dreg" periods are becoming MORE dreg. The current down cycle is no doubt a down cycle...but its worse than previous down cycles. The recent snowy periods weren't as snowy as past snowy periods. Over longer periods the downward trend is evident.

He is trolling... I should have noticed sooner. But no need to continue engaging with childish behavior.