January 2023 Mid-Long Range Disco

[MDScienceTeacher]

30 minutes ago, stormtracker said:

Damn WAR.  What is it good for?  Absolutely nothing. 

 

[Ralph Wiggum]

I feel like we just tracked a similar setup just 2 weeks ago:

 

[Ralph Wiggum]

We've seen WAR help us before just last January iirc. But yeah, 9 out of 10 times what is it good for? Absolutely nothing. Say it again!

[CAPE]

7 minutes ago, alexderiemer said:

This is kind of how we got the storm last January, no? A thread the needle type of situation with little Antecedent cold air? It was in the 60s the day before. Seems to me a lot of our recent events have arisen from similar such situations...

It was a well timed healthy wave moving along the boundary with some legit cold pressing in. There was also a bit of a bootleg -NAO. But yes there was plenty of intricate timing involved, and it came at the beginning of a pattern change as the western trough was shifting east and ridging along the east coast was breaking down.

[AlexD1990]

1 minute ago, CAPE said:

It was a well timed healthy wave moving along the boundary with some legit cold pressing in. There was also a bit of a bootleg -NAO. But yes there was plenty of intricate timing involved, and it came at the beginning of a pattern change as the western trough was shifting east and ridging along the east coast was breaking down.

Here's hoping we can pull off another hat trick. Would be almost a year to the day...

[aldie 22]

12 minutes ago, stormtracker said:

No

Say it again 

[CAPE]

6 minutes ago, alexderiemer said:

Here's hoping we can pull off another hat trick. Would be almost a year to the day...

This was the set up a few days before-

 

And here it is just prior to the event-

[cbmclean]

14 minutes ago, Ralph Wiggum said:

We've seen WAR help us before just last January iirc. But yeah, 9 out of 10 times what is it good for? Absolutely nothing. Say it again!

I dub thee God of WAR.

[WesternFringe]

15 hours ago, psuhoffman said:

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.  

 

@psuhoffman

When we grade students (you are in education like me, right?), do we use the median or the mean?  Why?  Do we use GPA (Grade Point Average) or GMA (Grade Median Average)?  Why?  We use the mean because it better represents all of a student's scores, not just the one grade in the middle.  Now, I am fully aware that outliers can skew the mean, but with an n of 136, that isn't an issue.  We worry about outliers skewing the mean when we have a low n (< 18), not with an n over 100.  This is why educators are usually required to have a certain minimum threshold for number of grades in determining a student's final grade.  I know no statistician that would be worried about skewing the mean with an n of 136, especially when none of the numbers in the data set are more than 4 times the mean.  If we had outliers of 200" of snow in a year when the mean is 15", then maybe.  Don't we wish.  But these annual snowfall outliers count, and should be represented in the data.  By using the median, one essentially takes all of the best years out of the data and reduces the n precipitously. This is a bad idea, especially with snow! lol

I am not saying that snowfall isn't decreasing for DC, but I am saying it has not been a drastic decrease (especially in our lifetimes).  This is the data set I used:

https://www.weather.gov/media/lwx/climate/dcasnow.pdf

I ran another linear regression starting with 1942, as you did.  The slope of that line is -0.058" and the standard error is -0.054".  The R squared is .01, which means 99% of the variability from year to year is random and not do to the independent variable, which in this case is time (presumably the climate changing over time).  

So, yes, DC is seeing .058" inches less of snow per year since 1942.  Most people wouldn't be able to notice the difference of .058" of snow per year.  If you can, you have superhuman perception.  99% (R squared) of the change in annual snowfall from 1942 is explained by randomness, and not due to the passage of time.  

The slope of the line goes down and up depending on the starting point, of course.  When I choose different starting points closer to present (to match the ages of folks in here and thus their winter memories), the slope of the line can be literally almost 0, or can actually be positive.  

In summary, I concede that the slope of the line is negative, and always have in my posts.  However, I also have learned that the human brain constantly looks for patterns and trends, even when they are non-existent or super small.  That is why I like stats and means and cold hard numbers.  Hats off to you sir if you can notice a decline of hundredths of an inch per year where 99% of the change is due to randomness, or statistical noise. 

No one can tell the future, but if I had to guess we have some monster years coming up in the El Nino years which will make the slope flatter and closer to zero. The sky isn't falling, we can still do snow, and good years lie ahead.  When 99% of the variability is random statistical noise, this tells me we are not in some inevitable downward spiral regarding snowfall.

Again, I stick by my conclusion that although annual DC snowfall is falling (no pun intended), the change is very small, not cataclysmic, and 99% due to randomness.    

[Ralph Wiggum]

4 minutes ago, cbmclean said:

I dub thee God of WAR.

If I ever go to WAR I will carry a needle as my weapon.

Whoops, wrong needle. Just having some fun today with quiet times upon us for now. I'm done with the ot stuff.

[AlexD1990]

Just now, Ralph Wiggum said:

If I ever go to WAR I will carry a needle as my weapon.

Whoops, wrong needle. Just having some fun today with quiet times upon us for now. I'm done with the ot stuff.

maybe not so quiet if this deal on the 6th sneaks up on us #Ialwaysstayoptimistic

[ravensrule]

1 hour ago, stormtracker said:

Is the GFS broken?

It's in Thailand getting your leftovers. 

[BristowWx]

GFS may have been headed in a fun direction at 384hr.  The big ones are sniffed out at 16 days so keep an eye on it folks

[Ralph Wiggum]

GFS op at range but after 300hrs shows what I feel is a viable progression towards a more workable pattern as we approach mid Jan. WAR and Scandinavian ridging feeds +height anomalies at HL. Mean trof nudges east and is replaced with neutral/pos PNA. PAC jet splits. 

[CAPE]

12z GEFS is wholly unimpressed with frozen chances for the 6-7th. Colder compared to the days prior, but not cold enough verbatim.

[cbmclean]

On 12/17/2022 at 2:46 PM, nj2va said:

Tracking shorts or sweats for New Years Eve?

Shorts.

[AlexD1990]

2 minutes ago, cbmclean said:

Shorts.

New Year's bonfires will be nice at least...

[CAPE]

My wag is it will take some time to get cold enough given how that massive trough out west is reluctant to weaken/retrograde, mostly Pacific jet related. Have been seeing some indications on the means of something closer to the 12th.

[psuhoffman]

2 hours ago, DarkSharkWX said:

Yeah, pretty sure DCA had no measurable snow before Jan in 2014-15, 2015-16, and 2021-22, and then things started to ramp up after the start of the New Year

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. 

[Ralph Wiggum]

7 minutes ago, CAPE said:

My wag is it will take some time to get cold enough given how that massive trough out west is reluctant to weaken/retrograde, mostly Pacific jet related. Have been seeing some indications on the means of something closer to the 12th.

Agreed. The look on the gefs mean is certainly moving towards a very workable look. PAC jet poleward look and the split out west would definitely be a welcome change. And you know we dont need bn temps once we get to this range for things to work in our favor. Optimistic. The progression on the means is fairly predictable on a hemispheric lw progression. Let's hope it isn't a head fake as we get past the first week of January.

[Ralph Wiggum]

And a bit farther out,more poleward and a clear -height anomaly evident over the Aleutian chain with the split flow increasing.

[Ralph Wiggum]

Just to add, these 'workable' looks are far from epic, unicorn, textbook etc. I will take workable over epic perfection tbh. Unicorns are make believe.

[Kay]

I didn't know where to put this, but since we have learners as well as knowers here I thought this was good. Article more involved/technical.

 

[BristowWx]

6 minutes ago, Ralph Wiggum said:

Just to add, these 'workable' looks are far from epic, unicorn, textbook etc. I will take workable over epic perfection tbh. Unicorns are make believe.

Agreed.  I will be happy to score with something sloppy for sure.

[Rvarookie]

4 minutes ago, BristowWx said:

Agreed.  I will be happy to score with something sloppy for sure.

Sounds like the right way to bring in the new year 

[Ralph Wiggum]

PAC help is on the way. Hopes for this not being a head fake. Not perfect but really workable. And we know by now PAC>ATL...though our side isnt horrible either.  +heights up top progressing as they had in early Dec but now maybe some PAC help. We can only speculate and hope for now but much rather see this than blue up top and out west. Jet retraction and poleward shift ftw:

[Ralph Wiggum]

10 minutes ago, BristowWx said:

Agreed.  I will be happy to score with something sloppy for sure.

@ravensrule do your thang

[Rvarookie]

1 hour ago, WesternFringe said:

@psuhoffman

When we grade students (you are in education like me, right?), do we use the median or the mean?  Why?  Do we use GPA (Grade Point Average) or GMA (Grade Median Average)?  Why?  We use the mean because it better represents all of a student's scores, not just the one grade in the middle.  Now, I am fully aware that outliers can skew the mean, but with an n of 136, that isn't an issue.  We worry about outliers skewing the mean when we have a low n (< 18), not with an n over 100.  This is why educators are usually required to have a certain minimum threshold for number of grades in determining a student's final grade.  I know no statistician that would be worried about skewing the mean with an n of 136, especially when none of the numbers in the data set are more than 4 times the mean.  If we had outliers of 200" of snow in a year when the mean is 15", then maybe.  Don't we wish.  But these annual snowfall outliers count, and should be represented in the data.  By using the median, one essentially takes all of the best years out of the data and reduces the n precipitously. This is a bad idea, especially with snow! lol

I am not saying that snowfall isn't decreasing for DC, but I am saying it has not been a drastic decrease (especially in our lifetimes).  This is the data set I used:

https://www.weather.gov/media/lwx/climate/dcasnow.pdf

I ran another linear regression starting with 1942, as you did.  The slope of that line is -0.058" and the standard error is -0.054".  The R squared is .01, which means 99% of the variability from year to year is random and not do to the independent variable, which in this case is time (presumably the climate changing over time).  

So, yes, DC is seeing .058" inches less of snow per year since 1942.  Most people wouldn't be able to notice the difference of .058" of snow per year.  If you can, you have superhuman perception.  99% (R squared) of the change in annual snowfall from 1942 is explained by randomness, and not due to the passage of time.  

The slope of the line goes down and up depending on the starting point, of course.  When I choose different starting points closer to present (to match the ages of folks in here and thus their winter memories), the slope of the line can be literally almost 0, or can actually be positive.  

In summary, I concede that the slope of the line is negative, and always have in my posts.  However, I also have learned that the human brain constantly looks for patterns and trends, even when they are non-existent or super small.  That is why I like stats and means and cold hard numbers.  Hats off to you sir if you can notice a decline of hundredths of an inch per year where 99% of the change is due to randomness, or statistical noise. 

No one can tell the future, but if I had to guess we have some monster years coming up in the El Nino years which will make the slope flatter and closer to zero. The sky isn't falling, we can still do snow, and good years lie ahead.  When 99% of the variability is random statistical noise, this tells me we are not in some inevitable downward spiral regarding snowfall.

Again, I stick by my conclusion that although annual DC snowfall is falling (no pun intended), the change is very small, not cataclysmic, and 99% due to randomness.    

This is probably good time to hop on quick zoom call to talk this one through 

[wintertime]

2 hours ago, stormtracker said:

Is the GFS broken?

Yeah. It's been broken for at least 15 years.

[pazzo83]

16 hours ago, psuhoffman said:

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.  

Don S was showing similar data regarding NYC.