December 2021 Medium/Long Range Discussion Thread

[Prestige Worldwide]

 

 

[Weather Will]

WB 12Z GEFS thru Christmas.

[Yeoman]

1 hour ago, Weather Will said:

WB 12Z GEFS thru Christmas.

10-20% - valid for any random date in winter

[WinterWxLuvr]

Is the dream dead? Not seeing many posts 

[Eskimo Joe]

4 minutes ago, WinterWxLuvr said:

Is the dream dead? Not seeing many posts 

I'm just hoping we get climo. Anyone expecting a banner pattern from this might be expecting too much.

[Weather Will]

1 minute ago, WinterWxLuvr said:

Is the dream dead? Not seeing many posts 

If it goes above 20 percent, will post an updated map. EURO ensembles also in 10-20 percent range.
 

[jaydreb]

Lol, 18z GFS at the end of its run teases us with a monster storm that gets suppressed by a 1049 high.  

[Ji]

If it goes above 20 percent, will post an updated map. EURO ensembles also in 10-20 percent range.
 

Thats the winter default when the pattern isnt a shutout

[Weather Will]

0% chances over the next week or so…But 18Z GEFS has hits after that through Christmas.   

[Ji]

0% chances over the next week or so…But 18Z GEFS has hits after that through Christmas.   

Do you have the 1 inch map?

[psuhoffman]

We could waste a good pattern. But there is no way to know that when it’s still 10+ Days away from even starting. All we can do now is identify very basic longwave trends. Those are all good. Whether we actually get a snowstorm is to be resolved way way later. I don’t get the people bringing up meso scale stuff as a reason to poop on a long range pattern. 

[Weather Will]

6 minutes ago, Ji said:

10 minutes ago, Weather Will said:

0% chances over the next week or so…But 18Z GEFS has hits after that through Christmas.   

Do you have the 1 inch map?

 

[Weather Will]

Models can’t figure out if it is going to snow 3 days out…I like the percentage maps in the long range simply because it gives someone like me who is not an expert a feel for whether we are going into a favorable period or not…

[WinterWxLuvr]

17 minutes ago, Weather Will said:

Models can’t figure out if it is going to snow 3 days out…I like the percentage maps in the long range simply because it gives someone like me who is not an expert a feel for whether we are going into a favorable period or not…

Problem with that is you’re always gonna have ens runs that give snow in the winter, especially when you get out past 7 days. Throw in a few good hits and voila you have a more than zero chance for accumulating snow.

[WinterWxLuvr]

For whatever reason, looking at the gfs ens, I’m intrigued by the period next weekend.

[psuhoffman]

29 minutes ago, Weather Will said:

Models can’t figure out if it is going to snow 3 days out…I like the percentage maps in the long range simply because it gives someone like me who is not an expert a feel for whether we are going into a favorable period or not…

Nothing wrong with using the probabilities maps as a quick indicator of whether things are improving.  But I don’t think we’re close enough for the guidance to “see” far enough into the ”better” pattern for those maps to pick up much yet. I know Xmas looms large and we all want the flip to happen in time and there is some potential to get a wave before Xmas if we time up a high but the much better pattern looks to settle in after Xmas. 

[CAPE]

5 minutes ago, psuhoffman said:

Nothing wrong with using the probabilities maps as a quick indicator of whether things are improving.  But I don’t think we’re close enough for the guidance to “see” far enough into the ”better” pattern for those maps to pick up much yet. I know Xmas looms large and we all want the flip to happen in time and there is some potential to get a wave before Xmas if we time up a high but the much better pattern looks to settle in after Xmas. 

This. To me those maps(snow maps in general) have value only when we have a discrete threat in sight, when we are in a 'good' pattern. Otherwise they usually produce the generic 10-30%, 1-3" output per 15 days, depending on exact location. Unless we are in a putrid pattern when they show literally nothing.

[BristowWx]

If it’s not a torch on Xmas it’s a win.  I want to roast chestnuts 

[CAPE]

49 minutes ago, WinterWxLuvr said:

For whatever reason, looking at the gfs ens, I’m intrigued by the period next weekend.

I kinda like the period a few days later. Although suppression/shredding is a risk, it looks more supportive of frozen.

[Ji]

I kinda like the period a few days later. Although suppression/shredding is a risk, it looks more supportive of frozen.

We usually underperformed when the pretty blue is right over us so maybe this will actually produce

[StormchaserChuck!]

Remember, the last 4 Christmas' in the midst of big +NAO Winter's

This coming -NAO may have less staying power? 

[thunderbolt]

1 hour ago, StormchaserChuck! said:

Remember, the last 4 Christmas' in the midst of big +NAO Winter's

This coming -NAO may have less staying power? 

And

[StormchaserChuck!]

It may be temporary.. we have been -NAO 70%of the time August-now so.. 

[Ji]

Euro with a close call big storm

[CAPE]

39 minutes ago, Ji said:

Euro with a close call big storm

All 3 globals are hinting at a storm during that period now. Euro amped, GFS too far north, CMC keeps all the moisture south. Long way to go, but the pattern looks supportive for something trackable during that time.

[WxUSAF]

Great thread this morning from @griteater. His best analogs for this MJO progression at this time of year in a Niña are 95-96, 01-02, and 17-18. Three wide ranging outcomes there showing @psuhoffmans reminder that luck always has a big role to play. 
 

 

[MN Transplant]

If anyone wondered whether there was a correlation between a dry Nov/Dec (<3" precip) and the winter snowfall...there is not.  DCA's average is 15" and median is 11.6" in those cases, which is pretty close to the average.

[psuhoffman]

16 minutes ago, WxUSAF said:

Great thread this morning from @griteater. His best analogs for this MJO progression at this time of year in a Niña are 95-96, 01-02, and 17-18. Three wide ranging outcomes there showing @psuhoffmans reminder that luck always has a big role to play. 
 

 

People forget we wasted this for a month in O1/02 

2 storms got suppressed. One phased late. One missed just northwest of us and a good overrunning setup under performed and de amplified as it got to us. But we got about as unlucky as possible from early December to Mid January. Then the bad pattern set in late January and so it was game over. 

One point specific to those other scenarios  2001/2 that look set in early December and broke around Jan 15.  If we repeat the same pattern but start around Xmas I like our odds better.  2018 we also got unlucky with a pretty good longwave pattern for about a month. But we never got much Atlantic help. In a Nina that’s huge.  The NAO is even more important in a Nina to slow down the fast NS and force it to dig and amplify under us. It’s really hard to get a significant snow here absent blocking in a Nina. So if the Atlantic cooperates some I’d like our chances more than Dec/Jan 2018 also.  But when I say that I just mean our chances to get a decent storm and make this year an ok one.  My bar is pretty low.  But it will still come down to luck  

I think some don’t like when I point out “luck” because some like to try to find reason and certainty and some think I’m excusing bad forecasting. But what I’m really doing is admitting we don’t have the skill to discern the meso scale factors that will determine one locations snowfall results at any range. We can try to identify some general longwave characteristics that will increase or decrease our probabilities at longer leads. But then we need the details to break our way and since we don’t yet have the ability to account for those little discreet details we label them “luck” or chaos. I don’t know if we will ever have the ability to accurately account for every little factor at long ranges (I kind of hope not) so for now calling it luck is good enough for me. 

[CAPE]

43 minutes ago, psuhoffman said:

People forget we wasted this for a month in O1/02 

2 storms got suppressed. One phased late. One missed just northwest of us and a good overrunning setup under performed and de amplified as it got to us. But we got about as unlucky as possible from early December to Mid January. Then the bad pattern set in late January and so it was game over. 

One point specific to those other scenarios  2001/2 that look set in early December and broke around Jan 15.  If we repeat the same pattern but start around Xmas I like our odds better.  2018 we also got unlucky with a pretty good longwave pattern for about a month. But we never got much Atlantic help. In a Nina that’s huge.  The NAO is even more important in a Nina to slow down the fast NS and force it to dig and amplify under us. It’s really hard to get a significant snow here absent blocking in a Nina. So if the Atlantic cooperates some I’d like our chances more than Dec/Jan 2018 also.  But when I say that I just mean our chances to get a decent storm and make this year an ok one.  My bar is pretty low.  But it will still come down to luck  

I think some don’t like when I point out “luck” because some like to try to find reason and certainty and some think I’m excusing bad forecasting. But what I’m really doing is admitting we don’t have the skill to discern the meso scale factors that will determine one locations snowfall results at any range. We can try to identify some general longwave characteristics that will increase or decrease our probabilities at longer leads. But then we need the details to break our way and since we don’t yet have the ability to account for those little discreet details we label them “luck” or chaos. I don’t know if we will ever have the ability to accurately account for every little factor at long ranges (I kind of hope not) so for now calling it luck is good enough for me. 

I think using the word luck is fine. Maybe it's more like randomness. There are failure modes even when guidance looks good at say 3 days out, due to inevitable errors in timing of wave interactions, etc. There is almost always a fine line in most winter storm situations in this region(esp the cities and east), and favorable patterns for snow generally don't last that long, so 'wasting' them often amounts to 2 or 3 medium range threats that don't work out for one reason or another.

[WxUSAF]

I remember how that pattern developed in 17-18. Looked like an amazing overrunning pattern at range and the models were keying in on a storm from D8-10, but then the cold push overwhelmed it and it was suppressed to hell and gone. We got a couple minor events in a cold and dry period.