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December 2021 Medium/Long Range Discussion Thread


North Balti Zen
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13 minutes ago, IronTy said:

Maybe it's confirmation bias but it seems like there is ALWAYS a MA snowstorm in the ~240hr range on the models.  Is there some sort of technical reason for this?  Like some sort of amplification or feedback that is inherently built into the models?  Anybody have a clue?    

Yeah I'd like to know the same thing!

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27 minutes ago, IronTy said:

Maybe it's confirmation bias but it seems like there is ALWAYS a MA snowstorm in the ~240hr range on the models.  Is there some sort of technical reason for this?  Like some sort of amplification or feedback that is inherently built into the models?  Anybody have a clue?    

Developers did it to piss off the weenies

 

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12 minutes ago, yoda said:

ORH in the SNE forum says Euro tried to phase everything (all 3 s/w)

It’s a pretty large run-to-run change. Finds this strong southern stream wave and does a sloppy phase of everything to our northeast (of course). 

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The main problem I see is that the system is coming across a little too far north.  Look we know the STJ is likely going to be non existent and so a HECS is very unlikely but if we want some decent snows (for a nina) this kind of setup repeated in winter when the jet will be further south would be a good thing.  So long as people don’t act stupid and get upset when we get 2-4” or 3-6” and Boston gets 1-2 feet. That’s just climo in a Nina and it’s going to happen.  Best to just enjoy what we get and ignore the bombs that happen to our northeast. 

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10 hours ago, IronTy said:

Maybe it's confirmation bias but it seems like there is ALWAYS a MA snowstorm in the ~240hr range on the models.  Is there some sort of technical reason for this?  Like some sort of amplification or feedback that is inherently built into the models?  Anybody have a clue?    

 

10 hours ago, Maestrobjwa said:

Yeah I'd like to know the same thing!

Math.  The NWP is working exactly as it should. Let’s just take the 3 major globals and ICON since it gets so many eyes due to TT. Thats 16 runs a day.  Any given 10 day period during winter has about a 10-25% chance of snow depending on the week and where in this sub you are.  If just one run of one model shoes snow in a day that’s not saying the NWP is predicting snow.  Climo probabilities would say several runs in any given day should randomly have a snowstorm.  If only 1-2 or even 3 runs a day have snow that’s below climo!  The vast majority of runs don’t have snow!  But no one pays attention to them.
 

Making things worse often when it’s boring people start to post obscure stuff like the JMA or some individual ensemble member. Now we’re talking crazy stupid low chances if we use probabilities when only one run like that has snow. When the majority of runs start to show snow that’s when it’s fair to say the NWP is indicating a high probability of snow.  They still bust in those situations too but many exaggerate by thinking the models are saying it’s gonna snow every time an individual run shows a fluke snowstorm when the majority of runs don’t. 
 

Then we get people like Tenman who come on and rant about how awful the guidance is and they show every possible solution.  Well yes if run enough times at long ranges you will get a lot of permutations. And that’s where understanding statistics and probabilities comes in handy. 
 

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8 hours ago, psuhoffman said:

 

Math.  The NWP is working exactly as it should. Let’s just take the 3 major globals and ICON since it gets so many eyes due to TT. Thats 16 runs a day.  Any given 10 day period during winter has about a 10-25% chance of snow depending on the week and where in this sub you are.  If just one run of one model shoes snow in a day that’s not saying the NWP is predicting snow.  Climo probabilities would say several runs in any given day should randomly have a snowstorm.  If only 1-2 or even 3 runs a day have snow that’s below climo!  The vast majority of runs don’t have snow!  But no one pays attention to them.
 

Making things worse often when it’s boring people start to post obscure stuff like the JMA or some individual ensemble member. Now we’re talking crazy stupid low chances if we use probabilities when only one run like that has snow. When the majority of runs start to show snow that’s when it’s fair to say the NWP is indicating a high probability of snow.  They still bust in those situations too but many exaggerate by thinking the models are saying it’s gonna snow every time an individual run shows a fluke snowstorm when the majority of runs don’t. 
 

Then we get people like Tenman who come on and rant about how awful the guidance is and they show every possible solution.  Well yes if run enough times at long ranges you will get a lot of permutations. And that’s where understanding statistics and probabilities comes in handy. 
 

Paying more attention to the large scale synoptics and the means and less to random op runs depicting snow at range might also help to mitigate these perceptions.

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  • WxUSAF changed the title to December 2021 Medium/Long Range Discussion Thread

I’d chime in with the fact that models at long range, especially the gfs has a bias of being too far south with fronts and boundaries, and therefore with cold air, and thus you get snowier solutions at long range than you do as you approach the time frame of any system.

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Just now, WinterWxLuvr said:

I’d chime in with the fact that models at long range, especially the gfs has a bias of being too far south with fronts and boundaries, and therefore with cold air, and thus you get snowier solutions at long range than you do as you approach the time frame of any system.

This 

It's not as bad as it used to be but the bias is real from 7 + days out and  Is almost always skewed to cold.

7 day + snow storms turn into 38 degree driving rain storms.

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Looking at guidance this morning, there's a consensus coming along on the handling of the s/w's on 5H that leans more toward what the ECMWF was showing yesterday, lending credence to snow threat being primarily north of I-70 threat. The upstream s/w over the GL area has trended a bit flatter and doesn't gain amplitude until cross through the OH valley, making it too late for the Mid Atlantic. There's still some solid PVA as the s/w pivots through the area, so a dusting to a couple inches up near the Mason Dixon line would be possible, but any further north trend or a weakened vort would nix probabilities sufficiently. Still very very early in the season for the sub-forum, so don't sweat it too much. The period from Dec 4-11th looks pretty juicy with a plethora of s/w's ripping through the flow. Something to monitor over the next several days.

In the meantime, Happy Thanksgiving to all. Hope you guys enjoy partaking in the three F's: Food, Family, and Football. Have a great day y'all! 

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3 hours ago, CAPE said:

Paying more attention to the large scale synoptics and the means and less to random op runs depicting snow at range might also help to mitigate these perceptions.

Definitely 100%.  Maybe we should bump those snowstorm climo 101 threads from years ago.  But I didn’t feel like typing a novel.  Simply not overreacting to every random fluke op run is a good start I think but yes to really use the nwp correctly you need to apply real pattern knowledge and analysis. And let’s be honest not everyone is going to master synoptic analysis. And that’s fine…there are lots of things I don’t know Jack about. 

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1 hour ago, psuhoffman said:

Definitely 100%.  Maybe we should bump those snowstorm climo 101 threads from years ago.  But I didn’t feel like typing a novel.  Simply not overreacting to every random fluke op run is a good start I think but yes to really use the nwp correctly you need to apply real pattern knowledge and analysis. And let’s be honest not everyone is going to master synoptic analysis. And that’s fine…there are lots of things I don’t know Jack about. 

Ya! Sure! LOL! The weenie in me hugs every snow depiction and finds heartbreak in every flip to nothing and milder! IT IS THE SEASON! :)

 

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2 hours ago, ldub23 said:

The  JB storms keep piling  up the snow. He  nailed  it  months ago

 

gfs_mslp_pcpn_frzn_us_63.png

Are you joking or not? If not then dude please lay off the JB praising. It’s like if someone said each month of the hurricane season would be dead then they got one right guess out of 10 wrong ones.

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