December 2021 Medium/Long Range Discussion Thread

[Stormfly]

If it's not gonna snow let's do wind!  If we have a day or two without lights in exchange for removing 50+ cubic meters of oak and maple leaves I'm all for it!  Then again last Saturday my Tempest "haptic rain gauge" recorded a surplus of about 0.08" due to the impact of spruce needles which in its own is amazing since it sits over 40' above ground level!

Jan 26, 2011 event I don't want but a Jan 23, 2016 event sounds good.  We stayed all snow and got a nice band for the last few hours that netted 37" which was utterly amazing.

[mattie g]

4 hours ago, CAPE said:

If the advertised block is legit we should have a period of 'cold enough' and chances for storms to track under us.

Totally agree.

I’m going to start putting the junk posters on ignore.

[Eskimo Joe]

1 hour ago, psuhoffman said:

@Eskimo Joe2002 started nothing like this.  The pac was opposite. We did have a good Atlantic but the pac ridge was south allowing North America to get flooded with warmth. When the Atlantic backed off it was game over. This isn’t progressing the same way. Of course there are multiple paths to a fail here. 
 

Good points. I'm really trigger shy after the past few years where "good" patterns were kicked down the road into March and we were desperate for a 2" - 4" slopfest.

[psuhoffman]

13 minutes ago, Eskimo Joe said:

Good points. I'm really trigger shy after the past few years where "good" patterns were kicked down the road into March and we were desperate for a 2" - 4" slopfest.

I know. Fwiw last year the pattern went exactly how I thought it would when the blocking started to show and the likely progression became apparent near New Years. My 50” up here was about what you would expect. But for 95 every storm was just a few degrees too warm. Several were perfect tracks too. I said it wasn’t likely to be cold just “cold enough” but it was slightly too warm. I have to wonder if it was 20 years ago would it have worked out better and 95 would have had ~20” which is more fitting with a year I have 50”.  If that’s the case was it a pattern fail or a climate change fail?  

[Eskimo Joe]

16 minutes ago, psuhoffman said:

I know. Fwiw last year the pattern went exactly how I thought it would when the blocking started to show and the likely progression became apparent near New Years. My 50” up here was about what you would expect. But for 95 every storm was just a few degrees too warm. Several were perfect tracks too. I said it wasn’t likely to be cold just “cold enough” but it was slightly too warm. I have to wonder if it was 20 years ago would it have worked out better and 95 would have had ~20” which is more fitting with a year I have 50”.  If that’s the case was it a pattern fail or a climate change fail?  

On a local/regional level, I argue climate change. Urbanization is changing the built environment in the DC/Baltimore/Frederick/Leesburg area. More concrete, more roads means we hold onto temperatures more and it kills marginal events. I see this every day on my drive to work. You go from 34 degrees in West Friendship, MD then it shoots right up to 40 degrees when you get on US 29. We're shifting the climate of the planet and it's just a fact at this point. 

[StormchaserChuck!]

A while back I plotted most extreme -PNA and +PNA times (330+days , and 330+days, since 1948), PNA leads to samePNA out to like 45 days. Less of a signal at 45-60 days. We are so opposite of last year all the time, I'm expecting a Jan-Feb (reverse of 22-23 too) less -PNA (if that makes any sense). 

[IronTy]

14 hours ago, CAPE said:

I was referring verbatim to the GEFS output. One of us is wrong, er engaging in nonsensical hyperbole.

I went back and looked, he was actually referring to global anomalies on the CFS.  I have no idea if he is correct but there is a lot of blue.  

 

 

[baltosquid]

The trend on the ensembles at the h5 level for next week is pretty interesting. All three have some combination of the NS trough digging more, SW to our south getting stronger and the ridging we’re under moving west, allowing some colder air to reach us. Decent agreement on a 50/50 low being around. Ridging continues to retrograde into/over/past Greenland and northern Canada. Just flipping through the past few days’ runs for Wednesday/Thursday, particularly the EPS and GEPS, show how things can look more workable heading towards Christmas, or at least become more winter feeling with less ridiculously high temperatures. Maybe we can sneak in a tracking opportunity before the holidays. Very curious to see if the 12z ensembles continue the trend, particularly the EPS which really wants to build ridging in the west more than the others. If that could come to fruition, despite the strong trough off the west coast we could potentially avoid the worst consequences of that.

[Wonderdog]

7 minutes ago, baltosquid said:

The trend on the ensembles at the h5 level for next week is pretty interesting. All three have some combination of the NS trough digging more, SW to our south getting stronger and the ridging we’re under moving west, allowing some colder air to reach us. Decent agreement on a 50/50 low being around. Ridging continues to retrograde into/over/past Greenland and northern Canada. Just flipping through the past few days’ runs for Wednesday/Thursday, particularly the EPS and GEPS, show how things can look more workable heading towards Christmas, or at least become more winter feeling with less ridiculously high temperatures. Maybe we can sneak in a tracking opportunity before the holidays. Very curious to see if the 12z ensembles continue the trend, particularly the EPS which really wants to build ridging in the west more than the others. If that could come to fruition, despite the strong trough off the west coast we could potentially avoid the worst consequences of that.

A trend back to the GFS run of a week ago would work. 

[midatlanticweather]

A definite La Nina Trend here - DRY -> 

[WxUSAF]

Ensembles appear reasonably confident that the Xmas-New Years week will be BN in temps. Not dramatically so, but a few degrees F perhaps. Probably works out to low 40s for highs and upper 20s for lows in aggregate. But the dry trend remains with maybe a little more action right around New Years. Definitely not a big snow pattern, but one that could produce frozen with proper wave timing. That’s sort of been the crux…we want one wave to go through and supply sufficient cold air and then a close trailing wave with some moisture. Both have been hard to come by and the southern plains ridging cuts off Gulf moisture to a large degree. 

[WinterWxLuvr]

The problem is that even though ens at long range are better than op runs, they are still largely unreliable. Today’s 6z for 72 hours vs. the 6z run for the same time 7 days ago …

[BTRWx's Thanks Giving]

26 minutes ago, WinterWxLuvr said:

The problem is that even though ens at long range are better than op runs, they are still largely unreliable. Today’s 6z for 72 hours vs. the 6z run for the same time 7 days ago …

That's not always the case.  It's just some years the models are more chaotic.

[WxUSAF]

^you’re mixing longwave and shortwave comparisons there. At D10, shortwave positions all get averaged together and washed out. But at D3, they’re well forecast. That’s a pretty good D10 longwave forecast: most of the eastern CONUS is ridging.

[ldub23]

JB  has announced when the  cold arrives.

 

 

[SnowenOutThere]

3 minutes ago, ldub23 said:

JB  has announced when the  cold arrives.

 

 

Got it, now know which day to wear shorts.

[Wonderdog]

2 hours ago, baltosquid said:

The trend on the ensembles at the h5 level for next week is pretty interesting. All three have some combination of the NS trough digging more, SW to our south getting stronger and the ridging we’re under moving west, allowing some colder air to reach us. Decent agreement on a 50/50 low being around. Ridging continues to retrograde into/over/past Greenland and northern Canada. Just flipping through the past few days’ runs for Wednesday/Thursday, particularly the EPS and GEPS, show how things can look more workable heading towards Christmas, or at least become more winter feeling with less ridiculously high temperatures. Maybe we can sneak in a tracking opportunity before the holidays. Very curious to see if the 12z ensembles continue the trend, particularly the EPS which really wants to build ridging in the west more than the others. If that could come to fruition, despite the strong trough off the west coast we could potentially avoid the worst consequences of that.

A trend back to the GFS run of a week ago would work. 

[Wonderdog]

Well, GFS has a coastal developing next week but more work needs to be done.

[WxUSAF]

2 hours ago, WxUSAF said:

Ensembles appear reasonably confident that the Xmas-New Years week will be BN in temps. Not dramatically so, but a few degrees F perhaps. Probably works out to low 40s for highs and upper 20s for lows in aggregate. But the dry trend remains with maybe a little more action right around New Years. Definitely not a big snow pattern, but one that could produce frozen with proper wave timing. That’s sort of been the crux…we want one wave to go through and supply sufficient cold air and then a close trailing wave with some moisture. Both have been hard to come by and the southern plains ridging cuts off Gulf moisture to a large degree. 

For demonstration purposes, todays 12z GFS has this two wave scenario from hour 324-360.

Some front end stuff is also on the table and GFS shows that type of scenario as well after Xmas. 

[Baltimorewx]

2 hours ago, WxUSAF said:

Ensembles appear reasonably confident that the Xmas-New Years week will be BN in temps. Not dramatically so, but a few degrees F perhaps. Probably works out to low 40s for highs and upper 20s for lows in aggregate. But the dry trend remains with maybe a little more action right around New Years. Definitely not a big snow pattern, but one that could produce frozen with proper wave timing. That’s sort of been the crux…we want one wave to go through and supply sufficient cold air and then a close trailing wave with some moisture. Both have been hard to come by and the southern plains ridging cuts off Gulf moisture to a large degree. 

Yeah looks like day after Christmas might be a time to watch…maybe won’t be the best storm track but as that Christmas cold air retreats might be cold enough for some sloppiness if the storm is there 

[IUsedToHateCold]

I feel like this has to be the right direction for the Dec 23rd storm

12z versus 6z GFS

[WinterWxLuvr]

15 minutes ago, IUsedToHateCold said:

I feel like this has to be the right direction for the Dec 23rd storm

12z versus 6z GFS

I’d have to go with too little, too late and too warm

But I hope you’re right

[WinterWxLuvr]

2 hours ago, WxUSAF said:

^you’re mixing longwave and shortwave comparisons there. At D10, shortwave positions all get averaged together and washed out. But at D3, they’re well forecast. That’s a pretty good D10 longwave forecast: most of the eastern CONUS is ridging.

I’m confused by this. The map I posted was for the 10 day forecast for Sunday. Either the 10 day forecast or the 3 day forecast is gonna be pretty far off. They both can’t be correct.

[SnowenOutThere]

2 minutes ago, WinterWxLuvr said:

I’d have to go with too little, too late and too warm

But I hope you’re right

It is till 7ish days out but ultimately unless there is a huge shift in the guidance soon I fear you are right. We always have next year for a White Christmas.

[SnowenOutThere]

12z CMC has the pre Christmas threat far further north like the GFS and a nice all snow start to the potential post Christmas storm.

[WxUSAF]

50 minutes ago, WinterWxLuvr said:

I’m confused by this. The map I posted was for the 10 day forecast for Sunday. Either the 10 day forecast or the 3 day forecast is gonna be pretty far off. They both can’t be correct.

You’d assume the D3 forecast will be pretty close to reality. A D10 ensemble forecast shouldn’t really be used for sensible weather at a single point. It’s showing the longwave setup, which will give you a general idea on temp perturbation from normal and storminess. It’s showing that the eastern CONUS is probably warm while the west is cool/stormy. And that will probably be a decent look from D10. 

[WinterWxLuvr]

4 minutes ago, WxUSAF said:

You’d assume the D3 forecast will be pretty close to reality. A D10 ensemble forecast shouldn’t really be used for sensible weather at a single point. It’s showing the longwave setup, which will give you a general idea on temp perturbation from normal and storminess. It’s showing that the eastern CONUS is probably warm while the west is cool/stormy. And that will probably be a decent look from D10. 

Ok. I just have a different perspective on that. For me, the 10 day showed distinct ridging. The 3 day, while still slightly above normal heights, is a trough look in the east and slight ridging in the west. That’s a pattern that can more easily provide a cold shot/snow event than the 10 day, which could never produce snow.

[BristowWx]

Euro and GFS on different planets on Xmas..interesting..long way to go but getting closer

[Eskimo Joe]

 

[WinterWxLuvr]

Euro is not far off for Christmas