ORH_wxman

Lavarock just saw this run

Yes, Dec 6-7 would be an overrunning/SWFE type winter system if it trends cold. The potential for coastal storms would be later into the pattern....most likely beyond 12/12.

To steal a term from Tip....when you have that type of arctic configuration, the "Correction vector" is colder for us more often than not.

The extremely amplified EPO ridge is often something that causes systems to trend colder inside of 7 days....we have been talking a lot about the developing monster NAO block, but in the early stages of that, we actually have a very stout EPO ridge dumping cold into Canada....see below.....this is what is starting to cause the flow to become flatter over the east....pressing the cold further south ahead of the Dec 6-7 system

Gotta hedge for being unlucky sometimes....we remember the good patterns that smoked us, but sometimes we have good patterns that don't produce...there's been some big disappointments in good patterns before (see Dec 1987, Jan 1985, Feb 2010 in SNE, Jan/Feb 1980) Man, the '80s sucked considering we had some good patterns, lol

2020-2021 def left some on the table. This year though, we do have significantly better blocking than that year had at least in December....we'll see how later in the winter goes. We also had a poor Pacific for the first 3 weeks of January 2021....even a neutral N PAC would've probably produced more snow events for us those first 3 weeks. Instead, we basically condensed winter in a 3 week period from end of January through mid-February....sans the 1 wintry week we had in December before the cutter from Dante's Inferno. Seems like you are going for a better N PAC in January than Jan 2021 had.

N PAC was also pretty damned ugly in Jan 2021 until later that month...once it shifted to a better look, we really went to town for about 3 weeks. The block also kept retrograding and became a Davis Strait block by the end of the month. We did have a bunch of close calls though earlier that January which easily could have been decent storms. That block essentially kept us from blowtorching all month....we didn't have any fresh cold, so it was still above normal, but if you recall, I think we struggled to get warmer than 40-45F in any of those days....most being in the 30s with lows in the 20s...minimums were a lot more AN than the maximums were.

Hard not to compare these two...people shouldn't expect the same results, but there's obviously potential

Full blown El Nino North Pacific look. I'm a bit skeptical it looks that nice, but the EPS were showing a more favorable PAC near the end of the run.

Yeah I think we want COD for the MJO right now after it passes through 8 and 1....no need to screw up a good pattern with some other variable.

Euro and EPS have really started compressing the flow after 12/5 so as Scott said last night, NNE may have to watch the 12/6-7 threat for more wintry solution. Still think SNE is skunked in that one but there could be a follow up threat around 12/8-9…and if that one doesn’t pan out there are likely to multiple additional threats beyond that. 00z EPS is a pretty loaded pattern.

I’m sure there will be OP GFS and Euro runs in the next week days that pop fantasy storms. It’s funny though how much hand-wringing there is over not seeing them consistently yet. GFS has shown some modest snow events out in clown range but the angst over no KU type storms showing up reveals just how much the operational runs are dopamine for some of the forum. Show me something inside 6 days, and then we’ll talk.

10 days a little short for snow threats if we're talking Euro OP....you're only out to like Dec 9 on the 10th day. I think msot threats would be beyond that date....save maybe if Dec 6-7 trends colder for NNE which is an outside possibility.

The PAC at the end of that run gives me hope that even if NAO starts to break down later in December, we won't go into a torchy pattern. That was a pretty weenie run of the EPS.

When it comes to ensembles, I usually look for a few things to be more confident: 1. Consistency.....are the runs more or less showing the same thing for several cycles in a row? 2. Timeline gets closer....is the pattern on the ensembles getting closer or staying out in clown range? Typically you want to see the pattern starting to get established inside of 10 days 3. Cross-guidance ensemble support. Are the EPS and GEFS agreeing with each other or are they showing different patterns? When you have multiple ensembles suites showing the same pattern, that increases confidence.

They will be quite a bit more accurate than operational runs though out in that time range.

I would also note that deterministic model guidance tends to perform quite poorly in high-magnitude blocking regimes...particularly during La Nina when storm threats are northern-stream dominant. But even just general longwave pattern verification tends to be worse in extreme blocking situations as per the literature on NWP guidance. I gave a presentation on this at the 2011 AMEX conference as it pertained specifically to east coast storms. The models were having a really hard time "seeing" storms more than a few days out. It was a decade ago, but same logic would apply. Models are better now, but their relative skill declines in these high latitude blocking setups. During that 2010-2011 winter. almost all the big storms we got hit by weren't well-modeled more than about 3-4 days out. The best one was probably the 1/12/11 event which was pretty consistent on guidance form 5-6 days out. But I recall plenty of storms that season where they were on model guidance 7-8 days out and then disappeared by 4-5 days out never to return, and then vice-versa....nothing at all and then they would show start showing up 4 days out. Boxing day was kind of a weird one in that it disappeared 3 days out only to return 24 hours out.

12z GFS could happen....I'd bet against it, but it's just one possibility out of many. Probably 70-80% of the possibilities will be pretty good for us. But there will be a small minority where things go belly-up like on the 12z GFS where it retros the NAO block almost into the arctic ocean and prolongs the SE ridging....but again, that is a weird deterministic solution 10+ days out so you'd bet against it.

Starting to get some weird cutoff scenarios on the OP GFS runs out in clown range. That is not uncommon with the type of block in place. You just hope you cash in on one of them.

Yeah. Late Feb/Mar 2010. That was the most recycled rotted airmass I can remember.

Didnt you poo-poo Feb 2013 and then two years later proclaimed that we would only get nickel and dimes?

Blocks this powerful typically last at least a couple weeks but the pattern beyond that is dependent on a lot of other things. In 2010-2011, the block hung around for over a month before breaking down during the 1/12/11 snowstorm. But the fun continued another few weeks because the Pacific became favorable and the Atlantic was still ok even after the massive block broke down.

Weeklies look good until near Xmas when they go to crap and stay that way into January. Take it fwiw....they've been pretty awful though this season...esp beyond week 2/3. They missed the upcoming pattern even just last week and they missed the mid-November flip.