psuhoffman

Yes but that’s a chicken or the egg argument. One of the reasons the storm track is so far north (even during periods with a half decent pattern) is the warmth. Storms will ride the zone of best baroclinicity along the thermal boundary between subtropical air and polar air. When that boundary is up in Canada we’re screwed no matter what the steering currents are.

I am with Webb on this. The look being thrown out there...west based NAO with a trough west of SW of AK is our best snow look. It’s the most common look that came up when I studied every warning event. Without a block the trough in the north Pac would be a death sentence. But historically a -NAO has been plenty able to offset that and essentially what we get is all that pac energy crashing into the CONUS and being forced under the blocking with just enough cold. It’s not a cold look. Most of our snowiest periods were barely cold enough to snow. Frankly everyone wishing for these pac patterns that lead to arctic outbreaks...that’s NOT our snow look. That’s a cold dry warm wet look absent blocking. 80% of our snow comes in “barely cold enough to snow” blocking patterns with domestic cold sources. Yes getting a big huge epo ridge and a -NAO would be great...and some guidance even suggests that’s possible, but that’s also super rare. When you have a ridge on the NAO side there is usually going to be a trough on the Pac side. That’s basic wave physics. Only in rare instances where the TPV has been completely obliterated (and this year might end up that) can you get a ridge across the whole northern Hemisphere high latitudes. If that’s what we need to snow now...well I’d like to believe that’s not true. We already need so many moving parts to go right. But there will always be this one other thing we could point to and say “well that isn’t perfect” but imo keeping it real that look SHOULD work. I’m not saying it won’t. I think models are underplaying the cold. And HM pointed out the cold usually lags the SSW by 20 days. He also showed a graphic that clearly shows the warmth surge into the eastern US around the time of the SSW supporting the hypothesis we talked about yesterday. We probably just have to be patient. But in the end if we get a west based block I’m not going to just dismiss its failure as “well the pac” because in the past the pac look we have now was just fine with a -NAO! As for your second point wrt #bootleg I agree. I touched on this last night. I do think there is some truth to that point in that the warmth is biasing the NWP towards higher heights. But there is ample evidence it’s not just that. When you look at individual runs of OPs and control runs there is legit ridging and even a Rex block at times. So why are we to believe the ensembles have the same height pattern but not the blocking? Furthermore, at that range those are some crazy anomalies to explain fully by warmth. Lastly the pattern around wouldn’t fit. If that was totally due to pac warmth you would see a wave 1 look with a full latitude trough in the pac and a full latitude ridge in eastern N America. We do see that for a time when the NAO is east based and more of a WAR. But once it retrogrades suddenly you see a trough migrate east under the blocking. You wouldn’t see that if it was bootleg with that pac. And like you said smoothing at that range will mute the lines. At a specific time members have the ridge centered over Hudson Bay, some Baffin, some Davis, some Greenland. Timing and location differences will smooth out details. I respect their hypothesis and the one piece of evidence to support that theory is the pathetic temp response to the blocking however that can be explained in other ways (the temp base state on our side of the globe is just horrid right now) and the preponderance of all other evidence doesn’t support that conclusion imo. ETA: what made 2014 and 2015 work were rare oddities. A huge full latitude positively tilted EPO PNA ridge in 2014 and a crazy displaced TPV in 2015. Those were super rare and not typical ways we snow. I don’t want to rely on that 1/20 year type pattern to get snow.

This post isn’t specific to our snow chances. So hopefully everyone won’t freak out. It can still get cold enough to snow. That temp profile would probably work. Barely. Let’s also assume (because it’s scary not too) that is skewed a bit warm by some outliers. But what’s scary is that is literally the perfect pattern for us to be cold. Look at our source region...straight off the North Pole. The coldest anomalies in the northern Hemisphere are over N America and it’s weak sauce. Mostly -2 to -4 stuff. That’s it. And even that is bottled up on the Canadien prairie without the depth needed to press and spread southeast. @cbmclean pointed out how Asia and Europe have been cold, but their cold source is different. Siberia is a huge land locked high latitude region that is perfect to build deep cold. It’s one thing to see cold there. But even when we get cross polar flow on guidance and the “cold” shifts to our side...it’s not really cold. I’ve been watching this for a while and I’d like to see some evidence we can still build true deep arctic airmasses over North America without that once in a blue moon direct shot from Russia. And even then it seems to moderate quickly once out of the Siberian cold seeding grounds.

I’m optimistic. We will see.

@WxUSAF tonight’s op gfs I think is more indicative of what the ensembles are “seeing” then the bootleg heights issue. From 300-340 there is a full Rex block centered near the southern tip of Baffin with a 50/50 trapped doing loops under it. If anything that should be too much blocking. And yet it rains to Montreal during that period. There is no cold. The flow is blocked. The systems shear out. However...that is the first major longwave trough after the block retrogrades. Imo, like you said, if the blocking persists I think each subsequent wave will likely have a bit more cold to work with. The euro weekly ensembles, however, never quite get to that critical tipping point where there is enough depth of cold to keep storms from either waiting and cutting or shearing out. I agree that’s unlikely. But the gfs shows that it’s a “real” block...and still warm.

Yes...and this is what he was talking about. Get a ridge into the EPO (AK region) and it sends cold continental air down east of the Rockies into the central and eastern US.

I dunno. I’m sure the mean is biased positive some by the warmth near Davis but those are some strong anomalies to get at those ranges from just that. You will never see the ridge signature past 10-12 days due to smoothing on ensembles but when I look at most individual runs and the controls there is legit ridging and even a Rex block at times. Plus with the pac trough where it is we wouldn’t see lower heights into the central and eventually the eastern US in the long range without legit blocking. There would just be a wave 1 signature with full latitude trough on the west coast and a full latitude ridge in the east. I think past day 10 the blocking signature looks real imo. Will it actually evolve that way and can it overcome the pac and a scorched N Amer thermal profile though...?

Agree

We had a nice AO block in Dec though but it was centered northwest of a true NAO block. I respect Tombo and others who are saying it’s just higher heights but I respectfully disagree with that take. First of all it’s impossible to see the ridge in the height lines past 12 days or so due to timing and location differences between members. One might have the block centered over Greenland. Another Baffin. Another Hudson Bay. The ridge meanders around. Those differences smooth it out. Then you add in the outlier members and seeing a ridge signature at that range is not happening. But at the same time those kinds of + anomalies would be unlikely without a ridge somewhere. If it was weak + heights maybe. But to get those kinds of positives at those ranges given the smoothing and outliers would be almost impossible without a ridge somewhere on most members. Also we wouldn’t get lower heights across the CONUS with that pac if there wasnt true blocking. Add in the fact that the control has a true block and when I look at most operationals and individual members they do have blocking the evidence suggests that’s not it. I respect their hypothesis but I don’t see evidence of that. I think the simplest answer is the best. The pac is less then ideal. We begin the period with all of N AM torched. Despite a really good h5 look it thinks we never recover in that regard. History says domestic cold should work in that look. But the eps weekly members obviously think it’s just not going to be cold enough to keep storms from cutting. I think it’s wrong. I’ve seen it run too warm at range. We’ll see

Yea but 82 was very snowy in the mid Atlantic which is more common with a west based NAO block. Sometimes that can favor further southwest then NYC.

I think it’s just smoothing. I’ve never actually seen a strong ridge signature on the height lines past day 12 or so. It’s been the same on ensembles as you pointed out but when I look at the individual members most have a true ridge or even closed Rex block. Take the euro weekly control for instance. These are just a sampling. It pulses and wanes obviously. But looks like real blocking to me most of the run.

Except do you know how many snowstorms we’ve had with that look? We shouldn’t need a PNA ridge and a perfect west based block! Historically a west based block mid winter with a mediocre pac is just fine. I could show you the h5 from our snowiest period ever in 2010. The pac was garbage. I mean at some point all this “well that one thing isn’t totally perfect and that other thing was only 3 standard deviations not 4...” makes us sound like the people in the southeast that have to wait years to hope once every blue moon 25 things line up exactly perfectly to have a chance at snow.

Yea there is a huge disconnect between the h5 and the temps/mslp/precip anomalies/snowfall. Those details all look like a +NAO pattern as I said above. I doubt it goes down that way. But...if we do manage that h5 look and torch with a storm track through the lakes right through it...I think it’s time to be a bit alarmed at what our winter climo might be now.

This H5 equals these temps lol

It's worth noting...the snowfall does NOT align with the H5 look at all...frankly the pattern to the snowfall mean matches a +NAO look more with the greatest +Snowfall anomalies from the upper midwest through Ontario and Quebec. Those are places that usually are warm (for them) and dry in a west based NAO blocking pattern. That said...I will take the H5 look over anything else 100 times out of 100 on a long range prog. Guidance is way more likely to get the large scale longwave pattern correct then any of the synoptic and meso scale details that dictate snowfall. But again...doesn't mean its not worth pointing out the oddity. Let's hope its just an oddity.

Before anyone jumps off a bridge I do NOT take snowfall maps at range seriously....just was posting that for a LOL more then anything else. Of course...come March if we had a west based NAO block all winter and DC doesn't get ANY snow...we can bump this post.

Euro Weekly control manages to have this 30 day H5 look...and not give DC even 1" of snow! LOL I only looked because despite a "weenie" H5 look the snow mean was pretty blah...about 6" in DC and only 10" up here...thats actually below climo snowfall for that 46 day period. So I looked at the control for a clue...I guess if there are runs that manage not to give us ANY freaking snow with that look...lol

The last couple times a SSW obliterated the SPV when the TPV was already weak the ensuing blocking regime lasted quite a while. Even in 2018 when the SSW coupled it set off a -NAO for the next 2 months. Although that was much later so not a great comp. Still I doubt the TPV would recover quickly from this.

All 3 ensembles look the same and pretty good by day 15.

I’m not overly hopeful but wxusaf had a great point the other day. It’s always good when we can see the other side of a bad pattern before it even sets in. And I’ll add it’s always good when we are tracking, even low level threats, during the bad pattern. When I’ve gone back and read threads from good years like 2014 & 2015...there were dead periods and complaining (that should embarrass us looking back) even in those years. I’m not saying this is going to be a good year. But there are signs the base state isn’t totally awful this year.

I’ve noticed the para is a euro clone a lot.

A great look on one side should only require a mediocre in the other.

That's not even cold to boot Ok have it your way

All you do is show 384 hour maps lol That’s not true...sometimes it’s 500 hours

Omg cold anomalies...!!! Lol