psuhoffman

So far...that TPV extension rotation through 50/50 is still there and maybe even stronger...but the two features diving around the back of the TPV are phasing earlier...thats potentially not good if the 50/50 feature moves out it could cut more.

Since my questions and tangents often seem to send the wrong impression...The 12z Guidance has been pretty good on the whole IMO. Don't let my quest to understand this one specific phenomenon skew the perception. I feel even better about our snow chances now than 2 hours ago. This is purely an attempt to understand something on my part.

@CAPE I have a theory but I wanted to see if anyone else has the same explanation before I put it out there. I am in no way confident in my theory... I am mostly just searching for WHY this same progression has happened a lot. And no the op gfs doesn't mean it WILL happen, but the fact its showing up means its still in there as an option and since its been happening often lately I am trying to understand. It's not something I saw a lot of historically. How can I forecast better if something new is happening a lot and I don't understand the why behind it?

Look at my last post...all those snows were in a -PDO.

There should be a trough there yes...but it should then get pushed east because of the EPO ridge dumping all that cold into the CONUS along with the blocking regime to the east...through history what happened was during a -PDO period that pac energy would crash into the SW, the NS energy would dive in above it, and then the trough would push east under the block. Look at this composite of the loading pattern before 5 of our big -PDO Nino snowstorms...this was the model for what I expected to lead to our snow this winter... Now look at that GFS run The only difference between the two longwave patterns there is the SER which is because that trough in the west digs to kingdom come, phases with the NS and cuts off instead of kicking east. That is what I am asking. The same longwave pattern in every way that used to lead to a trough in the east and snow threats has been leading to a HUGE SER lately. Why?

OK but people said that same thing a few times recently and then it happened. Maybe this time won't. I am NOT saying this is how I expect it to go down. But no one has ever answered WHY this keeps happening lately. Typically there is just a lot of "its a bad pac" nonesense, and its easy to get away with that because the pac has actually been awful most of the time the last 8 years with a Nina type dominant central pac ridge. But those fail periods don't bother me. Yea it sucked but when I saw the pattern coming in Dec 2019 and cancelled winter...I fully expected us to get no snow given the way the pac looked. That was expected. There are lots of other examples of those periods where yea it sucked to be stuck in a nina no hope pattern for us...but we SHOULD fail in that. But what bothers me is several times in the last 5 years we did get a period where the longwave pattern was GOOD and energy still dove into the southwest anyways. The problem was NOT the pacific, there was no huge central pac ridge...the longwave config there was good, but the same result. I showed this once last winter and no one explained it. How the pacific longwave configuration flipped completely opposite but yet the trough out west remained in the same damn place. The wavelenghts just shorted so the energy could still cut down into the SW regardless of what the upsteam pattern in the PAC was. That is what I want an explanation...why lately has there been a tendency for energy to cut into the west no matter what the Pacific longwave pattern upstream of it is?

@Bob Chill @Terpeast @WxUSAF @CAPE @brooklynwx99 Ok team...please save my sanity and help me understand WTF is going on here. And yes I know its a long range GFS op and unlikely to go down this way, BUT I have seen this actually happen several times the last few years so the point is why does this keep happening not whether this one run will or wont go this way. Look at this BEUTIFUL longwave setup Absolutely PERFECT pacific here, trough axis west of AK, huge beautiful EPO ridge, cut off pac energy (4) about to slide into the SW, old TPV sliding northeast towards the 50/50 space on the altantic side. Given the longwave pattern you would expect 1 and 2 to dig south into the plains and 3/4 to interact then slide east in this split flow. Right? But look what actually happens with 1/2/3/4 Depsite an absolutely PERFECT pacific AND atlantic longwave pattern, despite everything Ive' ever seen through history until the last few years...they all dive south/southwest and phase into a monster trough in the southwest somehow...dirictly UNDER the EPO ridge. This get's back to the argument I was having with chuck the other day where an EPO ridge has done us absolutely no good lately because instead of the cold coming in due to it pressing east which is historically what is supposed to happen, the wavelenghts just get incredibly short and whatever NS energy comes down just dives southwest and cuts off into the southwest UNDER the EPO ridge. It gets even more ridiculous from there So by the end of the run, dispite a picture perfect longwave configuration on both sides..a beautiful green land block, a perfect pacific and atlantic longwave configuration...we have a huge cutoff vortex in the west and a huge SER. Again...this is not to say this WILL happen...but I have seen this ACTUALLY happen several times the last 5 years or so. WHY? What am I missing here? Why is that longwave configuration leading to all that energy dumping into the west? I am tired of people just saying "its the pac" The pacific longwave pattern is perfect there...that trough shouldnt be there. Please help explain this.

12z GFS offered another way to fail lol....fails to phase threat 1. TPV stays west intially to suppress the next wave. Then it does slide east into the perfect spot...but a NS SW dives down from the north pole and dives southwest!!!! and phases with a system in California and cuts off on the west coast pumping a huge ridge in the east before anything else can come along. I have NEVER seen that before ever...a system that starts out over the north pole...with a trough in the east and an EPO ridge...dives southwest and cuts off along the west coast. WTF

it was close to a storm day 10 but just missed out on lining all the parts up. But it falls into the category of the GFS, doesn't phase the storm around the 17th so it rotates the TPV west and that is a suppressive look, it also could even open the door to another cutter if something were to phase. I know that sounds counter intuitive, how can it both be a more suppressive look AND more likely to cut. Because if you put the vortex over the upper midwest like that...any weak wave is going to get squashed. So we need something to phase for that to work. But if it does phase...with the trough anchored that far west...and without something in the 50/50 space to suppress the flow along the east Coast...the storm could cut north west of us. We are again, left needing more moving parts to go perfectly. And sometimes they do. Sometimes you just get lucky! But man I would feel way way way better if we could just get that TPV into the 50/50 space.

That took one of the craziest evolutions of all our HECS storms. A ridiculous 50/50 at exactly the right time despite a positive NAO, a 1040 arctic high in the exact right spot/time, and a STJ wave came along at the perfect time to take advantage but it was strung out initially so that it didn't push too far north as the block departed. There are no other examples anything like it among our 15" plus snowstorms and I would NEVER predict something like that again. Could we get a more modest overrunning event though, something like Jan 2004 comes to mind...sure. But the same general setup we need for a bigger storm is the same one for those. It's just in the lesser overrunning events we were lacking a stronger wave, or the confluence was too strong, or something went wrong to prevent a coastal from amplifying after the initial WAA precip, or like in the case of 2004 the coastal developed too late for us so we got WAA then missed out on part 2 of the storm.

I wanted to use last nights Euro to highlight how chaotic the period from the 15-22nd is going to be and why there is a lot of potential and several legit threads IMO but none are likely to resolved early on guidance. I know using an operational at that range for details is silly but all the ensembles agree on the same general pattern evolution and location of key features, the differences are all within the expected margin or error so in this case the euro op can show us what it COULD look like within the paradigm the ensemble guidance is hinting at. But I am NOT saying its going to look exactly like this...my point is actually with all the noise in the pattern there is no way any one run is going to nail all this, I just want to lay out some of the options. Look at the setup for the first threat next week on the euro Initially everything is anchored around the old weakening at this point TPV vortex, feature A. A strong NS SW, C, is rotating around behind while an STJ feature D is swinging by at the same time. A is way too far west for where we actually want it...but luckily on the euro the TPV is elongated east over the top with a feature B swinging through the 50/50 space and creates just enough suppression in the flow. The euro also perfectly phases C and D at almost the ideal spot for us. Without that none of this would work. There is also a kicker E. But look how noisy this is. These features are all interacting. This is not the same as if the vortex was out near 50/50 and left the playing field void of NS interference for some STJ wave to come along and attack the entrenched cold locked in by the 50/50. That is the simple nino path to a HECS and the one guidance can lock in on the general storm idea from 10 days out and we can reasonably get excited at long leads. This has potential, we have had many big snowstorms through history from a similar convoluted setup working out...but it can also fail easily if all these moving parts don't come together and there is no way in hell guidance will consistently show these features run to run correctly at range. For example lose the phase between C and D and its suppressed. Lose that feature B rotating through 50/50 and its a cutter. Change any one of these variables and the whole thing changes one way or another. And what happens with this sets up whatever comes after. Look at the op euro after this storm. This might be an even better setup for a big snowstorm here. But we are getting more NS interaction that ideal or normal for a nino. Look at A/B/C/D out west. How those all interact would determine how this goes. But the atlantic is so damn perfect here we simply need one of those to be dominant enough to dig. Our goalposts on the initial track of any wave ejecting from the west would be HUGE in that setup. But they could all run interference and squash each other during the 3 day window we have here where its perfect for something to come along. Or they could all phase out west and cut off and sit there until its too late. Ideally we would want one of these waves to eject as healthy as possible and slide east. But what happens with the first wave would determine if it even looks that way. The GFS doesn't phase C and D and so it weakly slides a wave off the coast...and the main TPV then doesn't weaken and get pulled into the new phased storm the euro has...and so it gets left behind to drop into the lakes and likely suppress and squash any chance we have for the window I showed on the op euro above. Looking across guidance...it seems we need a more phased solution from wave 1 to have a better chance at the next threat after. Whether that phased storm gives us snow or not...it pulls the old vortext east into the 50/50 and sets up a better scenario for around the 20th. So IMO we really really want to root for a euro win on that regardless of the eventual exact track of that storm. Hit or miss a phased bomb on that 16th storm sets up a better scenario after. But the main point is while this period has a lot of potential and I could see how we get back to back snowstorms...it also is crazy noisy and depends on a lot of NS moving parts that guidance is extremely unlikely to be correct on from any range at all.

Thanks for posting that discussion @CAPE

Some places that get banding will do ok but honestly yesterday I was looking at the midwest (I actually look at shit other than our back yard, I know cray cray) and observed even they are suffering some of the thermal issues we do. Obviously not to the same extent but the boundary is killing them too! In mid January with a 988 low taking theor ideal track, there is rain mixing at times along the lake fronts and surface temps in the mid 30s requiring heavy rates to accumulate. The snowfall results will be pretty pathetic across the region compared to what you would expect given the time of year, track, and intensity of the storm. I observed the same thing on my trip home from Vermont this weekend. At my friends house at 1400 feet there was ~16” with temps in the 20s. But I stopped in Bennington in the Valley Sunday evening and they didn’t have enough snow to cover the grass and it was 34 degrees! They had 2” of slop. Same story the whole way down. When I hit an area that got death banded near Poughkeepsie there was a foot of mash potatoes but places in between without elevation even up in interior New England looked like some Deep South 2” slush event. We are not the only ones having these issues lately. Luckily the longer this general pattern lasts and the deeper into winter we get (SSTs cool some) the colder the default air mass will get so I’m NOT cancelling winter. The pattern flipped right around Xmas. And each successive press of cold has been colder. Eventually we will have a window with a workable airmass and then we have to score! But winter is getting pushed back later and later which shortens our window and obviously since we would have less chances (single math) is gonna hurt our snowfall overall. I don’t agree Winter is extending. If you look back 100 years of records we’ve had past periods that snowed a lot in March. March has been snowier in comparison to early winter so it seems great but in reality it’s not getting snowier than it was historically. What is happening is March climo is being affected way less than Dec/Jan because the waters have cooled by then, so it makes it seem like it’s getting snowier in comparison because it’s not getting less snowy like other months. I probably butchered explaining that. Sorry. This year I am banking on the fact that in a Nino with the juiced STJ and a weak polar vortex we just need a couple weeks to cooperate to go big! We can absolutely dumped on quick if things line up in this kind of pattern. But in a year without a juiced up stj if all we get is a couple months to try to score all our snow it’s just not mathematically likely we get that much when other than ninos it typically takes 4 or 5 legit threats to score a big hit.

The same models runs that predict the mjo also predicted that look. You can’t separate one from the other. You’re choosing to believe the mjo forecast but not the rest of the output from the same run! Cherry picking. Besides the mjo is out of phase 4 by around Jan 17th. The mjo is likely why the guidance has a temporary breakdown of the pattern around Jan 22-28th. That’s the lag. A hostile mjo wave in mid January won’t cause February to be bad. Maybe Feb won’t be good but it won’t be because of what the mjo was on Jan 13-17th! It’s actually so ridiculous I honestly wonder if you’re trolling.

I was curious why the euro weeklies have such a low snowfall mean despite looking good. So I looked at the control. This 30 day pattern only leads to 3” of snow! Despite that look the snowfall remained pretty far north.

http://climod2.nrcc.cornell.edu

If you only look at the last 7 years DC snowfall has been more like southern NC or northern SC used to be.

I agree with this. That was why I used 2010 as the line. Maybe it is a shorter term cycle, probably some of that going on. But since 2010 DC has been more like NC used to be. And Richmond and RDU have become the "deep south".

That trailing "anafront" wave in December. It took a perfect track to give DC a nice little 2-4" snowstorm but was rain, boundary was just too warm, it was cold enough in the mid and upper levels. The boundary is warming faster than the other levels so this is what we will see more and more. And I don't disagree with your assessment, I don't think this past storm was ever a HECS or anything, but I think it would have been a nice 3-6" snow in a slightly colder base state. We haven't lost out on anything MAJOR yet but we are bleeding away all the little events that added up and made a decent year a good one, or a good one a great one. I didn't say we failed yet. We could still get some big storms to work out if we can actually get the WAR knocked down at some point. This could still end up good. But if it continues to fail with what has and looks to continue to be a good overall pattern that matches ones that produced a lot of snow...just saying we might have to consider it just doesn't work anymore.

That kinda just looks like what an ensemble at that range would look like smoothed v an op showing the same general thing. Yet mixed within that mean there are likely some better solutions...but it has all the main features centered in the same location and that TPV is still west of where we need it to give us a high probability for a snowstorm here.

Not yet but we knew coming in the concern. Nino patterns have historically been very snow...but also not very cold...and many of the snowstorms were in patterns that were marginally cold enough even in the past. Would that still work? We have had a couple perfect track rainstorms already. If that keeps happening we have our answer.

Now quite THAT bad...but I will stick this nugget here for reference... Since 2010 in the last 14 seasons DC has averaged 10.6" with a median of 7.8" From 1932-1990 Richmond VA averaged 14.2" with a median of 13.4" From 1930-1990 Greensboro NC averaged 10.6" with a median of 8.3 So since 2010 DC's snow climo has been like central NC was from 1930-1990

For now I am not. I think either we get things right and go on a tear or temps remain an issue and the rest of the season goes this way and we end up REALLY low...so no point changing. If we get to the "relax" with nothing AND the relax starts to look longer than expect that is when I will call uncle.

just a thought... we are about to get the canonical crazy blocking we expect at some point in a nino, but all the guidance is now targeting the upper midwest not the mid atlantic for the snow blitz we expect here. But...what if the warmer reality just means what we expect is happening...its just shifted north!

There were some key details that made that 0z run work. The TPV was elongated to the east as a lobe rotated around which compressed the flow some out ahead. Also, it split the energy of the trough diving underneath the TPV and had a trailing SW kicking the system east more. Those 2 little fluke details are what made it work because the trough axis is actually NOT good and the favored look for an amplified wave would be to cut too far west for us. And those little weird details are not something guidance could possibly get right from that range anyways. That's why I said this is not something I would feel optimistic in until very short leads. WIth the TPV there we would need some discreet details to break out way to mitigate the unfavorable trough axis with not enough confluence to our northeast .