psuhoffman

@showmethesnow better... The gefs made a slight move towards the eps at h5 at 6z I thought. I wonder if there is a way to get the first system to stay under us yet still get the TPV to exit east instead of a split and retrograde. I know I’m greedy.

I think that’s where this is heading but guidance might be rushing it a little. People will cringe at the pac but if the jet splits and cuts under that’s not a bad look. If you pull up the composite of some of our biggest storms the pac looks ugh. The blocking changes the equation. On the other hand look at Jan 1977 and everything looks “perfect” with a ridge bridge and perfect pac/atl and it was just frigid cold and bone dry. I’ll pass on that.

Thank you.

That was exactly what I was thinking.

CMC went north with the storm next week.

NC is going to love this gfs run. Lol

Gfs doubling down. Even more suppressive for the period after next weeks storm. 1047 high in the plains might try to suppress it

I know the MPAS utilizes a variable mesh grid on a global scale so that it depicts meso scale features without some of the boundary issues the regional models suffer from at longer leads. It’s also non hydrostatic I believe. I’ve not read anything about their accuracy wrt Rossby waves. Honestly you probably want to ask DTK or another NWP expert. I was never that into the NWP end of this other than to have a basic understanding of the physics behind it. You need to talk to someone who works on that end. As for what’s causing the TPV elongation and split on the euro...the tpv is caught in a squeeze play between the ridge to its north and south, and being tugged by the storm to its east and the trough to the west. The euro splits it. The gfs phases it into the storm to the east and because of that tug it squirts out to the east. Or the short answer. Shit happens.

It did but I didn’t want to go down that rabbit hole...yet.

I’m honestly not 100% sure how they calculate it now. I know when I was in meteorology at penn state in the 90s it was calculated as the differential in 1000 mb pressure anomalies between Iceland and the Azores. I guess then or now I never paid much attention because the actual look over the high latitudes matters more to us. We actually want a west based Greenland block not an east based Iceland one. And what is going on near the Azores doesn’t matter a whole lot to our snow chances typically. But using those 2 spots does usually give you a decent idea of the NAO regime but not as good wrt our specific snow chances as knowing how to interpret the h5 look. A ridge near the Azores can mute the numerical NAO index for instance. Here we are already improving in the AO domain from the big blue ball it was a week ago thanks to the EPO ridge building over the top. But the NAO is awful there But all guidance agrees on this look up top in a week. One possible reason the numerical NAO isn’t impressive is that it’s a west based block. Look at Iceland. Near normal pressure. Also perhaps there is a timescale curve and the previous very positive signal is muting it numerically. Not sure. Frankly don’t care. Those numbers aren’t as important to our snow chances as the location and orientation of the blocking. For example, several years ago during a Nina when I was doing research for the winter forecast I wanted to find out what accounted for the few anomalously snowy Nina periods. At first it was hard to pin because by numerical indexes nothing stood out. But when I went and looked at the h5 look for each snow I realized that almost every single one had some form of blocking leading into the event. But a lot of them the blocking was hidden on the numerical index because it was bootleg, or west based, or a Kara block not a canonical NAO. I hope this helped some. I don’t know if I explained it well enough. Sorry if I came off flippant earlier I didn’t mean to be.

The h5 look matters a lot more than that chart. Guidance all agrees with a west based block. Unfortunately most guidance ruins it with a hostile pac.

Massiello nailed the blocking episode mid month when he was all alone on that. Impressive.

I thought of that but since both ensembles generally agree with the respective op runs...and the features I was trying to show are clearer on the ops (not washed out) I went with that. I wasn’t trying to endorse an op run at range as likely. I suppose some will interpret it that way but oh well.

Unfortunately everything other than the gfs agrees with the euro progression so this is probably a moot point and we should root for whatever we can get from storm 1.

Instead of phasing the euro suppresses the system and the TPV elongates and splits but the major piece retrogrades west and feeds into the PAC trough. This pumps a full latitude ridge across north America and with no monster 50/50 its game over. We would eventually recover as that ridge lifts and the pacific energy cuts under but that would take a week or so.

I would bet its wrong, it also has an over amplification bias and that is more in play here, but it's the solution it comes up with day 5 that leads to that day 10 The whole sacrifice thing is just a mental exorcise since we don't get to choose...but I would root for the GFS progression. I doubt it is correct but if storm 1 phases with the TPV and pulls it under the block into a 50/50 position...that really does set up a classic HECS look. You can see the GFS scenario below The GFS phases the system into the TPV in Canada. This will amplify it, consolidate it, and pinwheel it east into a 50/50 location. This also prevents the TPV from pulling west and feeling into the trough along the Pac. This sets up the HECS look with a massive 50/50 under the blocking and very little of the TPV left in Canada to interfere and or feed into the western trough. That allows the energy out west to cut underneath. In the next post I will show what the euro does instead...

I agree our chances of getting some snow from this have gone up today. But I am not sure this progression is really what I want. I am probably on my own here...but the only way to get snow from this day 5 wave is to get a weak sheared out mess that gets suppressed. But if that happens...and all the guidance agrees on the great NAO blocking next week...but with that initial wave sheared and a non factor the TPV splits and a peice of it rotates east and out and another piece feeds into the western trough and with that setup we will torch just in time for xmas. It won't be prolonged, the jet would cut under and by New Years we would be back in the game...but no mistake we would be torching xmas week. Now with the GFS idea of a more phased system, the TPV remains more intact and pinwheels around to our north before exiting east whole...creating a monster 50/50 low to suppress the pacific flood plus not as much of it breaks off to feed into the pacific trough... the end result is a colder look leading into xmas and a storm threat with the next wave, and possible a bigger storm threat than this one. Now...I know sacrificing some snow for a lower probability of snow later is usually a big no no...but given the implications for the holiday...who would rather sacrifice the chance of a 2-4 type event now knowing it comes along with the probability of a 60 degree xmas for a chance at a bigger storm and a cold look around xmas?

^fringed

Hell of a block

I’ve not seen but I doubt it’s significantly degraded. Maybe @dtk can clear that up.

@Bob Chill FWIW 6z EPS was a big shift south at 144 from 0z 0z 6z like this look...

I didn’t know that was an option...

I know it has decent scores but I can’t remember a time when it was on its own showing a snowy solution (and it does that a lot) and was correct. Obviously it has some support right now just making an observation.

@showmethesnow about time... my coffee was getting cold waiting on my morning status briefing.

Some of the best analogs to the current combo of QBO, ENSO, PDO, and AAM were in the 60s. But I tossed them because that period featured such a persistently -NAO that it’s dangerous imo to use those years to set expectations. But if the NAO tanks all bets are off.