December 2019 Med/Long Range Disco

[Amped]

1 hour ago, osfan24 said:

That was exactly my thought when I saw it, too. I could go for that again.

Produces a very similar snow shield.  The FEB 2010 storm had a 50/50 low much further west,  and the ridge didn't fold over into the lakes like that.  I'd give this one a more 2016/ 1983 hybrid look. It would easily close off H5 and match 2016 if the kicker was 12 hrs slower.

[frd]

4 minutes ago, psuhoffman said:

uidance all agrees with a west based block. Unfortunately most guidance ruins it with a hostile pac.  

I wish once this winter we get all the players to combine. I am not getting any younger.  

I found my snow shoes in the basement under the ping pong table this weekend , maybe that is a divine sign of things to come. 

[Buddy1987]

@psuhoffman I have a question and Idk if it is beyond your or Bob's pay grade. So with my very limited knowledge the Model For Prediction Across Scales (MPAS) is supposed to help be able to help smooth things over top of TPVs and be able to more accurately predict these things beyond 6 days as that is the bar per say on where forecasting almost becomes a crap shoot per say for predicting these things. Do Rossby waves also have an effect on them to where you end up with a Euro or Gfs solution, both being polar opposites of an outcome imo? Basically very long story short what would ultimately cause the TPV to elongate or remain intact per say and do you feel like this is what is going to cause the ultimate outcome in the H5 pattern to get us a MECS or a heatwave for dec standards?

[CentralVaNATS]

CPC NAO outlooks range from "hmm" to "ugh" with a mean of "meh".     

 

 

I dont pay to much attention to that graph as it always waffles to +1 and then -1. Non-existent and always neutral overall but the H5 much more important in the 7 to 10 day range. Will watch for over running events for this winter and cutters, then will get our unicorn, KU Storm. Unless HH GFS materializes from the 18z run. Sent from my SM-N960U using Tapatalk  

 

 

 

 

 

 

 

 

 

[WinterWxLuvr]

The gefs and the eps are slightly different in their depiction of 850 temps at 10 days. Just a little different 

[psuhoffman]

27 minutes ago, cbmclean said:

Well that is what confuses me.  The chart mentioned that it is defined at 500 hp as opposed to the older 1000 HP.hp.  So are you just saying that the index, at whatever level it is taken, only gives a very rudimentary approximation of the state of blocking?

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. 

[psuhoffman]

16 minutes ago, losetoa6 said:

Off run and all but Eps looked to take a baby step towards the Gefs looking at hr 144 . 

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

[cbmclean]

17 minutes ago, psuhoffman said:

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. 

Yes, it is actually very helpful.  I really appreciate your taking the time to pass along this knowledge.

It will be a shame if our nice west-based block is wasted by blocking in Pacific poop. 

[psuhoffman]

58 minutes ago, Buddy1987 said:

@psuhoffman I have a question and Idk if it is beyond your or Bob's pay grade. So with my very limited knowledge the Model For Prediction Across Scales (MPAS) is supposed to help be able to help smooth things over top of TPVs and be able to more accurately predict these things beyond 6 days as that is the bar per say on where forecasting almost becomes a crap shoot per say for predicting these things. Do Rossby waves also have an effect on them to where you end up with a Euro or Gfs solution, both being polar opposites of an outcome imo? Basically very long story short what would ultimately cause the TPV to elongate or remain intact per say and do you feel like this is what is going to cause the ultimate outcome in the H5 pattern to get us a MECS or a heatwave for dec standards?

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. 

[psuhoffman]

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

 

[psuhoffman]

NC is going to love this gfs run. Lol

[StantonParkHoya]

We might end up warm around Xmas, but GFS wants to send us into the freezer next weekend.

[cbmclean]

4 minutes ago, psuhoffman said:

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

 

I have seen several posts recently showing damning evidence of notable cold bias for the east on NCEP products (can't remember if it was GFS or GEFS, or maybe both).  At this point, do you see any reason not to conclude that the GFS op if on on its own little fantasy tangent and can be safely discounted? 

[Maestrobjwa]

1 minute ago, psuhoffman said:

NC is going to love this gfs run. Lol

Man just the thought of that happening two years in a row...*rips hair out* Thankfully it's a far away fantasy as of now, lol

[cbmclean]

Just now, Maestrobjwa said:

Man just the thought of that happening two years in a row...*rips hair out* Thankfully it's a far away fantasy as of now, lol

Hey, what's wrong with that thought?

Seriously though I'm not going to be a rude guest in another forum and try to advocate for my backyard.  I dream of a big one where we all get slammed.  I think it happened back in the great 1899 cold outbreak.  That should score high on Maestrobjwa's WDI.

[psuhoffman]

CMC went north with the storm next week. 

[dallen7908]

... am at the AGU meeting this week and I "snuck out" of my session to hear a talk on the Unified Forecasting System: Some highlights:

Version 15.1 of the GFS officially became operational on June 12th of this year.  It has a 13 km horizontal resolution and 64 layers.  Data are assimilated at a 25 km resolution. Version 14 was retired on September 30.  A minor change was made to the GFS in early November.  It is now assimilating additional data sets including information from GOES-17. 

Version 12 of the GEFS is scheduled to become operational in August 2020.  It will have  the same dynamical core as version 15 of the GFS and its resolution will increase from 40- to 25-km and will include 31 members as opposed to the current 21.  The system will be run 4 times per day with the 00 UT run being 35 days in length and the other runs 16 days in length. 

Apparently, the ensemble system has skill out to 10.4 days versus 9.8 for the current system with 2-3 hours of the additional skill due to the additional ensemble members. 

The next version of the GFS (version 16) is scheduled to become operational in January 2021.  It is in the pre-operational stage now but has been frozen.  It should have 127 levels compared to the current 64 and has bias fixes including (hopefully) one for the lower tropospheric cold -bias.  Not sure what the fix is.

Version 13 of the GEFS is scheduled to become operational in FY2023.  It should be a "fully" coupled system that includes an ocean model, a wave model, an aerosol model etc. 

 

 

[cbmclean]

10 minutes ago, dallen7908 said:

Apparently, the ensemble system has skill out to 10.4 days versus 9.8 for the current system with 2-3 hours of the additional skill due to the additional ensemble members. 

What is the definition of "skill" in this technical context?

[yoda]

FWIW, 00Z EURO still likes Monday afternoon into Monday night... 2 to 3 inches of snow

[showmethesnow]

2 hours ago, dallen7908 said:

 

Version 12 of the GEFS is scheduled to become operational in August 2020.  It will have  the same dynamical core as version 15 of the GFS and its resolution will increase from 40- to 25-km and will include 31 members as opposed to the current 21.  The system will be run 4 times per day with the 00 UT run being 35 days in length and the other runs 16 days in length. 

 

Considering the effect that chasing Day 10-16 unicorns has on Ji, following Day 25-35 ones is going to launch him into a padded cell. 

[mappy]

....wrong thread guys

 

[mappy]

3 hours ago, yoda said:

FWIW, 00Z EURO still likes Monday afternoon into Monday night... 2 to 3 inches of snow

2-3" would include sleet too

[anotherman]

[CAPE]

0z EPS continues to expand the area of lower h5 heights eastward across much of the US under the HL block. 

Fwiw, temps around Xmas are average to a couple degrees above. With this look, the following week would be moderately colder. No super cold air in our source region though.

 

[showmethesnow]

The differences on the overnight runs gave a good example of how much the PV and its interaction (or lack of) with the mid-latitude trough will influence our region with the day 5 storm.

The GEFS below shows that the PV is interacting quite a bit with the trough and this can be seen if you follow the negative departures and how strong they are connecting the pv to the trough. This is sinking the isobars in the upper portion of the trough so naturally the ridging to the east in it's upper portions are getting bumped up as well.

 

But we aren't seeing that with the EPS. Though we are seeing a little influence to the trough from the PV we are seeing more of its energy diverted eastward. This is effectively knocking down heights in NY up into Canada giving us a flatter flow through that region. This will tend to provide resistance for our storm to move northward.

 

 

Looking at the surface of the GEFS you can see how this influences the storm. With a more N/S alignment to the front of the trough the low is given more room to strengthen and pull northward.

 

But we aren't seeing that with the EPS. With the blocking setting up in NY/S Canada we are seeing resistance to the lows northward movement. So we are seeing the storm initially move into the general area of E Kentucky/Tenn after that is where the questions come in. Chances are good we would see a transference to the coast somewhere at this time as the low meets too much resistance with the blocking up top. How far the initial western low gets northward as well as where we see the coastal take over will play a big part on what we can expect through our region. Needless to say the northern portions of the region would be favored for the initial WAA loft snows whereas the eastern portions for any possible coastal development. Of course we would more then likely also encounter the dry slot between the two lows that we often see occur as the low transfers. Another wild card here is that we are now seeing the trough just to the west of this low which could also throw a surprise in there. Still a lot of questions to be answered, many of which won't be resolved for a couple more days, but at least the EPS has us in the game.

 

 

[showmethesnow]

14 minutes ago, C.A.P.E. said:

0z EPS continues to expand the area of lower h5 heights eastward across much of the US under the HL block. 

Fwiw, temps around Xmas are average to a couple degrees above. With this look, the following week would be moderately colder. No super cold air in our source region though.

 

 

Was looking at the EPS thinking that it wasn't really grasping the idea of how a CONUS wide PAC torch should be run. Despite the modest warm anomalies we are seeing I saw some potential opportunities in the mix.

[psuhoffman]

1 hour ago, C.A.P.E. said:

0z EPS continues to expand the area of lower h5 heights eastward across much of the US under the HL block. 

Fwiw, temps around Xmas are average to a couple degrees above. With this look, the following week would be moderately colder. No super cold air in our source region though.

 

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. 

[CAPE]

1 minute ago, psuhoffman said:

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. 

Yeah as we well know, the "perfect" h5 looks often don't produce. I will take a -AO , a west based -NAO, and a mediocre PAC with a warm neutral/Nino background state and roll with it.

[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. 

[CAPE]

6 minutes ago, psuhoffman said:

@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'm ok with the advertised EPS progression even though it does dump a piece of the TPV into a developing EPAC trough. Its not a warm pattern by any means as depicted, and as long as the HL blocking is real, it wont necessarily be a shutout period either. As is verbatim, there would be a few days centered on Xmas with temps near/slightly above average for our region.