Met Winter 20-21: Pattern Drivers & Evolution

[Dsnowx53 11,792]

5 hours ago, 33andrain said:

It's great to see @Dsnowx53 online. Doug, we always welcome your thoughts we miss your participation.  

 

 

Hey all! I'd be lying if I could guarantee that I'll be posting in here as much as usual (I'm way busier now, I barely even ever tweet anything weather), but it's great to be back in here as we move into winter!

 

5 hours ago, rb924119 said:

Lots of great discussion in here over the last couple of days regarding the evolution of the extended. I wish I could add more, but I will say the following: I am still hesitant to get excited about any prolonged BN regime, and even significant snow prospects, in our area, and agree with @Analog96 in that I can see us averaging out near, maybe a little bit above average (i.e. something like 0-2° above average) during the next two weeks (or so). Even though I like seeing a 70/70 ridge trying to pop and the trough axis does seem to be backing off a bit, I fear that the modeled Aleutian trough will end up fracturing as we get closer in time and end up as a parade of troughs, with any amplitude that we do manage to see out west stunted by anti-cyclonic wave breaks over western North America and ridging then blasting along/near the U.S.-Canadian border as the energy trapped beneath is forced to ball up. Then, as one remnant ridge top evacuates to our northeast, the system will begin gaining latitude to our west. There’s just so much zonal momentum in the mid- and high-lat belts right now, coupled with generally unfavorable tropical forcing, I can’t see a prolonged and favorably amplified pattern taking hold.

 

Hopefully that makes sense, but I can’t elaborate further because I’m at work lol

 

I do think a lot of these concerns make sense, considering the high-latitude pattern still looks pretty poor, and the Pacific Jet will still have a good amount of background west to east momentum. Could make the aligning of the streams difficult, and I could see how this "mistiming" of streams with the flow splitting could lead to a Southeast US system as @Webberweatherwas alluding to. 

 

Regardless, though, these trends have certainly been nice to see on model guidance, and the EPS is not too terribly far off from the GEFS now, further evidencing that the MJO differences on the RMM plots between the GEFS and EPS is not necessarily making the GEFS solution erroneous. There's more going on here than what those plots dictate.

 

Despite the strong La Nina, I also never found an analog that I liked for this winter. A lot of the broader background signals looked pretty crappy as far as winter is concerned, but considering how we are already significantly deviating from the strong La Nina base state -- at the time of year when ENSO arguably has its strongest influences -- at the very least adds a lot more unpredictability to this winter than what has been implied. I'd much rather that than just locking in a torch for 3 months, that's for sure.

[Ace 808]

8 minutes ago, Dsnowx53 said:

I do think a lot of these concerns make sense, considering the high-latitude pattern still looks pretty poor, and the Pacific Jet will still have a good amount of background west to east momentum. Could make the aligning of the streams difficult, and I could see how this "mistiming" of streams with the flow splitting could lead to a Southeast US system as @Webberweatherwas alluding to. 

 

Regardless, though, these trends have certainly been nice to see on model guidance, and the EPS is not too terribly far off from the GEFS now, further evidencing that the MJO differences on the RMM plots between the GEFS and EPS is not necessarily making the GEFS solution erroneous. There's more going on here than what those plots dictate.

 

Despite the strong La Nina, I also never found an analog that I liked for this winter. A lot of the broader background signals looked pretty crappy as far as winter is concerned, but considering how we are already significantly deviating from the strong La Nina base state -- at the time of year when ENSO arguably has its strongest influences -- at the very least adds a lot more unpredictability to this winter than what has been implied. I'd much rather that than just locking in a torch for 3 months, that's for sure.

 

Deviation from the base state seems to be a common theme recently. What comes to mind is @earthlight tweet from late October highlighting one aspect of this (pattern observed in Sep/Oct). Expectations are low, but as always with seasonal predictions, there is a layer of unpredictability, perhaps this year more so than others.

 

[Analog96 7,570]

21 minutes ago, Ace said:

 

Deviation from the base state seems to be a common theme recently. What comes to mind is @earthlight tweet from late October highlighting one aspect of this (pattern observed in Sep/Oct). Expectations are low, but as always with seasonal predictions, there is a layer of unpredictability, perhaps this year more so than others.

 

Looks like more cold air seepage this year FWEIW.

[OHweather 2,020]

I will post the rest of the technical write-up during the day Saturday (it's too much for me to proof right now), but here is the month-by-month summary and maps at the end of my personal winter outlook. My apologies for being a bit tardy, but I've been busy and this took a while to put together. It's almost easier to do this in October, as enough happened this month to change the outlook and add quite a bit to the technical discussion.

 

December:

 

 

A +PNA to end November and start December leads to a very mild / warm start to the month across the CONUS (slightly cooler over the Southeast / East Coast)…however, an active STJ and a wavier pattern than the ensemble means will show at this distance may allow for enough polar influence for an opportunity or two at a winter storm across the central or eastern U.S. Given the +PNA and active STJ, this may occur in areas such as the Ohio / Tennessee Valley, Appalachians, Southeast or Mid-Atlantic, farther south than what you may expect in a La Nina and more typical of an El Nino. A +PNA, split flow, and active STJ are features that are frequently seen in an El Nino!

 

This window is brief, the first week or so of the month and with a questionable amount of polar air to work with, so it may not work, but there should be a bit to track on the models as this comes into range. Thereafter, the SPV moving away from Alaska, persistent +EAMT, and convection getting into the 120-150E area (and likely persisting a bit more as the GEFS has due to the lower frequency forcing in that region this fall) likely allows for a window of -EPO, and a pattern more typical of a December La Nina. I think there’s still enough momentum in the Pacific jet that this dumps into the Midwest and Northeast as opposed to the Rockies and Plains as typically occurs with EPO shots.

 

This trends towards cold edging towards the Northwest / northern Rockies into late December, with a Southeast Ridge cropping back up due to forcing becoming more focused on the Indian Ocean, and due to Indonesian convection beginning to teleconnect to a Southeast Ridge in later December.

 

With the start of end of December quite possibly warm for a large portion of the country, the month as a whole will be mild across the CONUS.

 

While I think the NAO likely ends up positive for the month, if we take advantage of the potential to develop a -NAO in early or mid-December, it would up the ante for snow in the Northeast and Mid Atlantic in that window, and may slow the warm-up later in the month. Even without a -NAO, I think there are opportunities for some snow in December in the central and eastern U.S. (even the southwest may have a window with the STJ, the NW and Rockies will be active and trend colder later in the month as well).

 

January:

 

 

January may start cold in the Northwest U.S. and warm across the southern and eastern U.S. However, I think the MJO has another opportunity to propagate east during the first half of the month. I believe the PV will be weaker and more receptive to the MJO producing a blocking response than it is in early December. This may cause another period of -EPO, -NAO, and a somewhat active sub-tropical jet for a couple of weeks starting the first or second week of January. This will bring another window of winter farther southeast towards the Ohio Valley, Mid-Atlantic, and perhaps even the Southeast.

 

I think we start trending towards a Southeast ridge later in January as the MJO fades and Indian Ocean forcing crops back up. How much blocking develops in the first half of January will of course influence how quickly this warm-up occurs.

 

February:

 

 

This is generally the warmest month in the analogs, with an amped central Pacific ridge dumping cold into Alaska, western Canada, and the northwest / north-central CONUS. If we have persistent Indian Ocean forcing and a strengthening PV to open the month, that will probably be the case again this year. If there’s cold available in Canada, the +NAO may lead to confluence east of New England that leads to high pressure over eastern Canada that can cause cold air to seep down into New England and perhaps the Great Lakes in February, causing some wintry threats in these areas…however, the pattern I envision for February is not snow-friendly in the Ohio Valley, and especially the Southeast and Mid-Atlantic.  

 

March:

 

 

Cold air likely remains available in Canada, so if the MJO becomes active again in late-February or March it may shake-up the pattern enough to bring it south and bring one last shot of winter in March. If this does not occur early enough, the Southeast Ridge dominates much of March and keeps the cold over the Northwest, Plains, and Midwest / northern Great Lakes / northern New England.

 

Seasonal snow:

 

 

EDIT: Here is a link to the entire technical discussion: https://jimsullivanweather.com/2020/11/21/jim-sullivans-2020-21-winter-outlook-write-up/

[PB GFI 37,670]

12 hours ago, PB GFI said:

 Nice correction on the EPS here 

 

 

 

 

 

 

 

 

What a way to run a warmup huh.

 

I think NNEs 1st snow is in this pattern.

 

[33andrain 61,338]

13 hours ago, Dsnowx53 said:

 

Hey all! I'd be lying if I could guarantee that I'll be posting in here as much as usual (I'm way busier now, I barely even ever tweet anything weather), but it's great to be back in here as we move into winter!

 

 

I do think a lot of these concerns make sense, considering the high-latitude pattern still looks pretty poor, and the Pacific Jet will still have a good amount of background west to east momentum. Could make the aligning of the streams difficult, and I could see how this "mistiming" of streams with the flow splitting could lead to a Southeast US system as @Webberweatherwas alluding to. 

 

Regardless, though, these trends have certainly been nice to see on model guidance, and the EPS is not too terribly far off from the GEFS now, further evidencing that the MJO differences on the RMM plots between the GEFS and EPS is not necessarily making the GEFS solution erroneous. There's more going on here than what those plots dictate.

 

Despite the strong La Nina, I also never found an analog that I liked for this winter. A lot of the broader background signals looked pretty crappy as far as winter is concerned, but considering how we are already significantly deviating from the strong La Nina base state -- at the time of year when ENSO arguably has its strongest influences -- at the very least adds a lot more unpredictability to this winter than what has been implied. I'd much rather that than just locking in a torch for 3 months, that's for sure.

Doug - It's great to hear from you and I think we can all agree that it's better to be tracking potential flies in the ointment of warm Winter guidance than knowing going in that we will have a Winter roast like 2011-12 with a raging east-based Nino. Look forward to tracking with you and everyone over the next few months and we will welcome any insight you might be able to share along the way. Cheers.

[PB GFI 37,670]

On 11/21/2020 at 7:38 AM, 33andrain said:

Doug - It's great to hear from you and I think we can all agree that it's better to be tracking potential flies in the ointment of warm Winter guidance than knowing going in that we will have a Winter roast like 2011-12 with a raging east-based Nino. Looks toward to tracking with you and everyone over the next few months and we will welcome any insight you might be able to share along the way. Cheers.

 

I expect the 1st tracking for western NY all the way to NNE in the 10 to 15.

 

 

And I think the GEFS makes the most sense in the east in the longer range with those heights pulled that far west into the Aleutians and a trough into Europe.

 

 

The trough " should be " in the east.

 

The EPS washes the trough out at 500, but it's SD is seeing where the main features are and does not respond in the east. 

I like the GEFS because that ridge axis is just west of the Rockies and the Euro agrees with it.

 

 

 

 

 

 

[NJwxguy78 24,016]

@Dsnowx53

 

 

wow!

[Allsnow 34,849]

This is fun 

[leo2000 184]

Very interesting indeed!

 

 

#ssw signs seems ahead in December....

@judah47

 

 

[33andrain 61,338]

7 minutes ago, leo2000 said:

Very interesting indeed!

 

 

#ssw signs seems ahead in December....

@judah47

 

 

Yes. A disclaimer however... he says this every year and relies only on GFS guidance. Rarely does it materialize, and even if it does it doesn’t mean it favors us. 

[NJwxguy78 24,016]

13 minutes ago, leo2000 said:

Very interesting indeed!

 

 

#ssw signs seems ahead in December....

@judah47

 

 

 

He is also a member here and we are more than happy to grant him the space to expand on his ideas.

[Allsnow 34,849]

13 minutes ago, 33andrain said:

Yes. A disclaimer however... he says this every year and relies only on GFS guidance. Rarely does it materialize, and even if it does it doesn’t mean it favors us. 

[Armando S 2,177]

Hey all!

 

I apologize for my absence as i'm currently in the "heat" of finishing up my undergrad, working on some side projects, and working with my advisor regarding, well grad school; that is a discussion for another time. To say i've been busy is an understatement, but nonetheless I thought why not jump right into this great discourse going on from catching up!

 

1. I already see the discussion heating up for early Dec. wintry fun prospects and shenanigans, so I wanted to further add a technical component to it from my perspective with some higher predictability confidence utilizing a AAM framework. We're going to see, probably our biggest +EAMT of the season given its current state of nearly 2 S.D's below normal. So, we're likely going to see a big rebound, hence why you can see via my animation of a large +MSLP that'll descend some of the largest mountain ranges in the world (Himalayas, Mongolian mountains, and Tibetan plateau). We're also approaching the special time of year (our favorite!) where baroclinic and diabatic forcings become maximized in conjunction with the seasonal alignment. A pacific jet extension --> retraction -> meridional downstream flow results. Throw in a surge (recently and currently proved) of building NA snowpack and now even a "NINO" early Dec look with some split-flow action (STJ), and we have ourselves a little window here for early-mid Dec.

 

2. RMM indexes also have largely underestimated a robust MJO wave currently propagating through the IO and into the MC. This synoptic-scale eddy forcing this +MSLP feedback on the tropical convection and the MJO's circulation, which actually is consistent with research that it even enhances it as it propagates through the MC and into the W.Pac (just look at that 5sigma -VP200 signal!). Also, dprog/dt last 18 runs of GEFS just to illustrate this adjustment we're seeing in NWP. There is obviously the pertinent little caveats and uncertainties regarding all of this and how this plays out "in our backyards", but nonetheless, it's at least exciting to see this development unfold and I concur with so many on here and long-range forecasts regarding December (Dec offers some good potential). 

 

Looking forward to this much NEEDED break from academia and hopefully will be tracking in December! 

[NJwxguy78 24,016]

@Armando S!

[HVSNOWSTORM 76]

On 11/20/2020 at 8:00 AM, PB GFI said:

It's nice to see the small EPS correct towards the cooler regime in the E US this morning.

Hopefully that trend can continue 

 

Notice if you stick the trough Fairbanks you drive the ridge through the GL.

Map compliments of 

@Webberweather

 

But when the negative can retrograde back towards the Aleutians, you center the ridge further W and open up the EC trough. 

 

The 6z GEFS really deepens the trough after this on the EC.

 

 

I agree with Grace. Probably a N temp regime but not the plus 5 it has been showing. 

For December,  I can deal with average, don't need extreme cold regime to produce snowfall off the coast in the Mdtl/ NE.

[leo2000 184]

1 hour ago, 33andrain said:

Yes. A disclaimer however... he says this every year and relies only on GFS guidance. Rarely does it materialize, and even if it does it doesn’t mean it favors us. 

But here is the catch it's not him saying it. It's coming from a Polar Vortex reseacher. He also doesn't only rely on GFS guidance. 

 

NOAA CFS modeling hinting at potential first-of-season stratospheric warming event by the third week of December.

 

 

[Analog96 7,570]

3 minutes ago, leo2000 said:

But here is the catch it's not him saying it. It's coming from a Polar Vortex reseacher. He also doesn't only rely on GFS guidance. 

 

NOAA CFS modeling hinting at potential first-of-season stratospheric warming event by the third week of December.

 

 

The CFS is based off GFS parameters.

[CCB! 29,886]

9 hours ago, leo2000 said:

But here is the catch it's not him saying it. It's coming from a Polar Vortex reseacher

Thank you for pulling some of that content & posting here, the more maps the merrier - Though I'd be wary of these sources & associated credentials. I'm not sure I'd label "pv-forecast" a researcher. I appreciate their posts from various pieces of guidance. But there's not much research going on there. It's mostly raw model output with little to no context, usually anything remotely pointing to a ssw is the modus operandi from what I've gathered. Nothing wrong with that though I might add!

 

You'd rather see signs of the SPV taking hits & potential ssw's on guidance than not, that's for sure. But similar to the tropospheric wave guide charts beyond day 7, the stratospheric modeling should be absorbed with some skepticism & is arguably even less reliable. 

 

Beyond that, some really great discussion in here over the past few days! Great to see some long lost forum favorites dropping in with "the goods" alongside the usual top notch crew! I especially appreciated @Dsnowx53's comment regarding the lack of quality analogs for this year, esp taking into consideration the base state, IOD & tropospheric response. We like to say "potential surprises" a lot in this field/hobby, but I don't know if that phrase ever rang more true than for a year like this!

 

Transient change/progressive flow or not, let's give ourselves some chances with a juiced STJ/potential +PNA as disturbances start riding down the proverbial slope heading into December... And why not throw in a few quality heating degree days if we can too . Happy tracking folks! 

[Allsnow 34,849]