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December 2021 Medium/Long Range Discussion Thread


North Balti Zen
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12 hours ago, CAPE said:

A more typical 'Arctic' airmass enhancing a baroclinic zone in a favorable pattern can produce some pretty cold/high ratio snow events. The Blizzard of 1983, a big storm, produced heavy snow with temps in the low to mid teens, as did the late Jan 2010 moderate snowstorm, just to name a couple examples.

Too much confluence resulting in a suppressed storm track is not a vodka cold thing. Sure a brutally cold airmass with a strong cold front sweeping through can push the baroclinic region wayyy off the coast and make for dry conditions. We don't get that kind of cold much though. This whole dopey convo started with someone commenting on a "vodka" cold airmass being on the doorstep of the US at day 15 of a GFS op run. So a couple things- it was a damn op run, and even if it did verify, that cold would dump well west of here. Reality is we don't usually get direct shots of brutal cold in this area, esp not in recent times. So worrying over that possibility and that it might be dry and not produce snow is a little silly, considering we have a multitude of other more likely failure modes.

I think there might be some conflation here with the tendency for us to see cold and dry following a mild rain storm. That is a function of our location/latitude, and the fact that we need a lot of elements to come together to have cold enough air in place and a storm that takes a favorable track.

Temps fell to 1F during Feb 2003 storm.  Very rare, but can happen. 

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2 hours ago, CAPE said:

Latest runs of the GEFS build heights nicely into the NAO domain leading up to Christmas. Eastern ridge is flatter/weaker, with more of a gradient pattern look, so not impossible to see something of interest in that timeframe as advertised. EPS moves in that direction but then backs off, leaving the +height anomalies near Scandinavia at day 15. CMC ens looks more like the EPS, but has leading edge of colder air bleeding into the N plains. 

I have been waiting to see some fantasy op runs that start to point to a -NAO developing in that timeframe.  As you know, these -NAO episodes are rarely picked up on in the long range but once inside D10-12 you can start to see glimpses on op runs and on the ens to a certain extent.  18z thru the 06z run this morning all featured a robust + hight atom moving into GL.  The first runs I have seen in a while and it has been 3 in row (4 if you count the 12z run yesterday). But still...like you said, we just can't know yet!  Hey, maybe we can get a nice block just before the holidays that produces like the 06z run.... 

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26 minutes ago, poolz1 said:

I have been waiting to see some fantasy op runs that start to point to a -NAO developing in that timeframe.  As you know, these -NAO episodes are rarely picked up on in the long range but once inside D10-12 you can start to see glimpses on op runs and on the ens to a certain extent.  18z thru the 06z run this morning all featured a robust + hight atom moving into GL.  The first runs I have seen in a while and it has been 3 in row (4 if you count the 12z run yesterday). But still...like you said, we just can't know yet!  Hey, maybe we can get a nice block just before the holidays that produces like the 06z run.... 

It would be nice to see the EPS get more enthused about a -NAO in that timeframe. Even with the PAC ridge extending more poleward into the EPO domain, the location/orientation appears to favor keeping the trough out west, at least initially. Need what the GEFS is advertising in the NA in order to counter the -PNA and beat down the eastern US ridge.

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19 minutes ago, CAPE said:

It would be nice to see the EPS get more enthused about a -NAO in that timeframe. Even with the PAC ridge extending more poleward into the EPO domain, the location/orientation appears to favor keeping the trough out west, at least initially. Need what the GEFS is advertising in the NA in order to counter the -PNA and beat down the eastern US ridge.

I agree....but at least over the past few weeks it seems like the GEFS have had a better handle on the LR than the EPS.  Just an observation but it wasn't too long ago the EPS was steadfast on a nice +PNA for early Dec and the GEFS wanted no part in it.  A consensus inside 10 days on a workable pattern sure would be nice. 

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34 minutes ago, CAPE said:

It would be nice to see the EPS get more enthused about a -NAO in that timeframe. Even with the PAC ridge extending more poleward into the EPO domain, the location/orientation appears to favor keeping the trough out west, at least initially. Need what the GEFS is advertising in the NA in order to counter the -PNA and beat down the eastern US ridge.

The Gefs is much faster moving the mjo into 8. The EPS is getting there but is a week slower and ends still in 7 but moving towards 8. That means the same changed on the EPS likely lie behind the end of its 15 days due to its slower pattern progression. 

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Since there’s nothing happening for at least a week…

If you squint, you can maybe envision an overrunning/southwest flow event around D8-12 (next weekend). TPV rotates down through central and eastern Canada perhaps while pieces of that Baja Low may eject out into the southern Plains. What we need is for the TPV to provide just enough cold air and suppression and for only a modest piece of the Baja low to eject so it’s not too strong and pumps the SE ridge again. It’s a long shot…we don’t usually score at the start of a pattern transition, but it’s the only thing I see in the next 15 days.

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1 hour ago, mattie g said:

GEFS is still trying to nudge the Scandinavian Ridge into the NAO domain as we get towards the end of the run. Would like to see some more changes in the Pacific, though we are seeing some higher heights getting up into Alaska.

GEFS and EPS both have several nice features by Xmas week: -EPO, ridge bridge across the pole with -AO, -east NAO. But both have a pig of a -PNA also. We need that EPO ridge to move east a bit to kick that trough at least out into the Plains. 

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1 hour ago, WxUSAF said:

GEFS and EPS both have several nice features by Xmas week: -EPO, ridge bridge across the pole with -AO, -east NAO. But both have a pig of a -PNA also. We need that EPO ridge to move east a bit to kick that trough at least out into the Plains. 

Can we score with pig -PNA?  If everything else is solid.  Overrunning or something 

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12 hours ago, psuhoffman said:

and ends still in 7 but moving towards 8

That is actually better for us. We want 8 into January. It is game on if that happens. And yes. I know the MJO can and has failed for us. But I am loving the amplitude into 7 from 6. Give me that with a tanking AO and a NAO that is at least neutral and I will take my chances. Yes. I live in place that likes to snow. But what I am seeing forecast in the LR looks like weenie heaven for the majority of us. 

 

ao.sprd2.gif

nao.sprd2.gif

 

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On 12/8/2021 at 5:26 AM, Ralph Wiggum said:

I take you back to winter 2020 when the amplitude was literally off the chart. Forecasts showed it moving along weaker into the next favorable phase but instead went right into the COD completely bypassing the forecast and traversed almost 180 into a warm regime. It was that particular situation that made me realize just how much of a dartboard that product truly still is.

That is obviously possible. But I like the AO and NAO forecast on top of the MJO. I cant remember What the forecast was for those in 2020 though. 

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18 hours ago, WxUSAF said:

Since there’s nothing happening for at least a week…

If you squint, you can maybe envision an overrunning/southwest flow event around D8-12 (next weekend). TPV rotates down through central and eastern Canada perhaps while pieces of that Baja Low may eject out into the southern Plains. What we need is for the TPV to provide just enough cold air and suppression and for only a modest piece of the Baja low to eject so it’s not too strong and pumps the SE ridge again. It’s a long shot…we don’t usually score at the start of a pattern transition, but it’s the only thing I see in the next 15 days.

6z kind of shows this in the 8 to 10 day time frame.

Doesn't get the job done but you could see a scenario with a bit of  stronger push from the north where a overrunning event could happen. Currently depicted the run has some snow up in PA.

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3 minutes ago, Chris78 said:

6z kind of shows this in the 8 to 10 day time frame.

Doesn't get the job done but you could see a scenario with a bit of  stronger push from the north where a overrunning event could happen. Currently depicted the run has some snow up in PA.

6z GEFS has a really good look on the Atlantic side, and the mean implies some waves moving east leading up to Christmas with some cold pressing in.

 

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7 hours ago, CentralVaNATS said:

We all know that's not happening. Only above normal anomalies verify 2 weeks out. Good luck to all this WARM WINTER!!!

Sent from my SM-G998U using Tapatalk
 

Its funny because like 1 panel after this the East is torching. Of course we don't even know exactly how this will evolve but this could be one of those years where we sneak in a snowstorm then the following day it's in the low 50s. 

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2 minutes ago, CAPE said:

6z GEFS has a really good look on the Atlantic side, and the mean implies some waves moving east leading up to Christmas with some cold pressing in.

 

LR certainly looking a little better in the Atl. Hopefully the cold air source doesn't get pinched off and disconnected as the TPV tries to settle into Western Canada/Alaska. One thing at a time tho....we need the Atl to play nice...thats a huge piece in this Nina....so I do like seeing that aspect improve on the LR ens.

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3 minutes ago, Ralph Wiggum said:

Its funny because like 1 panel after this the East is torching. Of course we don't even know exactly how this will evolve but this could be one of those years where we sneak in a snowstorm then the following day it's in the low 50s. 

Just like the blizzard of 2016. It snowed, then the next day we busted high on temps and IAD lost 8 inches of snowpack. The new normal.

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