Medium/Long Range Discussion

[tombo82685]

Even in the best case scenario, there's going to be another warmup when the SE ridge somewhat bridges with that NAO ridge while the PV is retrograding.

But hopefully we can get enough amplification of the Aleutian Ridge to keep a good cold air source and that PV doesn't go all the way back to Alaska. Also the OP runs are still showing that west-based block. I'm somewhat hopeful about a decent NAO in the 2nd half of the month, but still quite skeptical. We'll see.

Im still skeptical on the west based -nao. I think east based is pretty much locked in but with a pacific that bad, it may increase our chance 1%. Down here east based blocks aren't ideal, but its better than nothing. I'm just hoping the MJO gets a kick in the arse and starts moving like some of the models the week before christmas.

[Bobby EPAWA]

Im still skeptical on the west based -nao. I think east based is pretty much locked in but with a pacific that bad, it may increase our chance 1%. Down here east based blocks aren't ideal, but its better than nothing. I'm just hoping the MJO gets a kick in the arse and starts moving like some of the models the week before christmas.

Completely agree with this statement...

[tombo82685]

Adam or anyone, weeklies?

[tombo82685]

Nvm, just read them...lost the good west based -nao...looks like a swfe pattern, which makes sense.

[Bobby EPAWA]

Adam or anyone, weeklies?

I don't get mine until 7:30 usually... I am pacing back and forth in anticipation... lol

Btw... case in point about the 18z GFS... 18z GEFS paints a different picture - SWFE?:

[tombo82685]

I don't mean to scare anyone even more than I have already; but, if the pattern does something like what the 18z GFS is doing with a full blown polar vortex retrograde mid-late December....it is going to torch big time.

The way the 18z GFS retrogrades the vortex reminds me of last year when we had a brief window in January for a pattern shift but the vortex went hurling back to Alaska.

Also, don't say that in the sne forum, they are already jumping.

[Bobby EPAWA]

Week2 still has a good -NAO signal albeit east based. Strong Aleutian ridge with a ribbon of lower height anomalies over the US with temps a little below normal. Week 3 started a relaxation of the -NAO with a small slightly above avg contour near the Davis Straits. This likely indicated weakening -NAO through week 3. Still a good Aleutian ridge, and we have a stout -PNA and modest SE ridge.

Week 4 still featured an Aleutian ridge with a -PNA and stronger SE ridge signal. Temps verbatim were just above normal, but looks like a classic SWFE track. Of course, the typical week 3 and 4 caveats apply.

Not sure how he gets them so fast, but there ya go...

[HM]

We all hope that doesn't happen, but you can't do anything about it. Is the euro showing this to? Would a jump start in the mjo help steer this in a different direction? It looks like on the roundy and other mjo stuff that nearing christmas week the mjo should get a boost into phase 1. When you mean retrograde are saying how the gfs takes it from central canada and displaces it on the other side of globe allowing canada to warm up?

Im still skeptical on the west based -nao. I think east based is pretty much locked in but with a pacific that bad, it may increase our chance 1%. Down here east based blocks aren't ideal, but its better than nothing. I'm just hoping the MJO gets a kick in the arse and starts moving like some of the models the week before christmas.

The MJO could be the savior of course but there is still going to be a period of warmth, as Doug suggested. I think everything happens slower than we think. The ECMWF signal for the MJO may actually be confusing it for a kelvin wave. There has been a pretty steady oscillation of IO convection with internal KW / RW controlling convection.

Also, don't say that in the sne forum, they are already jumping.

Haha too late.

[tombo82685]

The MJO could be the savior of course but there is still going to be a period of warmth, as Doug suggested. I think everything happens slower than we think. The ECMWF signal for the MJO may actually be confusing it for a kelvin wave. There has been a pretty steady oscillation of IO convection with internal KW / RW controlling convection.

Haha too late.

Adam got me on the roundy stuff, granted its challenging for me. That seems to have a more realistic look after christmas for any major rise in convection. Also, when looking at the stratosphere/troposphere stuff. Do you want to look at the equator progs or Northern hemisphere stuff? Just asking because the equator progs look alright, with some warming in the 10mb area, granted it still has a long way to go to get down to 50mb

or do you look at the northern hemisphere stuff, because that actually is showing the stratosphere starting to cool off from the november warming (relatively speaking)

[tombo82685]

from HM...

This is the Chris storm and he is too modest to credit for seeing this potential. But anyway, I agree there is a threat then. If there is going to be a good storm, it is going to be when the NAO signal fades westward with split flow underneath. You still got to favor New England with this setup, given the teleconnections. If the NAO-west idea becomes legitimate, then perhaps the northern Mid Atlantic will be snowier than I thought.

But I'm still not feeling a west-based NAO yet so I think this ultimately is for you guys.

[chubbs]

or do you look at the northern hemisphere stuff, because that actually is showing the stratosphere starting to cool off from the november warming (relatively speaking)

Look at northern hemiisphere - 60N-90N. Large warming events can split/break-up PV leading to high latitude blocking and displacing polar air to mid-latitudes.

[NaoPos]

well, the 18z GEFS were promising. Still trying to bring the east based -NAO to the west. With the less than friendly PAC, its gonna hinge on the retrogression of the NAO to dictate how we end up. I've been harping on it for weeks to see what/where the -NAO can set up. As someone posted, HM was noted saying this earlier. I do think if we can get the -NAO/gradient pattern favorable, we could* cash in. Climo would favor areas just north and west as dual, but we wouldn't be outta it. (The more west the block can retro, the better off we are). Discouraging to see the weeklies lose the west based NAO. But it is what it is.

Here's the 18z GEFS 6-10, 11-15 days height anomalies.

I do think if we can get this to actually materialize, I'd like the 15-20th time frame. With a solid snowpack in all of Canada, and confluence and associated HP's to our north, could produce some dent cold air shots. It's the timing we'd have to worry about.

[NaoPos]

Euro long range likes the idea of the west based NAO...verbatim this run.

[tombo82685]

Euro long range likes the idea of the west based NAO...verbatim this run.

yea i almost did a double take when i just looked at it. Actually has some mix or snow for the region next tues with the 2nd wave idea. though this is confined to mainly north and west of the burbs, but i think philly gets some flakes before ending. Also, has a threat at the end of the period for something, though that may track over us but the cold air is in place before hand. Nice blocking especially later on in the run on the euro.

[am19psu]

I'd be wary of the Euro op today after D5. It's pretty different than the ensemble.

[tombo82685]

I'd be wary of the Euro op today after D5. It's pretty different than the ensemble.

this is hr 240, that doesnt look bad at all. The east based -nao has squashed the hgts along the east coast, that would atleast help to get some frozen into the picture even if its a swfe. Thought this is way out in time. That also would incline a pos a0 setup with the pv located at the pole. Also don't like the baginess of the trof around goa.

[tombo82685]

Tell roundy to stop falling behind on his mjo prospects, i think its 2 days behind now.

[am19psu]

this is hr 240, that doesnt look bad at all. The east based -nao has squashed the hgts along the east coast, that would atleast help to get some frozen into the picture even if its a swfe. Thought this is way out in time. That also would incline a pos a0 setup with the pv located at the pole. Also don't like the baginess of the trof around goa.

Agree with this assessment

[tombo82685]

Adam will probably rain down on this party to, but i like how the gefs towards the end start building the ridge back towards alaska, would lead to -epo if it continued.

hr 300

hr 384

[tombo82685]

For anyone that knows this. But what causes the waves to hit the stratosphere? How do you forecast when one is going to occur? On the map below the wave 2 response has dwindled but the wave 1 response is still modest.

do you look at this map for wave 1? How far down the warming gets i would think the more effect on the pv?

[am19psu]

Did you read the Garfinkel et al (2009) paper I linked in the other thread? It has to do with tropospheric Rossby waves propagating upward. Some tropospheric wave configurations are more efficient at displacing and reshaping the vortex than others.

[tombo82685]

Did you read the Garfinkel et al (2009) paper I linked in the other thread? It has to do with tropospheric Rossby waves propagating upward. Some tropospheric wave configurations are more efficient at displacing and reshaping the vortex than others.

I got some down time now, will do it now. Though i may not comprehend alot of it, so i may need you to assist. Some of that jargon goes beyond my head.

[tombo82685]

Did you read the Garfinkel et al (2009) paper I linked in the other thread? It has to do with tropospheric Rossby waves propagating upward. Some tropospheric wave configurations are more efficient at displacing and reshaping the vortex than others.

is it just the abstract or is their more to it?

[am19psu]

Sorry, here's the pdf: http://www.eps.jhu.edu/~cig4/GHetal10.pdf

[chubbs]

Adam will probably rain down on this party to, but i like how the gefs towards the end start building the ridge back towards alaska, would lead to -epo if it continued.

Like the W based NAO on the GEFS. Could give us a good period before Xmas. As HM pointed out however, consolidation of the PV in Siberia as per the 360 map could lead to a January torch

[tombo82685]

Ok Adam or HM or any other met that can help to see if I'm understanding this. Im about 1/3 done the article. So far from what i gathered;

-a warm phase of the enso coupled with above normal eurasia snow cover leads to increased chances of a SSW.

-Warm phase of enso also leads to more wave 1 and wave 2

-higher EP flux better shot of wave 1 and 2?

-A low around alaska or eastern siberia and high over europe lead to strengthening or formation of wave 1 and wave 2. Increase in these waves which leads to an increase in ep flux due to low wavenumber hgt field?

-shown that Low over goa region has a better teleconnecting response to increasing ep flux and wave 1 and 2 than a high over eastern europe

[am19psu]

Yup.

[usedtobe]

I'd be wary of the Euro op today after D5. It's pretty different than the ensemble.

You and me both. I don't know about your area but the CPC superens D+11 was pretty discouraging for ours. No snow on any of the 10 analogs.

[CoastalWx]

I read this article about 3 weeks ago and it cleared up a lot for me. Great article, and nice summary Tom!

[HM]

This paper is a good primer but there are a lot of not so clear cut scenarios and feedback processes (waves warm upper strat and that warming downwells...timing?). Hybrid placements occur usually and climatology of planetary waves, while subtle, does change from early to late winter. This paper suggests it's negligible, but it isn't.

A North Pacific Low is correlated well to a wave 1 but so is an upwelling high over the North Atlantic (there are mountains in Greenland and land/sea/ice differentials here). In fact this was part of the reason 2009 was so intense. If the N PAC low is further to the NW with a ridge into the NE PAC, this promotes a weaker back and forth wave 1-2 thing...hey just like this year!