Jump to content
Cold?
Local
Radar
Snow?

Stratosphere Temperature Watch 2015/2016


Recommended Posts

Yes Phil, the concern being that it ties in with the trop too much for my liking. we know the trop output will not verify at that range.

lol yeah i know what you mean.It depends who is leading the dance i guess. :)

Link to post
Share on other sites
  • Replies 1.2k
  • Created
  • Last Reply

Yes Phil, the concern being that it ties in with the trop too much for my liking. we know the trop output will not verify at that range.

Wouldn't be too sure about that. I have always been of the opinion that the GFS is at it's best at spotting trends post day 10 as opposed to the near term.

Link to post
Share on other sites

Going to be an interesting winter to watch how the stratosphere behaves for sure. On the one hand you have a westerly QBO helping strengthen the stratospheric PV, on the other El Nino and Siberian snow cover working against the PV by creating planetary waves to wear it down over time. However, with the strat PV quite strong for late November, it could take a while to fully disrupt it.

Link to post
Share on other sites

gfsgwo_1.pngALL_emean_phase_full.gif

 

Well.. what do you guys make of this?

 

It's a long way from the typical El Nino signature of orbits in +AAM such as we see coming to a conclusion over the next 5 days. It seems to be triggered by the MJO just hanging out in the middle of the Indian Ocean. The Phase 2 composite filtered by El Nino years fits quite well with much of the GFS output for next week onward:

 

DecENMJOphase2gt1500mb.gif

Notice also the support for that monstrous Siberian High to nose pole-ward - is this behind the strat. wave breaking such as GFS has been consistently calling for to some degree or other in the longer-term?

 

Lots of uncertainty though, with the 06z and 00z GFS det. runs markedly different in how the strat. and trop. output evolves from +240 to +384. The 06z is a bit bonkers really, with the Siberian High making it a long way toward the pole and morphing into more of an Arctic High, while the strat. vortex stretches and very nearly splits, with a prominent ridge developing over the Pacific.

 

npsh500.pngnpst30.png

 

Have we ever seen such warming in terms of location and persistence thereof during an El Nino winter?

Link to post
Share on other sites

Important part is here...

 

As we have shown in our research the favored high latitude atmospheric pattern in November that follows above normal October Eurasian snow cover extent is the expansion of the Siberian high across northwest Asia with low pressure to the east near the Aleutians and a secondary area of low pressure in the northern North Atlantic; a pattern that we refer to as the tripole pattern (Cohen and Jones (2012)).  

 

The current atmospheric pattern strongly projects onto this pattern.  This same pattern also favors the increase in wave activity flux or the vertical transfer of energy from the troposphere to the stratosphere during the month of December.

 

At AER we have developed a polar vortex model that predicts the strength of the polar vortex one month in advance.  It is predicting a major sudden stratospheric warming (SSW) in mid-December.  We currently feel that this forecast is unlikely because the model is overly sensitive to SSW and has many false positives and because a major SSW is relatively rare in December.

 

 Still given the polar vortex model forecast and strong projection of the current atmospheric pattern onto the tripole pattern, we are more confident in increased wave activity flux in December that will result in weakening of the polar vortex in December and likely continuing into January.  Also because the current dominant high latitude circulation is a wave two pattern, this would favor a polar vortex split relative to a polar vortex displacement in the event of a significant weakening of the polar vortex.  

 

One inhibiting background factor is the westerly phase of the quasi-biennial oscillation (QBO) that favors a strong vortex over a weak vortex. But if our expectations of a weakened polar vortex verify, this will likely favor an increased likelihood of severe winter weather across the continents of the Northern Hemisphere.  Of course all of this is highly speculative but the purpose of this blog is to push the boundaries of what is possible in weather forecasting beyond the skillful range of the weather models.

Link to post
Share on other sites

I think the important thing is the progress in the pattern. The updates 2 and 3 weeks said that the upcoming pattern did not resemble the one they wanted and last weeks only hinted that a more favourable one may develop while we now see one strongly resembling. 

 

It may be a dud as per winter 2014 (neg AO but no luck in the UK) however we can all be hopeful that an -AO is coming.

Link to post
Share on other sites

That's a considerable split from 100mb through to 7mb with the vortex stretched at 5mb.

post-7292-0-01189200-1447781396_thumb.gipost-7292-0-66748900-1447781397_thumb.jp

post-7292-0-61099100-1447781908_thumb.pnpost-7292-0-74160800-1447781947_thumb.pn

 

Pressure on the vortex from every possible blocking pre-cursor !

post-7292-0-59578200-1447781530_thumb.pn

 

EPO has gone beyond -5SD

post-7292-0-27914900-1447781590_thumb.pn

 

Good old black hole anomalies!

post-7292-0-22218000-1447781410_thumb.pnpost-7292-0-65789900-1447781442_thumb.pn

 

An awesome strat. model roller coaster just now, and the benefit of a couple of cold incursions, Nino re-engaging and a couple of cold shots to keep things interesting elsewhere. 

 

 

Link to post
Share on other sites

That's a considerable split from 100mb through to 7mb with the vortex stretched at 5mb.

attachicon.gifNH_HGT_10mb_288.gifattachicon.gifNH_HGT_30mb_288.jpg

 

Pressure on the vortex from every possible blocking pre-cursor !

attachicon.gifgfsnh-1-300.png

 

EPO has gone beyond -5SD

attachicon.gifgfs_epo_bias.pngattachicon.gifgfsnh-0-288.pngattachicon.gifgfsnh-15-300.png

 

An awesome model roller coaster just now, and the benefit of a couple of cold incursions, Nino re-engaging and a couple of cold shots to keep things interesting elsewhere.

What do you think will happen if this happens??

Link to post
Share on other sites

Aye, pretty much uncharted territory?

 

Maybe uncharted but not altogether unexpected considering the research that has been done on Arctic ice loss and how it may play out with forcing on the stratosphere. Some of the modelling is looking very similar to the patterns in the research papers.

 

A couple of recent examples ....

 

http://www.tellusa.net/index.php/tellusa/article/view/19375/html

 

http://www.researchgate.net/publication/265256754_Weakening_of_the_stratospheric_polar_vortex_by_Arctic_sea-ice_loss

 

gfsnh-12-288_spx9.png   qhOQxot.png?1

Link to post
Share on other sites

Certainly going to be an interesting few weeks and winter ahead. 

 

Just read a paper from Cohen on wave 1 and wave 2 activity as part of my dissertation topic and seeing what the general patterns precede each type of polar vortex disruption which was very interesting.

 

I did think last week the current patterns look very similar to what happens prior to a splitting event and continue to look even more in line with what they normally see (although I'm still learning so I could be off the mark). However one thing i have found is that El Nino year feature predominately wave 1 activity whilst La Nina favour Wave 2 which is interesting. 

 

In case anybody is interested in reading the paper 

http://web.mit.edu/jlcohen/www/papers/CohenandJones_JC12.pdf

 

Link to mean zonal wind anomalies and wave 1/2 annual activity 

http://www.cpc.ncep.noaa.gov/products/stratosphere/strat-trop/

Link to post
Share on other sites

We do seem to have some hybrid El Nino/La Nina signals coming along what with the change in AAM that the GEFS has been toying with.

 

Speaking of which;

gfsgwo_1.png

Impressive, this; an extreme spike in AAM, which I've come to know as a signature of major torque forcing events - and one which is going some way beyond what I saw predicted as of my last check on Monday. Are we looking at errors here or is the atmosphere genuinely going that far beyond what was expected?

 

Interesting to see the AAM now looking to perform another cycle just above neutral rather than going straight to negative. No wonder we've seen a flatter pattern start to emerge in the model output for next week. The prospects going forward seem uninspiring with respect to the fortnight starting Monday 23rd, with a prominent Azores High possible.

 

On the other hand, this resistance from the El Nino background is potentially a very good thing for a dance between wave 1 and wave 2 breaking into the stratosphere, building and sustaining a pinch on the vortex. It's going to take a lot of luck though as it could easily go wrong depending on how the feedbacks play out. What we need is for the AAM to climb back up rather than fall lower, to restart support for the Siberian High to induce wave breaking where we'd like to see it. A fall into -ve AAM territory with an Alaskan ridge drives wave breaking in locations that tend to cause us problems by displacing the stratospheric vortex to Greenland or thereabouts, as we saw last winter.

A short spell of wave breaking from such a feature followed a return to wave breaking via the Siberian High - that's the ideal scenario but probably the most difficult to achieve.

Link to post
Share on other sites

Without wanting to give too much away, the current pattern stratospherically is pretty much how we would expect the season to start. We are seeing a very strong upper stratospheric vortex which is slowly filtering down to the surface. There is a bit of a time lag before the full effects of the upper vortex is felt and it is during this time that the tropospheric vortex is realigning into a very traditional El Nino pattern. During this realignment  upwelling wave activity originating from the troposphere is disturbing the lower strat vortex and hence we have been seeing the trop modeling playing around with vortex splits in the 10 day time frame. However, this is unlikely to be sustained and then a strong lower vortex will reappear. The wave activity hardly makes an indent at 10 hPa

 

 

post-4523-0-51173400-1447941695_thumb.pn

 

 

 

 

The strong tropsopheric vortex is likely to have a strong Greenland based segment and the CFS is pretty typical of all the models outlook for weeks 3 and 4 - the typical El Nino pattern for December. Don't be surprised to see some large +ve NAO values during this month

 

post-4523-0-21448200-1447941636_thumb.gi

 

December typical El Nino pattern (lazily pinched off Eric Webb thanks)

 https://twitter.com/webberweather/status/666360086240100360

 

post-4523-0-87737900-1447942050_thumb.pn

 

But don't despair because this wave pattern is setting up for some interesting strat feedback in January, so it is exciting to see December's forthcoming outlook.

Link to post
Share on other sites

Following your Twitter debates Chio I sense a feeling that the cautious pessimism we went into winter with is starting to morph into something closer to cautious optimism - at least in terms of the chance of a SSW and possibly earlier than might have been expected too. However solar activity is falling - forecast to be very low on solarham. Am I right in thinknig that perversely we could do with an uptick in solar activity in December in order to reinforce the El Nino driven late season assault on the vortex?

Link to post
Share on other sites

Following your Twitter debates Chio I sense a feeling that the cautious pessimism we went into winter with is starting to morph into something closer to cautious optimism - at least in terms of the chance of a SSW and possibly earlier than might have been expected too. However solar activity is falling - forecast to be very low on solarham. Am I right in thinknig that perversely we could do with an uptick in solar activity in December in order to reinforce the El Nino driven late season assault on the vortex?

I don't think that that would be a bad thing. The pattern is setting up for a SSW - this is still against Holtan-Tan linkage but there are signs that this may still be overcome - especially the way late autumn has panned out so far (almost exactly as expected). My caution is more forecast based rather than snow based. I still think that a January west based -ve NAO with or without an SSW is favourite, it is just that with an SSW better chances for snow may occur as the trop disruption occurs before the -ve WNAO becomes established.

 

Also for those interested in the dynamics of the North America Mountain Torque and the corresponding internal upward propagating wave response then it is explained in this tweet from Anthony Masiello.

 

https://twitter.com/antmasiello/status/666758275644411907

Link to post
Share on other sites

Hi Sebastiaan - I admit to seeing it and glanced through it quickly but haven't read in detail yet. Quick glance seemed to suggest that it is in line with most thoughts this winter.

Link to post
Share on other sites

OK so the thinking (or general consensus) is that December will be mild this year? and the potential for blocking not until late December (or more likely - early January)?

I notice that AAM is not mentioned in that forecast Sebastian copied in from Americanwx. ***EDIT: Sorry AAM is mentioned.

Link to post
Share on other sites

Archived

This topic is now archived and is closed to further replies.

×
×
  • Create New...