February Pattern Disco

[Isotherm]

 

The vortex will be significantly weaker and re-position itself in a location that is much more favorable for EPO/AO blocking than we saw the first half of the winter. We may not see severe blocking, but that isn't necessary at least in the US for colder than normal weather. The tropical forcing is a factor, but there is a near equal frequency of SSW events in La Nina's and El Ninos. Actually, La Nina's are slightly favored over Nino's. I'm not crazy about the term "drive the bus" as I think there are many important factors, and it's difficult to isolate causation. Many of the Nino winters with -AO in the second half featured favorable forcing and a perturbed vortex in the stratosphere. Both contribute. If we had the vortex in the state we experienced in December, I think the AO would probably be consistently strongly positive right now.

 

 

VP.png

 

We started getting into a more favorable pattern heading past the beginning of Feb. We should again see better conditions later this month too. The problem is, the 10mb-50mb layer never really reversed or had a large impact as of now, and that's what matters. The displacement sure helps, but that was also aided by tropospheric response too. Models did a very good job showing the 10mb-50mb layer having a tough time staying perturbed and truly reversing. That's been my argument all along. The SSW that some hoped to switch the NAO negative did not happen. You simply can't expect a record cold strat to switch in a dime. Granted it did have a displacement that warmed up, but maybe if the QBO wasn't so positive, it would be easier.

 

 

 

 

Reversal of winds in the 10-50mb isn't required to see the downwelling of stratospheric anomalies, however. My argument has been for awhile that the evolution of stratospheric heights are critically important, and that a major SSW isn't necessary to see the impacts in the troposphere. The displacement event is in response to the extremely potent wave-1 flux originating in the troposphere, so we completely agree there I believe. The troposphere influenced the stratosphere, and the stratosphere further influences the troposphere (T-S-T coupling). The re-orientation of the 10-70hpa vorticies going forward will continue to promote higher heights in the EPO/PNA/AO domains, IMO. As I said before, as you see in the literature, Europe doesn't do well in displacements, mostly b/c of the lack of a persistent / strong -NAO, which looks to be the case here.

 

The tropical forcing, I agree. We have improved from January. But if you look back at December, the tropical forcing was fairly conducive overall (160-180), although we had some IO convective flare. But looking at the tropical forcing alone, you wouldn't think by that chart that a record warm December would result. The stratosphere plays a significant role (and by that I mean - it's response via tropospheric forcing and consequently feedback back / changing the tropospheric pattern via height/anomaly variations).

[CoastalWx]

Reversal of winds in the 10-50mb isn't required to see the downwelling of stratospheric anomalies, however. My argument has been for awhile that the evolution of stratospheric heights are critically important, and that a major SSW isn't necessary to see the impacts in the troposphere. The displacement event is in response to the extremely potent wave-1 flux originating in the troposphere, so we completely agree there I believe. The troposphere influenced the stratosphere, and the stratosphere further influences the troposphere (T-S-T coupling). The re-orientation of the 10-70hpa vorticies going forward will continue to promote higher heights in the EPO/PNA/AO domains, IMO. As I said before, as you see in the literature, Europe doesn't do well in displacements, mostly b/c of the lack of a persistent / strong -NAO, which looks to be the case here.

 

The tropical forcing, I agree. We have improved from January. But if you look back at December, the tropical forcing was fairly conducive overall (160-180), although we had some IO convective flare. But looking at the tropical forcing alone, you wouldn't think by that chart that a record warm December would result. The stratosphere plays a significant role (and by that I mean - it's response via tropospheric forcing and consequently feedback back / changing the tropospheric pattern via height/anomaly variations).

 

 

I think the added IO convection really flared up the December AO. Also, looked at the displaced ridging aloft north of Hawaii. That almost aided in getting a -PNA IMO. That was extremely not Nino...lol.  I guess my whole opinion is that I wasn't gung ho on the -NAO blocking...I was actually hoping it would happen in Feb, but nothing I saw on the models had me excited about a classic split to help. So you are looking at it from a more definition standpoint, but I am looking at it from a pattern point of view. I think we agree.

[Isotherm]

I think the added IO convection really flared up the December AO. Also, looked at the displaced ridging aloft north of Hawaii. That almost aided in getting a -PNA IMO. That was extremely not Nino...lol.  I guess my whole opinion is that I wasn't gung ho on the -NAO blocking...I was actually hoping it would happen in Feb, but nothing I saw on the models had me excited about a classic split to help. So you are looking at it from a more definition standpoint, but I am looking at it from a pattern point of view. I think we agree.

 

 

I agree; in order for the stratosphere to really induce a severe and persistent -NAO, generally you want complete splitting of the vortex. I was generally favoring displacement this winter due to the predominace of wv 1 over wv 2 action, but I know that there were some thinking split, which definitely would have aided the NAO. Agree about the IO and ridging influencing the Dec pattern too.

[Typhoon Tip]

I agree; in order for the stratosphere to really induce a severe and persistent -NAO, generally you want complete splitting of the vortex. I was generally favoring displacement this winter due to the predominace of wv 1 over wv 2 action, but I know that there were some thinking split, which definitely would have aided the NAO. Agree about the IO and ridging influencing the Dec pattern too.

 

The stratosphere doesn't correlate like that with the NAO domain space, causally.   

 

Evidenced (in one way) because, ... the EPO and NAO can also be physically motivated toward negative(positive) phases (blocking periods) by translating planetary wave events, ...disconnected from any top down coupling within the adjacent PV domain. 

 

The AOs, yes ... The NAO shares domain space with the AO, such that when the SSW phenomenon is causing the AO "pancaking" of the latitude-ring of the PV (spreading south and weakening geopotential gradient), that then can secondarily induce shared polar field indexes like the EPO and NAO toward their negative phase states as blocking tends to erupt in those domains spaces. 

[Isotherm]

The stratosphere doesn't correlate like that with the NAO domain space, causally.   

 

Evidenced (in one way) because, ... the EPO and NAO can also be physically motivated toward negative(positive) phases (blocking periods) by translating planetary wave events, ...disconnected from any top down coupling within the adjacent PV domain. 

 

The AOs, yes ... The NAO shares domain space with the AO, such that when the SSW phenomenon is causing the AO "pancaking" of the latitude-ring of the PV (spreading south and weakening geopotential gradient), that then can secondarily induce shared polar field indexes like the EPO and NAO toward their negative phase states as blocking tends to erupt in those domains spaces. 

 

 

I never argued that, but the fact remains that split SSW events are much more preferred over displacement SSW insofar as the initiation of tropospheric height rises over the NAO domain. One can see the differences in the temperature responses over Europe vs. the US. Many papers demonstrate this. The T-S-T coupling process that occurs with a stratrospheric vortex split into two daughter vortices is much more likely to induce significant height rises over Greenland. That's the point of my post. Most importantly, the position of the vortex and stratospheric heights are crucial regardless of a SSW. We can achieve stratospheric patterns that are quite conducive for -NAO blocking without SSW. The upcoming pattern is not one of those overall, unless we see some changes.

[Typhoon Tip]

I never argued that, but the fact remains that split SSW events are much more preferred over displacement SSW insofar as the initiation of tropospheric height rises over the NAO domain. One can see the differences in the temperature responses over Europe vs. the US. Many papers demonstrate this. The T-S-T coupling process that occurs with a stratrospheric vortex split into two daughter vortices is much more likely to induce significant height rises over Greenland. That's the point of my post. Most importantly, the position of the vortex and stratospheric heights are crucial regardless of a SSW. We can achieve stratospheric patterns that are quite conducive for -NAO blocking without SSW. The upcoming pattern is not one of those overall, unless we see some changes.

 

Ah see what your saying -- 

 

yeah ... that effect of the split at times being a leading indicator (though) is the secondary result of the totality of the SSW/tropopausal correlation - that's the important take away.  

 

for what it's worth ...I've been monitoring the data; I've been leaning away from this warm onset event as being significant. It could certainly prove otherwise, but the modeling doesn't seem to be evolving things in that favor.  time will tell I suppose

[Typhoon Tip]

By the way, ... it appears I was in error yesterday when I spoke of 'two threats' in the middle to extended range. 

 

I was in fact, upon closer inspection, looking at the same dern wave spacing ...just that the ensembles of the GFS were handling it in different times enough to throw me off.  ha.  

 

Anyway, just fyi - NCEP seems to favor the idea of winterstorm for the east next week.  I don't...wait...this belongs in the Model thread ?   

[Damage In Tolland]

Did ENS continue to mute any mild up next week?

[CoastalWx]

Did ENS continue to mute any mild up next week?

It's AN for awhile  until we step down again after the 24th or so.

[googmoog]

They certainly did at 12z. About 3-5F above normal for the area. Similar overnight?

[CoastalWx]

They certainly did at 12z. About 3-5F above normal for the area. Similar overnight?

 

Yep. It will be mild for a time I think. We may have to watch a sneaky system after early next week..but otherwise it's mild until late in the period.

[googmoog]

Yep. It will be mild for a time I think. We may have to watch a sneaky system after early next week..but otherwise it's mild until late in the period.

I can live with that. Is it mild/dry or mild with drizzle flurries? 

[ORH_wxman]

Torch def muted the past two runs. It will still be above normal and feel reasonably mild since it is almost 3 weeks into February at that point but it is not the monstrous torch that was advertised to last like 3 days. (Some runs were showing potential for 3 days of 55+)

We will still see on around D11...maybe the 50s crowd gets a bone thrown their way then for a day.

[googmoog]

Have to get my mind off Tuesday...what do things look like down the pipe?

[ORH_wxman]

Nice EPO ridge on today's EC ensembles.

 

The post-cutter (if it really ends up cutting) torch has been toned down quite a bit. We're typical late Feb mild for a few days while we wait for the EPO ridge to impact us...but we could actually probably support a winter wx event in that pattern...just to put it in perspective (i.e. that -1 or -2C type airmass that can give you a high 45-50 if it's sunny out)

[Damage In Tolland]

Down to 11.7

May go below zippo tonight

[CoastalWx]

Weeklies continue the -EPO with ridging off the east coast. Similar to ensembles. So, tough to say it will be cold, but cold lurks. Week 4 looks a bit wetter than normal too.

[googmoog]

Overnight EPS?

[CoastalWx]

Googly Moogly and gobbly gook.......I do say it had a nice look. Still a mild period possibly, but the end of the month snow we'll hopefully see.

[googmoog]

Googly Moogly and gobbly gook.......I do say it had a nice look. Still a mild period possibly, but the end of the month snow we'll hopefully see.

Poem or freestyle rap?

[EastonSN+]

Man the operational GFS looks terrible in the Long Range.

[CoastalWx]

Yeah hopefully that doesn't happen. Nothing is ever set in stone.

[googmoog]

Don't know if I'd lean too strongly on the OP GFS, but hey - we'll see.

[Ginx snewx]

EPS looks really nice that's a 2 say 40-45 then back in it

[googmoog]

EPS looks really nice that's a 2 say 40-45 then back in it

I like the sound of that. What 2 days do we moderate?

[Damage In Tolland]

I like the sound of that. What 2 days do we moderate?

So plan on 2 days of near 50 as thats too cold with the strong sun angle now, and what will likely be bare ground

[googmoog]

So plan on 2 days of near 50 as thats too cold with the strong sun angle now, and what will likely be bare ground

wat

[RUNNAWAYICEBERG]

I like the sound of that. What 2 days do we moderate?

http://www.tropicaltidbits.com/analysis/models/ecmwf-ens/2016021200/ecmwf-ens_T850_mslp_eus_11.png

[Damage In Tolland]

wat

Add 5-10 degrees to his 40-45. It's late Feb and there won't be any snowpack

[40/70 Benchmark]

I like the sound of that. What 2 days do we moderate?

The two days we have a storm near by.

 

#winter2016inanutshell