January? Pattern Change Thread

[Tropopause_Fold]

I don't think you quite got it actually. The Cryosphere has helped - As that annotation may just suggest, since there is an abundance of cold, such that the AO can be more effective at comparatively lesser negative values. That's the point I am trying to convey here.

As the annotation also shows, the only cool anomalies we've had in October, November, and December thus far have coincided with intervals of substantially weakened PV. I also furthered it by say the prog looks like it is headed for another nadir.

Only trouble I have with that is the struggle the gfs and its ensembles have had with ao forecasts over the last 45 days or so.

Hopefully they are right in seeing the downward trend but I feel like I've seen that model forecast all season and it keeps failing to verify, being delayed or ending up less impressive of a fall.

[CoastalWx]

Only trouble I have with that is the struggle the gfs and its ensembles have had with ao forecasts over the last 45 days or so.

Hopefully they are right in seeing the downward trend but I feel like I've seen that model forecast all season and it keeps failing to verify, being delayed or ending up less impressive of a fall.

There are signs of ridging in the Atlantic trying to develop, but the dam vortex is still there..lol. It just won't die. Even the weeklies have a stout +NAO.

Now I will say that you can see hints of maybe the beginnings of a semblance of something in the works....but I use the term semblance, very loosely. After all, the dam vortex has been at +3SD or better for weeks, so naturally it will relax eventually. I just don't see it happening anytime soon.

[Typhoon Tip]

Only trouble I have with that is the struggle the gfs and its ensembles have had with ao forecasts over the last 45 days or so.

Hopefully they are right in seeing the downward trend but I feel like I've seen that model forecast all season and it keeps failing to verify, being delayed or ending up less impressive of a fall.

Yeah, yep no arg there - ha. Of course ... that's all predicated on the assumption the GEF's heads been disconnected from it's ass lol

[bch2014]

I have seen many people comment on the fact that it is still possible to get good events during a hostile pattern. Are there any examples of a "legendary" east coast storm that happened during a bad pattern?

[40/70 Benchmark]

I don't think you quite got it actually. The Cryosphere has helped - As that annotation may just suggest, since there is an abundance of cold, such that the AO can be more effective at comparatively lesser negative values. That's the point I am trying to convey here.

As the annotation also shows, the only cool anomalies we've had in October, November, and December thus far have coincided with intervals of substantially weakened PV. I also furthered it by say the prog looks like it is headed for another nadir.

I figured you'd say that......you're right, actually....I was just basing things entirely upon snowfall, which is the prevailing bias of the board, asa you noted.

Everything else has been so hostile that I guess the effects have been muted.

[ORH_wxman]

The AO will try and dip some but not sure it gets negative any time soon...the dip is caused by some ridging on the opposite side of the pole.

I am just about 100% confident the NAO will remain positive through the next two weeks outside of maybe briefly going negative from a transient N ATL ridge or something way east-based like between Iceland and the UK.

[40/70 Benchmark]

I have seen many people comment on the fact that it is still possible to get good events during a hostile pattern. Are there any examples of a "legendary" east coast storm that happened during a bad pattern?

FEB 2006....I think the Megalopolis storm, too.

December '96, though that was crap for the cp.

[bch2014]

FEB 2006....I think the Megalopolis storm, too.

December '96, though that was crap for the cp.

What storm was the Megalopolis storm..?

[40/70 Benchmark]

What storm was the Megalopolis storm..?

Feb 1983....Will may correct me on whether or not it occured in a favorable regime.

[ORH_wxman]

I have seen many people comment on the fact that it is still possible to get good events during a hostile pattern. Are there any examples of a "legendary" east coast storm that happened during a bad pattern?

No, its just about impossible to get a KU in a really hostile pattern like this, but we can still get events...esp with some latitude. January 2006 was an example of that...there were some events that month that took advantage of marginal air masses despite an awful pattern.

The MLK 2010 event occurred during a putrid pattern as well. There's several others obviously, but just some off the top of my head. But none of them are KUs or anything.

[40/70 Benchmark]

No, its just about impossible to get a KU in a really hostile pattern like this, but we can still get events...esp with some latitude. January 2006 was an example of that...there were some events that month that took advantage of marginal air masses despite an awful pattern.

The MLK 2010 event occurred during a putrid pattern as well. There's several others obviously, but just some off the top of my head. But none of them are KUs or anything.

The patterns I mentioned prob weren't AS bad as this, but they weren't great.

[ORH_wxman]

FEB 2006....I think the Megalopolis storm, too.

December '96, though that was crap for the cp.

Feb '06 and Feb '83 occurred during decent patterns in otherwise terrible winters...not ideal, but not bad at all. Nothing like our current regime.

Dec '96 was a pretty terrible pattern.

[40/70 Benchmark]

Feb '06 and Feb '83 occurred during decent patterns in otherwise terrible winters...not ideal, but not bad at all. Nothing like our current regime.

Dec '96 was a pretty terrible pattern.

Thanks.

[Ginx snewx]

I have seen many people comment on the fact that it is still possible to get good events during a hostile pattern. Are there any examples of a "legendary" east coast storm that happened during a bad pattern?

Dec 5-7 2003 1-3 feet of snow region wide while this pattern was in place then boom.

[SnowGoose69]

Dec 5-7 2003 1-3 feet of snow region wide while this pattern was in place then boom.

November 03 was horrible and December was not much better, it averaged largely above normal for most of the nation outside of the SE, it was a similar month to 1993 and even 2002 in that a couple of snow events snuck in to what were otherwise above normal Decembers. Most people never realize that Dec 1993 was mild outside of the last 7 days, 2002 was mild outside of the first 5, and 2003 was basically mild entirely...snow can really throw you for a loop. Also, the NAO may have been technically negative for the 12/5 event but it was a very east based negative NAO.

[Typhoon Tip]

The AO will try and dip some but not sure it gets negative any time soon...the dip is caused by some ridging on the opposite side of the pole.

I am just about 100% confident the NAO will remain positive through the next two weeks outside of maybe briefly going negative from a transient N ATL ridge or something way east-based like between Iceland and the UK.

For what it's worth, both CDC and CPC (using GEFs cluster...) somewhat agree... The CDC's NCEP channel shows a discerned negative NAO by D8, while the ESRL is steady around +1SD. I have found in the past, however, that NCEP tends to lead the other by a couple/few days on early detection. The CPC shows a not an abrupt decline, but a steady declination where it approaches neutral from a starting point of ~ +2.5SDs.

The soft version, the NAO is falling but is in no hurry. ...At least, for the time being.

I find this ...a little intriguing. I'd be happy to find it very intriguing *if*:

a) it is proven to not merely be an incidental, non-influential node of warmth wobbling around in the PV;

it demonstrates downward propagating behavior.

The implications of either are important. For one, warm pockets of both cool and warm anomalies will pop in and out of detection across intra-weekly timescales, and of those variety, they don't demonstrate much correlation on ensuing AO tendencies. Contrasting, a stronger node (and they are usually more obviously large, meaning they have more mass) associated with SSWs will then show a "noded" descent in altitude. When the warm anomaly plume then interacts with the tropopause the domain tends to stabilized due to limiting vertical motion throughout the medium ... A more meaningful and longer lasting PV decay takes place and bona fide blocking then takes over the higher latitude circulation characteristic. That's the basics on "how to pancake" the PV using stratospheric influence from above.

Primer stated, he first warm event of the stratosphere over the poles this season is as of last night just emerging:

Caution: The AO just spent 45 days heavily positively biased, and during that time there was only modest cool anomalies (the preferred statistical correlation would have been more intense) in the middle stratosphere, certainly nothing propagating either. Clearly there were other factor causing the AO to remain elevated, where the temperatures of the PV appeared to be more symptomatic of those physics, and not instrumental on their own. Soft version: the temperatures did not cause the +AO during that time; something else did.

I personally believe the early recovery of the cryosphere (I know Ray wants to punch a face every time he reads that word...but) against the fact that virtually all the Global oceanic heat sources have above normal heat content at the middle latitudes, caused stronger than normal geopotential gradient. That led to in situ howling middle tropospheric velocities in the mean, where the PV boundaries with the ambient medium farther south. This is speculation, but it could atone for having stronger than normal PV, where it's strength was derived by gradient as opposed to stratosphere-tropospheric relays at higher altitudes - which again, there was no evidence during the +AO of that being causal. Soft version: the +AO and stronger then usual PV may have been caused by greater than normal gradient between the areas where it is cold/icy/snowy, and where there was an abundance of warmth. It is noted that ENSO remains in weak La Nina, but that doesn't stop the fact that overall, warm anomalies dominate the oceanic planet.

I think this emerging warm node has a chance to be more meaningful because the amplitude of the height field's Wave (1, there are 3 total) is impressive as this is emerging:

Look back at the 30 year data set, ALL propagating events were first detected as significant amplitude wave emergence at the upper boundary of the stratospheric altitudes. Why ... who knows... but here is just one example back in 2006 of a strong wave amplitude and apparent correlation with temperature flux and subsequent propagating behavior:

Conclusion: This is quite tentative indeed and one should not run to the bank with dreams of snowy white Knights to swoop in from the North and rescue you from your ennui. However, there are some evidences that validate monitoring this for possible more significant emergence and perhaps propagation. It should be concretely stated that propagation is very key in the correlation on the AO. The above annotations go some distance toward illustrated that. Also, there is a time-lag as is also implied. It's on the order of 15 to 20 days when peering back over the data set. So even if this proves useful as an early lead/detection, we should not count on it paying dividens until the middle of January. And storminess that we may encounter prior to then...perhaps guided along by a +PNA interval, is less likely related to any cold loading and subsequent storminess that would result from a forced PV weakening.

John

[CoastalWx]

John good post. I think we all agree that the stratosphere has warmed, but the question I have is whether this warming halts (which some models show) and also..how and when does it downwell. Some of those EP flux graphs are against downwell propagation at the moment.

[Typhoon Tip]

John good post. I think we all agree that the stratosphere has warmed, but the question I have is whether this warming halts (which some models show) and also..how and when does it downwell. Some of those EP flux graphs are against downwell propagation at the moment.

Yes, exactly - I addressed the same concerns in that, as to whether it propagates or not...

I think the Wave 1 geopotential product is interesting in that it shows there is a lot of mass involved so far with this early detection. That's not a bad thing...

The other thing, ...are we certain the EP flux is associated with SSWs? These SSWs origin in the 2mb level - which is the stratopause...

[OKpowdah]

Yes, exactly - I addressed the same concerns in that, as to whether it propagates or not...

I think the Wave 1 geopotential product is interesting in that it shows there is a lot of mass involved so far with this early detection. That's not a bad thing...

The other thing, ...are we certain the EP flux is associated with SSWs? These SSWs origin in the 2mb level - which is the stratopause...

The EP flux is associated with the potential for downward propagation

[dendrite]

The SE ridge gets beaten down a bit d11-15 on the ecens.

[CoastalWx]

Euro ensembles definitely try to disrupt the vortex in the longer range. There is a split flow like pattern in nw Canada with a Caspian ridge and another bulge trying to develop in the NPAC. Caveat being we still have the vortex and Pacific flow along with a +NAO.

[mahk_webstah]

Euro ensembles definitely try to disrupt the vortex in the longer range. There is a split flow like pattern in nw Canada with a Caspian ridge and another bulge trying to develop in the NPAC. Caveat being we still have the vortex and Pacific flow along with a +NAO.

A ridge in the Caspian brings cross polar no? Perhaps the vortex is a waning semi permanent feature that we just deal with. As long as we can get some PNA we have a storm track. Could the Caspian ridge and a PNA hook up and cut off that vortex a bit?

[CoastalWx]

A ridge in the Caspian brings cross polar no? Perhaps the vortex is a waning semi permanent feature that we just deal with. As long as we can get some PNA we have a storm track. Could the Caspian ridge and a PNA hook up and cut off that vortex a bit?

The Caspian ridge is sort of punching the PV in the side. Those ridges always could hook up which would split the PV in two, but it still might drive a +NAO. It's better to see it split, then have that big continuation of it, from Greenland to AK.

[mahk_webstah]

+NAO not so bad up here but worse for you guys....

I think the vortex will get split but will other forces strengthen the block or wiill the change be transient and the vortex returns. Maybe depends upon the Atlantic a bit to help out and bang the vortex from the east.

[CoastalWx]

Well after this cool down of sorts in the beginning, I think we may see a warm up possibly around Jan 7-9th or so. After that, it is a little up in the air as the AK vortex does try to make a comeback during the time I just mentioned. However, we may once again try to see heights builds into AK and force another cool shot south. Basically, it may warm up a bit after the first week, but it is also possible we may cool down again heading into the second week. I think the question is whether or not the second cool show gets muted because the pattern as a little hostile again. However, it doesn;t look like anything we endured, so it may not be all that bad, and climo is on our side as well. I also like seeing the ridge in the NATL. Not a -NAO yet, but the ridging is trying to develop.

[CoastalWx]

If you really want to weenie out, it looks like AAM is tending to rise too which will help build ridging out west for now.

[ORH_wxman]

We might torch again in the Jan 7-10 time frame, but its a bit uncertain right now. The cold shot looks pretty impressive, but its relatively transient...there is more cold that looks like it wants to come down around mid-month, but it also looks like we could have the aformentioned milder period.

[ORH_wxman]

One positive sign is that really for the first time all winter...the ensembles look to completely erode the AK vortex by Jan 10-12...it might be rushing it, but that is something that is nice to see. Hopefully it will get closer and closer until its in the D6-10 range and we can be confident on it. It splits the PV and send one piece all the way back down into Russia almost toward N Japan. This starts building heights over the EPO region.

NAO looks disgusting though...so our first hope is the PAC I think...if we get that going, we can do just fine even with a +NAO

[OKpowdah]

I think someone mentioned it already, but imagine if we had a negative NAO block during this surge of Canadian air. Man, that would be a decent arctic outbreak. Probably a better shot at a leading storm too

[codfishsnowman]

I guess it is a step in the right direction. It is amazing though that many areas on the cp will go down with the second trace Dec snowfalls in less than a decade. Just amazing, almost as amazing as the foot plus pre Halloween snow event in the lower ct valley

I remember reading Dr. Mels column in the Harford Courant when I was a kid and he used to wax philosophical about what a snowy month Dec was and back then in the mid 80s the Decembers were usually pretty terrible lol...