NH patterns Autumn 2018 - Forget the analogues ...

[Interitus]

On 13/09/2018 at 15:00, Interitus said:

This doesn't tell the whole story however as shown in this chart of running 20-year correlations between the indices and winter AO. Also included are a Mongolian z500 anomaly (50°N 120°E) which has been used to create an estimated POL -

The first few years are poor for all, this may be due to issues with data quality in the early reanalysis - the authors above use from 1958 onwards.

After this though, the Taymyr index is better than the POL except for the 3 year period 2005-2007 (interestingly the artificial POL also beat the Taymyr), but more than this it proves to be relatively stable providing consistently good correlations over time. The same can't be said of the POL however which is poor in the early years even anticorrelated to winter AO and this is more strongly the case for the Mongolian anomaly - it would suggest that the value of the POL is given by the node in the area of the Taymyr circulation and it is dragged down by its dipole in Mongolia.

In the second half of the period the Mongolian anomaly correlation improves which leads to better performance from the POL and there is also quite a marked sudden improvement for all including the Taymyr index. Couple of possibilities spring to mind - the timescales of Mongolian and POL correlations with winter AO are similar to the AMO. The 30 year correlation between the Mongolian anomaly and October AMO exceeds -0.7 when AMO leads by 29 years - but is >0.8 when AMO lags by 9 years (with over 0.95 for 10 year averaged AMO) - because of the timescales involved more data would be required to investigate this link further. The apparent sudden improvement in all indices may coincide with improved reanalysis with satellite data maybe.

Finally with regards to changes since 2007, it is worth noting that all the correlations have fallen since the 2007-12 period.

With regards to the above, the AMO was seen as a possible influence due to the length of the low frequency variability involved and also its known link with levels of Arctic sea ice. However, an interesting alternative with similar long term variability is the PDO. Below is an updated version of the chart above of 20 year correlations of the indices in October with winter AO but this time with 10 year averaged annual AMO and PDO -

Now it can be seen that the improved correlations coincide with a change of PDO from its negative to positive phase. For a while research has examined a so-called climate or regime shift after 1976 related to the PDO and in particular some papers look at the anti-phase relationship between the winter distribution of atmospheric mass as closely approximated by surface pressure, over the land and ocean regions of the northern hemisphere. When pressure is higher over land it is lower over oceans and vice versa. A similar anti-correlation exists between the ocean and ice-covered areas (with a moderate positive correlation between pressure over land and ice areas)

Whilst these correlations are consistent in the reanalysis data (from 1958-2002) the areas of the anti-phase pressure relationship changed after 1976 as shown in the composite charts below of the largest anti-phase anomalies -

(source: Interdecadal Change in the Eurasia-Pacific Anti-Phase Relation of Atmospheric Mass and Its Possible Link with PDO - Zhang & Guan 2017 - http://www.cmsjournal.net:8080/Jweb_jmr/CN/article/downloadArticleFile.do?attachType=PDF&id=1718)

Prior to 1976 the pattern resembled the AO with pressure over the Mongolian / southern POL node not significant. After the PDO change it is a much more zonal with a strong relationship between the pressure over Eurasia in the region of the Siberian high, and the north Pacific - a pattern known as the Eurasia-Pacific anti-phase relation (EPAR)

How this and the correlations have changed more recently and in the near future, as shown in the graph with the lower PDO but also lower ice and positive AMO phase will require more investigation.

Edited September 24, 2018 by Interitus

[Yarmy]

If, as the Kryjov paper reference by @Interitus above proposes, the October Taymyr Circulation Anomaly is an effective precursor method for predicting the winter AO then presumably the following snapshot pattern from this morning's GFS is exactly what we want to see (if we want to see a -ve winter AO):

 

 

 

[bluearmy]

4 hours ago, Yarmy said:

If, as the Kryjov paper reference by @Interitus above proposes, the October Taymyr Circulation Anomaly is an effective precursor method for predicting the winter AO then presumably the following snapshot pattern from this morning's GFS is exactly what we want to see (if we want to see a -ve winter AO

 

 

 

and interestingly ec mean is similar

[SMU]

Evening All

So my second main post in relation to Autumn / Winter 18.

Thus far the initial forecast for this first half of Autumn has been really satisfactory with some notable successes-

The Anomaly chart for Sept 1 to the 13th has shown that the jet has been forced off way to the North allowing perpetual Southerlies / SE winds to invade the UK & indeed western Europe-

* We have seen notable heat - nearly 80F on 13/10 Oct - 

* There havent been many 'westerly days' & rainfall has accumulated for some over short sharp bursts as opposed to the usual steady build up. ( Again highlighted in the first post )

* Also whats been a key player & also has close similarities with Summer is the depth of the blocking around the mid lattitudes - Record breaking High Pressure in July over Europe , & September sees record breaking High pressure over Alaska-

Sept 1-Sept 15 Global Anomaly

This anomaly thats lingered up until the tail of September has been the main reason that W Canada has had the very cold start to the Autumn & also why Siberia has been a little slow to start with snowcover -

The ice anomalies & low thermal gradient this year are really allowing for Higher than average pressure to exist in 'situ' even at Northerly Lattitudes - 

Examples of these powerful highs appearing at high lattitudes started appearing in 2010-

Note The december to Remember- The second spell started with a 'super high'

What these High pressures create is intense areas of WAA on the western flank & the same with cold on the eastern flank- they also allow for more Northward / southward penetration of the warm/cold 

So the conditions they bring are deemed 'extreme' for the localities on the recieving end of the advection-

Backing up this theory of Low ice / warmer arctic seas > Higher Arctic Amplification > Intense WAA/CAA is the range of the metric of AO which in the past 10 years has gradually been stretched scalewise up & down -

This Late Autumn / Winter - seems the perfect platform to deliver more of the same - Exceptional warmth interlinked with some potential for exceptional cold ! 

There are unlikely to be any over riding negative signals this winter-

- Neutral El Nino Signature 

- Downwelling westerly QBO unlikely to be to adverse to the pattern-

With more emphasis on positive links 

- Weak to possibly 'very' weak stratospheric vortex including a possible early warming event December to weaken the vortex further 

- Stronger disconnect in terms of tropospheric & stratospheric coupling - again the very shallow gradient weakening the 'westerlies'

- Very low solar activity supporting the westerly weakness 

- 'Super high pressures' migrating Northwards towards the pole creating sharp transitions / modality changes in teleconnection metrics ( AO / NAO / PNA & POL ) these will also create big Stationary patterns of warmth & cold around the mid lattitudes 

For me the signals are overwhelming & give us a range of solutions for Winter that strongly suggest a below average DJF with a high probability of at least a 1 monthly rolling period ( not to be confused with a recorded CET month ) being below 2c.

Higher incidence of Northerly & Easterly outbreaks.

I dont rule this out exclusive to DJF - but also with the pattern expected to flip towards the end of October we could see some of this blocking in place throughout November.

My eyes have turned to the stratosphere, which has seen a burst of activity lately bringing the zonal wind up above average of about 22 M/S - however the ensemble suite has shown that this may well be the peak for the moment as we drop back towards 20 M/S again in November ( the average being 30-40M/S as we head towards December )

So there we have it- some late Autumn / Early Winter insight -

- Big Flips in the AO with some decent negative values arriving

- Super High pressures retrograding up towards the arctic Circle generating significant CAA & stationary cold patterns 

- Possible early warming Late Nov / Early Dec to really take any Westerly sting out of the Jet

 

CIAO for now....

 

 

[BLAST FROM THE PAST]

Amen to that Steve....Winter of Discontent.....to start with ?

 

BFTP

[northwestsnow]

Thanks to Steve and others for this thread, i love to read peoples thoughts on were we are and where we might be heading.

Half way through October so November beginning to come into view now.

Insofar as Nov concerned i have an inkling we may see an attempt at a Greeny high late Oct and eventually a Uk high so some colder nights/possibly foggy weather, my favourite!!

[Dorsetbred]

A very interesting thread, thanks to all who have posted, I look forward to some more interesting reading as the weeks roll forward.

[Summer Sun]

wrong thread please hide/delete

Edited October 18, 2018 by Summer Sun

[SMU]

Another record has gone today-

We are currently today at the lowest ever ice extent in recorded history - surpassing 2016 in terms of recovery...

 

[Don]

Wishy washy northerlies this winter?!

[Snowyowl9]

Potent Nlys but straight Nlys are mostly dry anyway inland.

 

 

 

[SMU]

So, The last month of Autumn is just a few days away & with the clocks going back Sunday it will certainly feel very winter like this weekend...

However dont get used to the Northerlies I dont think we will see to many of them this side of December-

As we usher in the entrance to winter we look / hope for signs that we will get a cold one....

Well the next 4 weeks will go a fair way to setting the scene & potentially its good news, but a timely reminder we are by any means secure at the moment -

The starting point from the stratosphere doesnt look as good as 17/18 with the zonal wind running at record pace -

We are running about 12 M/S faster - which should indicate a fairly robust vortex - however Whats clear is that as we filter down the levels of the strat that robustness   & strength begins to wain - 50MB is pretty much on a par with the norm.

So what we are not seeing this year is downward propergation of the cold & coupling into the troposphere - we would see it in the graphs-

Now what was been discussed in the first post & needs to factored in this year is how the troposhere is propergating warmth into the pole & vertically, maybe more so than the norm -

The feedback loops supporting these transports are 

-record breaking heat domes of the summer / early autumn creating record breaking geopotential High pressures,- Think the huge -EPO high in sept

-The record breaking low exent of the ice this week teleconnecting to high pressure along the arctic circle around kara

-The bombardment of warmth transported north out if the tropics ( as well as the negativity of the sun ) 

The WAFz ( Vertical wave activity flux ) activity is whats supporting the current tropospheric disconnect ^^ with all of the above being the drivers.

Here is the current forecast -

As we can see the earlier GFS forecast was moderate in its intensity however now we are right up to 10MB -

In 2017 late October record breaking WAFz took place which temporarily split the vortex & had a big impact on the PV

Here is the 2017 seasonal WAFz chart linked with the polar cap geopotential height & the 10MB zonal wind-

We can see where the zonal winds took a hit, then recovered then took another hit before the SSW...

Heres 2015 with the super Nino figures

We see December had weak / negative WAFz & the vortex was strong - hence the polar cap & trop / strat couplet was strong & downwelled- = Blowtorch December...

So where do we start for November-

The WAFz is clearly keeping the stratosphere locked out for the foreseeable future so even though the zonal wind is recordbreaking it is NOT influencing the troposhere -

What the forecast?

( Source AER )

The vortex looks about to get hit by another wave of vertical flux which runs out into the first third of November-

* If this occurs it will certainly encourage the disconnect to continue, or better still disrupt the vortex so the Polar height cap warmth extends even higher -

The resultant outcome for November should tie in with the natural reduction of Temperature over the UK due to seasonality - however this comes with a twist-

The availablity of cold air in November starts to extend around the compass to include the East as well as the North & as a result of this & the expectation that we will end up with 1 or 2 standing waves in the second third of November there becomes the high chance of the UK hitting some either very warm weather or very cold weather - 

This may seem a little contrary to say very warm or cold - however the expectant flow is going to be blocked - not zonal. The standing waves could be -EPO / East  Scandi or +PNA to west Scandi which will become increasingly cold.

Also remember the PPN autumn forecasts - DRY but episodes of high rainfull- these a symptom of blocking highs & stationary flows....

So November Summary-

- High Varience in Temps V the Norm occuring from week 2- wild swings in temps

- significantly reduced Westerlies

- Weak rainfall episodes interspursed with spikes 

- Blocking to the East - high chance of North - North westward retrograde week 2...

Many thanks....

 

[BLAST FROM THE PAST]

Cheers Steve, yep I wouldn’t bet against that....I’m with you on this

 

BFTP

[SMU]

On 15/10/2018 at 21:11, Steve Murr said:

Evening All

So my second main post in relation to Autumn / Winter 18.

Thus far the initial forecast for this first half of Autumn has been really satisfactory with some notable successes-

The Anomaly chart for Sept 1 to the 13th has shown that the jet has been forced off way to the North allowing perpetual Southerlies / SE winds to invade the UK & indeed western Europe-

 

* We have seen notable heat - nearly 80F on 13/10 Oct - 

* There havent been many 'westerly days' & rainfall has accumulated for some over short sharp bursts as opposed to the usual steady build up. ( Again highlighted in the first post )

* Also whats been a key player & also has close similarities with Summer is the depth of the blocking around the mid lattitudes - Record breaking High Pressure in July over Europe , & September sees record breaking High pressure over Alaska-

Sept 1-Sept 15 Global Anomaly

This anomaly thats lingered up until the tail of September has been the main reason that W Canada has had the very cold start to the Autumn & also why Siberia has been a little slow to start with snowcover -

The ice anomalies & low thermal gradient this year are really allowing for Higher than average pressure to exist in 'situ' even at Northerly Lattitudes - 

Examples of these powerful highs appearing at high lattitudes started appearing in 2010-

Note The december to Remember- The second spell started with a 'super high'

What these High pressures create is intense areas of WAA on the western flank & the same with cold on the eastern flank- they also allow for more Northward / southward penetration of the warm/cold 

So the conditions they bring are deemed 'extreme' for the localities on the recieving end of the advection-

Backing up this theory of Low ice / warmer arctic seas > Higher Arctic Amplification > Intense WAA/CAA is the range of the metric of AO which in the past 10 years has gradually been stretched scalewise up & down -

This Late Autumn / Winter - seems the perfect platform to deliver more of the same - Exceptional warmth interlinked with some potential for exceptional cold ! 

There are unlikely to be any over riding negative signals this winter-

- Neutral El Nino Signature 

- Downwelling westerly QBO unlikely to be to adverse to the pattern-

With more emphasis on positive links 

- Weak to possibly 'very' weak stratospheric vortex including a possible early warming event December to weaken the vortex further 

- Stronger disconnect in terms of tropospheric & stratospheric coupling - again the very shallow gradient weakening the 'westerlies'

- Very low solar activity supporting the westerly weakness 

- 'Super high pressures' migrating Northwards towards the pole creating sharp transitions / modality changes in teleconnection metrics ( AO / NAO / PNA & POL ) these will also create big Stationary patterns of warmth & cold around the mid lattitudes 

For me the signals are overwhelming & give us a range of solutions for Winter that strongly suggest a below average DJF with a high probability of at least a 1 monthly rolling period ( not to be confused with a recorded CET month ) being below 2c.

Higher incidence of Northerly & Easterly outbreaks.

I dont rule this out exclusive to DJF - but also with the pattern expected to flip towards the end of October we could see some of this blocking in place throughout November.

My eyes have turned to the stratosphere, which has seen a burst of activity lately bringing the zonal wind up above average of about 22 M/S - however the ensemble suite has shown that this may well be the peak for the moment as we drop back towards 20 M/S again in November ( the average being 30-40M/S as we head towards December )

So there we have it- some late Autumn / Early Winter insight -

- Big Flips in the AO with some decent negative values arriving

- Super High pressures retrograding up towards the arctic Circle generating significant CAA & stationary cold patterns

- Possible early warming Late Nov / Early Dec to really take any Westerly sting out of the Jet

 

CIAO for now....

 

 

Evening-

Parts of the forecasting coming to fruition now with a (probable) record breaking positive height anamoly developing next weekend to the NE of the UK

Heights circa 588 DAM + the unusual location of the high make it a part of this winter which will herald record after record being broken globally

 

l

 

 

Edited November 11, 2018 by Steve Murr

[Lettucing Gutted]

With a blocking Scandi High of 588 DAM there must some exceptionally warm air tied in with that one!  Even my wildest blowtorch predictions have never foreseen a 588 DAM Scandi High in the middle of November.  That must be unprecedented for late autumn and winter.  Even in summer heatwave patterns, 588 DAM Highs in High and Mid-High Latitudes are exceptional and noteworthy.  You'd think though, that such a 500 HPA High would be impossible without low level maximum temperatures in the 30C+ range?

Edited November 13, 2018 by Lettucing Gutted

[Snowyowl9]

November 1985 coming again.

[bluearmy]

4 hours ago, Lettucing Gutted said:

With a blocking Scandi High of 588 DAM there must some exceptionally warm air tied in with that one!  Even my wildest blowtorch predictions have never foreseen a 588 DAM Scandi High in the middle of November.  That must be unprecedented for late autumn and winter.  Even in summer heatwave patterns, 588 DAM Highs in High and Mid-High Latitudes are exceptional and noteworthy.  You'd think though, that such a 500 HPA High would be impossible without low level maximum temperatures in the 30C+ range?

In late November ??? 

Highest actual dam I can find is 560 around n uk correlating with the  current Scandi high predicted of 580 on the z500 height charts 

 

Edited November 13, 2018 by bluearmy