Stratosphere and Polar Vortex Watch 2020

[Griff]

Your latest zonal installment... 

[ALL ABOARD]

4 minutes ago, Griff said:

Your latest zonal installment... 

Almost a 15 day reversal going by the mean? Could be even longer..... 

[Blessed Weather]

56 minutes ago, Vikos said:

All parameters fullfiled. Not only tempraise and zonal wind change. There are a few...

 

51 minutes ago, sebastiaan1973 said:

Never heard of. Do you have a paper/ article for this?

This 2018 paper by Dr. Amy Butler and Ed Gerber might help. There are some variations in the definition of a major SSW that do exist and Dr.Butler has been striving for some years to reach a universal agreement:

Optimizing the Definition of a Sudden Stratospheric Warming
Various criteria exist for determining the occurrence of a major sudden stratospheric warming (SSW), but the most common is based on the reversal of the climatological westerly zonal-mean zonal winds at 60° latitude and 10 hPa in the winter stratosphere.

[Vikos]

4 minutes ago, Blessed Weather said:

 

This 2018 paper by Dr. Amy Butler and Ed Gerber might help. There are some variations in the definition of a major SSW that do exist and Dr.Butler has been striving for some years to reach a universal agreement:

Optimizing the Definition of a Sudden Stratospheric Warming
Various criteria exist for determining the occurrence of a major sudden stratospheric warming (SSW), but the most common is based on the reversal of the climatological westerly zonal-mean zonal winds at 60° latitude and 10 hPa in the winter stratosphere.

Thank you!

Adding current and forecasted ozone in 30hpa

  ->

[sebastiaan1973]

13 minutes ago, Blessed Weather said:

 

This 2018 paper by Dr. Amy Butler and Ed Gerber might help. There are some variations in the definition of a major SSW that do exist and Dr.Butler has been striving for some years to reach a universal agreement:

Optimizing the Definition of a Sudden Stratospheric Warming
Various criteria exist for determining the occurrence of a major sudden stratospheric warming (SSW), but the most common is based on the reversal of the climatological westerly zonal-mean zonal winds at 60° latitude and 10 hPa in the winter stratosphere.

Thanks Vikos. Honesty I think yo u make things more complicated. We have to stick to that one and not making things more difficult than they are

Edited January 7, 2021 by sebastiaan1973

[Vikos]

3 minutes ago, sebastiaan1973 said:

Thanks Vikos. Honesty I think yo u make things more complicated. We have to stick to that one and not making things more difficult than they are

I am sorry, but every SSW is different, and studies on impacts and outcomes are not finished. But we will see, for us on the continent things look good and you will have your chance of canal ice-skating

[Blessed Weather]

A timely reminder from Simon Lee today that the impact of a SSW in the lower strat/troposphere lasts long after the initial event up at 10hPa.

The most important aspect of a major SSW is the long, subseasonal persistence of the negative NAM/weakened vortex in the lower-stratosphere. This raises the likelihood of a neg tropospheric NAM & mid-latitude coldwaves across this timescale. For example, the 2004 SSW:

Source: Twitter @SimonLeeWX

[Mike Poole]

1 hour ago, Interitus said:

Yes, they do!

It may well have picked it at 384, it will also falsely pick many others that don't materialise.....

Yes, I’m sure GFS and GEFS have predicted 10 of the last 3 SSWs.  

Looking at the NAM plot for todays 0z GFS, it looks like the trop response is OK again, just a bit of a hiatus along the way, caution just one run but if we see this continuing it will give us an idea when the SSW really starts to affect our weather.  

[bluearmy]

Very amusing Mike .......

Ec op expands that Atlantic daughter vortex ........becoming quite flaccid though but expanding to almost reach U.K. 

if the pattern imprints with enough southward suppression then it’s more than ok 

[Blessed Weather]

Today's (7th Jan) ensemble forecasts show more members (17 of 75) going for a split in the SPV over the next 10 days, up from the forecast from 5th Jan (8 members) and I note in Dr Butler's tweet she has added a "but" sentence reminding us that models struggle to predict splits further out than a week.

A clear distinction between 2 possible futures of the polar vortex over next 10 days - some ensemble members seeing a split vortex w/the larger lobe over Eurasia, while majority still see a displacement. But, forecast models struggle to predict splits more than a week ahead of time.

Source: Twitter @DrAHButler

[Don]

56 minutes ago, ALL ABOARD said:

Almost a 15 day reversal going by the mean? Could be even longer..... 

Will we benefit?  Time will tell.....

[chionomaniac]

Lol. A full SSW.

like a mini tornado.

BW linked to Amy’s paper and this is the recognised definition of an SSW. Whether or not the strat PV is totally destroyed or not, is not relevant to the definition, but is definitely relevant to what happens after

[Vikos]

22 minutes ago, chionomaniac said:

Lol. A full SSW.

like a mini tornado.

BW linked to Amy’s paper and this is the recognised definition of an SSW. Whether or not the strat PV is totally destroyed or not, is not relevant to the definition, but is definitely relevant to what happens after

No need to lol, I explained myself...

[chionomaniac]

Just now, Vikos said:

No need to lol, I explained myself...

Apologies. I didn’t mean to offend, but you brought a smile to my face. No mean thing in these times!

[Vikos]

1 minute ago, chionomaniac said:

Apologies. I didn’t mean to offend, but you brought a smile to my face. No mean thing in these times!

It's ok

It's a bit hard for my to explain such difficult things in a (for me) foreign language. I try not to use google translate too much as it in many ways just kills the sense of my minds and mkes chopsuey of things

[chionomaniac]

6 minutes ago, Vikos said:

It's ok

It's a bit hard for my to explain such difficult things in a (for me) foreign language. I try not to use google translate too much as it in many ways just kills the sense of my minds and mkes chopsuey of things

I admire anyone who tries and explain things in a different language. Us brits have a special sense of humour too.

[Vikos]

5 minutes ago, chionomaniac said:

Us brits have a special sense of humour too.

I love it...! let's get back to topic

[SqueakheartLW]

GFS + Parallel

The Parallel like the main GFS and ensembles now brought what was initially looking like the PV killer blow 2nd warming into close range now

Looked so promising about a week ago when this warming which has been toned down a lot delivered the final blow to the vortex. However the GFS + ensembles and the parallel are sticking to their guns about the 3rd warming and are bringing this closer and closer every day now

Still some hints of a double hit warming showing up. The parallel delays this right up to 384 hours away today. However the operational GFS has this double hit warming a bit closer at 354 hours away

The overall stats since the 3rd warming began to show itself in the GFS + parallel are as follows

GFS and GFS Parallel Figures

                               00z-12z 00z-12z  00z
Warming Peak     06/01     07/01     08/01
-28                         5             0 (1)        0 (1)
-24                         11           1 (4)        0 (1)
-20                         11           1 (9)        0 (8)
-16                         20           5 (5)        0 (8)
-12                         23           30 (7)      11 (4)
-8                           10           38 (10)    17 (6)
-4                           6             19 (3)       5 (5)
0                            9             4 (4)         0 (0)
+4                          4             0 (0)         0 (0)
Av Peak               -13.21    -8.73        -8.73

Double Hit Peak               (-12.96)    (-13.82)

As can be seen 3rd warming signal still present and strong and it has come down to around 250 to 270 hours away now. The double hit element is present in all 33 runs now but the timing of this is far more variable from very soon after the 3rd warming right out to 384 hours away with some of the runs

GEFS Legacy

Now time so see if the GEFS Legacy is picking up more of the 3rd warming signal and if it also has hints of this double hit element to this warming

Warming Peak     06/01    07/01     08/01
-32                         2            0             0 (0)
-28                         0            0             0 (0)
-24                         4            0             1 (1)
-20                         6            5             0 (0)
-16                         6            9             6 (2)
-12                         2            4             7 (2)
-8                           1            2             5 (5)
-4                           0            1             1 (4)
0                            0            0             1 (4)
+4                          0            0             0 (0)
+8                          0            0             0 (1)
AV                         -19.43   -14.86    -11.81

Double Hit Peak                              (-6.74)

GEFS Legacy is now more full on board with this 3rd warming and has continued to strengthen the signal too. It is now picking up on this double hit warming too with 19 of 21 members showing it and unlike GFS which has the double hit as a less warm warming the GEFS Legacy has a smaller 3rd warming followed by a stronger double hit soon after it

ECM

ECM now showing signs of this 3rd warming right at 240 hours on the 10hpa chart

JMA

Although a slight warming showing up over Siberia on the JMA right at the end it still isn't showing the 3rd warming at this stage

GEM

Looks like GEM is now starting to see the 3rd warming too

NAVGEM

NAVGEM not seeing the 3rd warming yet but it does only go up to 180 hours but unlike other models it appears to have the vortex in pieces by this stage

NASA

NASA starting to see a warmup over Siberia right at the end of the run, maybe the 3rd warming getting underway

CMA

CMA seeing the 3rd warming and at under 240 hours away too and unlike most other models has little left of the vortex already

FIM

FIM has little sign of the 3rd warming today but it may just be out of the 240 hours range of this model

MODEL SUMMARY

Below is the list of all the featured models and if they see the 3rd warming or not

GFS                   Yes
GEFS Legacy    Yes
JMA                    No
GEM                  Yes
ECM                  Yes
NAVGEM          No
NASA                Yes
CMA                  Yes
FIM                    No

So far 6 out of 9 models on board with the 3rd warming so a high chance it may come off at present

[Interitus]

14 hours ago, Mike Poole said:

Yes, I’m sure GFS and GEFS have predicted 10 of the last 3 SSWs.  

 

Hehe, maybe the best way to visualise variability of model runs is by use of chiclet charts. Here is a form of chiclet covering the whole of the 2019 SSW in GFS forecasts -

It's not annotated, so to explain - it is 10mb 60°N wind speed, red westerly, blue easterly.

Y-axis represents the model time step, T0 analysis at the bottom - what actually happened. T384 forecast at the top. X-axis is the 6-hourly run, 4 times per day, advancing from left to right.

So moving from left to right, forecast winds gradually advance diagonally down to the bottom of the graph and become the actual values.

It can be seen that to the middle or just beyond of runs, accuracy is good and forecast winds progress downwards fairly consistently. But at the top of the graph, there are wild fluctuations in forecasts, from SSW to vortex intensifications, often from run to run giving the vertical stripiness, which don't materialise.

At best it can be suggested that averaged over a number of runs, a weaker vortex and perhaps more particularly, a stronger vortex may be expected from the long range GFS values.

Edited January 8, 2021 by Interitus

[snowking]

And just in time to try and contradict the above post (entirely unintentional!)

GEFS mean 10mb zonal wind forecast from the last 4 0z runs - note the emerging trend for a much slower recovery of any zonal flow. Still a forecast so we’ll see

[Interitus]

5 minutes ago, snowking said:

And just in time to try and contradict the above post (entirely unintentional!)

GEFS mean 10mb zonal wind forecast from the last 4 0z runs - note the emerging trend for a much slower recovery of any zonal flow. Still a forecast so we’ll see

That doesn't contradict it at all 

[SqueakheartLW]

A rather interesting GFS 06z Operational run in regards to the 3rd warming or rather in this case a continuous series of warmings rolled into one

+216 hours

It all begins at +216 hours when the 3rd warming gets underway

+258 hours

We see the first peak of -4 at +258 hours

+276 hours

A slight cooldown takes place and we drop from -4 to -8 by +276 hours

+288 hours

At +288 hours we see another warmup again as we head back up to -4 again

+312 hours

We see a bigger cooldown after this second burst as we drop back to -16 by +312 hours but this isn't the end of the warming either

+384 hours

Instead of the expected cooldown we see yet another burst of warming which sees the peak warming creep back up to -8 where it generally hovers right to the end of the run

I have yet to look through the control and the other ensembles to see if this is a new pattern that the GFS is now seeing with a triple hit warming instead of the double it has been seeing so far

[Windysun1]

4 minutes ago, SqueakheartLW said:

A rather interesting GFS 06z Operational run in regards to the 3rd warming or rather in this case a continuous series of warmings rolled into one

+216 hours

It all begins at +216 hours when the 3rd warming gets underway

+258 hours

We see the first peak of -4 at +258 hours

+276 hours

A slight cooldown takes place and we drop from -4 to -8 by +276 hours

+288 hours

At +288 hours we see another warmup again as we head back up to -4 again

+312 hours

We see a bigger cooldown after this second burst as we drop back to -16 by +312 hours but this isn't the end of the warming either

+384 hours

Instead of the expected cooldown we see yet another burst of warming which sees the peak warming creep back up to -8 where it generally hovers right to the end of the run

I have yet to look through the control and the other ensembles to see if this is a new pattern that the GFS is now seeing with a triple hit warming instead of the double it has been seeing so far

Hi squeakheart,

Thanks for the updates.

But what does this actually mean as regards weather effecting the UK down the tracks. A lengthened continuation of weather coming from an eastely direction, which you would imagine would be colder than average?

[DOdo]

Just another question. Was there a slight warming in the Stratosphere responsible for the present cold snap. Did this warming occur atound December 15th  or am I imagining something

Thank you

[bluearmy]

16 minutes ago, DOdo said:

Just another question. Was there a slight warming in the Stratosphere responsible for the present cold snap. Did this warming occur atound December 15th  or am I imagining something

Thank you

There was a short dip to mid twenties zonal flow around dec 15 but there is no evidence that this had any influence on the lower strat and into the trop.