Model Output Discussion - Into February

[January Snowstorm]

Is the SSW in the bag now or is there still a chance it won't happen?

[blizzard81]

2 minutes ago, bluearmy said:

Considering there isn’t a reversal in the upper strat until the 15th, yes you are ! 

Maybe there's such a thing as ITR

[bluearmy]

1 minute ago, Mike Poole said:

Spot the difference!

6z (left) and 12z (right) zonal winds, just to illustrate the uncertainty, very different towards the end of the run after similar profile of the initial warming, 6z showing a lot of promise with the downwelling, 12z just looks to fizzle out.  More runs needed.

 

The 12z didn’t particularly downwell but was quite polar field reversed in the trop (unrelated to the strat). And then the trop began to push stronger zonal flow up into the lower strat 50-70N.  As that’s trop activity later week 2, it can be ignored. The chart you show from the 12z illustrates that uptick.  I’d stick with the eps and glosea for now which means Exeter’s forecasts and stuff on social media 

[blizzard81]

Very appealing vast, stagnant deep cold pool building over western Russia. Something to tap into down the line. 

[bluearmy]

4 minutes ago, January Snowstorm said:

Is the SSW in the bag now or is there still a chance it won't happen?

It’s not in the bag and even if it verifies, there is little indication at the moment that it’s going to be anything other than a technicality in the records until we see downwelling waves next month. 

[alexisj9]

16 minutes ago, Mike Poole said:

Spot the difference!

6z (left) and 12z (right) zonal winds, just to illustrate the uncertainty, very different towards the end of the run after similar profile of the initial warming, 6z showing a lot of promise with the downwelling, 12z just looks to fizzle out.  More runs needed.

Meanwhile, GFS and GEM at T240, flirting with height rises in scandi once more:

Too early to be anything to do with the SSW, but when it’s effects do filter down it would be helpful if we were not starting from scratch to build blocking in a favourable place, so nice to see…

At least GFS is not alone this time, even the met is looking like some sort of high latitude block is coming.

Edited February 7, 2023 by alexisj9

[nick sussex]

Absolutely atrocious ECM.

The PV is one ominous rounded blob later . Dreadful output for coldies and the SSW at present even if it does change the NH pattern will do so at a snails pace.

We really needed a QTR and ended up with the LPTTR! 

Like pulling teeth trop response ! 

[Drifter]

A slightly odd ECM in that nothing seems to happen between days 8, 9 and 10.

[North-Easterly Blast]

1 hour ago, Cold Winter Night said:

No, they're not.

There are records of SSW's since the late 50s.

SSW's were quite common in the 60s, 70s and 80s and then "disappeared" between 1989 and 1998.
Then they happened regularly again (almost yearly) during the 2000s, but over the last 10 years not as frequent.

They get discussed a lot more, but that has everything to do with forums such as this, social media and increased access to data and model output.

We any of the SSWs in the 1960s to 1980s followed by a significant cold spell in the UK shortly afterwards?

Apart from the SSW in January 2009 leading on to the cold spell in early February that year, I do not think that any of the other SSWs in the 2000s were followed by much in the way of a cold spell shortly after, so unless we know when all the SSWs were, and if the UK did get a cold spell soon after, we do not know how favourable SSWs are in bringing a significant cold spell to the UK.

[Mike Poole]

4 minutes ago, North-Easterly Blast said:

We any of the SSWs in the 1960s to 1980s followed by a significant cold spell in the UK shortly afterwards?

Apart from the SSW in January 2009 leading on to the cold spell in early February that year, I do not think that any of the other SSWs in the 2000s were followed by much in the way of a cold spell shortly after, so unless we know when all the SSWs were, and if the UK did get a cold spell soon after, we do not know how favourable SSWs are in bringing a significant cold spell to the UK.

I’ve posted this up before, it’s a chart of winter weather regimes (+NAO, -NAO, scandi blocking, atlantic ridge) which I’ve hacked to mark the approximate time of all the SSWs with an ‘S’.  A string of -NAO or scandi blocking days after a SSW might indicate a cold spell, +NAO the reverse. Obviously the regimes are wider than the UK, so no guarantee as to exactly what weather the UK experienced.  

[ANYWEATHER]

1 hour ago, Weather-history said:

The mentioning of them has become become frequent because until about winter 2007- 2008,  I don't recall much talk about them if at all. Netweather is 20 years old, did people talk about the stratosphere during the winter of 2003-04?  

I think the last 5 or 6 years its got mentioned a lot more ,and now its all the time!!!

[sebastiaan1973]

3 minutes ago, Mike Poole said:

I’ve posted this up before, it’s a chart of winter weather regimes (+NAO, -NAO, scandi blocking, atlantic ridge) which I’ve hacked to mark the approximate time of all the SSWs with an ‘S’.  A string of -NAO or scandi blocking days after a SSW might indicate a cold spell, +NAO the reverse. Obviously the regimes are wider than the UK, so no guarantee as to exactly what weather the UK experienced.  

This one is important as well  

https://twitter.com/SimonLeeWx/status/1582372470027272192

[Stuie]

6 days, UKMO and ECM, different page.

[Cold Winter Night]

20 minutes ago, North-Easterly Blast said:

We any of the SSWs in the 1960s to 1980s followed by a significant cold spell in the UK shortly afterwards?

Apart from the SSW in January 2009 leading on to the cold spell in early February that year, I do not think that any of the other SSWs in the 2000s were followed by much in the way of a cold spell shortly after, so unless we know when all the SSWs were, and if the UK did get a cold spell soon after, we do not know how favourable SSWs are in bringing a significant cold spell to the UK.

It remains difficult to attribute cold spells to SSW's with certainty.

Take for example the one in late January 1963. That winter had already earned a place in the hall of fame as the SSW hit, but more cold was produced in February. We can speculate, was that Feb 63 cold the result of the SSW? Or would it have followed anyway, since it was a cold one already? Or did the SSW perhaps prevent an even colder month?

Some SSW's were followed by cold spells, some were not. It is far from 1+1=2, if you consider that, for example, SSW's can be both the result and the cause of blocking events. That's why in many cases a serious cold spell preceded the SSW.
If you subdivide SSW's according to ENSO state and seasonal timing, you are left with very small sample sizes that do not show homogeneous outcomes. The complexity increases even more if you include MJO phases.

It is a subject that still needs a lot of research, that's for sure.

Edited February 7, 2023 by Cold Winter Night

[Rain All Night]

12 minutes ago, sebastiaan1973 said:

This one is important as well  

https://twitter.com/SimonLeeWx/status/1582372470027272192

What a fantastic graphic. This one needs stickying at the top of each page of this thread!

[Nick2373]

12z still follows the theme of unsettled from the 15th onwards, like this morning if this trend continues looking likely South West winds. This needs to change in the next few days. 

[Stuie]

1 minute ago, Nick2373 said:

12z still follows the theme of unsettled from the 15th onwards, like this morning if this trend continues looking likely South West winds. This needs to change in the next few days. 

It does but it also shows what current stage is FI (fantasy island)

Keep looking at close cluster, forget the chaos, for now.

[Methuselah]

36 minutes ago, Mike Poole said:

I’ve posted this up before, it’s a chart of winter weather regimes (+NAO, -NAO, scandi blocking, atlantic ridge) which I’ve hacked to mark the approximate time of all the SSWs with an ‘S’.  A string of -NAO or scandi blocking days after a SSW might indicate a cold spell, +NAO the reverse. Obviously the regimes are wider than the UK, so no guarantee as to exactly what weather the UK experienced.  

Is that Breakout? If it is, I can't find the Start button!

[damianslaw]

24 minutes ago, Stuie W said:

6 days, UKMO and ECM, different page.

Important to see the differences here, the UKMO transports energy in the PV to the NE, ECM maintains most energy to the NW but signal it is draining and stretching eastwards. Keep an eye on the position and strength of the PV in the coming days I say, not much else to look at with the omipresent high pressure just sitting to our south and east.

[Nick2373]

4 minutes ago, Stuie W said:

It does but it also shows what current stage is FI (fantasy island)

Keep looking at close cluster, forget the chaos, for now.

It’s a reoccurring trend that’s the problem looking at the cluster if I was a betting man I’d say just above average with similar conditions as of late. 

[Stuie]

4 minutes ago, Nick2373 said:

It’s a reoccurring trend that’s the problem looking at the cluster if I was a betting man I’d say just above average with similar conditions as of late. 

No, tighter (lines) = high certainty

Low cluster = high uncertainly.

There is no betting unless you want to chase the low clustering.

[Ali1977]

Early March from the GEFS long range , that set up wouldn’t lead to warm spring conditions Could we end up having a colder March than both Jan and  Feb I wonder

[North-Easterly Blast]

19 minutes ago, Ali1977 said:

Early March from the GEFS long range , that set up wouldn’t lead to warm spring conditions Could we end up having a colder March than both Jan and  Feb I wonder

The last time that happened was in 2013, and before that in 1962, but it is very rare to get a March that is colder than both the preceding January and February.  In actual fact in 2013 the March was colder than all three months before it.

That said that chart is over a month away so it cannot be taken too seriously.  On top of that a cold early March does not guarantee a cold month overall - back in 2005, March looked promising for a cold month early on with a pretty cold first fortnight, but then the very mild second half came along and pushed the month above average overall.

Edited February 7, 2023 by North-Easterly Blast

[Cheshire Freeze]

27 minutes ago, Ali1977 said:

Early March from the GEFS long range , that set up wouldn’t lead to warm spring conditions Could we end up having a colder March than both Jan and  Feb I wonder

April-

[bluearmy]

12z eps mean pretty much loses ssw on the run - it may just about make it. given that we are ticking down, you’d expect things to be firming up