Model discussion - hunt for cold Christmas period 2021

[North-Easterly Blast]

2 hours ago, Valleyboy said:

That’s what I’m saying John.  If the correlation between warm Septembers and the following winters were true, then this theory was completely bust in 78/79 which was the coldest winter since 62/63.  Weather doesn’t work like that, it’s too chaotic.

September 1978 wasn't extraordinarily warm, it had a CET of 14.2, so only slightly above average unlike 2021.  

[North-Easterly Blast]

2 hours ago, Wingman Blue said:

1962 had a very warm September, 27.8C on the 3rd….?

September 1962 actually did see a brief warm spell at the start, in what was a cool month overall with a CET of 12.6.  It is not uncommon to see brief warm spells in a cool period overall, albeit short lived.

[Snowing41]

17 hours ago, booferking said:

Early December was primed for cold blocked weather heading into xmas the EC46 etc screaming for it along with other drivers and what did we get nationwide very little only for a selected few, January screaming almost the opposite can the weather make fools of us again absolutely it does what it wants all the models and drivers can be fooled like ourselves. 

They never fail when mild wet weather is forecast though 

[sundog]

14 minutes ago, North-Easterly Blast said:

September 1978 wasn't extraordinarily warm, it had a CET of 14.2, so only slightly above average unlike 2021.  

Anyway its more so warm Septembers of the last 25 years or so..being more correlation 

Edited December 29, 2021 by sundog

[swfc]

Looking at the 6z gfs control "I know I'm bored" has very little Heighths way south to the UK. The point being low pressure Dosnt want to dive sse be it fi

Edited December 29, 2021 by swfc

[Frosty.]

For sure there’s some beguiling output this morning for long suffering coldies regarding next week with the chance of some colder air and even some snow in places, I’m just happy to see some seasonal weather indicated, the Gfs 6z op for example shows repeated colder incursions..anything is better than this infernal mild filth..see I’m completely unbiased!  

[Methuselah]

8 minutes ago, sundog said:

Anyway its more so Septembers of the last 25 years or so..being more correlation 

Which only goes to show that any kind of September is now less-likely to be followed by a severe winter than was once the case?

[booferking]

14 minutes ago, Snowing41 said:

They never fail when mild wet weather is forecast though 

Yep so true.

[Snowing41]

18 minutes ago, sundog said:

Anyway its more so warm Septembers of the last 25 years or so..being more correlation 

What we need right now is 2 weeks or so of cold dry frosty weather. In Leeds it seems every day its raining , its horrendous. 

[sundog]

22 minutes ago, Ed Stone said:

Which only goes to show that any kind of September is now less-likely to be followed by a severe winter than was once the case?

Indeed but most especially a very warm one. 

[booferking]

14 hours ago, Mike Poole said:

Right now, with the climate situation as it is, a whole lot of things can be a big concern for the winter:

• Britain existing east of a warm Atlantic Ocean.
• Any new teleconnection arising out of the blue like the Indian Ocean Dipole in 2019.  
• EQBO will either fail to produce the goods or fail completely.
• Wherever we are in the MJO or AAM phase space, a reason will be found why the UK will favour mild.
• The strat is our only hope, but a SSW 2 of every 3 years, and only 70% of those likely to deliver, it isn’t good odds, except it may be the only game in town.  
• And it is most likely to deliver in March if it happens.  Has to perfect though, for the south, 2018 was, 2013 was a few hours slush. 
• If persistent meridional jet over 1 year from last year’s SSW hasn’t delivered, that is a worry because that doesn’t often happen. 
• All the seasonal models bar the Japanese and Chinese going for mild (happens every year now).  
• The October fog index .  

But no, I’ve never heard of a theory that a warm September is a thing to worry about, in that regards.

Mike

This year its sunspot activity need to add that to the list.

[Anthony Burden]

Hi GFS 06z continues with the pressure rise in very favourable position with Atlantic still looking 

less aggressive still on track for a cold period.Some disagreement with the stratisphere polar vortex,

ECM going for strong throughout while Juda Cohen climatologist going for a much less aggressive PV.

This could be a major factor in wether we see -NOA against a +NOA which is why I am looking for

pressure rising in mid Atlantic following Juda Cohen scenario,fingers crossed.

 

[booferking]

Surprised no wind warning the day from the metoffice for N.Ireland already seen 70mph gust on North Coast.

[Nick F]

Only crumb of comfort I can find this morning for next few weeks prospects are a cluster representing a 1/3 of the 00z EPS members hinting at height rises over Scandi via the arctic in the extended range, but the other 2/3rds zonal westerlies with low heights centred to our N and NW.

Other than that, we are looking at brief cold incursions on the back of lows moving east. I do wonder, with the EC now showing the MJO heading into phase 8, whether we'll get another go at amplification in a few weeks to shake things up, or whether the MJO effects toward mid/high latitude patterns will continue to be muted / overridden by La Nina forcing and the strong PV.

[phil nw.]

The outlook into next week looks colder on the latest runs.A northerly brings the colder air back south.With the mean jet staying further south we stay on the cold side after,Whether this continues to evolve into something even colder still remains to be seen.

The trend seems to be of lowering heights into Europe in week 2 and the move west of the Azores high into mid-Atlantic which would see the jet path on a more nw-se angle.

There is still some Atlantic mobility to come but at least we see signs that this mild spell isn't going to last too long and the medium term doesn't look so dire for coldies.

[BurwellWeatherWatch]

i've done a quick test on the September versus Winter theory, though I think it is only ever proposed fairly anecdotally on the twitter feed of the other main weather site.

I took 100 years of September CET data (1921-2020) and then did a correlation co-efficient to the following winter. This gave a correlation of 0.125 (i.e. negligible).

However, I appreciate this wasn't the question posed - i.e. it was whether mild Septembers lead to mild winters rather than whether September correlates per se.

So I filtered for Septembers with a positive average anomaly and then correlated them to the following winters. This gave a coefficient of 0.29.

So it is a slightly stronger coefficient but unlikely to pass a test of statistical significance. Anything below 0.3 is considered fairly irrelevant.

So I'd personally put the theory on the backburner!

Edited December 29, 2021 by BurwellWeatherWatch

[North-Easterly Blast]

1 hour ago, sundog said:

Indeed but most especially a very warm one. 

I think that the September theory works only one way but not the other - whilst it is not clear that a cool or average September appears to have any bearing on the winter that follows, it does appear that there is a link between a significantly warm September and that the following winter will be mild with just a small chance that it will be average and virtually no chance of a colder than average winter to follow.

[Don]

2 minutes ago, North-Easterly Blast said:

I think that the September theory works only one way but not the other - whilst it is not clear that a cool or average September appears to have any bearing on the winter that follows, it does appear that there is a link between a significantly warm September and that the following winter will be mild with just a small chance that it will be average and virtually no chance of a colder than average winter to follow.

Gavin Partridge did an interesting video on the September vs following winter theory back in the autumn.  I would say worth a watch.

[alexisj9]

12 hours ago, syed2878 said:

 Yes I have had the same earah few times today I had to close my browser re-open the browser and refresh that’s how I got it sorted but maybe the tech’s can take a look sometimes

Edit, never mind, it the reaction one. Misread, thought it was the content one.

Edited December 29, 2021 by alexisj9

[MATTWOLVES 3]

What can I say about the ens...theres plenty of interest amongst em..from Ntlys to scandy blocking...further into January could be a tad more exciting...Worth noting though that many have a very strong vortex and signs of a coupling....obviously some good scandy Heights would put us in the game because not every cold spell will revolve around NW heights.....but after this mild week a tad more exciting for me!

And I have this overwhelming feeling there's gonna be a huge amount of cold air bottled up over the Arctic towards the end of the season...just watch it come flooding south through March and beyond...

[That ECM]

3 hours ago, Ed Stone said:

If 'parroting climatology' makes one an 'idiot', what on earth does spending months' predicting 'Murr sausages', and the like, make one?

Popular. If the output suggests mild wet and windy the that’s part of the discussion.

 

This September thing is as bad as suggesting the output went rubbish because I wasn’t wearing my lucky pants. 

Edited December 29, 2021 by That ECM

[Sunny76]

32 minutes ago, North-Easterly Blast said:

I think that the September theory works only one way but not the other - whilst it is not clear that a cool or average September appears to have any bearing on the winter that follows, it does appear that there is a link between a significantly warm September and that the following winter will be mild with just a small chance that it will be average and virtually no chance of a colder than average winter to follow.

I’m not sure I agree with the warm September theory, leading to a mild winter.

Septmeber 2009 and 10 were both relatively warm and sunny, after mediocre to poor summer months in those years. Winters that followed were both cold or had very cold spells with less frequent mild spells.

Septmeber 1994, 2001, and 2013 were all cool or slightly below average, but the winters that followed were all mild or very mild, especially 94/95 and 2013/14.

[Mike Poole]

5 minutes ago, Sunny76 said:

I’m not sure I agree with the warm September theory, leading to a mild winter.

Septmeber 2009 and 10 were both relatively warm and sunny, after mediocre to poor summer months in those years. Winters that followed were both cold or had very cold spells with less frequent mild spells.

Septmeber 1994, 2001, and 2013 were all cool or slightly below average, but the winters that followed were all mild or very mild, especially 94/95 and 2013/14.

I certainly don’t agree with it - I would agree with the statement ‘virtually everything leads to a mild winter’ these days.  Let’s see if we can get some colder air south with this northerly on the models in the semi-reliable, and see where we go from there.

[Stu_London]

2 hours ago, Ed Stone said:

Which only goes to show that any kind of September is now less-likely to be followed by a severe winter than was once the case?

Perhaps we should start a petition to get September removed from the calendar.

Only needs 100,000 and then it would have to be debated in parliament.

[Don]

7 minutes ago, Stu_London said:

Perhaps we should start a petition to get September removed from the calendar.

Only needs 100,000 and then it would have to be debated in parliament.

I would definitely be up for that as that would mean I would no longer have any Birthdays and therefore not get any older!! 

Edited December 29, 2021 by Don