Winter 2018/19 – cold long range models, SSW events and favourable global drivers… where did it go wrong? A review.

[stodge]

2 minutes ago, North-Easterly Blast said:

No, winter 2008-09 could not be described as a mild one by any means.  It had an overall CET of 3.53; both December and January of that winter were below average, and the first half of February was cold, it was only the second half of February of that winter that was mild.  Winter 2008-09 did come out as a reasonably cold one overall although it wasn't especially so.

Yes, I stand corrected on that. I recalled two particularly cold spells but I'm sure later February was quite mile verging on warm.

As you say, the overall numbers were on the cold side - I was just trying to tease out if there was any linkage to this notion of the winter before a minimum being not desperately cold or even mild.

[Weather-history]

2 minutes ago, stodge said:

Yes, I stand corrected on that. I recalled two particularly cold spells but I'm sure later February was quite mile verging on warm.

As you say, the overall numbers were on the cold side - I was just trying to tease out if there was any linkage to this notion of the winter before a minimum being not desperately cold or even mild.

There was a cold spell at the start of the winter.  28th November-15th December 2008 had a CET of 2.1C 

 

[summer blizzard]

13 hours ago, CreweCold said:

I think the PDO has been a major thorn in our side over recent times. The set up Pacific side has been just so wrong for us the majority of the time- with N America often seeing deep cold outbreaks.

Essentially SSTs were wrong for us on both sides this winter- Pacific and N Atlantic. I hope to see a May tripole this year.

PDO has actually been close to neutral this winter. Not to blame in my opinion.

50 minutes ago, Quicksilver1989 said:

Yeah 2009 was a strange one because the usual signals such as ENSO and SSTs would have favoured a mild December, yet it turned out to be very blocked... maybe it's 10 year anniversary winter will try and surpass it...

Top 20 spotless years have a good bias towards colder than average Decembers and January's following. We were unlucky this year in that regard.

[North-Easterly Blast]

Winter 2008-09 also had a westerly QBO; so for a winter in westerly QBO 2008-09 was good.  I suspect that the easterly QBO along with it being very close to solar minimum helped 2009-10 to be a cold winter overall.

[bluearmy]

14 hours ago, CreweCold said:

I think the PDO has been a major thorn in our side over recent times. The set up Pacific side has been just so wrong for us the majority of the time- with N America often seeing deep cold outbreaks.

Essentially SSTs were wrong for us on both sides this winter- Pacific and N Atlantic. I hope to see a May tripole this year.

The av T2’s over n America are well above average thus far 

our issue in nw Europe is the failure of the euro trough to verity. When it was there we were cold ...... with no strong HLB, a Euro trough is required 

[BlueHedgehog074]

Great thread - this was an interesting read. Thank you!

Certainly a lot of passion and thought injected into your findings and reasons! 

[stodge]

24 minutes ago, bluearmy said:

The av T2’s over n America are well above average thus far 

our issue in nw Europe is the failure of the euro trough to verity. When it was there we were cold ...... with no strong HLB, a Euro trough is required 

Isn`t the problem that when we get the trough disrupt into Europe, we aren`t seeing consequential height rises over Scandinavia so the pattern flattens each time. 

[TEITS]

What I find rather interesting is when I joined this forum alot of focus was placed on the Atlantic SSTs which is understandable. However in recent years less focus seems to be placed on this with more and more teleconnections being used in forecasts. I actually think that since forecasts have become more technical on this forum the accuracy has decreased  So I shall ask a few more questions.

1. Should we take a more basic approach at forecasting next winter by for example keeping a closer eye on the Atlantic SSTs?

2. As many on here (including myself) are biased to cold. Do you think that maybe we are looking at signals that point to cold too often? Should we also look at signals that might point to the contrary. Allowing your bias to skew your forecast is one of my biggest faults and I openly admit that!

Good thread this by the way.

 

[BruenSryan]

5 hours ago, DiagonalRedLine said:

Great thread - this was an interesting read. Thank you!

Certainly a lot of passion and thought injected into your findings and reasons! 

Totally agreed. Kudos to you Quicksilver1989 on that intriguing read. Will certainly be of help to the evaluation of my Winter forecast when I do it at the beginning of March! Some interesting comments here too. 

[DAVID SNOW]

16 minutes ago, TEITS said:

What I find rather interesting is when I joined this forum alot of focus was placed on the Atlantic SSTs which is understandable. However in recent years less focus seems to be placed on this with more and more teleconnections being used in forecasts. I actually think that since forecasts have become more technical on this forum the accuracy has decreased  So I shall ask a few more questions.

1. Should we take a more basic approach at forecasting next winter by for example keeping a closer eye on the Atlantic SSTs?

2. As many on here (including myself) are biased to cold. Do you think that maybe we are looking at signals that point to cold too often? Should we also look at signals that might point to the contrary. Allowing your bias to skew your forecast is one of my biggest faults and I openly admit that!

Good thread this by the way.

 

One thing that has stood out(imo) is the Met Office long range/further outlook daily updates, time and time again they continually pointed to a protracted cold, possibly v cold outlook, with winds from the east, sure we had a cold spell in January, but even then the CET still ended close to average. Add December(mild) February(mild)  and it would seem certain drivers/signals were missed? Or perhaps misunderstood or weighted incorrectly against one another?

Complex, bordering on chaotic.

[BLAST FROM THE PAST]

Stodge

funny that....I’m getting stacks of fog now.....

 

Quick...nice piece...something to mull over.  

 

BFTP

[Derecho]

22 hours ago, TEITS said:

What I find rather interesting is when I joined this forum alot of focus was placed on the Atlantic SSTs which is understandable. However in recent years less focus seems to be placed on this with more and more teleconnections being used in forecasts. I actually think that since forecasts have become more technical on this forum the accuracy has decreased  So I shall ask a few more questions.

1. Should we take a more basic approach at forecasting next winter by for example keeping a closer eye on the Atlantic SSTs?

I think its role was perhaps underestimated but the complication arises from the role of other factors. How different would this winter have been if there was a huge El Nino or La Nina event?

2. As many on here (including myself) are biased to cold. Do you think that maybe we are looking at signals that point to cold too often? Should we also look at signals that might point to the contrary. Allowing your bias to skew your forecast is one of my biggest faults and I openly admit that!

I think that is perhaps human nature, we look for the things we want to see and in such cases its easy to overlook things that could possibly work against us.

Good thread this by the way.

 

 

[Dunstable Snow]

An enjoyable and interesting thread to read and some interesting thoughts to be developed further over the coming months as we try to make sense of this season. It will be very interesting to see what, if anything,comes out from the Met Office by way of a post mortem. As referenced above, they have been much more bullish than they would normally be for much of this season regarding east or north easterly winds and cold and snowy conditions develop within the 16-30 day range. This has only heightened the frustration with what has been delivered !

[knocker]

 

Edited February 16, 2019 by knocker

[North-Easterly Blast]

I wonder if what has gone wrong for February and how it is panning out to be such a mild month was started with the failed easterly around January 24th / 25th.  Had this easterly materialised, we could have seen a notable freezing spell in the final week of January which would have resulted in a below average CET month, possibly closer to 3*C rather than what it ended up.  If late January had panned out like this I feel that the pattern for this month could have been very different with the chance of further cold spells.  Instead, as the easterly failed to materialise, we had a milder couple of days, and then we were left with a much more watered down cold spell from the NW, with no significant northern blocking to create any building blocks for further cold outbreaks to develop for this month.  Without any northern blocking in place, the mild air soon won out in the first week of this month, and we are now left with a Euro block in totally the wrong place for any cold air to reach the UK.

 

[North-Easterly Blast]

In actual fact whilst looking at records a westerly QBO does increase the chance of a milder winter in the UK, this is still not a guarantee by any means.  Even the relatively recent winter of 2008-09 had a wQBO and it still managed to be colder than average overall.  Going further back, winter 1985-86 had a wQBO, yet was still a cold one overall, in particular with a notably cold February.  The QBO was still just weakly westerly in 1978-79, and look at how severe that winter turned out.  So a westerly QBO, or at least a QBO that is not easterly, in these facts has not always precluded notable cold spells in the UK.  Although the rest of the winter wasn't cold, a wQBO also co-incided with a cold month in Feb 1983.  Also although not cold in the rest of the winter, we still had a notably cold month in Dec 2010 with a wQBO.

When you look at all of the above, one cannot totally think that this winter's wQBO has fully led to a milder than average season.

Edited February 16, 2019 by North-Easterly Blast

[Steve C]

I quite like these sort of things tbh. When events test our preconceptions, we learn. All good in the long term.

[Mike Poole]

On 14 February 2019 at 16:02, Quicksilver1989 said:

 

Good post, I had promised a review of what went wrong in the model thread, but there's no need to as you have covered all the main aspects.  If I could just make a couple of addional points:

• I think sea surface temperatures may have been a bigger factor, they we're rarely discussed but acknowledged to be less than favourable at the start of winter, here 1 Dec:

Helped intensify the jet maybe?

• Given the amplification or otherwise of the jet stream is just wave physics,  it is possible that two conflicting signals caused destructive interference, maybe the MJO and SSW.    I remain slightly unconvinced by this theory as it's 2 dimensional, whereas the SSW has a third dimension to it.
• We were just unlucky?  Who knows!  

[Weather-history]

Didn't somebody post about the large failure of past SSWs events under certain criteria in the stratosphere thread? Wasn't this winter under the same criteria?

I'm sure a saw a post on this.

[North-Easterly Blast]

I think the situation is that although an SSW increases the chance of significant cold spells in the UK as has happened with some SSW events.  However, an SSW is by no means a guarantee that blocking will set up favourably to deliver cold to our small part of the world, and I certainly do not think that all past SSW events have brought notable cold spells to the UK.  I would say that the SSW in early January this year was one of those events where the UK was left unlucky and that it did not result in blocking setting up favourably to deliver us notable cold.  We have had the carrot dangled in the second half of January this year bringing us a watered down cold period but a failed easterly later in the month, and then this month blocking has set up in totally the wrong place to deliver cold to the UK.

[StormyWeather28]

This Winter is set to be the mildest ever recorded at many stations in Ireland. 

[chrisbell-nottheweatherman]

On 15/02/2019 at 20:04, TEITS said:

2. As many on here (including myself) are biased to cold. Do you think that maybe we are looking at signals that point to cold too often? Should we also look at signals that might point to the contrary. Allowing your bias to skew your forecast is one of my biggest faults and I openly admit that!

Good thread this by the way.

 

Many on here will be aware that I am far from being a meteorologist; I do, however, have a science background as a biology graduate and ex-Masters research student, albeit several years back now.  Your comment reminds me of a couple of principles in science that support you post:

1.  Researchers, often under pressure to generate positive results in order to generate further funding, often pay insufficient aattention to, and fail to make best use of, negative results.  Often, finding that something is not the case or that the factor you assumed must be responsible for what you're researching has nothing to do with it tells us more than confirming a link.  In this instance, the finding that a serious cold period didn't  emerge from promising signals will help us to understand things in greater depth than had events proceded as expected.

2.  If we only consider evidence that supports our preconceptions and existing hypotheses, we can miss important hints to the contrary and can end up in a position of confirmation bias.  Often, the greatest scientists have been those who have frequently critiqued their own hypotheses and searched for contradictory evidence.  If you're a cold fan, you ought to ask yourself whether there are routes to milder conditions even when models are producing cold outputs for the UK, and mild fans ought to ask themselves how things could go cold even if the indications are that zonal or Bartlett conditions are likely.

[damianslaw]

19 minutes ago, chrisbell-nottheweatherman said:

Many on here will be aware that I am far from being a meteorologist; I do, however, have a science background as a biology graduate and ex-Masters research student, albeit several years back now.  Your comment reminds me of a couple of principles in science that support you post:

1.  Researchers, often under pressure to generate positive results in order to generate further funding, often pay insufficient aattention to, and fail to make best use of, negative results.  Often, finding that something is not the case or that the factor you assumed must be responsible for what you're researching has nothing to do with it tells us more than confirming a link.  In this instance, the finding that a serious cold period didn't  emerge from promising signals will help us to understand things in greater depth than had events proceded as expected.

2.  If we only consider evidence that supports our preconceptions and existing hypotheses, we can miss important hints to the contrary and can end up in a position of confirmation bias.  Often, the greatest scientists have been those who have frequently critiqued their own hypotheses and searched for contradictory evidence.  If you're a cold fan, you ought to ask yourself whether there are routes to milder conditions even when models are producing cold outputs for the UK, and mild fans ought to ask themselves how things could go cold even if the indications are that zonal or Bartlett conditions are likely.

Good logical thinking.. never cast aside the opposite of what is expected to happen happening then!

Its all about the 'forcings' for me, you can often gain a sense of how things might pan out, by watching how forcings develop, which route and formation they take,  take the current pattern, all the forcing is from the atlantic, pounding down on the ridge, it will eventually win out, and the set pattern is a sinking ridge scenario - this is borne out by the fact central core heights don't look like repositioning much from current position - the key player is the northern arm of the jet, set to power through on a more southerly path - this is the key 'forcing' feature and the dominant force. The hard bit is picking out the dominant force, and accurately pinpointing how it will impact on us. Sometimes its easier to pick these out and predict there behaviour than at other times. Long may the weather continue to make fools of us all!

[Stu_London]

Thank for the review - a good read.

I think we have to accept that in a temperate maritime climate such as ours, the form horse will always be the least extreme option on the table (the form horse doesn't always win, but statisically is most likely). 

The notable thing for me this winter was how badly at times the main global forecast models performed. I began model watching over 20 years ago and as winter output goes, this has been one of the worst performing I have seen. I'm struggling to see how they have improved that much in terms of accuracy over 20 years. Perhaps this year the SSW threw them and they are maybe playing catch up with emergent patterns resulting from changes to climate and sea ice, but in an age when technological advances are accelerating as quickly as they are, I'm slightly disappointed that global forecasting models have not really progressed in terms of cracking the 96-168 hour period. 

I firmly believe that severe spells in winter will still occur in future and with a climate as complicated as ours, things are sure to fall right for us again sometime, although as the author of this thread notes, the dice might be loaded slightly more against us than has been historically.

We can console ourselves that the last decade has produced two and a half months (Dec 10, Mar 13, Mar 18 H1) of severe winter weather that would be notable in any historical era, so it stands to reason that this will reoccur sometime in the future.

 

 

[Nick F]

Worth reading this analysis from Isotherm on AmericanWx re: where it went wrong this winter. Although it is on an American weather forum, the points Tom makes are relevant for Europe aswell: https://www.americanwx.com/bb/topic/51698-my-winter-outlook-2018-19/?do=findComment&comment=5184369

From what I can glean from his analysis in respect of Europe, in a nutshell, easterly QBO at 50mb helped trigger the SSW, but descending  westerly QBO at 30mb going into winter + weak El Nino was forcing an unfavourable northern hemisphere pattern with Nina-esque pattern of sub-tropical blocking and expanded Hadley cells rather than sub-tropical troughing typical of El Nino. So even though we saw the -AO in January following the SSW, the Azores sub-tropical high would not not be suppressed, so at best the NAO was neutral but mostly slightly positive, despite some height rises over Greenland at times, so we never really saw a decent -NAO to bring deep cold. The MJO was active, but amplified in the warmer phases because of more uplift/convection over the Indian Ocean (warmer phases) and subsidence over Pacific (colder phases). All in all, the Pacific forcing (ENSO/MJO) along with QBO structure and resultant SSW and +AAM in the wrong places all transpired to prevent high latitude blocking. Tom makes an interesting observation that the easterly QBO at 50mb and westerly QBO at 30mb has only occured twice since the late 70s, these two years Nina like in winter patterns.

Caught many long range forecasters out, not because of poor forecasting but more a case of bad luck the way the QBO has transpired at different levels of the tropical stratopshere and it's impact on extra-tropical patterns but also background weak El Nino /neutral ENSO and lack of pattern response to the SSW. No only was winter poor for snow lovers in northern and western Europe but also for NE/E USA. The La Nina-esque pattern does favour western USA for cold and snow, as we've seen and still see Seattle, Las Vegas, large parts of Arizona and New Mexico buried in snow, even higher parts of LA seeing snow. Also Nina type patterns for Europe means most cold and snow is confined to NE/E/SE Europe. Hopefully winter 2019/20 sees more favourable pattern driving align, Solar minimum perhaps impacting too.

 

Edited February 23, 2019 by Nick F