Model Output Discussion - heading into April

[Djdazzle]

1 hour ago, mb018538 said:

I take it you mean the ‘formerly known as summer month’ August?

Wasn’t too bad last year - CET over 17 and the warmest since 2004. Also contained the hottest August bank holiday weekend on record. But yes, August has been naff this century. Even 2003 didn’t have an amazing second half.

[chrisbell-nottheweatherman]

16 hours ago, damianslaw said:

Direction of travel eventual Atlantic driven pattern, look at jetstream profile forecasts beyond 240hrs, yes 10 dats off but show jet taking a more direct flow to the UK on a westerly trajectory, you can see the stirrings in chart above SW flow incoming. Until then lots of fine settled weather. Not saying it will mark the start of a lengthy unsettled spell, but more so after 2 months of little Atlantic weather there are indications it will make a comeback before month is out. Someone also mentioned sst profiles favour rapid cyclogensis south of Greenland through summer, ushering in more unsettled weather to the north, less so in the south. Chart above echoes this, deep low formation in that vicinity of Atlantic.

 

14 hours ago, Thundery wintry showers said:

I tend to agree with Damianslaw, it looks to me as if we're going to get one last high pressure spell (which in fairness may well last until near the end of May), but there are signs for the long term that the high pressure will slowly get shunted away eastwards and allow those lows to start coming in off the North Atlantic.  It's a long way off though, and certainly high pressure looks set to dominate in what's normally seen as the reliable timeframe.

 

3 hours ago, Singularity said:

It's an interesting situation, as the Arctic loses the last of its deeply cold air this week but not into regions that encourage broad and deep Atlantic lows to develop and trouble us.

So we're left with a weaker than usual temperature gradient in the North Atlantic, hence the very 'stuck' weather pattern with little attempt by lows to advance from the west. Even GFS, with its progressive bias, is unable to achieve that convincingly without relying on a large movement of relatively cold air into the N. Atlantic from Arctic parts of Canada. That being a plausible but not likely scenario (a lot has to fall into place).

Cold air is often released from the Arctic in May, as the polar vortex breaks down. For this reason, it has historically tended to be a more westerly-dominated month than April. 

For a few years now, the cold air release has largely avoided the North Atlantic in favour of Europe and/or the USA, allowing for more fully-anticyclonic or easterly weather in May. If the next few behave similarly, that will raise eyebrows. At the moment we can't tell if it's a new climate trend or a fluke of natural variability.

As heat builds to the south, changeable westerlies become harder to avoid in June without major driving forces working in favour of subtropical ridge displacement north-eastward from the Azores.

Without wishing to be moderated, it seems to me that these slightly varying analyses, based as they are on the same set of outputs, shows that those of us without an academic background in meteorology cannot honestly say that we know what will happen to the NH set-up later this month.  Personal preferences seem to negatively affect some Model thread posters: undertandably, we tend to focus on outputs that show conditions we enjoy and it can be easy to end-up in full confirmation bias, in particular for those whose prefererences are to the more extreme ends of the meteorological spectrum than others.  Sometimes, those of us who like a more moderate, changeable (more classcally British) climate can feel like reactionary heretics, but, despite climate shifts, more often than not, our climate regresses to nearer the mean. 

From my layman's perspective, though I've noted the slack gradients in the Atlantic, it must be said that the low south of Greenland in damianslaw's post does seem fairly strong.  Whether it will be enough to shift the ridge (if indeed it even verifies) is a question I'm unqualified to answer, but I do know that set-ups must change eventually.

Edited May 11, 2020 by chrisbell-nottheweatherman

[Mike Poole]

GloSea5 out today for the summer.  Some thoughts.

First, 2m temperature tertiles, for Jun-Aug, and for Jul-Sep:

So a higher probability of warmer than average, but additional information comes from comparing the two charts, the probability of warmer than average is lower for the later period, suggesting a particularly high probability of high temperatures in June, and less so in August - maybe no surprise there given August's 'performance' recently!

Next, the outer quintiles for Jun-Aug, and the same chart from May 2018 runs for comparison:

So a significant probability of well above average temperatures, but nowhere near as strong as 2018.

Geopotential heights Jun-Aug, tertiles and outer quintiles:

So higher heights more likely, and especially he further SE you go significantly so from the quintiles plot for the SE.  Looks hot here.

Finally, no clear signal on precipitation:

So, overall, looks promising for a warm or hot summer, unclear whether that is hot and dry or hot and thundery, or a mix.  And maybe a signal too for the hotter weather to be most likely in the early part of summer.

[Fourty Point Three Degrees]

There seems too be far too much talk about August here. Lets take May & June first,  I am confident that another lengthy hot dry summer is waiting in the wings.  Remember 2003 was a good summer, but 2006 was better.

[Faronstream]

42 minutes ago, Mike Poole said:

 

 

 

So a significant probability of well above average temperatures

 

 

 

 

So, overall, looks promising for a warm or hot summer, 

I would not say 25-40% possibility for "well above 2m temperature" is that high really since it's still under 50% so it can go either ways. Also don't forget that we are now entering a la nina period  so it's a bigger possibility for a cool wet summer

[Mike Poole]

Just now, Faronstream said:

I would not say 25-40% possibility for "well above 2m temperature" is that high really since it's still under 50% so it can go either ways. Also don't forget that we are now entering a la nina period  so it's a bigger possibility for a cool wet summer

They are quintiles, so 25-40 is significant compared to the 20% that it would be if everything was equal for the top quintile.  Agree La Niña could be a factor later on in summer, and that may be this years excuse for a poor August.  

[Methuselah]

Yay! 12Z looking good by Day 6! 

    

Anyway, chaps...I'll quit moaning about August until, well, August!

[Zak M]

How nice is this; high pressure is paying us a visit! 

   

[Zak M]

UKMO is okay @144

Edited May 11, 2020 by Zak M

[Djdazzle]

5 minutes ago, Zak M said:

UKMO is okay @144

Looks even better on Wetterzentrale.

[Methuselah]

Well, the 12Z temperature ensembles are nae bad!

    

And, in anticipation of @Eugene's reply...Yes, there may well be some clouds on Day 10!

[northwestsnow]

First of all, greetings to my friends on the model output thread,hope everyone is keeping safe and blessings to all yourselves and families.

What a wonderful EC this evening, Azores high nudging in by next weekend and temps hopefully into the low 20s by next monday.

And i can escape self isolation by finding a nice quiet pond and treating myself to some fishing.

Take care all and stay safe

 

Edited May 11, 2020 by northwestsnow

[Zak M]

Looks like there is some agreement between the ECM and UKMO at 144!

   

[Djdazzle]

ECM mysteriously goes off the rails from 168 onwards. So different from the 0z, it’s crazy. Expect it to be a huge outlier.

[northwestsnow]

1 minute ago, Djdazzle said:

ECM mysteriously goes off the rails from 168 onwards. So different from the 0z, it’s crazy. Expect it to be a huge outlier.

Its probably one of the options longer term but for many sun/mon/tues and wed for most looks lovely.

 

[mb018538]

11 minutes ago, Djdazzle said:

ECM mysteriously goes off the rails from 168 onwards. So different from the 0z, it’s crazy. Expect it to be a huge outlier.

Definitely has a wobble at day 8-10. Compare that to GEM which holds the high strong. As you say, expect that ecm to be bottom end or an outlier.

[Mike Poole]

Another stonker from the GEM 12z tonight, I missed the 0z but in recent days this model has been very consistent in my view.

[MATTWOLVES 3]

As others have said ECM goes a little astray at day 8 onwards, but perhaps the mean a little later will put it back into place.. Plenty of cracking weather from the end of the week into the weekend and early next week for sure. And with a lifting of people's movements a chance to get out to the countryside or local parks and get a good top up of endorphins.. And would just like to say bless @northwestsnow thanks for those kind words mate, shows your a good considerate kind of chap.. You and your family take care to..

[Mr Frost]

8 hours ago, Man With Beard said:

It basically translates into a UK high around D7-D10 (I share some concerns as others, that this looks susceptible to flattening)

Indeed and there is a hint of that on the latest GFS and now the ECM...

GFS 6Z earlier was a massive outlier also.

GFS 12Z

ECM:

 

 

Who knows what will happen next week - form horse would be below average for a few days yet this week - up to average by Friday and then slightly above Saturday/Sunday. (Temperatures - especially South East England probably 20C at least somewhere on Sunday)

Next week low 20’s to start the week down South and then it gets tricky! (Either a hot spell or high teens/low 20’s afterwards)

Really hope that ECM run is wide of the mark for up here - bit of a shocker! Cool and wet! 

Real mixed bag on offer at the moment but it is only May so nothing to worry about - still lovely Spring weather showing on the charts!

Something for everyone really and keeps the cool Spring lovers and the warm Spring lovers happy. (Previous/current and near future weather)

I will see you all again soon to discuss runs that will be totally different again numerous times a day! 

Why do we even bother! 

Have a good night and all the best to you all.

Edited May 11, 2020 by Mr Frost

[Guest]

It’s a pretty pleasant look right across the model suite this evening through to at least day 8, probably 9 or 10 once the initial cool air is mixed out. All the models really consistent, bit of a wobble from ECM but that’s ok currently at day 8. Expect any warmth to ‘home grown’ with a lack of any real advection from the south so warm days (cant see anything above 25/26c which is still pretty decent for May) and probably still quite cool nights, although not as cold as currently. No signs yet of anything Ts related it’s just dry, dry, dry! 

[Daniel*]

There’s no real indication of a sustained warm spell or anything particularly warm on ECM 12z, there’s definitely a trend for more mobility in N Atlantic, it is currently blocked off, but not for long, NW U.K. I think your days could be numbered cloudier and wetter at first could be mild. However, I agree with @damianslaw there has been a suggestion for a while in GFS fairyland of a change in final third of May, to a more westerly driven picture. All quite normal I don’t see us entering the start of an protracted epic warm spell, which will take us through into summer, what is this obsession with 2018? Not sure people register how rare these summers are, the backdrop appears dissimilar away from SSTs. There’s nothing scientific about this but there’s only so much anticyclonic weather we can have.

[Mike Poole]

ECM ensemble mean 12z, here at T168 and T240:

Still very positive, maybe the T240 slightly flatter, less amplified than we've seen in recent days but probably splitting hairs at this point.  

I think this is the first day since the start of lockdown that I've spent more time in the MOD than in the Covid19 threads, maybe that is progress of a sort...stay safe everyone!

[MATTWOLVES 3]

The ECM mean for me is still a good run with High pressure dominating the scene, any low pressure if this happens is likely to be to the NW... how long will this pattern hold, will the high collapse SE!! it's to far away to worry about... And there is no point in even bringing up the Atlantic will sooner or later break through... It may, it may not.. Its in the hands of the weather gods and not us armchair weather gurus... Enjoy while you can.. 

[mb018538]

18 minutes ago, Daniel* said:

There’s no real indication of a sustained warm spell or anything particularly warm on ECM 12z, there’s definitely a trend for more mobility in N Atlantic, it is currently blocked off, but not for long, NW U.K. I think your days could be numbered cloudier and wetter at first could be mild. However, I agree with @damianslaw there has been a suggestion for a while in GFS fairyland of a change in final third of May, to a more westerly driven picture. All quite normal I don’t see us entering the start of an protracted epic warm spell, which will take us through into summer, what is this obsession with 2018? Not sure people register how rare these summers are, the backdrop appears dissimilar away from SSTs. There’s nothing scientific about this but there’s only so much anticyclonic weather we can have.

Is 20-25c not warm for the middle chunk of May? looks good to me! The op run is an outlier at the end too.

[Djdazzle]

12 minutes ago, mb018538 said:

Is 20-25c not warm for the middle chunk of May? looks good to me! The op run is an outlier at the end too.

Well said! One operational outlier and suddenly that’s used to justify an unsettled end to May!

Let’s see what future runs bring.