Model Output Discussion - Spring Has Sprung

[Alderc 2.0]

Actually GEM starting to look troughy towards the end of next week too

[Addicks Fan 1981]

 Alderc 2.0 it's only towards the end of the GFS 12Z run that the northern blocking relinquishes its grip.   We need the jet stream to be on our side, bottom line of it all.   

[Alderc 2.0]

 Addicks Fan 1981 off course, but even then as the chart you posted shows even with northerly blocking reducing it doesn’t mean decent weather for us, lowish pressure, cloud and fronts coming down from the north west. 

[Rain All Night]

Saturday is at day 5 now, and the models are homing in on a forecast that looks very "May" - fairly warm, some sunshine, some showers, better further north?

Come Monday, it seems we might be having some difficulty shaking off that upper-level low, and there might be another disturbance starting to approach us from the west (or even south of west) around that time:

[WYorksWeather]

 MattStoke Yeah I was aware of that, but my point is that the GFS still 'flipped' in the sense that the true max in that scenario would have been perhaps a degree or two higher, maybe 41-42C, but certainly not 43-44C. And definitely not 48C in northern France!

[SunSean]

Ah, I see most of the models are showing garbage weather just in time for my week off next week! Yaaaaay!

Someone give me a few rays of hope??

[Alderc 2.0]

 WYorksWeather well, look what I have on my phone. Pretty sure I remember one run showing 47-48C in northern France as well.
 

Edited May 13 by Alderc 2.0

[Addicks Fan 1981]

 WYorksWeather back to the here and now.  What to the ensemble mean runs indicate, and what does the UKV indicate?

[WYorksWeather]

Rather than looking so much at individual runs, I think the overall pattern from the GFS ensemble tonight is pretty instructive. Picking Leeds as an example, but the general trend is the same in a lot of places:

 

Above average 850hPa temperatures likely for the next 10 days (too much scatter beyond that, but if anything warm outliers increase towards the end). Above average temperatures by day (when adding usual 1-2C for GFS under-reading) and significantly above average by night. Pressure recovering to average or above average after a dip early this week.

Overall based on these charts I'd be favouring a warm end to May, and probably increasingly settled again. Difficult to call whether it will be changeable from day-to-day or whether we will see a more long-lasting area of high pressure before month's end. But nothing suggests to me that the medium term outlook is poor. And even the next few days will not be universally poor everywhere.

 

Edited May 13 by WYorksWeather
Deleted the random ECM cluster chart from last night.

[Catbrainz]

 SunSean From what models are showing it appears to be more a convective slack medium pressure area (If there's such a thing for pressure between say 1000-1015mb) rather than a Atlantic low carpet bombing run. Not a expert but I would guess a mix of showery weather with some sunnier and warmer spells mixed in. 

Edited May 13 by Catbrainz

[WYorksWeather]

 Alderc 2.0 Don't want to derail the thread with this so will be my last reply on this point (happy to discuss elsewhere though).

I think you might have misunderstood my comment - the point I was making was that a significant number of pro forecasters stated in debates at the time that those temperatures were fundamentally impossible because of a flaw in the GFS. I wasn't suggesting that the GFS didn't show those temperatures, but that they couldn't quite have corresponded to reality. 41-42C might have been possible for the UK, but not 44C.

I don't want to get hit with a moderation stick - this is potentially moving off direct model discussion around UKV vs. GFS and more of a retrospective of July 2022. Happy to carry on this conversation but not in this thread .

[WYorksWeather]

 Addicks Fan 1981 I posted a comment on the GFS output for the rest of the month - still awaiting ECM, which I might not get around to posting as I'm back at work this week and up fairly early tomorrow. Depends what time it rolls out fully.

On UKV, tomorrow looks like the 'worst' day with many areas stuck around mid-teens and plenty of rain around, but its hard to call it atrocious as some areas that have brighter spells will still see 20C in between showers.

Wednesday is a better day overall but still poor in some parts of central and eastern England for temperatures. Elsewhere warm and mostly dry, albeit generally cloudy. Max of 24C for Scotland, 21C for England.

Thursday is fairly similar to Wednesday.

Friday looks to hold temperatures down a bit more - showers and cloud seem more widespread. Some of them look thundery.

Now probably getting a bit beyond the reliable for this sort of detail but just for fun Saturday looks a bit worse than Friday if you're further north or east but still decent in the south and west.

Summary

In short - is it the best weather you could possibly hope for in May? Probably not. Is it terrible? Also no. It looks like a fairly standard mid-May period - a mixture of sunny spells and showers, cloud, and slightly milder than average by day and well above average by night. Again, depending on location your mileage may vary from day to day but I think across the week as a whole most areas will get a reasonable range of conditions.

Today in my area for example has been sunny through most of the early to mid-afternoon and warm with temperatures over 20C, whereas elsewhere it has been a fairly poor day. That sort of regional variation is probably going to be the story of the next few days. The exact pattern probably won't be as shown here - especially beyond day 3 or so as it becomes harder to nail that sort of detail even with a high-res model like UKV.

Beyond that, as my previous post with the GFS showed, models are hinting at higher pressure into the middle to end of next week, but it's too early to be absolutely sure of the strength of that signal.

[damianslaw]

Comment on the GFS 12z but not the ECM 12z probably because it shows a stubborn deep trough anchored over the UK at day 10 with only brief reprieve at the 6-7 day range, also extensive blocking to the NW. Yes just one op run, but if verified can't see an easy to path a predominantly warm settled end to May. All looks very slack airstream/trough influenced, warm and unsettled to me.

Edited May 13 by damianslaw

[WYorksWeather]

 damianslaw I didn't comment on the ECM 12z yet because the ensemble hasn't finished rolling out yet. Not much point commenting on it if it's amongst the worst/best in the suite for settled weather.

We do have the clusters though.

All 3 look reasonably settled at days 5-7, especially further north.

At days 8-10, cluster 1 looks mixed, 2 is generally settled, 3 is generally unsettled.

In short we have a settled interlude looking fairly likely at day 5-7 especially further north, and 8-10 just a lot of uncertainty.

[Alderc 2.0]

GFS and ECM look like remaining low pressure dominated until D10, unsurprisingly a trough hanging around longer than initially expected. 

[northwestsnow]

Lots of Shannon entropy right now.

EC looks OK with sunshine and showers and looks to be heading in a much more desirable outcome by day 10..

Yesterday 12z 

this morning day 9

 

by day 10  on this mornings 00z run 

 

[northwestsnow]

It should be noted last nights ec46 was not pleasant viewing so here's hoping the overnight data is a change of direction..

[Scorcher]

 Alderc 2.0  Pressure looks average rather than low for most of the country. Given the average pressure at sea level is 1013 mb I think it's misleading to call it 'low pressure' over the next week or so.

Especially given the air mass is not at all like what we've had a lot of over the last few months and with an easterly flow there may not be a lot of rain at all. Probably sunshine and some showers and some areas will remain dry on some days.

 northwestsnow Good job it's almost never accurate.

Edited May 14 by Scorcher

[northwestsnow]

Mean by day 10 is lifting the jet stream north..

key timeframe 144 to 168 hours..

[ANYWEATHER]

21 minutes ago, Scorcher said:

Pressure looks average rather than low for most of the country. Given the average pressure at sea level is 1013 mb I think it's misleading to call it 'low pressure' over the next week or so.

I would call it a "Slack Pressure Gradient"  Nothing to extreme either in weather terms ,with a fair mix of dry periods ,but potentially thunderstorms too. All in all not a bad outlook at all!☺

[danm]

Better output this morning, looking less trough dominated over the weekend. Not a raging strong 1035mb area of high pressure, but higher pressure than what has been showing. All look like giving some decent weather at times. So no, not wall to wall sunshine, but we will get some good sunny spells, mixed with a few showers, plus staying warm. The best of the dry weather will probably be in northern Scotland. 

UKMO

 

GFS

 

ECM

  

[Alderc 2.0]

Have to say I’m surprised by the level of optimism here, each of the last 4 GFS runs have had widespread accumulated rf totals of 40-80mm over almost the entirety of E+W, ECM slightly less but still notable given we’re in one of the driest months of the year. Conditions look very meh, and considering recent history will do little to dry the ground out and nothing to usher a proper warming trend. 

[Rain All Night]

23 hours ago, Rain All Night said:

0z ensemble means, out to Tue 28 May (day 15)

Interestingly, the models have shifted back towards some of the more positive solutions for the coming weekend and beyond.

The ECM ensemble mean in particular suggests warm air kicked up over the UK by low pressure to our west from next week.

0z deterministic runs, on Mon 20 May (day 7)

Really interesting seeing all these frames this morning, as this wasn't the way I thought the situation was trending. Half the models have a little pocket of heights to the north of Britain by Monday, and the other half have the heights nosing in from the southwest instead.

 

0z ensemble means, out to Wed 29 May (day 15)

The weekend looks as though it should improve for most of us as it progresses.

ECM is suggesting a new disturbance or trough diving into us around the middle of next week, GEFS is less keen and even suggests ridging over the UK later on.

0z deterministic runs, on Tue 21 May (day 7)

The upper-level low is still there to our south by Tuesday.

ECM is showing most clearly a disturbance coming in from our WSW, which potentially could merge with that upper low.

Edited May 14 by Rain All Night

[CoventryWeather]

Mentioned the other day about a low anomaly to our south west and highs over Europe. 

GFS keen on this again in FI on the 6z, and is the solution I'd bet on for the latter part of the month. 

Backed by ECM Hov-moller from last night again, very consistent with the forecasts. A wet spell looking even more unlikely this morning, mainly showers for the vast majority and generally these overnight. 

[Cleeve Hill]

 Alderc 2.0 nice temperatures though, Alderc.