Model Output Discussion - Spring Has Sprung

[WYorksWeather]

 TwisterGirl81 Yeah it's not surprising it's wrong in a few areas - it tends to be to be honest even at very short notice. But overall I do think UKV is much better for on the day temperatures than most of the other models. GFS and ECM are absolutely chronic for under-reading.

[LetItSnow!]

 WYorksWeather You'd think they'd fix the issue by now... This problem existed when I first started avidly browsing weather models in 2014-2015.

[Addicks Fan 1981]

 WYorksWeather Charlwood in Surrey has reached 26.8 C so UKV were incorrect to downgrade.   

Correction as its 26.4 C.    

Edited May 12 by Addicks Fan 1981

[Rain All Night]

On 11/05/2024 at 12:44, Rain All Night said:

0z ensemble means, out to Sun 26 May (day 15)

The ECM ensemble seems to feature some more pleasant options for next weekend, and early the following week, than the other two. Beyond that, northwest/southeast split synoptics perhaps favoured. at the moment.

0z deterministic runs, on Sat 18 May (day 7)

Next Saturday looks OK, presumably some showers and an unwelcome wind direction for some. At least the worst of the weather will have been during the first half of the working week.

0z/6z ensemble means, out to bank holiday Mon 27 May (day 15)

I'm not sure what to make of next week yet. I get the impression there are a plurality of ensemble members showing troughing to our northwest.

0z/6z deterministic runs, on Sun 19 May (day 7)

Still think next weekend looks like it will be decent for many. Funny how the Icelandic low isn't there on the GFS.

[WYorksWeather]

 Addicks Fan 1981 You are right in fact though as it seems that Iver has reached 27.0C (rounded to 1 dp). In any case probably splitting hairs a bit at this point - overall not a bad performance from UKV hovering between 26C and 27C. I'd only really call it a miss if we'd seen 28C or 29C, or vice versa if we'd seen 24C or lower.

[WYorksWeather]

 LetItSnow! I think it's more complicated than that. From my understanding of discussions online a couple of years ago, it is a case of how the models deal with soil moisture content. In generally wet areas like the UK, the bias is towards underprediction. But in much drier regions, and on rare occasions you'll see this in the UK after exceptionally dry spells like July 2022, particularly in the case of the GFS, you can start to see overprediction. E.g. some rogue GFS runs predicted 48C for NW France and 43-44C for the UK if I remember rightly, which was never really feasible.

In contrast, the UKV, being a Met Office model and at a more local scale for the UK and its immediate surroundings, is tuned to conditions in the UK, and of course is run at a much higher resolution feeding in from the UKMO. It therefore has a much better ability to predict temperatures, but of course has the disadvantage that it is limited to the UK only.

Very happy to be corrected on this by the pro forecasters on here if I've missed something important or got something wrong - this is solely based on my memory of the comments of a number of forecasters on Twitter in the run up to the July 2022 heatwave.

[Sherry]

Ukv was a lot closer to the mark than any other model, gfs and ecm generally had low twenties as max seems places widely reached mid twenties today, 26 recorded here 

looking at the week ahead chance of reaching low twenties is still possible so not a cool week 

[Rain All Night]

Next weekend still seems quite uncertain... not too keen on some of the solutions that are appearing... these are all day 6 charts...

Edited May 12 by Rain All Night

[WYorksWeather]

Right, latest UKV update. I'm back at work tomorrow (I picked a good week to be off!) so won't be around for too many of the evening model runs, but have time to do tonight's UKV.

Starting with tomorrow, we have a warm day to come for eastern areas but much cooler further west due to a band of rain.

Much cooler on Tuesday overall, though some western and south-western areas will have a warmer day than Monday. Absolute maximum is 21C in northern Scotland but very localised. Most places will see mid-teens.

Wednesday looks better away from central and eastern areas, with temperatures quite widely into the high teens or low 20s. Again Scotland the warmest spot with a localised 24C.

Thursday is showing widespread high teens or low 20s, with an absolute max of 22C.

Friday is similar with fairly widespread high teens and low 20s, and an absolute max of 23C.

Summary

Overall, tomorrow looks like the worst day for southern and western areas. Tuesday the worst overall day for most areas. Tuesday and Wednesday worst for many central, eastern and northern areas (away from Scotland).

Overall though - it's not looking like a horrendous working week, more of a mixed one. A fair bit of rain around, but it doesn't look anywhere near as bad as it looked a few days ago.

 

[Snowyowl9]

Easterly winds for the whole of may would bring far more interesting weather the atlantic is dead..

Not expecting the most spectacular thunderstorms on record which this gave in May 1993 and a temp of only 13c max and a tornado..

But thunder is more possible from the east..

[Scorcher]

The persistence of the warm air for this time of year is quite remarkable on this morning's runs.

No exceptional warmth but consistently above average 850 hPa temps for most of the UK into the weekend and probably beyond.

The chances of a 14C+ month are increasing all the time.

[johnholmes]

15 hours ago, Sherry said:

26 recorded here 

where is 'here' please?

[danm]

The output all looks quite messy this morning. All of the models see the trough this week almost squeezed out of existence, giving what is likely to be a mixed week of sunshine, a few showers, some cloud at times.

The pick of the bunch for this coming weekend and into early next week is the UKMO, building pressure across the entire country:

 

The ECM keeps pressure slightly lower over the south, higher pressure to the far north:

 

The GFS is similar to the ECM:

 

I'm hoping the UKMO is closer to the mark, but the ECM and GFS are pretty similar. The residual lower pressure over the south on the ECM and GFS next weekend is very shallow and slack, so I'd probably expect some warm sunshine mixed with a few heavy showers. 

All we can say at the moment is that this week starts unsettled in the west, with the east getting some rain tomorrow morning, then a mixed picture with sunshine, some cloud and some showers. Into the weekend, and it becomes more uncertain.

 

 

[Downburst]

 danm Great Summary. To your point "and it becomes more uncertain." It was ever thus  and next week is certainly uncertain. The regime charts are a coin toss. The 500 anomaly may paint a better picture and looking at the surface and the latest ECM operational it suggests something like this picture. 

I don't think we will have a raging Atlantic with the overall northern hemisphere in a wavy Jet Pattern next week. Lets see. 

[MattStoke]

 WYorksWeather The GFS runs that showed 43-44'C had the hottest airmass over the UK Tuesday afternoon but this ended up occurring during the Monday night, so timing was also a major factor. We could probably have reached about 42-43'C if things had timed differently, so less of an over prediction by the GFS.

[ANYWEATHER]

Looks as though in the days ahead away from the next few days , a slack pressure pattern establishing itself across the nation , so some useable weather , generally warm , but the caveat of thunderstorms too. In my book, then , good weather for just about all , growers, gardeners, holidaymakers, and thunderstorm nuts like myself, something for everyone it seems in the next 10 days or so , without putting too much finer details on it! 

[CoventryWeather]

Certainty a trend I've noticed over the past few days is the Azores Low. Seems that we are heading back to a typical summer pattern where us and Europe are likely to see constant plume scenarios. 

The ECM day 10 chart this morning likely to be a start of a warm dry spell, likely intervened with a breakdown or two if it went on. Got a holiday down to Torbay early June so would love a dry warm pattern to set up by then. 

[Alderc 2.0]

Hmm a slow filling of the trough through the week although spells of heavier rain could be  likely, GFS, ECM and GEM all appear keen on a spell of heavy rain moving east to west Thursday into Friday and with low pressure I’d expect any gaps in the clouds to be filled in quite quickly.

Maybe a steadier rise in pressure through early next week and maybe some decent weather at times but while a long way off we may have to watch out for another trough / low pressure coming in for the bank holiday weekend. 

[Rain All Night]

20 hours ago, Rain All Night said:

0z/6z ensemble means, out to bank holiday Mon 27 May (day 15)

I'm not sure what to make of next week yet. I get the impression there are a plurality of ensemble members showing troughing to our northwest.

0z/6z deterministic runs, on Sun 19 May (day 7)

Still think next weekend looks like it will be decent for many. Funny how the Icelandic low isn't there on the GFS.

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.

 

4 hours ago, Snowyowl9 said:

But thunder is more possible from the east..

Genuine question - why is that?

[ChannelThunder]

 Rain All Night easterlies from a warming continent at this time of year can bring with them modified plumes, that swing up from the med around low pressure across western France/Biscay (see 2 weeks ago) or pockets of mid-level instability that just need a trigger like a shortwave along with them to go boom. Also there's homegrown surface based potential if pressure's low enough along with ample solar heating

[Addicks Fan 1981]

Still looking OK to me from the GFS 6Z for the next BH Monday, the ridge isn't exactly in the right orientation for warmth, but quite respectable on the face of it.  

[Addicks Fan 1981]

And to add to my above post the GEFS 6Z ensemble mean is looking very nice up to the end of the run.   

[Snowyowl9]

 Scorcher

Well thats what we need to get some thundery showers in..as more easterly flow much cooler further south and east mind..fresh easterly winds..

Today is a 10c drop on yesterday here at 14c max..

 

Edited May 13 by Snowyowl9

[Alderc 2.0]

Bit of a painful 12Z from GFS as our trough decides it likes the UK and hangs around for an eternity to the back end of next week. GEM thankfully disagrees building higher pressure but it’s still flirting with the idea of lower pressure to south into next week so we’re maybe not 100% in the clear just yet.

[Djdazzle]

The 12z GFS is totally different from the 6z.

Enough said really!