Model Output Discussion - Spring Has Sprung

[Addicks Fan 1981]

 Man With Beard glad you are back on the forum with your superb insight and second to none contributions.  It did look pretty respectable on the ECM ensemble mean charts tonight i have to say especially at day 10 although extremely low confidence of a heatwave.

[northwestsnow]

A swing back of the pendulum this morning,perhaps.

Still differences at 144,UKMO looks decent so fingers crossed  

By day 8 GEM looks lovely

Edit by 168 ukmo is indeed brill

You couldn't make it up ,EC is awful.

Fed up of this now time for a break.

Edited April 30 by northwestsnow

[Penrith Snow]

ECM says no to high pressure next week with a chilly North Westerly by day 8.

Big difference with MetO and GFS which has high pressure in control for most of next week.

Surely ECM is wrong?

Andy

[Mike Poole]

Just looking at this morning’s clusters T192-T240:

There are six clusters, spot the odd one out!  Clusters 1,2,3,4,6 all have a ridge of high pressure taking hold in the region of the UK.  Cluster 5 - which contains the ECM op and control - does not.  As it only has 6 members, I think I’m inclined to discount the ECM op solution this morning in favour of the other models, supported by most of the clusters.

[danm]

 Mike Poole good news Mike. Considering the EC op is on its own, even within its own ensemble set, I’m inclined to say it’s pretty much another clean sweep of almost total cross model agreement for high pressure to take control next week. 

[summer blizzard]

Suspect the model differences relate to the progression of convection through the Pacific. Although I don't have the Euro chart, the GFS has weakened this a lot in recent days though it is still progressing.

[ANYWEATHER]

Given the high level of Shannon entropy  for next week ,perhaps stay clear of illusive details at the moment! Bank holiday weekend ,could well see sizable dry periods even though pressure is fairly low. My advice is to keep tuned to the rainfall radar, much better than the vague rainfall predictions from all models.....!☺

[Sherry]

 ANYWEATHER sometimes low pressure don’t always mean days of rain, can be showers and some places may miss it altogether 

[raz.org.rain]

 Penrith Snow ECM were wrong about the weekend if I recall correctly? Like, pretty drastically wrong too.

[Addicks Fan 1981]

 raz.org.rain let's wait until @Rain All Nightcomes online to have the cross model concensus.    

[danm]

 

[WYorksWeather]

And proving that caution where we don't have cross-model agreement is a good idea - the GFS is now having a wobble. Days 8, 9 and 10 on the 12z vs. the exact same timestamp from the 00z:

12z:

00z:

Absolutely massive downgrade.

In contrast, GEM is still strong with the high at days 8, 9 and 10:

 

So out of the big three only ECM to wait for - still looks like we're not going to have cross-model agreement tonight. I think the wait goes on until we get agreement on the broad pattern for next week.

Of course also ensembles to check out later - not worth considering only the OP runs - in particular we need to see whether the GFS was rogue or whether there is ensemble backing for a downgrade.

 

 

[Howie]

If we lose next week I'm actually going to leave the country

[ANYWEATHER]

It's not very often you find colder 850s moving from south to North from gfs ,but it's modeled towards the weekend ,and winter looks like greeting us once again from day ten!!! Models are determined not to let the weather settle down any time soon!

[Addicks Fan 1981]

 WYorksWeather the op runs are definitely an outlier and not backed by the mean at all link below here:

 

Ensemble probabilty weather forecast for London

WWW.THEWEATHEROUTLOOK.COM

---

Probability weather forecasts for UK and overseas locations. These use ensemble model data to help asses confidence levels. Fully updated every 6 hours.

 

[WYorksWeather]

 Addicks Fan 1981 Yep, I was going to come back later to comment.

The mean sometimes gives a misleading view through averaging various scenarios in the model view format, so I prefer the numerical ones. For the GFS at least you're right that the GFS outcome is on the bottom end of the ensemble for MSLP, but it's not a ludicrous outlier. It should be noted that MSLP is only above 1020mb on the mean from the 8th-11th.

ECM ensemble / clusters to follow later, which I guess will give more insight.

[Cambrian]

I was going to wait until the morning but there’s something very appealing about posting on the cusp of the month itself. And May is typically a lovely month of the year. Lovely long evenings, but rarely too hot, and relatively free of buggy insects nibblin’ at ya!

Another motivation was that today’s 12z EPS charts are the most compelling for a fair while in terms of setting up positive synoptics for a properly settled spell.

Here at day 9, the same slow moving 5-wave hemispheric pattern that has held us for a protracted spell under the influence of a trough now with clicking forward 45 degrees very much becomes our friend, with a firm build of heights shown in the anomaly shading and a most handsome ridge displayed in the contour lines, 569-576 gpm a convincing signal for a meaningful build in surface pressure. 

This is actually evident a day earlier with a 1028+mb high pressure at day 8 on the MSLP charts, slap bang over the UK and Ireland and there through to day 10 at least, impressive for an ensemble mean product at that range.

To look beyond that stage is always a bit ambitious, but a swift return to below average pressure from there looks unlikely. May looks to be shaping up.

That the projected pick up doesn’t fall for us for the bank holiday weekend is neither here nor there for the quality of the weather itself and its impact on nature.

The fact that it coincides with the second week of May, at a time when the rate of seasonal warming is at its most rapid - bringing the potential, if it transpires as indicated, for a meaningful spell of fine weather as the days get long, the sun becomes strong and the land responds in earnest to the warmth - after the last couple of months in particular, will be very welcome indeed. 

[minus10]

Well after the mixed bh weekend where there will be rain about but also some sun to be had the signal from the gefs for settling down next week still strong from the 0z this morning...

..quite a pronounced high there..

..although no heatwave there is scope for low twenties in favoured spots i would think..

..the op going for higher pressure lasting a bit longer...

 

..as usual orientation crucial...ecm 0z op while also showing the high its placement not as favourable..

..although south western areas would do ok temps generally bit lower..gfs 850s and ecm..

...nice to see high pressure on the charts after what seems ages...while the upcoming bh may well be disappointing for many areas ( as per bh usual it seems) ..we can hopefully look forward to some fine or better weather after for at least a while with the usual caveats of hp orientation to be confirmed...

...misty here this morning but the air feels warmer and...kinder...have a good day...

 

 

[Mike Poole]

Strong support for a settled spell continues on the ECM clusters, T192-t240:

Clusters 1 and 2 both good, with cluster 2 the better orientation.  Cluster 3 is less good, high never really takes hold, but that has only 5 members so a 10% shout at worst.

T264+:

Starting to see some hints at longevity here, most notably cluster 1 with 13 members, which holds the the high out to day 15.  Clusters 2 and 4 also suggest continued influence from a ridge.  The others have the ridge placed further west allowing colder air from the north to affect the UK.

[Andrea]

I have a question. All models seem to agree on a strong HP over us mid next week, why forecast temperatures are so low for May?

[In Absence of True Seasons]

 Andrea Because it's Britain and we can't have nice things

[Djdazzle]

 Andrea Probably because the air source is cold. Eventually, if the high sits over us, things will warm up.

[richie3846]

 Andrea I thought the 850s shared in previous posts would translate to some decent warmish conditions for early May. The sun is strong now, so good weather can produce warm days in average air masses. 

[Rain All Night]

On 29/04/2024 at 12:10, Rain All Night said:

0z deterministic runs, out to Mon 6 May (day 7) - bank holiday Monday

Warmer air arrives from Thursday, and then I can't call what happens over the weekend - it won't be ECM's previously-suggested anticyclone, but there are some options here that aren't too bad, particularly UKMO.

0z ensemble means, out to Tue 14 May (day 15)

ECM 9th May  - only shame is it's not a Saturday!

The high still seems to retrogress slowly from then on...

0z ensemble means, out to Thu 16 May (day 15)

There seem to be more ensemble members than before featuring Atlantic lows riding in over the top of the high, especially from 12th May onwards. The signal for the high to move west into the Atlantic seems weaker now than a few days back.

0z deterministic runs, on Wed 8 May (day 7)

UKMO and ICON show little lows getting in the way of the ridge pushing up from the south, which is an outcome that seems to have been averaged away in the ensemble means presented above.

Edited May 1 by Rain All Night

[Downburst]

 richie3846 And the wet ground will take some heating to get warm. Basically the heat energy is absorbed into water in and on the ground. It's like a big battery there sucking up the energy.