Model Output Discussion - Spring Has Sprung

[Scorcher]

 Alderc 2.0 The Met Office- who are notoriously  conservative with cloud amounts (and temperatures)- clearly don't agree with your assertion. For this area at least.

Where are you getting your info from?

I will say though that I am slightly disappointed to see the high looking less robust than it did a couple of days ago.

 

[ANYWEATHER]

Nice to see some orange colour's appearing on the temperature chart for next week......☺

[Alderc 2.0]

 Scorcher  it’s not like I’m making it up.

ECM for this week looks pants 

Tuesday

Wednesday

Thursday

 

Friday

[Northern Lurker]

 Alderc 2.0  And what do the other models show? Utterly pointless posting 1 models guess at cloud amounts several days in advance 

[Alderc 2.0]

 Northern Lurker GFS similar, GEM probably the best. 

[danm]

 Alderc 2.0 those charts are utterly useless at this range.
 

Not sure what some people want - the output still looks largely excellent this morning. 

[Alderc 2.0]

 danm so it’s ok to post the charts showing the sun and warmth but if it diverges away from that it’s not? Looking at the models this morning there’s a greater hint conditions could be a lot poorer at the surface despite a stout upper level high in place. 
 

[LetItSnow!]

If anything the GFS 0z looked to be further gradual improvements. It’s no heatwave but there looks to be a nice anticyclone that’ll give nice low 20s weather and should be quite sunny plus the nights will be comfortable and perhaps rather chilly. The 0z has also put back the idea of a breakdown a couple of days. Could be signs the high may last a little longer than it did yesterday.

That being said, the ECM does show perhaps a little pressure weakening around the 13th as does the ensemble. To me it looks similarly as it has down for a while, a nice spell of weather for a couple of days then perhaps turning unsettled again around the 13th.

 

Edited May 4 by LetItSnow!

[danm]

 Alderc 2.0 I haven’t seen anyone post those specific charts for any time period. We’ve been posting the pressure charts. 

The charts you posted detailing where it may be cloudy or sunny, or where there may be some light rain this far out are pretty much useless. 

[Rain All Night]

22 hours ago, Rain All Night said:

0z ensemble means, out to Sat 18 May (day 15)

It looks likely that the new Atlantic trough will have pushed our high away by around the 13th/14th, by which point we may have had around five days of fairly settled weather nationwide (depending on specifics of the surface high), including a weekend.

Beyond that there are signals both for Atlantic ridging, and for shallow troughing to our immediate west.

The former signal for direct retrogression of our high into the Atlantic with cold trough formation to our east is gone now.

0z deterministic runs, on Fri 10 May (day 7)

There's that new Atlantic trough in development, while we are under the influence of the high, which is looking a bit squashed.

0z ensemble means, out to Sun 19 May (day 15)

0z deterministic runs, on Sat 11 May (day 7) - for all your Eurovision Song Contest parties

GFS op wants to carry on the party with continued anticyclonic activity well beyond the frame shown here.

Edited May 4 by Rain All Night

[Cambrian]

Day 4 and 5 on the 0z EPS are great charts for the UK and Ireland. High time (sorry!).

 

But subtle changes can make all the difference.

As pointed out a few weeks ago, the 5-ridge hemispheric pattern is getting reduced to a 4-ridge pattern at times, and it’s happening again here. If we look out west, the ridge running down through eastern Canada to the Gulf of Mexico at day 4 is cut off at day 5. 

Looking at the jet stream on the 0z GEFS, a pulse of energy over the US at day 4 leads to an extension into the Atlantic at day 5. 

 

This throws the models into some disarray for the following days - by day 7, the EPS forms an authentic Atlantic basin low that ultimately trundles through to the UK and Ireland by day 10 as it weakens…

 

…while the GEFS only flirts with this formation at day 7, producing a shallower trough approaching Western Europe by day 10 with heights keen to build once more behind it over the Atlantic, the ridges much more pronounced than on the EPS looking like squeezing out the trough quite quickly. 

 

By then, the EPS has reverted to 5 ridges, though the two on the Atlantic side are weaker, while the GEFS sticks with 4, which allows stronger Atlantic ridges, the presence or absence of the Kazakh-Siberian ridge acting as the compensating factor.

At the moment, it doesn’t look like the 5-wave pattern can sustain 5 strong ridges to pin the pattern down, while the slowly waning PV is clearly still able to generate pulses of energy running through the jet stream that are injecting a touch more mobility into the Atlantic at times. 

This is keeping the pattern just a tad flatter, restricting the building of high pressure to modest cells in the 1020’s mb ranges, meaning that they are susceptible to being pushed on after just a few days by even a modest injection of energy into the jet stream, a hemispheric pattern that will serve to keep the weather at our end of the Atlantic unremarkable for now - though nevertheless with it being May, this will at times be very pleasant indeed. Have a lovely bank holiday weekend.

[WYorksWeather]

GFS 6z is one of the best runs I've seen in a long time for prolonged dry weather, albeit probably very mild to warm-ish rather than very warm. Interesting to see first signs that after a weakening in pressure around day 7 or beyond, that there is a further signal for a build in pressure beyond that.

High builds in at day 3:

Still going at day 5:

And day 7:

Possible slight weakening at day 10:

A slightly more showery interlude at day 12:

By day 15, another high builds:

And even at day 16, the low to our NW will likely miss or just graze the north of the UK:

This signal for a further build in pressure is beginning to be seen on the ensembles, e.g. here on the GFS 00z with the mean having a renewed rise in pressure towards the middle of May:

All a very long way off, but encouraging that we have a generally very mild to warm and largely but not entirely dry week to come, and then beyond that we can already see a signal for another high after any breakdown. Those developments a very long way off of course but nice to see a run that doesn't see a full-blown Atlantic breakthrough.

[Rain All Night]

2 hours ago, Rain All Night said:

0z ensemble means, out to Sun 19 May (day 15)

0z deterministic runs, on Sat 11 May (day 7) - for all your Eurovision Song Contest parties

GFS op wants to carry on the party with continued anticyclonic activity well beyond the frame shown here.

I just noticed that I forgot to insert my commentary on the ensemble means. It's not good news - the GEFS is similar to yesterday's runs with a shallow trough incoming, but the ECM is even more aggressive about shifting the jet stream way down south and introducing a vast Atlantic trough. Enjoy this coming week or so while it lasts.

[Howie]

 Rain All Night

Infuriating...

[Scorcher]

 Rain All Night It's an ensemble mean- it doesn't mean it's definitely going to happen.

I think people jump to conclusions by focusing on the mean when the mean is simply a middle ground between the more settled and less settled scenarios.

The means shift all the time anyway and aren't very reliable more than 5 days out.

Only about 10 days ago the ensemble mean was showing prolonged below average temperatures and within 2 days it had flipped to above average 850 hPa temps.

[Rain All Night]

 Scorcher The clusters suggest there weren't many more settled scenarios in that ensemble run.

We are fortunate that the two GEFS runs this morning weren't as negative as the ECM and that the worst period was beyond day 10, so we can hope for a flip. We can also still have nice days under poor synoptics at this time of year with the strong sun, so that helps.

[Northwest NI]

5 minutes ago, Rain All Night said:

We can also still have nice days under poor synoptics at this time of year with the strong sun, so that helps.

When someone posts something like this, it’s a big red flag!

[Addicks Fan 1981]

 Northwest NI wonder if there's some sort of mountain torque event that is limiting the warm air advection coming into our country? 

i know that some of the new CFS members have delayed the start of la niña and la niña may not even happen at all, always a good idea to follow the new members rather than just bullet point ways of looking at it.   

This I also believe will transfer to the atmosphere and I think we are due for it anytime soon, @summer blizzardmaybe able to help us with some of the teleconnections as things stand.   

[Addicks Fan 1981]

 Rain All Night I think the CFS weeklies are better at the moment than the ECM at long range, @Gavin Phas highlighted it on X.   Would love to hear some of his input on here to be honest.    

[Sherry]

Looks like turning unsettled again pretty quickly 

[danm]

7 minutes ago, Sherry said:

Looks like turning unsettled again pretty quickly 

If we limit ourselves to the semi reliable timeframe and just look at the output over the next week, then there is lots of dry, sunny and increasingly warm weather on offer. Not much point worrying about the week of Monday 13th May at this stage. 

Yes, turning unsettled at the very end of the ECM run, but before that lots of fine weather. 

In fact, the UKMO shows it potentially warming up even further towards next weekend with a SE’rly air flow and some warmer uppers:

Edited May 4 by danm

[Addicks Fan 1981]

 danm and GFS/ECM are having a battleground at day 10 with evolutions, GFS are going with an easterly whereas on ECM its westerly atlantic driven weather.   

On a side note I hope we get a linear decline into la niña if it is to happen with it starting a bit later to do our weather ahead a favour.   

 

[Scorcher]

 Rain All Night Yes I was going to make the point about May 2018- on the face of it it wasn't an outstanding month looking at the charts through the month.

High pressure came and went and was generally fairly weak until the last week.

Here we had an excellent (and extremely sunny) month despite it not being high pressure dominated until the last week or so.

[danm]

 Scorcher yep May 2018 was a warm and sunny month. There were a few days where we had some big thunderstorms, mixed in with some very warm and sunny weather. 

[damianslaw]

Large variance between GFS 12z and ECM at the 10 day range, not unusual, but the fact they are opposite each other suggests models are struggling. The GFS eventually pulls in an atlantic trough, ECM much sooner.

All conjecture given the timeframes, the GFS had a retrogressive signal then dropped the ridge SE, now it advects it NE.. none the wiser.

In the meantime, from Tuesday onwards high pressure building over the UK bringing first nationwide fine settled warm spell, pity it is due to arrive after bank holiday.