Model Output Discussion - Spring Has Sprung

[Rain All Night]

11 hours ago, Rain All Night said:

0z deterministic runs, out to Wed 10th (day 7)

I've dug deep looking for another run that looks like the UKMO, but have come up short.

0z ensemble means, out to Thu 18th (day 15)

The second half of next week still looks decent, and it appears we have some prospect of not falling straight back into an Atlantic trough situation afterwards.

12z deterministic runs, out to Wed 10th (day 7)

The semi-reliable period of our deterministic runs ends this afternoon on the first day of our anticipated upcoming settled spell. UKMO again wants to make this spell appear more anticyclonic for the UK than any of the other models. Before we get there, though, we may have to endure the passage of a rather nasty-looking low pressure system on Monday and Tuesday.

12z ensemble means, out to Thu 18th (day 15)

Happily, the ensemble means all agree on mild and settled conditions spreading from the south between Wednesday and Saturday next week. After that, the signals diverge, but none of them are suggesting a return to a deep Atlantic trough.

[Atleastitwillbemild]

 lassie23  You bet it can. 

[Derecho]

 WYorksWeather Perhaps the source of the air at the surface wasn't particularly warm, it was a southerly wind at midday over the surface. (Upper wind would have been SW'ly going along isobars)

Back in June 2019 we had an area of +20C 850s and surface temps were not much higher. This is because the breeze at the surface was from the North Sea and that cooler air was undercutting the warm uppers.

The 29th of Feb 1960 synoptics were quite different to the above but a similar process may have been at play.

[ANYWEATHER]

 LightningLover thanks for the info about that . Was going to post this but too tired last night and couldn’t find it. This weekend’s plume is not extraordinary by any means …..

[danm]

ECM settles things down across the south from the middle of next week:

ECM pressure mean for the SE looks OK, better than it has been for some time, at least temporarily:

GFS similar:

 

GFS mean also looking good later next week for the south:

 

Edited April 4 by danm

[Rain All Night]

11 hours ago, Rain All Night said:

12z deterministic runs, out to Wed 10th (day 7)

The semi-reliable period of our deterministic runs ends this afternoon on the first day of our anticipated upcoming settled spell. UKMO again wants to make this spell appear more anticyclonic for the UK than any of the other models. Before we get there, though, we may have to endure the passage of a rather nasty-looking low pressure system on Monday and Tuesday.

12z ensemble means, out to Thu 18th (day 15)

Happily, the ensemble means all agree on mild and settled conditions spreading from the south between Wednesday and Saturday next week. After that, the signals diverge, but none of them are suggesting a return to a deep Atlantic trough.

0z deterministic runs, out to Thu 11th (day 7)

Keeping an eye out for any signs of the Azores high failing to push as far over Britain as expected.

0z ensemble means, out to Fri 19th (day 15)

After the Azores high recedes, ECM is keen on ridging coming in from the west which would cool us back down again, GEFS doesn't show this but develops ridging over the UK in deep FI.

[WYorksWeather]

 ANYWEATHER It's the warmest at this time of year in one of the 850hPa record datasets that goes back to 1979. I'd still say 'warmest in 45 years' is pretty extraordinary even if it's not completely unprecedented.

[WYorksWeather]

Got a bit more time tonight. First post will be again on Saturday's plume event.

GFS 12z

850hPa peaks at 11am with the 16C just clipping into the SE. The highest raw surface temperature in the afternoon is 18C.

UKV 15z

850hPa peaks at 9am on the hourly with quite a widespread 16C, possible 17C in the far SE corner. The highest raw surface temperature is 21C.

Summary

ECM isn't out yet, so will leave that one for now. Still no agreement though - GFS continuing to stick to high teens as the max temperature, but UKV is going for low 20C or higher over a pretty wide area. Probably a very difficult one to call as very small differences in timing of the clearance east will affect the likelihood of achieving 20C.

[WYorksWeather]

GFS 12z ensemble is increasing the signal for something drier for the south around the 10th. Still a lot of questions though around whether the Azores high can ridge far enough northwards to bring a countrywide dry spell. Still probably an improvement for most areas though compared to of late, even if the north and west is still subject to the greatest risk of showers.

[Allseasons-Si]

Hey guys,...you missed me!!!

i see tentative signs of things settling down as we go through mid month,...i asked mystic meg,yeah right

but i will try to be informative...

latest cpc  looks predomantly south of west so milder than of late

how far can the Azores rigde push north to settle things down is yet to be determined so stay tuned

P.S ,i have missed so much in here that i will not go back on reading all the post's and the reason beeing is that my OH is ill and could end up in a wheelchair soon but i hope not,she is suffering ATM from (not comfirmed) MS or sciatica,so bare with me and i will post when i can

good night all and take care,you don't know what is next around the corner,...just saying

P.S next up,...summer is coming,i am fed up of all this rain it is crazy,...a flip of fortunes to better weather can't come soon enough.

good summer to all.

 

 

 

[minus10]

 Allseasons-Si sorry to hear that ....did wonder where you were..hope your OH is not suffering too much and that her situation can improve..certainly could do with an improvement with the weather..looks more promising ..all be it temporary with increasing  hp influence to the south on the gfs 18z..

..resulting in a warm up..

...but more importantly a dry up...how long for though is the question...

[donnerundblitzer]

Am I correct in thinking that positive NAO is supposed to bring us Atlantic weather; milder, windier (southwesterly's), wetter weather. Whereas negative NAO, generally cooler (in winter, hotter in summer), drier, more settled conditions? At the beginning of this month there was a very negative NAO and lots of Atlantic weather! Anyone know why? Or is this theory not properly proven? 

Edited April 5 by donnerundblitzer

[rwtwm]

 donnerundblitzer 

The NAO is basically  the difference in pressure between the Azores and Iceland. 

The North Atlantic Oscillation

WWW.METOFFICE.GOV.UK

---

The term 'North Atlantic Oscillation' is used by meteorologists to refer to variations in the large-scale surface pressure gradient in the North Atlantic region.

So low pressure over the Azores and higher pressure to the north gives a negative NAO. This has been the case a few times this winter, but the jet hasn't been south-shifted enough for the low pressure to miss the UK. Instead low pressure has been tracking along the south of the country. 

The rainfall anomalies in March had Southern England in particular, much wetter than normal. In the northwest of Scotland, where the low pressure would normally track, they had a drier and sunnier month than normal.

[ANYWEATHER]

 donnerundblitzer basically the difference in sea level pressure between the Azores  high and the Icelandic lows. The difference tightens up the pressure in the Winter due to a strong thermal difference between the poles and the Azores high. Less so in the summer months where there is a much less differential temperature between Pole and the sub -tropical high.....☺

[johnholmes]

From the latest NOAA 500 mb outputs there is a ‘slight’ indication that ‘perhaps’ some extension of ridging seems to be shown on the 6-10 chart from the Iberia region. This in spite of the continuing strong 500 mb flow across the Atlantic into the UK.

Even the 8-14 is along similar but more muted lines.

As usual give it 2 or 3 more outputs to see if this current trend is kept and, hopefully, increased.

Climate Prediction Center - 6-10 Day 500mb Outlook

WWW.CPC.NCEP.NOAA.GOV

 

[Rain All Night]

On 04/04/2024 at 12:40, Rain All Night said:

0z deterministic runs, out to Thu 11th (day 7)

Keeping an eye out for any signs of the Azores high failing to push as far over Britain as expected.

0z ensemble means, out to Fri 19th (day 15)

After the Azores high recedes, ECM is keen on ridging coming in from the west which would cool us back down again, GEFS doesn't show this but develops ridging over the UK in deep FI.

0z deterministic runs, out to Fri 12th (day 7)

The best of the more settled weather now looks like it will be at the end of next week rather than mid-week.

0z ensemble means, out to Sat 20th (day 15)

Let's hope ECM is wearing its "best model" hat today, as it's offering an appealing sequence of events to come: the Azores high extension we've already been expecting, followed by an Atlantic ridge approaching and initially sending a chilly northwesterly over us before the ridge moves directly over the UK, followed then by suggestion of further heightened activity from the Azores high. GEFS is not in concordance from the Atlantic ridge onwards (at least not on the 0z run - the 6z run is looking rather better).

Edit: Here's that better-looking GEFS 6z run.

Edited April 5 by Rain All Night

[Uncertainty]

 Rain All Night good spot on the 6z GEFS. Along with the op, it’s the best ensemble set for U.K. high pressure I’ve seen since the January spell (ie the ‘last’ spell )

But, as @johnholmes wisely points out, we need a few days of this sort of U.K. high type output to have any confidence that it’s a trend and not a whim.

Given the tendency the modelling has had to underestimate the flatness of the pattern since last June, I remain highly sceptical of any pattern change - especially up here in the nw; things do look more optimistic for the se. That said, it has to happen sometime and - if the last decade is anything to go by - maybe when it’s stops, it’ll stop if you know what I mean. When the 19/20 barrage ended we went dry for ages. Similarly after the horrors of the 15/16 winter 16/17 had many a long dry period. Long wet spells have generally given way, after 6-9 months, to a drier trend. Especially, like now, after a Nino has faded.

Perhaps the latest ec seasonal - with a +nao and heights close to the U.K. might be suggestive of better things to come in the summer.

Indeed, most seasonal output does seem to be suggesting a +nao and thus the possibility of a warmer, drier summer.

We can’t say we haven’t earned it.

[LetItSnow!]

Signs of potentially quite a potent little feature on Monday on the 6z. The worst of the winds are reserved for the south coast but it's a notably windy day for April. April 2024 is certainly bucking the usual anticyclonic nature of the month of April so far.

After that, the signs for a solid area of high pressure are somewhat shakier than my post the other day but this run does manage a pleasant ridge by the 12th and the 13th, though the uppers are actually relatively average with this so perhaps temperatures restricted to the mid to upper teens, still pleasant and we may even have the semblance of a cool night! Unsettled again by day ten though so no signs of a pattern flip so far.

[minus10]

Be interesting to see where this gfs12z op lies in the ens ??

Ouch.....

...has been hints after the higher pressure spell in the south later next week of a north westerly as next ridge moves in but this must be the extreme edge of the envelope...

Edited April 5 by minus10

[damianslaw]

Emerging signal for something less unsettled overall through next week, once the secondary low feature that the models are showing for Mon-Tues zips through. Azores ridging being shown later through the week, but, the atlantic also shown to have enough oomph to prevent any major height rise through the UK. Instead its shunted west and by mid month a chillier NW flow sets in, though we may see a more pronounced mid atlantic ridge. The synoptics on offer look more seasonal than recent and current output. Could end up though being a very mixed April and not very April like, and quite interesting if you want variety, whilst often a quiet benign month, it can throw up the biggest extremes of any month, the classic southerly/northerly switcharounds. 

Edited April 5 by damianslaw

[Sun Chaser]

Just caught up on today's GFS 06z.

What a run! A strong high smack bang over the UK from day 10 right until the end. Just what we need after the wettest 18 months on record.

The less said about the 12z the better

 

 

Edited April 5 by Sun Chaser

[*Stormforce~beka*]

 Sun Chaser you mean it was there for one run and gone again?!

[CoventryWeather]

Think the broad area of travel is:

- Weak High mid to late next week

- High retrogression to Mid Atlantic - dry northerly to NWerly, showers inland from surface heating. 

- High most likely to end up over the UK/NW Europe just after mid month..

Pretty decent agreement up to day 10, bar the odd timings of warm and cold fronts etc. Seems a mixed April could be on the cards. 

Edited April 5 by CoventryWeather

[raz.org.rain]

 CoventryWeather unsettled and wet first half with a dry and warm second half perhaps? 

[stodge]

Evening all

The signal for a drier 3-5 days with HP just to the south of the British Isles remains and is now into the reliable.

We have to get through the weekend and a small but quite vigorous LP crossing southern Britain Monday into Tuesday with the latter looking a particularly chilly and wet day for many.

From there, just in time for the Grand National, the weather improves but signs from the 12Z suite it's a transient change rather than a significant patter shift. GFS OP and Control build heights to the north suggesting the E'ly some of us have been waiting for many weeks might be on the cards at last. However, a very long way off and a lot to get through starting with this weekend which might be plume-time for some but further west and north just looks plain wet.

Some relief for southern and eastern parts after the winter deluge though by no means completely dry but plenty of rain for northern and western areas even up to T+240.