Model Output Discussion - Spring Has Sprung

[Addicks Fan 1981]

 Metwatch it does look mainly ridge driven, but the finer details will obviously have to be ironed out before more confidence can be piled in and we have a more coherent path to ridging.   

We also need to hope that there isn't some sort of a mountain torque event that could also change things, although I can't see any evidence of that and it would be good if something was provided.   

I'm no expert in that area so MattH would be a more appropriate person to enable me to understand more about stuff like that.    

 

[johnholmes]

A look at the 500 mb predictions

THREE weeks since last did in depth check!!

Sunday 28 April

NOAA first then ECMWF

Well at long last little signal for Upper ridging CLOSE to the UK but still very much in evidence in polar regions. Small +ve showing where the major winter trough usually resides (ne Canada/sw Greenland. Very slack flow into the far northern UK from s of west whilst almost nil for the major part of the UK. Main signal for contour troughing is around 40W and 40 N; (the remains of the major winter troughing perhaps?). By the 8-14 and the chart, to me, shows what we should expect for mid spring from the far west across into Europe? A very small +ve anomaly showing over nw Iberia.

Turning to the ECMWF output for much the same 6-10 day NOAA set of charts, actually 4-8 May,

It starts with the ridge just ne of Scotland extending sw with troughing still showing over ne Europe. During the period the 500 flow becomes a more general westerly over the approaches and the UK itself into Europe with the trough moving east with it showing north of the Black Sea and Turkey by the 8th May.

So pretty similar really to the flow at 500 shown on the NOAA outputs. Not exact of course but one could say about on the same pages!

As they are fairly similar, and from occasional peeps over the last few days, the pattern seems to have evolved fairly sequentially, I would imagine the upper flow will not be too different in the 6-10 period and beyond.

This is likely to see, at least, a decrease in what seems like the UK’s own monsoon season for many to a, not completely, but drier interval. Also with some local variations (sorry East coast effects at times), somewhat more seasonal temperature values than the late January sample many have had recently. As to any specifics then possibly still more ppn for southern parts at times but I feel the ppn will be more likely to affect other areas also. Whether thundery developments develop is beyond this brief peer into what may happen.

Good luck, sometimes this use of 500 MB flows does give a good idea of the next 2 weeks at that height but minor day to day variations can and do play havoc with attempts at predicting what the bottom 18,000 ft of the atmosphere can turn up!

[Mark Parsons]

 Summer8906 anything can happen within a Col.........

[TSNWK]

 johnholmes great post... really is the reasonable limit!  be the 2 week annomies for broadbrush forecasting.  As shown with at least 3 failures last Summer and this past winter teleconnections and forecasting beyond 2 weeks is subject to unforcastable chaos.. beyond our knowledge..

 

Edited April 28 by TSNWK

[KTtom]

 SunnyG ...maybe not! Tonights UKMO hinting at a switch towards a less settled weekend .. GFS ridiculed for being on its own this morning.. two options on the table at the moment..brave person to call this.

[Bats32]

 KTtom ECM and GEM looking less settled too.

[KTtom]

 Bats32 yea, ECM for Sunday, compared to overnight has suddenly found an Atlantic low

[Howie]

Of course...

[Alderc 2.0]

ECM has again bowed down to GFS ….

[viking_smb]

too far ahead

[WYorksWeather]

GFS 12z was on the cooler end of its ensemble from about day 5 to day 12.

General consensus around the idea that despite potential for wind and rain at times it will turn much warmer than it has been of late. Contrary to what some say about warm rain I do find at this year changeable weather feels much better than it does earlier in the spring, and though there is rain about at times it's unlikely to be of the heavy frontal variety very often.

Temperatures generally above average for the first half of May by the looks of things, albeit with huge uncertainty beyond next weekend. As I mentioned yesterday a few cooler runs but now quite a number of very warm runs appearing. In terms of the daytime temperatures there's nothing absolutely astounding appearing but the consistent warmth with double-digit lows is quite impressive. This should at least put an end to the need to use heating!

For the shorter term, here are UKV afternoon temperatures for the next 5 days (Mon-Fri):

I couldn't blame those of you in Wales or SW England for feeling a bit disgruntled with this forecast, but for most other areas it looks like a very big improvement on this week. Helpfully as well the warmth isn't focused in the same place every day so those who miss out on a certain day will have other chances. Something for everyone really away from the aforementioned areas.

Big questions still around exactly how warm - absolute max is forecast to be around 22-23C but if we did get some clearer skies I wouldn't be massively surprised if we got a random 24-25C somewhere.

Beyond May Day the trend is still as the above charts show for something on the warmer side of average, but exactly how warm is the key question, and that won't be answerable for some time yet.

[danm]

 Alderc 2.0 ECM looks cracking into early next week though. The weekend was always more of a Q mark due to model disagreements. 
 

[Mike Poole]

 danm GFS and GEM similar by day 10, I still think a build of pressure looks most likely, it is a question of when.

Next weekend maybe just a little premature.

Edited April 28 by Mike Poole

[ANYWEATHER]

You have to admit ,Ecm is just laughable with its output, .....

[Kirkcaldy Weather]

On 21/04/2024 at 02:04, Kirkcaldy Weather said:

I've discussed the teleconnective feedback playing into our ongoing 500hpa developments and looking into the MJO composites with recent and ongoing progression of this cycle not surprising seeing high pressure - blocking being a prominent feature again trends continuing into Greenland. The UK trough / Low Pressure can also be noted within these MJO phase feedback. There may be opportunities for some high pressure extending toward the UK and Ireland at times though there isnt any concrete signal for this in current modelling though the 00z GEPS did hint toward the latter part of May week 1.

 

On 24/04/2024 at 21:37, Kirkcaldy Weather said:

Could be a brief window for above average temperatures during the first days of May as High Pressure looks to build to our East.

Nothing overly surprising given MJO and overall teleconnective feedback as discussed in the above posts .

A few points of interest I'm watching closely ATM.

A significant rainfall event develops across parts of France into the Spanish border and Italy then a low develops in the Tyrrhenian Sea and heads Northeastwards bringing further heavy snowfall in the Alps with a significant rainfall event and flash flood risk at lower elevations in Italy, possibly Switzerland and again into France during the first days of May. There are numerous discrepancies between models but could be potential for significant rainfall as the low starts to influence the UK from the East & Southeast, along the border of above and below average temperatures is where this rainfall is likely to develop with current timing heading into the 2nd of May.

Something to note from the above is we are likely to see the 552 dam air crossing into the UK from the East and Southeast which is a good indicator of warm / hot conditions which is also shown if we use the 850hpa temperatures with +10C moving in from the East and Southeast. 

European Plume Event I'd class this as.

This also is evident with the most significant above average surface and upper level temperatures moving across Northern UK and Ireland.

As discussed in the first quotation in this post and from my previous posts of late, with MJO feedback and connecting with passage of above average / higher 200mb Velocity Anomalies still looks like the latter stage of May week 1 could give a window for high pressure developments from the South Southwest ie Spain, Portugal perhaps Africa etc extending toward the UK / Ireland.

On 24/04/2024 at 21:37, Kirkcaldy Weather said:

Currently this looks to be brief warmth as this high retrogrades and reinforces the prominent theme for further high pressure and blocking to our North Northeast and particularly Northwest with trends hinting at the Atlantic Ridge regime by May week 2 with further trough developments to our East & NorthEast.

Really beginning to watch as the MJO feedback comes to the fore which I showed in this post 

 

High pressure retrograding into the Atlantic and toward Greenland & Canada typically El Ninò characteristic.

[Rain All Night]

11 hours ago, Rain All Night said:

0z deterministic runs, out to Sun 5 May (day 7) - bank holiday Sunday

Discordance at day 7: GFS and AIFS are showing us what I meant previously about there being plenty of ways for the bank holiday weekend to go wrong, but the regular ECM shows us how it could go just right.

0z ensemble means, out to Mon 13 May (day 15)

Each ensemble prefers the take of its own deterministic run on how we will fare over the bank holiday weekend.

They start to agree again around 9th May on a resurgence of high pressure from the south, though it appears this could be followed once again by retrogression of high pressure into the Atlantic and another cold trough setting up to our east towards mid-May.

12z deterministic runs, out to Sun 5 May (day 7) - bank holiday Sunday

It's OK, ICON is the only model that matters  #atleastitwillbemild

12z ensemble means, out to Mon 13 May (day 15)

GEFS perhaps not quite as keen as ECM to send the high packing over the Atlantic towards mid-May?

[Alderc 2.0]

Beyond disappointing output this morning, any settled spell now looking like it’s going to be pushed well into next week. Ironically GFS now looks the least unsettled for the weekend with ECM/GEM delivering a rotten spell of weather Saturday into Sunday. 

[minus10]

Well although models differ wrt bank hol weekend with ecm0z not looking that great..

..by day 10 they are both in the same ball park...

...warm south easterly...lets hope this doesnt stay at day 10..

.although op is almost an outlier at 850 there are a fair few runs looking warmer now helping to push the mean up a bit..

..reduced rain here after this week hopefully

..today should feel a bit warmer ...in fact next few days down here...thats not difficult though...

 

[Summer8906]

12 hours ago, WYorksWeather said:

emperatures generally above average for the first half of May by the looks of things, albeit with huge uncertainty beyond next weekend. As I mentioned yesterday a few cooler runs but now quite a number of very warm runs appearing. In terms of the daytime temperatures there's nothing absolutely astounding appearing but the consistent warmth with double-digit lows is quite impressive

On the other hand double-digit lows with not-especially-warm daytime temps suggests cloudy, humid and oppressive weather. May 2022 type stuff - a month I regarded as unpleasant. Clear, settled weather should maintain lows well down into the single digits this time of year.

Edited April 29 by Summer8906

[SunnyG]

 Addicks Fan 1981 Look who was right. It's just always the same, rinse repeat.

 Alderc 2.0 If it's pushed into next week then it's not gonna happen, next week or the week after that

[Azazel]

ahhhh day 10.

[ANYWEATHER]

 Alderc 2.0 ecm is now the poor man's model. It's performance is dwindling all the time , Gfs is the king now out of the two. EC  paints a poor bank holiday weekend, although given its performance stats ,I won't take any notice of it!  BBC week ahead forecasts use the 00z ecm run in there forecasts ,must be very embarrassing for the forecaster who said yesterday , high pressure will be in charge, now they will be saying the opposite! Need to be taking more notice of the gfs IMO .

Edited April 29 by ANYWEATHER

[danm]

Next week still looking good on the morning output. This coming weekend never had any cross model agreement for fine, settled weather. 

Day 7 onwards on the GFS looks increasingly good:

 

ECM also shows a strong pressure build starting to appear from overnight next Monday onwards:

 

GEM very similar:

 

GFS mean for the middle of next week:

 

ECM mean for a similar timeframe:

Edited April 29 by danm

[Addicks Fan 1981]

 danm in other words both mean charts are offering a northerly tracking jet with LP steered towards iceland.   

Edited April 29 by Addicks Fan 1981

[ANYWEATHER]

 danm yes good by day ten! Where have I read that before