Model Output Discussion - Spring Has Sprung

[viking_smb]

well the met office have said that low pressure hasn't even developed yet

[Bats32]

 dryfie Lol, not many will get that.

[baddie]

 viking_smb If it doesnt, then we're good. A cyclonic Easterly is 

[SunnyG]

 

We all know what will win out instead....

[viking_smb]

 SunnyG my bet is on the atlantic low

[LetItSnow!]

The last two GFS runs are playing with the idea of a waft of very warm/hot air to our south-east as we enter May but with low pressure nearby as always. The 12z shows the risk of the Atlantic sweeping it away and remaining cool whereas the 6z was more of a unstable scenario with warm air aloft on an easterly for a time, but the risk of cloud and rain also and perhaps thunder.

Warm air surging northeastwards with already weak pressure in place is a recipe for low pressure so I expect unsettled conditions to persist into early May. Whether it's of the cool and breezy kind or warm and thundery kind is unknown. I wouldn't be surprised if a few hot runs pop up. What with the similarities to 1998 I've talked about I wouldn't be all that surprised if warmer weather arrives soon.

Regardless, both low pressure dominated scenarios can be quite convective.

[WYorksWeather]

Interesting ECM meteogram tonight. Unusually high confidence given the time horizon I would say. Suggestion of a continued cool or very cool pattern for the next few days, then high confidence in a brief switch to something more southerly and much warmer around the turn of the month, but then indications as we go further into May of a cooldown again back to close to average or a little below with more in the way of northerlies, albeit a long way off at this stage so could still change.

 

[Addicks Fan 1981]

 WYorksWeather it all depends now I think on the zonal winds and if a zonal winds recovery is predicted.   At the moment our zonal winds are negative, i did see on world climate service x account that next month that we are meant to be having a negative AO/NAO combo.  The way i see it is they are probably right.      

[Cambrian]

Little point ducking the issue. A quacking weekend in store…

 

0z ECM op for day 4, as another low pressure system finds us with impressive timing!

Further ahead, some more positive signs - once we start seeing this type of “super-meridional” pattern - ambitious building of heights up through the Atlantic and more spectacularly, through all the S’s - Sahara-Sweden-Svalbard-Siberia-Seguam like here at day 6 on the 0z ECM op…

 

…it’s only a matter of time before we start seeing the trough becoming over-extended with the cutting off of the low at the base of the trough, it sinking south, the heights linking up through the UK and Ireland like here at day 8…

 

Yes, add Skegness and Sandymount to your list, spectacular super-meridional S thing!

After that, a weaker version of the trough tries to reassert itself from the northwest, which the GFS op has been keenest on, though looking at the 0z ensemble mean, the pressure never really falls away again, a steady rise to a respectable 1020mb for Birmingham by the end of week 2…

…which is consistent with the ECM charts and the pincer movement of heights weakening the polar trough at its stem - so though nothing wall to wall by any means, the chance of a somewhat more promising setup emerging into early May.  I’ll post again around then. All the best.

[joggs]

Too far out but odd sign of improvement. This spring has been absolutely dire. 

 

[Mike Poole]

I have to say, I am seeing very little of hope of a substantial warm up in any of the models.

Maybe something on ECM clusters 2 and 3 in the T192-T240 timeframe:

But otherwise the pieces aren’t in the right place, and that doesn’t look like changing on the T264+:

Maybe clusters 3 and 4 show an inkling of setting in the region of the UK.  What we can say, is that the outlook is not wall to wall unsettled, like the earlier part of spring which is a pyrrhic victory, I suppose.

At this time of year, I am usually on the lookout for signs of any self-reinforcing pattern setting up with an eye to summer, but no signs of that at all.  First steps would need to be a build of some sort of heat over the near continent of which there is absolutely no sign, GFS 0z T360, for example:

Meanwhile, above us the final warming in the stratosphere looms, in a few days on GFS 0z:

The change to easterlies as shown (blue) on the left plot at 10 hPa 60N has been very clearly advertised for a while now, but there is no big driver to affect our weather with this, that (from the SSW) petered out a couple of weeks ago, and the strat is drifting now into summer mode as the vortex disappears.  So one hopes the weaker drivers of summer edge the tropospheric patterns to something more favourable in due course, but for now the wait continues…

Edited April 24 by Mike Poole

[northwestsnow]

 Mike Poole thanks Mike I'm afraid I'll breach every NW filter imaginable  if I type what I really think of the last 6 months of "weather " locally.

As always, in unsettled phases the NW cops for the majority of Atlantic systems but this period has been beyond the pale.

Like many others I'm desperate for some warmth and sunshine but I'm struggling to see anything resembling this on the 00z NWP .

Late season SSW is disastrous for Spring so I always get a feeling of dread when we see SSW's in late Winter.

One year we'll see a major SSW in November and get the benefit HL blocking when most of us want to see it,ala Dec/Jan NOT April/May..

 

[danm]

37 minutes ago, northwestsnow said:

Late season SSW is disastrous for Spring so I always get a feeling of dread when we see SSW's in late Winter.

Precisely, just posted this in the moans thread. This time of year always has a greater likelihood of northern blocking, but a late season SSW simply locks in a pattern of high latitude blocking for far longer than we’d otherwise expect, which more often than not results in the UK being a trough magnet or keeping us under cool northerly or easterly winds. It happened last year too. 

Until this works its way through the trop, we’re unlikely to get anything substantially warm and dry until mid May at the earliest. 

Edited April 24 by danm

[CoventryWeather]

Certainty on models have been quite good for the past few weeks, although there is some uncertainties past day 6 on majority this morning. 

Of course the likelihood of a dry settled warm spell seems unlikely, but there were hints a few days ago, and the MET ensembles for 192 seems a little interested in the idea. Icon also interested this morning on a decent ridge from the Azores. 

Wouldn't rule anything else, seems the uncertainty is coming from the stratosphere behaviour I believe. We all know how rapidly changes can occur. 

[Rain All Night]

On 23/04/2024 at 12:48, Rain All Night said:

0z deterministic runs, out to Tue 30 Apr (day 7)

0z ensemble means, out to Wed 8 May (day 15)

It is as yet far from clear that the ridging activity that is evident from the Azores high in the first week of May is going to reach the shores of Britain... it currently seems that more ensemble members are going for it pushing up unhelpfully to our west instead...

We have now entered the four month period of the year with the best solar input... my frustration levels rapidly increase if we don't see favourable synoptic patterns during this precious time!

0z deterministic runs, out to Wed 1 May (day 7)

Could we see that warmer easterly right at the beginning of May? Both flavours of ECM plus the UKMO seem to think it's possible...

0z ensemble means, out to Thu 9 May (day 15)

The ECM mean wants to support its op on the idea of warmer air coming in briefly from the east right at the beginning of May. Beyond that we have clear signs of anticyclonic activity in our vicinity in early May, but with an equally clear risk that this will remain too far to our west or southwest for us to warm up.

Why did it feel so darn cold when I woke up this morning?!

Current temperature (colours) and wind (lines) at 850hPa (left) and at the surface (right), screenshotted from https://earth.nullschool.net/ at something like 10am this morning.

Edited April 24 by Rain All Night

[danm]

 

[Rain All Night]

Ooh hello:

[*Stormforce~beka*]

 Rain All Night Not happening don't get excited ...

[summer blizzard]

Something to watch but signs of a WWB progressing east into May which may generate mid-lattitude blocking closer to mid month. 

[stodge]

Evening all

Early stages in viewing the 12Z output but, other than GFS, there seems broad agreement for the LP to end up just to the west of the British Isles by next Monday introducing South or South westerly winds so something a bit warmer or less cool for many.

12Z GFS OP goes a slightly different route keeping the LP to the south and building heights to the north after which it's a north-south split under an E'ly airflow. Dry to the north but windy but with the trough in charge further south a greater chance of rain or showers and quite high rainfall totals for the far south up to the first May Bank Holiday weekend. Control is more unsettled until far FI.

ECM at T+168 follows to an extent with a good old-fashioned late April easterly (GFS 12Z OP at T+168 next to it for comparison):

[WYorksWeather]

Still hard to see much of a warmup on the cards, especially further north, if the 12z GFS turns out to be anywhere near the mark. Still early days for my thoughts on May.

Looking even further ahead, as I mentioned a stronger polar vortex than normal going into May is a positive sign for at least the early summer. The ECM forecast fits this idea - maybe a sign to watch out for, though we still have a few days left for the forecast to change before the start of May itself.

The ECM 00z meteogram (don't have time to wait for the 12z) shows temperatures recovering and moving above average by the turn of the month, but it's hardly anything spectacular. Wouldn't surprise me if we scrape an odd day or two into the high teens or low 20s, especially further south, but it's not anything to write home about really by this point in the year.

Beyond the turn of the month at this early stage we still see a tendency for things to turn cooler again with a further northerly outbreak.

Summary

In short, plenty of time for things to change from here, but right now it looks like a very low chance of seeing anything notably warm in the next 10 days or so. 

 

[Kirkcaldy Weather]

On 11/04/2024 at 20:28, Kirkcaldy Weather said:

As shown in my post from October and other occasions a negative PNA can lead to a cold - potentially significantly cold temperature anomaly from the Northeast-East

Recent GFS outputs.

Quite exceptional performance from the GFS particularly with the European cold anomalies.

On 17/04/2024 at 22:06, Kirkcaldy Weather said:

Overall a prolonged period with below average temperatures will continue with some significant anomalies across Europe in particular, we then look during April week 4 as the High retrograde gets going for these below average conditions to extend into the UK > Ireland.

The UK, Europe and North + Northwest Africa Cold Anomaly can be noted here within recent MJO feedback.

On 17/04/2024 at 22:06, Kirkcaldy Weather said:

During the latter stage of April week 3 through April week 4 the Atlantic and Ireland-UK high will begin to take on the MJO and PNA feedback of blocking to our Northeast > Scandinavia and Russia, this will also retrograde into Iceland and Greenland as discussed prior with a good representation of many of the major European weather regimes / teleconnective feedback.

As low pressure interacts with the below average temperature airmass we'll have a mix of wintry conditions with increasing precip moving in tonight combining with a Lowering Isotherm this will fall as snow particularly across Northern Scotland and parts of Northern England, predominantly higher elevations with accumulating snow though mixing of sleet snow and maybe hail can't be ruled out at low levels. We'll have the 528 dam and low isotherm values present for a number of days especially for Northern England and Scotland with a focal point clinging onto the North Sea Coastlines. We'll see multiple chilly nights with frosts for some areas worth noting for gardeners, all in all very noteworthy given its April week 4.

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

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.

All fits excellently with feedback of El Ninò, IOBW warm phase, SSW, PNA and NAO in particular.

Credit JMA

KW

[viking_smb]

noticed on the current UKV that the rainfall for sat night has made a sharp eastward shift

Edited April 24 by viking_smb

[Addicks Fan 1981]

 WYorksWeather I agree with @summer blizzardon this to be honest with you.   Hovmoller plots are probably a better proxy to look at than ensembles.   We need to be careful with what we use and interpret.    

if we can get some westerly interia going then it shouldn't be too bad at all.   I also supported the very sensible post by @Mike Pooleearlier as well and think that clusters should never be dismissed.   

I feel also that the ECMWF 0Z ensemble mean was encouraging today, not necessarily for heatwaves but shall we say for a bit of a drying trend with a mid Atlantic ridge.    

[raz.org.rain]

 Addicks Fan 1981 I think at this point, any above average temperatures accompanied by drier weather would be welcome, heatwave or not.