Model Output Discussion - Spring Has Sprung

[WYorksWeather]

Worth just mentioning I think how remarkable (in a negative way, if you want dry weather!) recent weather patterns have been. Here is the NCEP reanalysis chart for March sea level pressure so far. We're over 10mb below the average. Absolutely ridiculous. At the centre of a giant blob of low.

Next, all of February and March combined. Still 8mb below average.

It genuinely isn't an exaggeration to say that we've been having probably the most unsettled weather in the entire Northern Hemisphere since the start of February.

And since I have a feeling someone would ask for this one if I didn't post it, here is the sea level pressure since the start of July 2023. Again, the UK and Ireland amongst the most unsettled places in the entire Northern Hemisphere.

This is why I find it hard to believe this pattern will go on much longer, having had a look at this. We can't keep on being target practice for the most unsettled conditions in the entire Northern Hemisphere. At some point, the larger scale pattern will change.

 

[Neilsouth]

 Summer8906 Perfect thank you, just bookmarked it!

[Summer8906]

 WYorksWeather Indeed, it's already unprecedented, it's got to change soon.

No other notably wet - or notably dry - period in recent times went on so long. Even things like the 1995 drought didn't feature a long run of dry months (e.g. 1995 the run was only 6 - March-August. Sep was wet, as was Nov, and in the south, Dec).

And superimposed on this is the particular wetness of Feb and March. Aside from July, the spell seems to have mutated into its most extreme phase in the past two months, starting around Feb 7th. At times, autumn wasn't too different to normal, given autumn is a pretty wet season anyway.

Edited March 28 by Summer8906

[WYorksWeather]

Can we count this down from week 4, any takers? The low finally drops out to our west.

My abrupt flip prediction for around mid-month could yet come off if we see the transition somewhere towards the end of week 3?

Anyway, in all seriousness this is far beyond the reliable, but it's about as much hope as I can muster up at the moment - the promise of something better in week 4. You just have to laugh.

EDIT: worth mentioning that this sort of idea also has the EC46's backing. We lose the mean trough signal around the 15th-22nd:

And then we have a positive height anomaly for the 22nd-29th:

Edited March 28 by WYorksWeather
Added EC46.

[suxer]

If your idea has ec 46 backing then it's probably not going to verify 

 

[WYorksWeather]

 suxer I tend to agree 

In all seriousness, the forecast skill is very low. I've been sort of casually saying there'll be a flip to dry around mid-April for a week or so now - it'd be nice to have one of my predictions come true.

The fact that both models seem to at least be interested in the idea is a start. But I don't trust it until its within day 5 - we've had so many attempts to put an end to this miserably wet pattern that just disappear like mirages as soon as they enter the 7-10 day range.

[Jordan S]

On 25/03/2024 at 00:37, Jordan S said:

lower chance that southerly tracking lows continue right through the second week to mid April and beyond, continuing the wetter than average theme for southern UK in particular and continuing the exceptionally persistent pattern that has effected the UK since July last year for the most part, worrying if that where the case and would raise questions as to just what this could mean for the rest of Spring, especially as I don't expect the wet weather to continue all the way to mid April and beyond, but the first week of April definitely likely which is problematic in itself, again especially in southern UK at times, but for those wanting late season snowfalls then there is interest in that regard further north if the lesser likely outcome further into April materializes, as well as the expected wintry precipitation at times in north early April mostly in form of showers/ especially high ground.

It's rather clear now that this synoptic possibility quoted above that I deemed slightly lower likelihood around 40% is closer to the mark for the second week of April. Wetter conditions continuing, especially further south and then western UK later on,  confidence rating in this being 70%

A widespread drying trend from the northwest is less likely now for week 2 of April as a whole, would deem this 10% Upto 10-11th April, but still expect possible further wintry showers/longer spells of wintry precipitation on occasion in north and still it overall looks less wet than south at first, the wetter conditions favour the northwest/west for a time later week 2.

Potentially still warmer by mid April in the south as the blocking shifts around slightly with a southwest to northeast elongated trough/areas of low pressure over us and  especially to our west/southwest with higher pressure still over close to Greenland, heights also build to our southeast over central Europe but any drier than average spell over the UK and northwest Europe most likely from end of week 2 at the earliest, most likely for far north/ and or the south/southeast of England if it where to happen but the signal only loosely favouring a proper drying trend by then for now, with unsettled weather the main theme before then. Causing potentially large rainfall totals. 

Take care. 

Edited March 28 by Jordan S

[SunnyG]

 WYorksWeather 'Some point' may be in 5 years' time, for all we know.

[andymusic]

Latest GFS 06z run buries northern Scotland in snow for the first week or so of April - even in la la land it's suggesting that Southern England could have a splattering as well!

[Summer8906]

Could this be the wettest April since 1966? (EDIT: sorry, ignore that - I long assumed '66 was the wettest on record but it appears both 2000 and 2012 were wetter - the forecast synoptics reminded me of 1966 which is why I mentioned it).

The GFS 06z is literally worse than any April of my lifetime, including 1983, 2000 or 2012.

The 00z is better, it looks almost normal for week 2: I just hope that's closer to the mark.

 

Edited March 29 by Summer8906

[baddie]

 Summer8906 According to Met Office, the first 4 days of April are looking dry, cold and cloudy with winds from the E half

[Summer8906]

 baddie I hope so though the GFS paints a grimmer picture. We need the low track to shift perhaps 200 or 300 miles further south (or 1000 miles further north!)

Edited March 29 by Summer8906

[Downburst]

06z is a horror show, but as Summer8906 says at least the 00z wasn't as bad. But looking at the 06z the polar front at the end of the run is close to the Canary Islands for heavens sake, with the jet way south. Have to expect unsettled for at least next two weeks and perhaps up to 3 weeks from today. I'm not sure how I am going to get the grass cut 

[Bats32]

GFS 6z op looks off the rails..... hopefully. .. nothing great though, unsettled.

Edited March 29 by Bats32

[Summer8906]

One crumb of comfort is that even on GFS 06z, Week 2 of April is ever so slightly better than Week 1. Still some deluges but a few slack pressure interludes too meaning a chance of one or two sunny days. The constant barrage of frontal systems seems to eventually be replaced, around mid-month, by one huge slack low pressure zone covering much of Europe and the North Atlantic with a few flabby-looking centres. By then though I hate to think of what the rainfall totals will be.

Week 1 is simply horrific on both GFS 00z and 06z and comparable with the very worst historic weather outside the Oct-Jan period. It's perhaps worse than the worst weather of summer 2012, incredibly (but comparable with the worst of 2007). I've never known anything as bad in April, including in 2000 and 2012. I suspect by the end of next week much of the southern UK will be suffering a severe flooding crisis. Locally, we're already at the point where we simply cannot take any more heavy rain and perhaps 75mm in the first week alone will be simply too much.

We get low pressure in April but it's normally slack and slow moving. Frontal system after frontal system after frontal system, every 2 days or so, and directed straight over southern UK (such as is showing for the first 8 days) is incredibly rare bordering on unprecedented. If such conditions were to occur in  October or November it would seem very poor (though not unusual) for the time of year - that really does say something.

After all that, whatever week 2 offers will probably be an improvement in comparison, though to recover from Week 1's horrific conditions it needs to be properly dry and settled.

 

Edited March 29 by Summer8906

[WYorksWeather]

GFS 12z has a slightly better solution in deep FI - more along the lines of what CFSv2 and EC46 were showing yesterday. But before that, it's pretty torrid.

Count them - five low pressure systems.

1 - T+24:

2 - T+96:

3 - T+144:

4 - T+192:

5 - T+240:

Eventually though, by day 12, a bit of a ridge gets thrown up.

By day 16, still no sign of an imminent Atlantic return, with the mean trough stalled well out west.

As I've said, this sort of idea very much in line with the EC46 and CFSv2 from yesterday evening - the trough stalling well to our west, allowing heights to build over and to our east. Perhaps not universally dry, but still a much drier pattern. Significantly warmer as well - the GFS raw numbers reaching 18C on the 9th, and in practice, maybe our first 20C of the year? Cold and dry though in the north.

Weeklies from CFSv2 also show some improvement at week 4 as they did yesterday. Maybe some disagreement over timing, but perhaps some signals being picked up of a possible pattern change. We lose the mean trough over the UK by week 4, and some indication of heights building to the south and east.

All in all, possibly some very tentative signs of a transition to something drier (temperature will depend on the orientation of any high at this time of year). But before that, some truly awful weather to get through. And as usual, any look ahead to mid-month comes with a lot of uncertainty. I'm still hopeful that mid-April will prove a turning point, but I don't believe in selling rubbish - if the signal disappears I'll come back here and hold my hands up and admit that I got it wrong.

 

[stodge]

Evening all

@WYorksWeather has picked the bones out of the Good Friday evening output. Relentlessly unsettled through the coming week and into the following week too with the best on offer transient ridges between Atlantic LP.  The signs of something more settled on 12Z GFS OP once again but still far from the reliable and Control keeps the unsettled theme.

The ten day rainfall accumulations continue to look very bad especially for large parts of southern, western and northern England and all of Wales. Driest areas look to be NW Scotland and the Western Isles.

I presume the higher evaporation rates will help to a degree.

Temperature wise nothing too concerning though a very cold night next weekend with severe frosts in northern England and Scotland.

[KTtom]

Dont know why, but in my mind this UKMO 144 chart seems to sum up the last 4 months, Atlantic low to our west held firmly in place via a chocolate fireguard high to the north west whilst Scandinavia and particularly Finland continues to freeze.

[Penrith Snow]

 KTtom Correct and it's the worse possible set up, worse than proper zonality which at least gives the occasional sunny day and frosty night between depressions.

But a semi permanent low out west just gives relentless south westerlies, mild  in winter, cooler relative to average in summer but wet and persistently dull with little sunshine all year.

It's like the climate depicted in the film Blade Runner and maybe the weather that reflects modern Britain.

Andy

Edited March 30 by Penrith Snow

[ANYWEATHER]

The Ecms charts look about the same now as they do in ten days time!  Hope the ten day chart is wrong!

[damianslaw]

 KTtom Yes the synoptic we've seen most of since October. A bit of a negative west based NAO which just throws up rain and mild air to our shores, whilst to our NE a cold pool holds sway, advects into north atlantic firing up low and low after which come unstuck to our SW thanks to heights to our SE. If holds through late spring and summer, oh dear what a poor prospect. 

Edited March 30 by damianslaw

[johnholmes]

The 6-10 day 500 mb anomaly chart from NOAA shows a fairly marked Confluent ridge leading into a Diffluent trough off the coast of n America. This can lead to the development of a surface low, possibly rapid deepening. So at some stage in this time scale we could expect a fairly deep surface low to form in that area. The flow is then shown as SW'ly fairly strong at 500 mb. So a rather unsettled outlook in the 6-10 day period seems quite likely

[WYorksWeather]

Depends on how you count them, but I counted seven distinct lows over the UK in the next two weeks or so according to the GFS 6z. Just sums it up.

One:

Two:

Three:

Four:

Five:

Six:

Seven:

Couple of brief ridging attempts, but none of them are very successful. It looks pretty relentless.

Accumulated rainfall out to T+384 shows how ridiculous this is. Average England and Wales precipitation for the entirety of April should be 63mm. For just the first half alone, we have 70mm almost everywhere, and widespread totals over 100mm for Wales, the South West, most of Northern England and Scotland, and parts of the Midlands.

In short, we may quite possibly already be guaranteed a wetter than average April by the halfway point, even if it were to then turn drier.

[LetItSnow!]

 WYorksWeather An exceptionally wet April really one to watch out for. The succesion of lows at least in the reliable range would be remarkable for December let alone April. Despite potentially bringing issues, it's fascinating from a meteorological standpoint.

EDIT: Also, looking at those charts and it looks like the lows are tracking a little further south than they looked like a few days ago. Is this a trend to perhaps something less mild? Either way, whether mild or cool, it will be extremely wet.

Edited March 30 by LetItSnow!

[Rain All Night]

On 28/03/2024 at 11:54, Rain All Night said:

0z deterministic runs, out to Thu 4th (day 7)

0z ensemble means, out to Fri 12th (day 15)

I cannot think of anything interesting to say about these runs 

0z deterministic runs, out to Sat 6th (day 7)

0z ensemble means, out to Sun 14th (day 15)