Model Output Discussion - Spring Has Sprung

[damianslaw]

Need more runs, but, we may be about to see a significant change on the way, courtesy of heights ebbing west, introducing a cooler flow from between north and west. Lets see if this theme continues tomorrow, but its the way the models are heading. 

[Mark wheeler]

Nooooo , Not now , do one . 
 

 damianslaw yes they're gaining in momentum in the last 24 hours .

 

ps , got sunburned on my bald head at Thorpe park today waiting for the rides . Sun wasn't that prevalent either. 

Edited April 6 by Mark wheeler

[damianslaw]

 Mark wheeler The classic spring southerly then northerly switcharound, very common second half of Spring, all very normal, northerlies and easterlies reach their annual peak mid April to end May. Any other time, I'm sceptical of northerlies and easterlies but not in said timeframe. 

[Cambrian]

As the great man himself promised, Kathleen is being taken back home again, to be reabsorbed within the PV by day 5, here on the 0z ECM operational run. 

   

As a result, for the UK and Ireland, a vastly improving picture over the coming week as heights build northeast from the Azores, temperatures picking up by the end of the week for a while too if the T850s are anything to go by. 

Before exiting east, Kathleen ejects some energy westward to help the next system along, this one passing east further north through Iceland, to set up over Scandinavia from day 6 through to day 10. 

   

The bulk of Kathleen has by then rejoined the PV from the Siberian side, helping it pivot to be elongated down towards the Norwegian Sea, fuelling the dropping of the trough down through Scandinavia, bringing the UK and Ireland into a cold northerly flow for several days. 

After this rather dramatic phase (following three inches of snow in west Wales last week and three days of gales in the west of Ireland this week!), Kathleen looking to help ultimately deliver something for everyone - a storm, briefly something a bit warmer, followed by some clear Arctic air and the possibility of a quieter, more standard meridional pattern as we head into the second half of April.

So I guess it’s only fair to leave the man have the last words:

“And when the fields are soft and green

I will take you to your home Kathleen”

[ANYWEATHER]

At last it looks like the Atlantic is going to slow right down ,both gfs and ecm show a pattern change in the later stages of about a weeks time ,halting the rain train. This chart although a very cold airmass for the time of year would probably be bone dry for most of southern Britain, although any precipitation would be wintry. Plenty of sunshine away from the far northwest of Britain.  Anyway some good news at least on the rainfall aspect, but still need to be careful of Jack Frost sniffing about the gardens with charts like thus one!

[MP-R]

 Mark wheeler Ugh… yawn. Swapping autumn southwesterlies for winter northerlies . Was rather hoping the previous runs’ building of heights would gain traction. Still time of course for the cold weather to vanish but of course one almost expects the least seasonal outcome to win these days. 

[Downburst]

 raz.org.rain well it’s the 3 month combined forecast so very hard to get much of a take. Have to wait for the monthly. I wouldn’t be surprised at some point this year to get a lengthy dryer than average season, just because of swings and roundabouts.

[WYorksWeather]

Main uncertainty beyond the warmer and slightly drier spell around the middle of next week is how far any cold air can push and how long it lasts for. You can see that GFS has pretty high confidence in a cold push reaching as far as Newcastle, with only a few outliers, whereas in London there are still quite a few outliers that keep it mild or even warm all the way through, which would of course result in quite a strong temperature gradient over the UK.

In terms of the 850s as well still far too early to be sure - if we do go colder it's still far from clear whether it'd be a cool but not overly cold NW flow or a cold N to NE flow with fairly widespread hill snow and frost.

As others have said, it would be ironic if we do get a really dramatic northerly - about six weeks too late to really deliver any prolonged snow.

Personally though, this is not what I want to see in April. Much rather have some warm and dry weather, but of course we don't get to choose.

[johnholmes]

For what it is worth ECMEF seem currently to be going with the rather colder but brief version

[Cloud 10]

Hopefully the Low Pressure crossing the country on Monday/Tuesday will be the last one for a while as pressure builds to the south,and then to the west,which should provide drier weather overall compared to what we have had.

 

[Atmogenic]

 Mark wheeler  we need a  reaction when cold stuff is showing in April 

[Summer8906]

 MP-R Not so sure the northerlies will be bad though. Possibly bright or even sunny at times with a few aesthetically-pleasing scattered shower clouds around, separated by large areas of clear blue sky. Possibly feeling warm in shelter from the wind.

A big upgrade on the first part of April (apart from the 1st and yesterday) arguably.

Edited April 7 by Summer8906

[Summer8906]

 Mark wheeler With that setup, I'm struggling to see where the next low will come from, though - which can only be good. As I said, likely much brighter and away from the east coast, on the dry side. Rather April 2021-ish.

[MP-R]

 Summer8906 Need to see those isobars widening. Less of a screaming northerly and more a springlike slack northerly. Still time for that to be the case and, in fact could be rather pleasant down on the south coast.

[Scorcher]

 MP-R That is close to what the latest GFS run shows- a slack northerly flow wouldn't be too bad if we had some blue sky and sunshine.

[MP-R]

 Scorcher Yes a much better GFS run in that regard. Much more high pressure around too which can only be a good thing right now!

[Kirkcaldy Weather]

On 03/04/2024 at 22:05, Kirkcaldy Weather said:

There is likely to be further cyclonic development during the beginning of next week with a dip in the upper level dynamics however discrepancies on the track with some indicating the Bay of Biscay wheras others pull it into this weekends cyclonic developments with movements toward the UK.

As this cyclonic system develops and crosses the UK there are a multitude of developing dynamics.

• Sharp Thermal Gradient.
• Significant flash flood risk with a significant rainfall event.

As this system continues to develop and undergo cyclogenisis as it crosses the UK there will be a sharp thermal gradient occuring on its northern and particularly Northwestern flanks, this combination will aid in the formation of a significant rainfall event with an associated significant flash flood risk, a few discrepancies on precise track between the models however South and Southeast Ireland, West and Northwest Wales, particular focus into Northwest England, and Scotland.

As the sharp thermal gradient continues to intensify this will turn the rain to snow particularly across higher routes however mixing at low levels can't be ruled out, I expect main accumulations at this stage to be across the Pennines and Scottish Highlands.

These below average temperatures will lead to a cold night on Tuesday with a frost a possibility.

Into midweek the PWAT values once again become highly anomalous, wouldn't surprise me if records are broken at upper levels of the atmosphere for moisture.

On 27/03/2024 at 03:06, Kirkcaldy Weather said:

With further trough developments into the latter part of April week 1 in the North Atlantic this will bring an increasingly above average precipitation setup adjusting further north through Ireland and the UK.

Similar to Kathleen/Olivia this moisture inflow is tropically sourced. 

We'll return into an above average temperature setup with this systems influence.

 

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

With the teleconnective pairing of the move from a strong -NAO toward positive NAO values with recent stronger +AO values we'll see a focus of troughing and cyclonic developments more centering effects for Northwest and Northern UK and Ireland with a building of higher pressure having greater impacts toward southernmost UK and Europe.

All fitting in ideally with expectations this is an excellent teleconnective configuration for significantly cold air to be entreched across the Arctic I expect helping the Arctic Ice too @Midlands Ice Age 

Heading toward Mid April I'm watching for a plunge of Arctic air as troughing develops to the North of the UK and moves toward Scandinavia and Europe bringing a flow from the Northwest and North.

Thanks for Reading. 

KW

[WYorksWeather]

GFS 12z has now removed most of the outliers that don't introduce a cooler spell around day 8 - we can now be reasonably confident something will happen. Still too early to have any idea of duration, though the mean shows a fairly brief cooler spell before normal service resumes.

For areas further south, the Reading ECM meteogram seems to favour westerlies or north-westerlies over true northerlies, and hence the cooldown is much less pronounced. The mildness of the coming days can be seen quite dramatically - if this cooldown is relatively brief and not too dramatic, we could still be looking at another exceptionally mild month anyway, just on the strength of the first half.

[Daydream Boy]

Could you possibly change the title now to something like Spring has sprung or not as the case may be? Or something similar?

[Badgers01]

 Daydream Boy a totally new thread would be even better !

[BlueHedgehog074]

Changed the title for now, but we’ll probably try getting a new one up and rolling later. Did feel tempted to put Spring Has Sprung and then the phrase, (Or Has It?), because of how rubbish (bar a few odd brighter periods) the weather has been

[danm]

No comment on the models this morning? 

In a nutshell, we have a nasty little feature tomorrow that'll give many of us cool, windy and damp weather. After that, pressure builds to the south and SE, bringing sunshine and temperatures up to 20c across these areas by Thursday and through the weekend. 

The ECM then makes more of that NW'erly blast, bring cooler temperatures again by early next week, but the GFS doesn't make too much of that and quickly rebuilds pressure from the west, settling things down nicely. The UKMO only goes out until next Sunday, but looks similar to the GFS in that it looks a lot less primed for a NW'erly in the way that the ECM shows. 

Step by step, this is what each run shows for tomorrow:

 

Then later this week with the build of pressure to the south and south east:

 

 

 

Then towards early next week, here's how each of them deal with the chillier NW'erly:

ECM:

 

UKMO only goes out to Sunday:

 

GFS - keeps any NW'erly very brief, with a quick rebuild of high pressure:

 

 

What about the means:

Less bothered about 850's at this stage, so looking at pressure, the GEFS has a short dip before pressure builds again by the middle of next week - graph is for London:

 

...and for Manchester:

 

The ECM mean unfortunately is less keen on a quick rebuild of high pressure and keeps any rebuild fairly weak:

 

So we can confidently say that tomorrow looks awful for many, then much warmer, sunnier and drier across the south/SE midweek onwards and into the weekend, less so further north and west, then uncertainty over the potency and longevity of the NW'erly and how quickly and to what extent high pressure rebuilds into next week. 

Edited April 8 by danm

[raz.org.rain]

 danm I suspect it's a sort of fallout from the storm passing through, yo-yo-ing between low and high pressure.

[Rain All Night]

On 06/04/2024 at 10:15, Rain All Night said:

0z deterministic runs, out to Sat 13th (day 7)

0z ensemble means, out to Sun 21st (day 15)

Gotta head out and don't have time to wait for the full ECM ensemble to load, so the first 10 days will have to do...

0z/6z deterministic runs, out to Mon 15th Apr (day 7)

Once we've got the nasty little low out of the way today and tomorrow, we get our long-awaited pressure rise from the south, peaking on Friday. Conditions look pleasant for me down here on that day, though it seems that wind will remain a feature.

It's not clear yet how chilly the subsequent northwesterly might be, and on the GEM it even looks like it could have a stormy flavour to it.

Possibly a storm for the Azores propping up the Atlantic high.

0z/6z ensemble means, out to Tue 23rd Apr (day 15)

The Atlantic ridge looks as though it could sink down through the UK (though on ECM it stays to our west), which might provide some further settled weather (or chilly if it stays west).

Interestingly, all three models currently see significant, though at this stage non-specific, height rises in our region into the final third of April.

Edited April 8 by Rain All Night

[Summer8906]

6 hours ago, danm said:

In a nutshell, we have a nasty little feature tomorrow that'll give many of us cool, windy and damp weather. After that, pressure builds to the south and SE, bringing sunshine and temperatures up to 20c across these areas by Thursday and through the weekend. 

Is there a likelihood that the latter part of the week - Wednesday onwards - will be cloudy due to the moist nature of the airmass? Slightly concerned with one or two of the posts above (such as that of @Kirkcaldy Weather) which appear to show a frontal system passing through on Wednesday and Thursday albeit with high pressure, and mention mild and moist air - which is concerning for sunshine amounts. If so, it could be that the best weather could come through on Tuesday night!

At least after tomorrow it won't be silly wet, and perhaps this NW-ly cooldown at the weekend will bring in clearer and sunnier air.

Edited April 8 by Summer8906