Model Output Discussion - Spring Has Sprung

[stodge]

Evening all

After three or four very pleasant days in the south in particular this week, we have another change as the HP regresses back into the Atlantic and the trough comes south introducing a more NW'ly flow through the weekend and into early next week.

From there, your guess is better than mine with all sorts of options on the table though it looks more settled than not with HP somewhere to the north or perhaps north east but you couldn't call it at this time.

[Addicks Fan 1981]

 damianslaw to be honest I think that we are less likely to see below average temps, we can't just take deterministic charts in isolation and we need Tamara online to use some GSDM accessories so we don't get too lost in NWP output and take it at face value.  We need to not treat too much NWP op charts as gospel.    

[Alderc 2.0]

 Addicks Fan 1981 to be perfectly honest the models have been going pretty well with the overall pattern in the last month. GfS sniffed out the extremely unsettled pattern going into Easter and again highlighted at 10plus days the quietening down of things so but so anyone else will do any better to be honest.

[danm]

Dry, settled and warm for the south from Thursday until about Sunday this week, up to 20c in the SE, with some good sunshine. Then a chilly NW’erly early next week. After that, this is what each model run shows this morning:

ECM - the Atlantic high moves east, back over the UK

 

 

GFS - the NW’erly is very brief before the high starts moving back east settling things down again. It’s not a very robust high so I wouldn’t expect wall to wall sunshine, but largely dry with some sunny spells and reasonable temperatures.
 

 

UKMO - only goes out to Monday night but also shows the high moving back east:

Edited April 10 by danm

[Summer8906]

 danm Not atypical for this time of year, seems quite common for brief NW-ly plunges to be followed by anticyclonic.

Ironically, when we get a straight N-ly it's then more likely to regress into cyclonic again which seems counter-intuitive. What tends to happen in this case is the N-ly is followed by an active low from the NW which moves southeast to be centred over the UK and displaces the Atlantic high SW-wards. April 2008 is a good example, and the start of May 1997 is another, and the famous April 1981 snowy spell is yet another.

Edited April 10 by Summer8906

[northwestsnow]

Thank God the 00z runs are moving towards HP having more influence from mid month.

It's hardly stopped raining since October in the North west....absolutely appalling 6 months of Atlantic dominated weather.

 

Edited April 10 by northwestsnow

[Cambrian]

Looking at the next ten days, which cover the middle third of April, t’s good to see the relevant part of the annual cycle, in the form of the springtime waning of the PV, well underway. 

It is happening a bit later than the last couple of years, but is striking nonetheless, here on both the 0z ECM operational run and ensemble mean, day 1 - 10 animations, the PV very much on the wane, being nibbled away by evolving mid-latitude ridges, with the core PV diminished and returning from the Siberian Arctic to the pole. 

 

This leaves us with a solidly meridional 5-wave hemispheric pattern by day 10, shown nicely on the op and mean anomalies, ridges by then through western North America, up through the eastern seaboard, Western Europe, Kazakhstan up into Siberia, and the far east of Russia. 

 

The picture for the UK and Ireland alternates from seeing a shallow ridge over the next few days, to being under the influence of an active low pressure system passing through with the trough around days 5-6, before the arrival of a better amplified ridge by day 9-10 as the more meridional pattern firms up.

Day 10 provides a convenient juncture for the UK and Ireland for showing the potential for something more settled getting a bit further north to be more widely shared, op and mean again.

 

However, it looks very much like it’s a snapshot in a slow but steady revolution of the 5-wave ridge / trough pattern around the pole, with approximately 4 days appearing to be the current phase for the ridge to trough transition, hinting at a period of drier, brighter spells of 3-4 days alternating with more changeable spells of 3-4 days.

A much more normal and much more pleasant a pattern on view as spring more clearly shows its hand. 

[Rain All Night]

On 09/04/2024 at 00:13, Rain All Night said:

12z deterministic runs, out to Mon 15th Apr (day 7)

Do you notice how the UK never really escapes those tighter isobars throughout the whole of these runs?

12z ensemble means, out to Tue 23rd Apr (day 15)

ECM still doesn't want to let the Atlantic high move over us, but it's nonetheless looking good for 'spring' beyond that.

0z deterministic runs, out to Wed 17th Apr (day 7)

The return to westerly and then northwesterly flows from Saturday to around the middle of next week appears to be but a blip...

0z ensemble means, out to Thu 25th Apr (day 15)

...the ECM still tries to avoid moving the Atlantic high over the UK, but by Friday 19th it has relented, and from then on, on all three models we see the start of something potentially beautiful, at long flipping last, with signs of anticyclones and reversed flows over the UK out until the end of these runs.

Edited April 10 by Rain All Night

[Jordan S]

Whilst higher pressure than we've been use to for last week of April is still favoured along with occasional brief wetter conditions especially from our south, there is obviously a lower possibility that the evolution below takes place which I was going to post on yesterday but got completely sidetracked, would take us to square one and my previous posts then being too ambitious shall we say of drier weather than we've been use to by then.

Thankfully the synoptic pressure pattern being low though around 30%

Not worth worrying about at this stage, with a fine few days to come further south at last in the meantime.

Will try and do an in depth update later in the week, especially in regards to late April, but mental health isn't doing me well atm so may post less often. 

 

Take care.

[danm]

 

[Methuselah]

 danm It's slow, it's painful, Dan. But potential improvements are afoot! 

[ANYWEATHER]

Instead of a dartboard low over the UK , we have at day ten a flabby dartboard high.....

[Methuselah]

But that's Day Ten. Who cares?!  

[raz.org.rain]

 ANYWEATHER much better than the Arctic blast that was being suggested 

[damianslaw]

 raz.org.rain Look a little further ahead and the GFS 12z pulls the high quickly NW and a cold N/NE flow envelops the UK. All conjecture at such range, but its a theme appearing on a few GFS runs latter stages of output. ECM interestingly also suggests the high will be shunted west and north west quick as well. 

Lots of uncertainty on finer details as we enter second half of April, but an emerging trend is a settling down with strongish heights near or over the UK, but they do look quite fragile prone to loose footing, the question is where will they end up. At this point in the year quite often they retrogress west and north as we lose the core of the PV, or east and north east.. 

Edited April 10 by damianslaw

[Sherry]

 damianslaw the gfs op was right at the bottom of the pack at the end of the run, so currently 0% chance of happening  

[damianslaw]

 Sherry Ah yes I expected that might be the case. Still lots of uncertainty second half of April, its a tricky time of year to predict. 

[Cambrian]

A good indication of how far the models have come since the weekend in terms of bringing some anticyclonic promise to the UK and Ireland is provided by the MSLP charts of the 12z EPS and GEFS, and comparing today’s day 9 charts with the day 12 charts from Sunday.

EPS for the 19th, 7th + 12 days / 10th + 9 days

 

GEFS for the 19th, 7th + 12 days / 10th + 9 days

 

Both EPS and GEFS now picking up on a signal for high pressure over or near the UK and Ireland, for a few days at least. Looking a lot better.

Much more positive signs as we approach the middle of April, and high time for the models to be finally picking up on a more solid drier spell. 

[WYorksWeather]

 Sherry It does have to be said though (and I say this as someone who isn't a fan of this idea!) that there is a bit of an ensemble signal for a second cooler spell from around 21st onwards. Whether it amounts to anything is of course highly uncertain at this range. Probably useful to await the verdict of the ECM.

[WYorksWeather]

Off work this week but been pretty busy. Others have covered the general outlook quite well, so I think worth me taking another of my regular looks at the ECM sea surface temperature.

Here are the North Atlantic SST anomalies for days 0, 5, 10 and 15.

As has been seen so often, our old friend the Azores SST anomaly is still very much there. As we progress towards day 10 and beyond this seems to intensify but focus further east, closer to the Iberian Peninsula and NW Africa. It does of course raise the possibility of some exceptionally warm weather from that direction if the synoptics are right.

Closer to home, there is also a signal for warmer than average SSTs close to the British Isles, especially around England and Wales, less so for Scotland and Ireland. The key point here is that coastal breezes will probably produce less moderation of any warm spells than you might normally expect at this time of year.

For some additional perspective, here are the SST actuals for days 0, 5, 10 and 15.

The green colour in the 10-12C range encroaches across much of southern England by the end of the run. Of course, we expect SSTs to start to rise quite rapidly from this point on as the inertia from the winter wears off. As a reminder, we expect these temperatures to peak in September as a rule.

One final longer term update. The ECM is projecting that the final stratospheric warming will occur in the first week of May.

This is later than climatology, and generally correlates to a warmer and drier summer compared to an earlier final warming, for what it's worth.

 

[Rain All Night]

9 hours ago, Rain All Night said:

0z deterministic runs, out to Wed 17th Apr (day 7)

The return to westerly and then northwesterly flows from Saturday to around the middle of next week appears to be but a blip...

0z ensemble means, out to Thu 25th Apr (day 15)

...the ECM still tries to avoid moving the Atlantic high over the UK, but by Friday 19th it has relented, and from then on, on all three models we see the start of something potentially beautiful, at long flipping last, with signs of anticyclones and reversed flows over the UK out until the end of these runs.

12z deterministic runs, out to Wed 17th Apr (day 7)

12z ensemble means, out to Thu 25th Apr (day 15)

My concise and balanced review of these charts, particularly from Friday 19th onwards, would be: YAAAAAYYY!!!

[WinterOf47]

 Rain All Night i really hope yaaay! Wins, as the GFS op runs have been showing Noooo!

[carinthian]

Morning all. After a record warm first week to April in The Eastern Alps , snow and lower temps have returned to higher elevations.  Still waiting to book a trip back to the UK  but holding back as that chart from UKMO does not really float my boat for The British Isles. Those chill winds off the North Atlantic definitely not to my liking. I will just have to wait and see a big fat high sat over Northern England before booking a flight from SZG to MAN ! Having the thought of visiting a decent pub and sampling a pork pie remains very enticing though. What do you think of all those trough lines over North Africa. How the hell do they align them ?

C

Edited April 11 by carinthian

[ANYWEATHER]

Quick summary. Best charts I’ve seen in a long time for eventually the weather settling down. The change is underway, but needs a little more time for the complete settled weather to arrive! Anyway, trends looking the best I’ve seen all year….

[Frigid]

Quite a chilly outlook going by the 0z ens. April could be a strange first half mild, second half cool..