Model output discussion 14/04/18

[Mike Poole]

I think that the key to getting some memorable early summer weather is a link up of the high pressure systems over the Azores and Scandi and it looks like this is happening with this frankfurter type feature on the GEM at T192:

Roll on to T240:

[Frosty.]

What an absolutely beautiful evening, still 24c 75f in places at 19.15!..looking at the Gfs 12z there's plenty more summer like weather to come during mid to late May with lots of high pressure around!

[Singularity]

The MJO phase 1-2 response of height rises N Atlantic to Scandinavia is strongly reflected in the way that all the models keep heading toward that sort of pattern for next week onward.

Much still to be resolved, though, when it comes to the Arctic pattern and how much this allows or denies the ridging access; if it opens warms wide there’s a risk that fine weather becomes limited to northwestern UK or even north of there in the most extreme cases (i.e. we all lose out and the Faroe Islands steal the good stuff).

On the other hand, there’s been a fair few occasions in recent months when Arctic height rises have been overblown by the models at more than 5 days range. In this scenario it could be northern residents finding themselves uncomfortably close to a trough. 

Or, just maybe, the large scale of the height rises (thanks to the MJO assist) allows for the whole UK to experience an extended spell of fine weather (5+ days). It can and does happen!

Edited May 7, 2018 by Singularity

[Frosty.]

The Ecm 12z shows another very warm and rather more humid day tomorrow across many central, southern and eastern parts of england with plenty of sunshine and temperatures up to 26 / 27c around 80f in the most favoured parts of the southeast but unlike today which was unbroken sunshine for many, tomorrow there is an increasing chance of catching a few heavy showers and thunderstorms. After tomorrow we are all into a progressively cooler, fresher oceanic airflow with rain at times interspersed with sunshine and heavy / thundery showers, still some pleasant intervals towards the southeast..following a generally cooler / unsettled spell this run shows an improvement from around tuesday next week with the trough filling and pressure starting to rise and temperatures recovering again, becoming pleasantly warm with more in the way of dry weather and sunny spells.

[Cheshire Freeze]

On 06/05/2018 at 03:00, CreweCold said:

Hints in the extended range that the HP positioning may not stay favourable for us to continue with the warm and settled weather with a mean tendency for HP to locate further to our N. Little agreement at present as to whether this blocking locates to the NE or the NW of us...though those wanting a continuation of the settled weather would probably prefer the former.

. 

GFS 0z has come on board with the ECM op idea, and reaffirms what I was saying a couple of days ago. Still FI for now though so I guess we see where we head in the coming days.

[mb018538]

BBC long ranger the last 2 nights has said high pressure will build in....I just haven’t seen it on the output at all, all I see is a pesky low like a fly in the ointment possibly making things cooler and unsettled. This mornings runs are similar again....not too sure where they are getting it from?

[Summer Sun]

GEM is one of the most favourable with the position of the high this morning

[Summer Sun]

UKMO at t168 has the UK dry

[Frosty.]

33 minutes ago, Summer Sun said:

GEM is one of the most favourable with the position of the high this morning

Yes the Gem 00z is the pick of the bunch, ends very nicely indeed and actually the Ecm 00z is a lot better than the Gfs too..hopefully it won't be long before the summery weather returns..in the meantime, enjoy today's glorious summery warmth again further s / e.

[carinthian]

23 hours ago, carinthian said:

Nice early summer spell over in Blighty. So pleased you for guys. Just wondering if the highest temps today could be in southern parts of Northern England with the longer land flow ? ( outside the heat island of Greater London ). Our mixed spring continues over here , plenty of rain forecast in the extended forecast period and yes we have snow predicted at our elevation for the early part of next week with upper cold pool over Central Euroland. We will see ! 

NB. Of topic just seen highlights of the Tour De Yorkshire, shown widely on Euro TV. The Scenery looked wonderful. A good advert for the county and the crowd numbers just amazing. On par with world cup event, so they report over here. Well done to the super folk of the White Rose County .

 C

Nice to see many parts enjoying the high temps across Blighty yesterday. Highest temps seem to have been along an axis , say from Dorset to Yorkshire.  Our medium term charts continue to show, yes, a cold pool development early next week over parts of mainland Europe. A moderate snowfall at elevation in some Alpine regions (we have been issued a warning ). Looks southern Britain could be in the influence of a continental cyclonic flow by 144t/168t, maybe mixed with a warmer air mass from the east. Northern Britain  getting the best of any sunshine and nice temps. Certainly, interesting Spring weather this season with some extremes, especially across Britain.

C

[stodge]

Morning all

A glorious early summer spell continuing for many into a fourth day with the highest temperature values of near 29c to the west of London. Clear signs of a moderation in temperature this week but into mid month there were, last week, notable hints of renewed northern blocking.

This morning's medium term analysis takes us to Friday May 18th and starts as always with ECM 00Z at T+240:

It's an interesting evolution. LP approaches from the NW through the coming weekend but disrupts in situ. However, as HP tries to build in from the west, LP over Europe re-asserts and by T+240 a shallow LP centred over western Britain controls the weather so the forecast would be showers or longer spells of rain possibly thundery developing across southern and south western areas in particular. The Azores HP is ridging to the NW of the British isles and the trough remains over continental Europe.

GEM 00Z at the same time:

GEM keeps the weather fine and settled for many for the foreseeable. The Atlantic incursion over the coming weekend amounts to very little and is pushed back NW allowing the Azores HP to build across the British Isles and by T+240 a large HP cell covers the British Isles with light if not calm winds and plenty of fine weather. A deep LP looks becalmed far out in the Atlantic and all that does is prop up the HP.

GFS OP 00Z at T+240:

Another very interesting evolution, closer to ECM than GEM in all honesty. The weekend LP tries to disrupt SE through northern parts of the British Isles but a renewed push of heights from the Azores HP keeps southern areas reasonably settled. However, early next week the heights start to recede as LP becomes more organised first to the north and north west before sinking SE through the British Isles and linking with the trough coming north from Africa and southern Europe. The Azores HP ridges more north toward renewed heights over Greenland and to the north of Scandinavia. At T+240 there is a brisk N'ly over western areas but eastern areas are under much lighter winds but with rain or showers developing over the British Isles and especially for eastern parts.

Further into FI we get 36-48 hours of unpleasant cool and wet conditions from a small LP in the southern North Sea before the trough transfers NW back into the Atlantic and heights build in again from the SW.

GFS Control 00Z at T+240:

Cool and unsettled with the LP sinking south toward the British Isles. Further into FI the trough remains close to the south and east while heights build to the north and west leaving winds in the easterly quadrant and a greater risk of rain or showers for southern and eastern areas.

The 00Z GEFS at T+240:

http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=240

Two main clusters on offer - one has the Azores HP building strongly in from the SW and the other doesn't meaning LP over or close to the British Isles so, if you like, the GEM evolution versus the ECM solution. Further into FI and the signal for northern blocking remains with only two or three members keeping the Atlantic as the dominant force. The northern blocking varies in position and orientation considerably.

In summary, two possible evolutions into medium term this morning. The GEM evolution keeps the weather settled with the Azores HP ridge taking over once the weekend's Atlantic incursion disrupts and retreats NW. The ECM/GFS OP solution is messier and brings low heights over Europe into play with enough energy phasing from the disrupting Atlantic trough to invigorate the trough over Europe which spreads north. The question then is one of energy transfer - with GEM there is no transfer of energy and the anticyclonic ridge builds back through the British Isles but with ECM and GFS enough energy spills SE across the British Isles to re-invigorate the European trough and send it north.

Which model is correct or are both wrong ? As ever, more runs are needed.

 

[Man With Beard]

ECM clusters as we head past mid-month - far from conclusive, but the main Atlantic trough is generally staying west of the UK. The percentage play therefore remains a flow with a southerly origin (so potential for more warm/hot spells), but working out the disruption through Euro/Scandi ridging means detail on any forecast will not be possible until within the D7 range at best. A very real chance of a minor trough getting stuck somewhere close to the UK for a few days, which would change everything.

D9:

 

D12:

 

[Frosty.]

Already 26c 79f in London at 13.00...maybe a similar max to yesterday around 28c

Looking at the Gfs 6z...much better low res than the 00z with a strong return to high pressure and summery warmth.

[Frosty.]

Mid / longer term prospects look increasingly good according to the GEFS 6z mean with the upcoming cooler more unsettled spell not lasting very long and replaced during next week onwards by high pressure and warmer conditions again...so, following a very nice 6z operational low res...a very encouraging mean longer term!

[Summer Sun]

Not bad at t144 from UKMO could be a lot worse

[Singularity]

 

For some reason GFS has always been more reluctant than the other models to detach small lows from the polar jet and send them down into Europe.

Here we see a classic example of this when comparing GFS (left) with UKMO (right) at +144.

The GFS run goes on to try settling things down, but is having trouble with that as of day 9 (+216) due to it still having the polar jet dangling into Europe. I get the impression it will at last break the connection on day 10 but way to make a mountain out of a molehill, GFS!

 

Admittedly, we can't absolutely rely on lows splitting away more readily than this model shows, as exceptions can and do occur, but based on the GEM 00z and UKMO 12z, I sense we'd be unlucky to see much worse than a small low traversing the country within the space of a day or two.

Now just watch it all fall apart .

These emotes are tiny! 

[Mike Poole]

GEM 12z finishes with a cracking setup:

Later half of the GFS run looks none too shabby either:

[Frosty.]

38 minutes ago, Mike Poole said:

GEM 12z finishes with a cracking setup:

 

 

I think that's the Gem 00z mike, I don't think the 12z is available yet, I keep checking.

[Mike Poole]

45 minutes ago, Frosty. said:

I think that's the Gem 00z mike, I don't think the 12z is available yet, I keep checking.

D'oh!  Yes, well spotted.  Still no sign of it.  ECM rolling though, T168 looks the point at which settled weather might take hold again, await the rest of the run though:

Edit. Yes, high pressure nosing in at T192:

Edited May 8, 2018 by Mike Poole

[Frosty.]

The Ecm 12z shows our weather becoming more unsettled and cooler from the west during the rest of this week with more average temperatures as a slow moving atlantic low / trough pushes up against the blocking high to the east, the trough over the uk then gradually fills in-situ with pressure starting to rise again during next week with increasingly fine and pleasantly warm conditions developing, turning more unsettled across the far NW by the end of the run with the best of the weather across southern uk by then. 

Edited May 8, 2018 by Frosty.

[Summer Sun]

1 hour ago, Frosty. said:

I think that's the Gem 00z mike, I don't think the 12z is available yet, I keep checking.

12z rolling out now on meteociel

[Frosty.]

2 minutes ago, Summer Sun said:

12z rolling out now on meteociel

Cheers gavin, I should have mentioned in my post above that although the Ecm 12z shows our weather becoming cooler and more unsettled from the west from tomorrow, there is still some fine and pleasant weather too, especially further southeast through most of tomorrow and then with a bit of a ridge on thursday before that slow moving atlantic trough edges in during fri and sticks around for the weekend but again in any sunshine between the showers it will feel warm..then improving generally next week.

[Summer Sun]

12z GEM appears to be getting the high in better than the 00z

12z

00z

Edited May 8, 2018 by Summer Sun

[Mike Poole]

Two model runs showing now, the delayed GEM 12z and the ECM ensemble mean.

Take the ECM mean first. Here at T240 still showing good ridging from the Azores to Southern areas, 

 

GEM finally going with the warm settled solution but not until late in the run, T228, but then goes for it, decent chart:

 

...and few better ways to land on Vendredi 18 Mai:

Another high pressure, and will probably push on right over the UK. 

Edited May 8, 2018 by Mike Poole

[Summer Sun]

10 minutes ago, Mike Poole said:

Two model runs showing now, the delayed GEM 12z and the ECM ensemble mean.

Take the ECM mean first. Here at T240 still showing good ridging from the Azores to Southern areas, 

 

GEM finally going with the warm settled solution but not until late in the run, T228, but then goes for it, decent chart:

 

...and few better ways to land on Vendredi 18 Mai:

Another high pressure, and will probably push on right over the UK. 

Plenty of promise during next week as things stand. How far north the high goes open to debate but turning warmer again

 

Edited May 8, 2018 by Summer Sun