Model Output Discussions 12z 08/03/17

[Matthew.]

UKMO has this for the 25th

[knocker]

The first thing to note vis the gfs this morning is that it has changed it's mind regarding the handling of the depression early next week and is more in line with the ecm solution. Assuming of course the ecm doesn't also change it's mind.

By 12z Monday the low is NW of Ireland 994mb but from this point high pressure builds from the south west whilst the low fills and tracks east to be north of Scotland by 18z on Tuesday. Thus most of Britain comes under the influence of the HP, the exception being Scotland which will be in the showery influence of the low.

From this point it would appear that the key to the evolution for the rest of the week and the weekend is how quickly the battle between the high pressure over the UK and the trough tracking slowly east from the Atlantic is resolved.

By Saturday 00z the trough is beginning to gain the upper hand (to some extent) as the centre of the high pressure is pushed north. albeit it's still hanging in there.

But, hey ho, it's a false alarm and the HP fights back and the upper trough deconstructs creating another cut off low off the coast of Portugal whilst the HP is still established to the NE/E leaving the UK in a light, warm, southerly drift.

So in a nutshell the story for next week, (post Monday) and the weekend from the gfs this morning is dry and quite warm with temps maybe a little above average. Of course this is subject to change but this morning's GEFS is okay with this.

[knocker]

Broadly speaking the ecm is not dissimilar to gfs, albeit the detail is different. It has the upper trough sliding south at the beginning of the weekend so the surface features fail to make any ingress vis the UK. Thus the latter ends up in a quite messy, slack gradient area, which weather wise would be great, dry and quite warm

[mb018538]

Much more promising today - and even more so as yesterday the bulk of ensemble members didn't favour high pressure being dominant. Being picky it would be nice if the SE European trough pushed a bit further east allowing the high to move across slightly....but any high pressure over the UK in late spring/early summer will be pleasant enough. Finer details to be ironed out.

[Summer Sun]

I like the way UKMO is trending hopefully a sign of things to come later in the month

UKMO extended

Looks nice for anyone attending the RHS Chelsea flower show later next week if UKMO is on the money

Edited May 19, 2017 by Summer Sun

[northwestsnow]

There seems to be a bit of momentum gathering for a period of dry and warm weather for the UK in a week or so, the GEFS ens for manchester have flipped overnight, the precip ones in particular have dried out quite markedly, fingers crossed..

[Summer Sun]

A hot and humid end to ECM - plenty of thunderstorms would develop from that

[stainesbloke]

41 minutes ago, Summer Sun said:

A hot and humid end to ECM - plenty of thunderstorms would develop from that

That is the kind of chart I want to see many times over a summer. 10 days away though, so of course we are all treating such charts as merely 'of interest', and won't have a massive tantrum when they change completely as time goes on, just like in winter. Aren't we? 

Edited May 19, 2017 by stainesbloke

[Singularity]

1 hour ago, Summer Sun said:

A hot and humid end to ECM - plenty of thunderstorms would develop from that

I can't recall many occasions in times past where a trough has been west of Iberia in combination with an extensive area of high pressure centered near Svalbard.

It makes me wonder just how things would progress from there; usually an Iberian low drifts N and then moves over the ridge but that's because the ridge is usually to our east or southeast. With blocking to the NE the low may either get trapped over the UK (thundery showers merging into longer spells of at times thundery rain... not the best of outcomes!) or split away from the Atlantic and pay a visit to Central/Eastern Europe (now that would be interesting as warm, moist air continued to feed in from the SE without a full-on breakdown!).

[knocker]

The EPS mean not looking too bad either.

[Tamara]

On ‎14‎/‎05‎/‎2017 at 12:55, Tamara said:

Set against the background ENSO factors, despite the very vulnerable arctic sea ice (but no imminent down-welling to the surface of an easterly QBO wave to help engage a high latitude tropospheric response such as happened in 2007) and assuming steady eastwards progress of the tropical signal and propagation through to the extra tropics via frictional and mountain torque mechanisms, then crucially seasonal wavelength changes will help assist removal of the Atlantic ridge/UK trough pattern solution and there is good reason to expect to see a steadily improving picture timed quite nicely for the approach of summer

So, the steadily improving picture emerges, from a sea of apparent doubt, and as suggested is timed quite nicely for the approach of summer

That background ENSO neutral > weak Nino signal imprinting itself on the atmospheric circulation with the models clearly too progressive in trying to instill Scenario B for any sustained time (the UK trough) only for Scenario A to emerge as drops in atmospheric angular momentum related to erratic tropical convection forecasting are overestimated. Hence the brakes have been applied on this in NWP over the last 24 hrs or so.

Scenario A:  Atlantic trough and downstream ridge for the UK and other parts of Western Europe

 

Give or take just a week or so those chart look fairly familiar to the start of a certain flaming June. And also a summer with a Nino imprint by the way.

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So whilst we cannot obviously suggest precisely identical synoptic evolution as through that summer, it is clear that where the patterns are trying to take us.

With kind thanks @Nouska for supplying some elusive charts on my behalf due to a frustrating lock-out of data access, its been possible to get updated AAM/GWO plots (with some impressive googling detective work on her behalf) as well as get a glimpse of the newly updated EC46 

Whilst of course we must take the ECM extended charts based on their unreliable history with a pinch of salt, it is encouraging it has flipped in its most recent update to come into line with some of the other longer range consensus.

So, the Global Synoptic Dynamical Model incorporating tropical and extra wind-flows expressed by measurement of global atmospheric angular momentum, has proved again that is a highly valuable tool in terms of being able to read between the lines of NWP and help question apparent medium to longer term trends

With tropical convection poised to head slowly eastwards through the tropics and eventually into the Western Pacific by early June, atmospheric angular momentum tendency looks set for further boost.

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Notwithstanding a possible hiccup following the settled synoptic scenario emerging in the coming week, there is good reason to see renewed tranches of downstream rossby wave amplification across our locale of the Northern Hemisphere - reinforcing the Atlantic trough and downstream ridge arrangement once more and increase chances of it becoming an early summer default pattern

That would be nice

This scenario translates to pendulum swing interplay between the disrupting trough and ridge features providing fine summer weather spells alternating with thundery re-sets as we head through June

 

 

[Man With Beard]

Is this called a Camborne clipper?

Seriously though ... a very nice turnaround in the models over the past two days and at a fairly short time range. The weakness of the Atlantic meant that ridging from Iberia always had the chance to disrupt the pattern and push heights north in a favourable way and - voila!!

How warm it will get is extremely uncertain - seems delicately poised between a NE flow (good for me) and a S or SE flow (good for almost everyone else) - but the sun should have its hat on alot in the D4-D10 period, I think.

[knocker]

Actually the timing of this may well be be quite fortuitous as the ext EPS and EC46 are indicating a fairly quick breakdown after the weekend with the first week of June being trough dominated and quite cool.

[snowray]

Nice upgrades again if your looking for an early start to summer.

 

GFS playing catch up as usual.

 10/10 UKMO, was on the money again.

[Summer Sun]

Settling down nicely next week

[Captain Shortwave]

Well this week has been pretty wet for some with slow moving fronts bringing a lot of steady or heavy rain, but it looks like our fortunes will change over the weekend as pressure builds slowly from the south.

   

Next week sees high latitude heights wane with a more typical pattern developing with heights building strongly over Europe and from the Azores, the results we see dry conditions in the south from Sunday onwards with this pushing northwards next week.

Day 6 charts (GFS/UKMO/GEM)

      

High pressure right over the UK with warm sunshine and light winds. It does appear we will see low heights maintained to our west/south west which would support some very warm air to move our way so certainly the potential to see temperatures into the mid twenties by the end of the week.

GFS for Wednesday/Thursday/Friday (Just for fun)

      

First taste of summer looks likely, fingers crossed at least. 

 

[Man With Beard]

Now you're talking ...

Saw a lot of this type of thing late last summer, led to some great mini-heatwaves

By the way, forecast is for temps to go over 100F in Spain by the end of next week - a little variation on this chart could bring this direct from Spain to us and something not far off 90F in favoured spots  

[phil nw.]

Nice looking charts today with modeling showing the promise of a significant improvement next week.

That Siberian upper low still the dominant feature and Sub-Tropical ridging pushing the Atlantic jet further north resulting in a more typical pattern across our part of the world..

We have all had a dose of much needed rain over the last week or so and now the signs of a drier,warmer and sunnier spell with temperatures looking to head in the 20's C.

[comet]

4 hours ago, knocker said:

Actually the timing of this may well be be quite fortuitous as the ext EPS and EC46 are indicating a fairly quick breakdown after the weekend with the first week of June being trough dominated and quite cool.

That would be the form horse imho not wanting to get suckered in by the models just yet.

[snowray]

1 hour ago, Man With Beard said:

Now you're talking ...

Saw a lot of this type of thing late last summer, led to some great mini-heatwaves

By the way, forecast is for temps to go over 100F in Spain by the end of next week - a little variation on this chart could bring this direct from Spain to us and something not far off 90F in favoured spots  

OMG, don't do it MWB, we get enough of this type of ramping in the Winter months for Chrissake!

 

ECM looking ok.

[knocker]

16 minutes ago, comet said:

That would be the form horse imho not wanting to get suckered in by the models just yet.

That doesn't necessarily make the models wrong. At the moment it looks like the breakdown and the Atlantic trough making some inroads will be around the latter part of the weekend ( as illustrated by taking a snapshot of the GEFS this evening ) Quite knife edgy but this is over a week away and will no doubt be adjusted. The question is which way. In the meantime some very nice temps quite possible

 

Edited May 19, 2017 by knocker

[Summer Sun]

The GFS ens supports the idea of a warm dry spell developing next week

[snowray]

Oh my.....Come on ECM you can do it!

[Matthew.]

10 minutes ago, snowray said:

Oh my.....Come on ECM you can do it!

The tropical ridges looking very strong on the ECM. 

[I remember Atlantic 252]

14 minutes ago, snowray said:

Oh my.....Come on ECM you can do it!

Good charts, FI still, any plume could be delayed to Whit Tuesday, as plumes tend to arrive around midweek, good signs of improvement though as early as next Wed