Model Output Discussions 12z 03/05/2016

[Frosty.]

These are the charts I should have posted before showing the GEFS 6z mean and perturbations..Fingers crossed its on to something.

[Man With Beard]

31 minutes ago, Karl. said:

The Gfs 6z op run was not alone with its warm settled extended outlook, the GEFS 6z mean looks good again and there are some peachy perturbations..if the charts look as good by midweek I think we can breathe a sigh of relief and look forward to our most anticyclonic spell of the summer so far. If not, at least it won't be for the lack of trying to get this summer to take off!

Can I just make a point while we wait for the next installments of the model show (this is in addition to your post, not against it, Karl!) - IF we end up with a scenario like the GFS is showing at T192 getting to T144, then this would have a MUCH better chance of leading to a settled outcome over the UK than the Azores High "poke your nose in from the south west" charts. The latter allows the jet to flatten the pattern southwards enough to miss us. The former blocks the Atlantic out, and any flattening of the pattern only pushes the High further over us. The risk then is even further retrogression to a full on Greenland High, but that would be an almighty move from this stage. So what the GFS is showing is a far better route to more sustainable summery weather.

It would be good to have the ECM on board but not essential until T144 as in my opinion the GFS will usually be more accurate when dealing with heights around Greenland.

Still, needs to be showing in 48 hours time really to be taken too seriously.

[Frosty.]

6 minutes ago, Man With Beard said:

Can I just make a point while we wait for the next installments of the model show (this is in addition to your post, not against it, Karl!) - IF we end up with a scenario like the GFS is showing at T192 getting to T144, then this would have a MUCH better chance of leading to a settled outcome over the UK than the Azores High "poke your nose in from the south west" charts. The latter allows the jet to flatten the pattern southwards enough to miss us. The former blocks the Atlantic out, and any flattening of the pattern only pushes the High further over us. The risk then is even further retrogression to a full on Greenland High, but that would be an almighty move from this stage. So what the GFS is showing is a far better route to more sustainable summery weather.

It would be good to have the ECM on board but not essential until T144 as in my opinion the GFS will usually be more accurate when dealing with heights around Greenland.

Still, needs to be showing in 48 hours time really to be taken too seriously.

Agreed, I think the GEFS 00z mean was more emphatic for an anticyclonic spell. I would love cross model support, hopefully we will have that by midweek.

[Summer Sun]

Not a bad start to next weekend if UKMO is on the money for England and Wales

[Matthew.]

2 hours ago, Karl. said:

 

If that's 1035mb over the Uk there that's only 3mb off the all time record for August

[Frosty.]

The Gfs 12z op run shows high pressure ridging in by Friday across southern uk, a warm day further south, still a few residual showers in the east but many parts becoming dry with good sunny spells and saturday looks better, fine and warmer across most of England and Wales but the north takes a bit of a battering from a depression which brings a spell of wet and windy weather across n.Ireland and scotland which takes a little while to clear off to the NE. The effect of the weekend low makes sunday a fresher day but still largely fine further south. The north of the uk never really settles down during this period but the Azores / Atlantic high pressure does muscle its way in across southern uk from the west / southwest for most of week 2 with predominantly fine and pleasantly warm weather further south whereas the northern half of the uk, to the north of the high, stay unsettled and cooler but later in the run high pressure builds in more strongly from the south and it becomes very warm or hot across the south of the uk and eventually very humid which ends in a thundery breakdown...so it's really a north / south split and for the south it looks very respectable. I hope the eventual outcome will mean all parts of the uk settle down and warm up but there are some issues...i.e...the exact track of next weekend's potential low.

[Frosty.]

The Gem 12z shows how next weekend's autumnal looking depression could really mess up a potentially warm anticyclonic week 2 but next weekend still looks dry and warm in the south under a ridge of high pressure. A settled extended outlook is possible but nowhere near a done deal. 

Edited July 31, 2016 by Karl.

[Frosty.]

46 minutes ago, Matthew Wilson said:

If that's 1035mb over the Uk there that's only 3mb off the all time record for August

A pipe dream at the moment though unfortunately.

[Man With Beard]

We have a 1030mb high on the mean chart by D9:

The 1030mb mark on the GEFS mean has been significant for me over the past couple of years, as I take it to mean very high confidence that it will actually happen - I used it successfully to predict two weeks of mild weather last November due to a 1030mb mean high over Eastern Europe out to T300.

So I'm now going to assume that there will be a high in the position shown on the chart above, for two days before and two days after.

This is probably close enough to affect the UK, but not quite - I'd prefer to see it just a little nearer at least to ensure a fully settled week. 

As far as the UK is concerned, I think it leaves one greater possibility and two lesser possibilities.

The greater possibility is that the high is close enough to the UK to affect it all week, and we do indeed end up with a nationwide anticyclonic spell of at least four days, probably more (the south will already have begun this coming weekend) - winds will originate west or north-west, so warm rather than hot and perhaps even a little chilly first thing in the morning. But lots of sunshine.

One lesser possibility is the high is squashed slightly by the jet and disturbances do keep getting through on a westerly flow, but weakened significantly by the presence of High pressure nearby, so their significance is much less compared to recent weeks.

The final lesser possibility is the high retracts a little west from where it is, and a trough could set up over Scandi, allowing a northerly flow to set in. In this scenario, west would be best and still probably settled, but much cooler.

One thing that looks very unlikely on the chart above is a continental influence - that would seem to be out for the duration of the week - maybe at the beginning of end of the week. So I'm not sure it will ever quite be hot enough to be called a heatwave. Unless that 1030mb centre can drift a little east in coming days, as the op run does...?

So not home and dry with the settled spell just yet - but odds looking pretty good for much more drier and sunnier weather in places like N Ireland than for some time.

[northwestsnow]

Things starting to look 'up' insofar as todays runs are concerned.

All the big 3 look to be promoting a lovely warm weekend next away from the North west as pressure ridges across the UK, -

UKMO 144-http://old.wetterzentrale.de/pics/Rukm1441.html

ECM 144- http://old.wetterzentrale.de/pics/Recm1441.html

And GFS while not overly hot looks quite dry, again more so away from the NW.

All in all the trend is your friend, im hopeful of a change in the meto outlook tomorrow

[Summer Sun]

The low which is near the UK develops significantly as it moves into NE Europe

[northwestsnow]

ECM looks very nice indeed !

After going slightly faulty at 192 it then goes on to 

216-http://old.wetterzentrale.de/pics/Recm2161.html

Fingers crossed the ECM is on the ball because if it is, August suddenly looks to be shaping up a lot better then previously assumed..:D

[phil nw.]

Encouraging signs for the end of next week especially further south with all the big 3 nosing the Azores in as soon as day 5.

An eye needs to be kept on the quite vigorous little low zipping across to the north later in the week,exact track can mean a difference in the weather further north with strong winds and rain for time.

[Frosty.]

Next weekend's potential autumnal depression (an unusually deep low by early august standards) could scupper our hopes of a warm settled summery week 2. There are a number of 12z perturbations which show a very windy, unsettled and cool nwly / nly airflow with low pressure the NE and high pressure well to the west but some nicer ones too. The GEFS 12z mean shows high pressure ridging in but the core staying centred further southwest  in the atlantic meaning it's really only the south and west which would benefit with fine and warm weather, we really need that Azores / Atlantic anticyclone to muscle its way in and become centred over the uk..all to play for still but next weekend's low is a fly in the ointment, if that proves to a red herring and just brushes the far north, we could be in for a good spell.

[Man With Beard]

6 minutes ago, northwestsnow said:

ECM looks very nice indeed !

After going slightly faulty at 192 it then goes on to 

216-http://old.wetterzentrale.de/pics/Recm2161.html

Fingers crossed the ECM is on the ball because if it is, August suddenly looks to be shaping up a lot better then previously assumed..:D

That's a highly dodgy run. First am I right in thinking it beefs up that mid-Atlantic low out of pretty much nothing - almost in tropical fashion? Secondly, yes you can see a breakdown from the north coming by T216 but the transition to T240?

[northwestsnow]

1 minute ago, phil nw. said:

Encouraging signs for the end of next week especially further south with all the big 3 nosing the Azores in as soon as day 5.

An eye needs to be kept on the quite vigorous little low zipping across to the north later in the week,exact track can mean a difference in the weather further north with strong winds and rain for time.

Oh im more excited than you Phil

Track of the system will of course be critical for who gets the wind and rain, as it stands it looks like the worst of it will be north of the border.

Anyway, ECM brings a decent spell of weather for many beginning friday and staying dry and mainly warm away from the North west.

[Frosty.]

4 minutes ago, northwestsnow said:

Oh im more excited than you Phil

Track of the system will of course be critical for who gets the wind and rain, as it stands it looks like the worst of it will be north of the border.

Anyway, ECM brings a decent spell of weather for many beginning friday and staying dry and mainly warm away from the North west.

I'm the one suddenly being cautious about all this, even Mr Spock raised an eyebrow..

[Tamara]

A -ve GLAAM state has continued to thwart any chances of sustained warm air advection amplification in our part of Europe.

However, the outlook as far as the next 10 to 15 days is concerned, is not clear cut.

Set against the relatively unremarkable summer background atmospheric circulation, there are now nevertheless some interesting updates to the atmospheric angular momentum budget which part contribute to the hopes of a burst of warm advection next weekend, into the early part of the week - albeit uncertain how settled on  a national scale. Depending on the precise track of a tropically derived low pressure system that draws rich heat and moisture ahead of it, there could be seasonally relatively high impact weather for some, as well as the prospect of some summer warmth, and also sunshine for others at the same time!

Latest ECM operational adjusts the track of the low NW'wards - lots more intra model/day output to come on this.

.

 

Frictional torques have met a new wavelength (timescale) and have climbed to be weakly neutral/positive for the first time this summer.

This, in addition to previously discussed tropical convective feedbacks, has given a boost to atmospheric angular momentum tendency

 

The Global Wind Oscillation has responded and very recently moved into Phase 4

 

As a result of increasing frictional torque, there is the prospect of  a +ve Asian mountain torque event and then to follow a corresponding inverted -ve American mountain torque that look set to provide some Northern Hemisphere dual amplification

.

 

This means that the GWO is likely to perform a swift orbit from Phases 4/5 back to 8/1.  GFS therefore looks good enough value here with this forecast

 

 

A small Rossby train in response to the +ve MT looks set to boost sub tropical ridging (Bermuda and Azores high) northwards. Also, this small amplification kick in the Atlantic appears as if it will coincide with the trajectory of a myriad tropical depression that interacts with the temperature gradient and jet to deepen it sufficiently to enable the downstream Azores ridge to attain enough further strength to push further north across the UK.  Extent yet uncertain.

At the same time, a Rossby wave train downstream from Asia across the Pacific will invoke the US -ve MT that creates a vacuum - effectively slamming the breaks on,  decelerating the downstream jet with the result that the mid Atlantic ridge is pulled back and re-ampified just to our west in the wake of the tropically sourced depression as it exits to our NE. 

This eventuality coincides with the GWO back in Phase 1 - following the US MT. This phase, in these synoptic circumstances, does (initially) allow for the possibility of some kind of cut-off close to the amplified Atlantic High that might support the ridge enough to sustain some of the advected warm air for a day or two.

An interesting 10 to 15 days weather watching ahead

Edited July 31, 2016 by Tamara

[Frosty.]

Nice Ecm 12z from Friday onwards, BBQ weather next Sat / Sun across southern uk and more high pressure week 2...what could possibly go wrong!

[Frosty.]

Tonight's  Ecm 12z ens mean shows a lot more high pressure / ridging influence from late in the week ahead compared to last night's which was more trough dominated..so that's a tick in the box. Hoping for more good news tomorrow!

[mb018538]

ECM is great this morning, could see temps up around 30c in places if the sun comes out to play! Looks like this vigorous low is helping to drive things along....

[mountain shadow]

9 minutes ago, mb018538 said:

ECM is great this morning, could see temps up around 30c in places if the sun comes out to play! Looks like this vigorous low is helping to drive things along....jh

[mountain shadow]

Great for who though MB?. The overnights continue the persistent theme of troughing to the NW of the UK maintaining the unsettled theme to the Summer. 

Yes,  the odd warmer and drier day or two particularly in the South East but nothing to get excited about. 

[Frosty.]

The GEFS 00z mean doesn't show any downgrades since yesterday, still showing increasing high pressure / Azores ridging influence towards the weekend and through next week with a warmer and more settled spell further south with temps rising into the mid 20's celsius range. I'm not seeing a cool unsettled extended outlook, looks very decent, at least across the southern half of the uk!

[Man With Beard]

18 minutes ago, mb018538 said:

ECM is great this morning, could see temps up around 30c in places if the sun comes out to play! Looks like this vigorous low is helping to drive things along....

Yes heatwave conditions from the ECM, especially in the south

doesn't fit in the ensembles as far as the mid-Atlantic is concerned though, so low confidence on that one. Doesn't mean it's wrong.

Here's one that does fit in with the ensembles, on the more pessimistic side it must be said - the GFS at T192

The GEM - somewhere between the two?

All models seem agreed now on a hot weekend for the south - possibly into N England / S Scotland too but it's touch and go for them