Model Output Discussion - Into Autumn 2020.

[Daniel*]

4 minutes ago, LRD said:

Well, I can't be bothered to look back but I seem to recall that on Friday and Saturday a N'ly or NE'ly was being modelled by the ECM and that a proper GH was being considered at that time. Admittedly it was 168/192 hours away so not to be trusted but that was kind of the point of my original post. Not to trust models promising this, that or the other more than a week out. I see you've posted a chart that is 9 days out.

It's going to be cool later this week, no doubt, but the coming weekend is looking quite different to what was modelled at the start of the weekend just gone

That was shared for reloading theme I’m seeing. I think you ought to go specsavers, all models showing cool northerly/northeasterly winds this Friday and Saturday. 

Edited September 21, 2020 by Daniel*

[LRD]

16 minutes ago, Daniel* said:

That was shared for reloading theme I’m seeing. I think you ought to go specsavers, all models showing cool northerly/northeasterly winds this Friday and Saturday. 

And I think you ought to pick up a dictionary and understand what 'sustained' N'ly means. In other words, something more than a 1 and a half/2 day wonder was showing a couple of days back

 

Don't patronise me pal

Edited September 21, 2020 by LRD

[Frosty.]

Looking at the GEFS 12z, according to the mean it trends more benign in early October and looking through the 12z members there’s support for unseasonable warmth too..I did mention something similar regarding the 6z GEFS..if anything, the support here is even stronger!...October BBQ anyone?

[Daniel*]

11 minutes ago, LRD said:

And I think you ought to pick up a dictionary and understand what 'sustained' N'ly means. In other words, something more than a 1 and a half/2 day wonder was showing a couple of days back

 

Don't patronise me pal

lol maybe a miscommunication sorry... but it seemed to me from your post we had escaped altogether many will see grass frost this weekend, with highs in Scotland of 8C so it is a pretty cold flow if quite brief, I don’t feel things are markedly different to that looking at 12Z from two days ago, I think GFS has been more aggressive with sustained and colder flow. Regardless who cares about this nonsense in September. I’d rather an Indian summer but little to suggest that heading into early October not looking particularly dry or wet to me. 

Edited September 21, 2020 by Daniel*

[Zak M]

Just now, Jon Snow said:

Looking at the GEFS 12z, according to the mean it trends more benign in early October and looking through the 12z members there’s support for unseasonable warmth too..I did mention something similar regarding the 6z GEFS..if anything, the support here is even stronger!...October BBQ anyone?

I'll bank those charts, thanks Karl. 

The GEM ensembles aren't too bad either:

      

      

[LRD]

16 minutes ago, Daniel* said:

lol maybe a miscommunication sorry... but it seemed to me from your post we had escaped altogether many will see grass frost this weekend, with highs in Scotland of 8C so it is a pretty cold flow if quite brief, I don’t feel things are markedly different to that looking at 12Z from two days ago, I think GFS has been more aggressive with sustained and colder flow. Regardless who cares about this nonsense in September. I’d rather an Indian summer but little to suggest that heading into early October not looking particularly dry or wet to me. 

Ok mate, fair enough. I wouldn't mind a bit of autumn now and we'll certainly be getting that. The highest ground in Scotland might even get a bit of very early winter

[Mr Frost]

Evening all

You both have a point - charts a few days back looked a bit more unsettled/snowy over the Scottish mountains for example @LRD so I can see what you are saying. (More of a dusting now over 800/900 meters)
I see you live in Bedfordshire? Great spot for watching distant thunderstorms - just ask @Zak M  but I don’t think you were ever at risk of anything exceptional this week/weekend with regards to anything interesting weather wise. (Cool days/nights from midweek and a soggy Wednesday?)

As @Daniel* stated it looks cool/chilly for many of us midweek through to Saturday/Sunday - especially further North.

UKMO:

 

Winter coat/hat weather for many in the South. 

Lots of sunshine and not much rainfall about - which is great! (Not bad at all for myself and many others throughout the UK and Ireland)

ECM accumulated precipitation:

 

So much cooler from Wednesday, not too bad from a rainfall point of view, plenty of sunshine about and the risk of a ground/air frost or two for quite a few of us! (North to South)

Decent Autumn weather for large parts of the UK and Ireland. 

All the best to you all and have a good week!

Edited September 21, 2020 by Mr Frost

[viking_smb]

I hope it is a bit windy this weekend, as we have our shanghai cup at cbyc so will be in the channel aboard CBYC 5 (tornado 5.4 60hp) pic enclosed (she now has a towing bridle fitted - rope around engine for towing attached to the transom) as mark laying, so i do hope its windy so i can have a little play . (dont worry i'm a fully trained and extremely experienced rib driver) 

another note it will be odd if we have snow in october esp down our way   

Edited September 21, 2020 by viking_smb

[bluearmy]

Gem has a pretty mad start to October ......

[cyclonic happiness]

2 minutes ago, bluearmy said:

Gem has a pretty mad start to October ......

It's almost the Union flag!   Maybe it's the Arctic's way of saying "this is gonna be the UK's year, this year"

Knowing the way everything else has gone, I can imagine we're in for a shocking end to the year

[NApplewhite]

15 minutes ago, cyclonic happiness said:

It's almost the Union flag!   Maybe it's the Arctic's way of saying "this is gonna be the UK's year, this year"

Knowing the way everything else has gone, I can imagine we're in for a shocking end to the year

Turning briefly a little milder this weekend according to the GFS. Then colder with wind and rain following . A little drier for the far south

[Frosty.]

Please forgive my shameless cherry picking from the GEFS 0z ..I haven’t fully gone across to the dark side..I mean cold side of the force just yet..cough ..not until the chance of summery warmth is over!..anyway, there’s some lovely eye candy here for those of us who like autumn warmth!!!?

 

[mb018538]

ECM again the best of the bunch if you don't want a full on zonal low pressure assault.

[mb018538]

Slightly playing catch up, but a fall in AAM has now been picked up on by global models, hence our downturn in weather. 

Matt Hugo posted the ECM forecast yesterday, which clearly shows as the forecast time progressed, the AAM forecast got more and more negative. There is potential for an improvement into October as the MJO gets a move on again.
 

 

[joggs]

19 minutes ago, mb018538 said:

Slightly playing catch up, but a fall in AAM has now been picked up on by global models, hence our downturn in weather. 

Matt Hugo posted the ECM forecast yesterday, which clearly shows as the forecast time progressed, the AAM forecast got more and more negative. There is potential for an improvement into October as the MJO gets a move on again.
 

 

Is there a lag time from when the AAM goes up and down to when it effects our weather?

[mb018538]

1 hour ago, joggs said:

Is there a lag time from when the AAM goes up and down to when it effects our weather?

It's a tricky one - there is usually a bit of a lag between momentum rising and falling and a change in the weather.

If we take this chart for September (via Matt Hugo twitter) - momentum through September has remained in a negative state, but momentum has increased almost constantly during that time - which helps to explain the mainly warm, dry, sunny and settled September so far. It's set to turn pretty unsettled here by Thursday, but at that time AAM is still rising, so you'd not necessarily expect such unsettled weather. When you chuck a major hurricane into the mid latitude jetstream though, it can upset the apple cart.



A lot of this is far beyond my knowledge, so it may be better that someone like @Tamara gives a better understanding. I'm learning on the job too, much like a lot of the members here! 
 

[carinthian]

This evening produces some really interesting charts to end the week. Both GFS and UKMO models showing an unusually cold air mass for the time of year into the British Isles during Friday and into Saturday.  Strong gradients in potential temp at 850 hpa as well as  500/1000 hpa thickness field values ( note the close proximity  of the 528 dam line to the British Isles) are the best parameters when identifying  the passage of a Arctic front. Certainly this is very unusual at this time of the year, even in the winter.  Winter time would see snow in this flow, especially in the east but at this time of the year the passage of the front is likely only to introduce lower dew points and gusty winds for 24 hours before dying out. Certainly ,Saturday into Sunday morning as a weak ridge develop[s looks ripe for the first real widespread air frost of the season. 

C

Edited September 22, 2020 by carinthian

[tinybill]

looking  at  the  out look me thinks the shorts  can beput away now

[damianslaw]

Even quieter in here today than yesterday.. because nothing especially promising in the charts, and today marks the end of an excellent 10 day spell of weather by and large.

No change in the models, predominantly unsettled outlook for the foreseeable, colder than normal, notably so in the north, no obvious signs of anything other than a return to near average temps as we end the month and start October. Trough looks destined to plague the UK for a bit.

As long as the Russian high holds steadfast, the trough has nowhere to go other than align on a NW-SE path through the UK and out into central/SE Europe.

This would be a very wintry cold pattern if the depths of winter, alas it's September and it means chilly weather but not especially wet away from any frontal activity and the north and west, convection looks limited at least to begin with, but with a more defined atlantic flow rather than polar flow, perhaps more general rain and cloud as time moves on.

[stodge]

56 minutes ago, damianslaw said:

Even quieter in here today than yesterday.. because nothing especially promising in the charts, and today marks the end of an excellent 10 day spell of weather by and large.

No change in the models, predominantly unsettled outlook for the foreseeable, colder than normal, notably so in the north, no obvious signs of anything other than a return to near average temps as we end the month and start October. Trough looks destined to plague the UK for a bit.

As long as the Russian high holds steadfast, the trough has nowhere to go other than align on a NW-SE path through the UK and out into central/SE Europe.

This would be a very wintry cold pattern if the depths of winter, alas it's September and it means chilly weather but not especially wet away from any frontal activity and the north and west, convection looks limited at least to begin with, but with a more defined atlantic flow rather than polar flow, perhaps more general rain and cloud as time moves on.

Yes, the block is too far east to offer the possibility of the trough sitting out to the west of the British isles and allowing for a S'ly flow though GEM OP this evening keeps the HP a little closer to Scandinavia and is certainly the direction of travel you'd want to see if you fancy some autumnal warmth.

Otherwise, it looks distinctly unsettled and often quite wet. GFS OP and Control in far FI try to re-set the pattern by having the LP dive south east through the British Isles allowing the Azores HP to build in between but that's too far off to be anything more than wishful thinking for now.

[mb018538]

Looks like we are well and truly getting wedged into a very unsettled pattern as we go out of September and into October. High pressure either wide of the UK, with a deep trough plonked straight on top of the UK with nowhere to go: 



Check out the jet amplification across the USA (below). Very high and potentially record breaking temperatures across the west with a huge area of very hot air (above 25c 850 temp) in place. Massive dip in the jet across pretty much the entire eastern side of the states, with some very cool air (4c 850s) making it all the way down to the Gulf coast. The big ridge out in the Atlantic is pulling some warmer air up, and creating a big thermal gradient, which is powering across the Atlantic straight at the UK. The Atlantic conveyor in 'full steam ahead' mode, a symptom of an ever cooling Arctic region clashing with heat left over from the Northern Hemisphere summer.

[johnholmes]

I agree with the post above from mb and my update on the 500 mb anomaly charts is a similar theme

Wed 23 Sept

Ec-gfs and both show very similar with a deep trough uk area and a marked ridge with –ve heights west of this, also similar further west with ridge trough set up, could last a while perhaps?

Noaa is pretty much as ec-gfs over the whole chart! Not that often one sees such agreement and its 8-14 keeps a similar thing, position and even intensities, rather unusual for the 8-14 to follow the 6-10 so strongly.

Having said this sods law will probably operate and it will all change in 2-3 days! Currently it looks on the cold and pretty unsettled side for pretty much all of the uk

On top of this we have the huge uncertainty whenever an ex hurricane/tropical storm gets caught up in the jet stream.

Also the 500 flow shows a signal in the UK area for divergence, especially in the NW. This can lead to a fairly rapid deepening of any weather systems running out of the Atlantic, so deep surface lows and some very strong winds 'could' occur, most for the NW'ern half but perhaps one also affecting areas further south!

http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

https://www.cpc.ncep.noaa.gov/products/predictions/610day/500mb.php

Edited September 23, 2020 by johnholmes

[mb018538]

9 minutes ago, johnholmes said:

I agree with the post above from mb and my update on the 500 mb anomaly charts is a similar theme

Wed 23 Sept

Ec-gfs and both show very similar with a deep trough uk area and a marked ridge with –ve heights west of this, also similar further west with ridge trough set up, could last a while perhaps?

Noaa is pretty much as ec-gfs over the whole chart! Not that often one sees such agreement and its 8-14 keeps a similar thing, position and even intensities, rather unusual for the 8-14 to follow the 6-10 so strongly.

Having said this sods law will probably operate and it will all change in 2-3 days! Currently it looks on the cold and pretty unsettled side for pretty much all of the uk

On top of this we have the huge uncertainty whenever an ex hurricane/tropical storm gets caught up in the jet stream.

Also the 500 flow shows a signal in the UK area for divergence, especially in the NW. This can lead to a fairly rapid deepening of any weather systems running out of the Atlantic, so deep surface lows and some very strong winds 'could' occur, most for the NW'ern half but perhaps one also affecting areas further south!

http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

https://www.cpc.ncep.noaa.gov/products/predictions/610day/500mb.php

Looks a fair analysis to me. We're actually entering a quiet period where convection is suppressed over the Atlantic development region, so for now we shouldn't have any more hurricanes to contend with. It'll spring back to life soon enough, but for now i think we can be fairly certain that it's staying unsettled for quite a while.

[Tim Bland]

Deep Fi but early October looks potentially  more settled, especially further south, with high teens still possible...

 

[snowking]

I thought this may be of interest:

So now alongside the EC45, we get to obsess daily over the GFS35....what could possibly go wrong just as we approach the winter season...