Model Output Discussion - Into Autumn 2020.

[cyclonic happiness]

6 hours ago, Geordiesnow said:

What I'm finding really interesting in the model output is the fact if we do get some northerly flow of some sort, the ECM especially wants to develop a massive ridge over Western Russia with what probably be record breaking heat so you think, well if Western Russia is getting record heat, there must be some cold weather over Siberia forecast given there will be a dip in the jet stream. Well absolutely not, not only we got above average temperatures, there is barely any snow cover and there is hardly anything in the forecasts so for those who think lots of snow cover over Siberia is a good sign for winter will be very disappointed with the forecasts. I for one I'm not too convinced by that link but a lack of snow cover means above average temperatures and above average uppers so coupled with lots of warm open water over the Arctic then cold air could be in short supply I feel. 

Well, it's a good job this morning's GFS is shoving the -4'c/-5'c 850s down as far as Oxford later this month.

Extraordinary cold northerly considering how early in the season it is, and how warm the planet is atm!!

[sheikhy]

Hmmm ecm and gfs showing a lot colder air for the last week of september!!maybe not cold enough for snow but defo for a frost!!and most certainly shall be a lot colder than we have been used to!!aint gona help with the covid19 situation either

[mb018538]

14 hours ago, NApplewhite said:

Turning very stormy next week across the whole UK

 

Yeah - I did also say in another post that tropical activity is the big 'unknown' in all of this....and major hurricane Teddy is largely to blame for the plunge into very unsettled weather. The track up the Eastern seaboard in the next few days is going to buckle the jet stream quite significantly. Unfortunately we end up on the wrong side of this! Prepare for some win, rain and much colder weather!

[jcw]

I didn't think the a Hurricane can cause a buckle to the Jetstream (from papers I had read will try and find them again). Isn't it a case of the buckled Jetstream being the driver to the track of the Hurricane?

Either way, @mb018538, as you say, we're on the wrong side of the Jet next week and it's going to be a shock to the system, relative to what we've been experiencing..

Joe

[Scorcher]

A really horrific GFS after midweek- hope this is modified as we get closer to the time. Always amuses me how these storms plough across the Atlantic like there's no tomorrow and then instantly grind to a halt once they reach the UK- it's like someone is playing a big joke on us. 

The one saving grace is the fact that uncertainty is always high at this time of year in an active hurricane season.

Hopefully it will clear off more quickly than the GFS shows and I really think the GFS is a worst case scenario this morning for the depth of cold air that comes down. Would probably just mean a lot of unpleasant wind and cold rain at this time of year.

Edited September 18, 2020 by Scorcher

[Wimbledon88]

12 minutes ago, Scorcher said:

A really horrific GFS after midweek- hope this is modified as we get closer to the time. Always amuses me how these storms plough across the Atlantic like there's no tomorrow and then instantly grind to a halt once they reach the UK- it's like someone is playing a big joke on us. 

The one saving grace is the fact that uncertainty is always high at this time of year in an active hurricane season.

Hopefully it will clear off more quickly than the GFS shows and I really think the GFS is a worst case scenario this morning for the depth of cold air that comes down. Would probably just mean a lot of unpleasant wind and cold rain at this time of year.

Its coming into autumn now. If you want 12 months of summer then you are in the wrong country mate. 

GFS looks great this morning. Proper autumn weather at last. 

[mb018538]

11 minutes ago, jcw said:

I didn't think the a Hurricane can cause a buckle to the Jetstream (from papers I had read will try and find them again). Isn't it a case of the buckled Jetstream being the driver to the track of the Hurricane?

Either way, @mb018538, as you say, we're on the wrong side of the Jet next week and it's going to be a shock to the system, relative to what we've been experiencing..

Joe

They can and definitely do effect the jetstream - this tweet from Mike Ventrice shows how a Typhoon in the Pacific a couple of weeks ago caused the heat in the western USA, the sudden drop of 37c to snow in a day in Colorado, and eventually the recent heatwave in Europe.

[johnholmes]

500 mb update

Friday 18th

Ec-gfs both show large -ve heights and a deep contour low in the uk area couple with gfs showing ridging/+ve heights Greenland area, much less so on ec,but both show lowish contour heights with a flow n of w into the uk

Noaa has also gone, last evening for a large jump towards this idea. Not sure about this but wait for a couple more outputs although the 8-14 shows similar.

Assuming all 3 models are in the right area then a cool/coldish unsettled spell for the next 2 weeks or so.

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

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

 

Edited September 18, 2020 by johnholmes
spelling

[carinthian]

Morning all, most models now showing a rather cold and unsettled end of the month. This particular overview picture below indicates potential for some snow over the mountains of Northern Britain.

C

[Scorcher]

32 minutes ago, Wimbledon88 said:

Its coming into autumn now. If you want 12 months of summer then you are in the wrong country mate. 

GFS looks great this morning. Proper autumn weather at last. 

Haha the coldies are out in force already...give it a rest. At what point did I say I expected 12 months of summer? There is still plenty of time for settled, reasonably warm weather. It's happened many times before in late September and into October.

[LRD]

Pretty good agreement between the GFS and ECM for a significant change next week

What a contrast from today to this time next week if this GFS frame verifies:

And the ECM is in broad agreement:

Very autumnal. And, remarkably, maybe even a little bit wintry over the higher Scottish regions

[Don]

3 hours ago, cyclonic happiness said:

Well, it's a good job this morning's GFS is shoving the -4'c/-5'c 850s down as far as Oxford later this month.

Extraordinary cold northerly considering how early in the season it is, and how warm the planet is atm!!

We'd struggle to get a northerly that cold mid winter these days let alone late September!! 

Edited September 18, 2020 by Don

[Frosty.]

Looking at the ECM 0z ensemble mean, it’s best to make the most of the current benign, pleasant anticyclonic conditions as it looks like we will shortly be plunged into the depths of autumn with a very unsettled and much cooler spell..but, by day 10 there are glimmers of hope as the unsettled conditions gradually relaxes its grip and the Azores ridge begins to nose NE towards the south.

[Zak M]

This mornings ECM chart @240 caught my eye:

Could we be looking at a potential Azores-Scandi linkup here?! 

If not, it should bring some settled weather from that scenario at least with the Azores ridge.

Edited September 18, 2020 by Zak M

[ChannelThunder]

Enjoying those ECM and GFS charts for mid-next week. A nice deep low right over the south for once, for my birthday on Weds (well, the day after, mostly). Possibly a named storm, too?

Edited September 18, 2020 by Mapantz

[LRD]

3 hours ago, Zak M said:

This mornings ECM chart @240 caught my eye:

Could we be looking at a potential Azores-Scandi linkup here?! 

If not, it should bring some settled weather from that scenario at least with the Azores ridge.

I reckon that Low in the Atlantic will roll over the High. Although it's hypothetical of course as, at 240, things probably won't look like that

Edited September 18, 2020 by LRD

[Tim Bland]

Looks like fine wether returns by day 10...

[LRD]

A cool unsettled run from ECM

Does this chart indicate a wash-out in the SE on Wednesday, with a stalling cold front?

 

 

Edited September 18, 2020 by LRD

[Frosty.]

There’s something of a recovery towards the end of the ECM 12z operational as a ridge of high pressure from the west topples SE across the u k but it may only be temporary respite with another depression poised over Iceland but before that possibility, it becomes very unsettled and gradually much cooler for all, you could even call it cold, especially further north where it could become cold enough for snow on higher hills / mountains..for a time...a real shock to the system is on the way, the first major blast of autumn.  

Edited September 18, 2020 by Jon Snow

[LRD]

2 minutes ago, Tim Bland said:

Looks like fine wether returns by day 10...

Could go one of two ways that - the High could build in or get pulled out into the North Atlantic in a repeat of what will happen Tuesday onwards this week. That low over Iceland looks primed to plunge SE

[Daniel*]

12 minutes ago, Tim Bland said:

Looks like fine wether returns by day 10...

It doesn’t look like that to me Atlantic ridge sharpening back again and repeat. 

Edited September 18, 2020 by Daniel*

[LRD]

A week today on GEM. Fresh and breezy. Showers about I'd imagine

[damianslaw]

Models continue to suggest a much cooler unsettled spell ahead just after the equinox. A cold trough digging in as heights build north into Greenland. After a week or so of late summer, from Tuesday onwards a week or so of very autumnal weather likely. Big contrasts with northern parts forecast to be decidedly chilly.

[Mike Poole]

34 minutes ago, damianslaw said:

Models continue to suggest a much cooler unsettled spell ahead just after the equinox. A cold trough digging in as heights build north into Greenland. After a week or so of late summer, from Tuesday onwards a week or so of very autumnal weather likely. Big contrasts with northern parts forecast to be decidedly chilly.

Yes, ECM mean clearly showing a particularly unsettled spell at T144:

T240 and there is little signal at all, so all bets off here:

It is about now that we look for one of those major changing seasons moments, in this case the last time we really feel the warmth of the sun before the descent into winter.  This weekend may be it, but I wouldn’t write off one more resurgence of warmth turn of the month....AAM forecasts suggest this is possible..

Have a good weekend everyone.

Mike

 

[damianslaw]

54 minutes ago, Mike Poole said:

Yes, ECM mean clearly showing a particularly unsettled spell at T144:

T240 and there is little signal at all, so all bets off here:

It is about now that we look for one of those major changing seasons moments, in this case the last time we really feel the warmth of the sun before the descent into winter.  This weekend may be it, but I wouldn’t write off one more resurgence of warmth turn of the month....AAM forecasts suggest this is possible..

Have a good weekend everyone.

Mike

 

A step-change in the feel of things takes place through late September, as we descend into Autumn more fully and cross the natural seasonal divide. Through most of September there is a tug of war a pull and push between summer and autumn, by October, the release into autumn is finally kicked, any dry settled sunny weather even if temps get into the 20s has a definitively different feel about it. Indeed statistically we see the most marked temp differential between two adjacent months in September and October. The same step change takes place in late March. There are therefore two step changes in the autumn season, whereas the spring season feels has perhaps just the one in late March, followed thereafter by a propelled movement through the splendour of spring, rushing headfast into summer.

In overall feel the most major step-change of the year takes place when the clocks go back, far more marked a change than when the clocks go forward. Key factor loss of daylight.

Edited September 18, 2020 by damianslaw