Model Output Discussions 12z 01/09/2016

[Frosty.]

8 minutes ago, Grimers said:

You know what that means? The easterly flow continues...

In a perfect world, that would be true

[knocker]

6 minutes ago, Grimers said:

Actually, that's a point. If the high pressure moves north, it could mean that low pressure could move in from the SW... But, I feel that the easterly flow will win in the current setup, but who knows.

By moving north I just meant slight ridging to the west of the UK which would just veer the upper streamlines a little to maybe WNW.

[Grimers]

Just now, knocker said:

By moving north I just meant slight ridging to the west of the UK which would just veer the upper streamlines a little to maybe WNW.

I understand now. Thanks for clarifying.

[Frosty.]

The Ecm 12z looks increasingly trough dominated as time goes on but at least temperatures recover once we lose the ESEly, but in the next 3/4 days it's actually going to be feeling even chillier as winds strengthen from the ESE. 

Edited October 10, 2016 by Frosty.

[Captain Shortwave]

It looks like we will lose the easterly influence by the weekend according to most model output.

      

Low pressure looks like becoming centred just to our west allowing temperatures to recover a touch to near normal but with rain or showers at times. The perceived undercut during the latter half of this week appears to pull low pressure away from southern Europe allowing a more typical Euro ridge to develop to our east though it won't benefit us for the most part if you are looking for warmer conditions.

So the story remains that we will see increasingly unsettled conditions develop from midweek though again there isn't a strong trend towards a zonal pattern developing as conditions still look to be slow moving.

[Grimers]

On 10/10/2016 at 20:15, Frosty. said:

The Ecm 12z looks increasingly trough dominated as time goes on but at least temperatures recover once we lose the ESEly.

Yes, just had a look now that the run has completed. This is one corker of a low giving gale force W winds around exposed coasts next Tuesday, still it's quite far off, but as well all know the ECMWF is quite an accurate model.

Edited October 14, 2016 by Grimers

[Frosty.]

33 minutes ago, Grimers said:

Yes, just had a look now that the run has completed. This is one corker of a low giving gale force westerly winds around exposed coasts next Tuesday, still it's quite far off, but as well all know the ECMWF is quite an accurate model.

Agreed, the Ecm is the top performing model and its looking like we will all see a change to increasingly unsettled but less chilly weather late this week onwards.

Edited October 10, 2016 by Frosty.

[Frosty.]

The Ecm 12z ensemble mean doesn't become as full on unsettled as the op with the trough held further to the NW. Temperatures look like recovering by the weekend as we will have lost the fresh to strong ESEly by then and actually into next week winds look much lighter under a filling trough with sunshine and showers being the main weather type with chilly nights where skies clear..doesn't look so bad!

[bluearmy]

All the extended ensemble modelling show a marked upper ridge on the other side of the NH in two weeks. A high height anomoly showing all the way up at 10hpa on the gefs mean at the same locale. 

I have a feeling that this projected upper ridge is going to play quite a role in the development of the NH winter, helping to continue the neg AO we have seen thus far with the consequential Siberian cold T2m anomoly and Arctic Ocean high one. 

Taking a hemispheric view of the modelling is always worth the effort at this time of year. 

 

[damianslaw]

Slow moving is the word to describe synoptical evolution show by the models today. A slow decline in the easterly feed, as a fairly half-hearted upper trough feature drifts in from the SW, unsure about itself and where to settle, cutting off the easterly feed, and instead bringing weak cyclonic flow with temps near normal. The trough feature looks like becoming squeezed or trapped in situ, with heights building from the SW, but there are signs of a more pronounced atlantic assault through next week, but this time from the NW - so a possible return to something resembling a more typical October, the colder SST values to our NW likely to come into play and perhaps pulling down the first 'cold' pulse of air with polar origins this autumn.

[knocker]

The EPS post day ten continues to show less amplification with ridging just the west of the UK veering the upper flow NW but returning to SW as the ridge slowly moves east. Temps around average and becoming drier after an unsettled spell, I can't post the EPS but NOAA illustrates the de-amplification and is along the same lines although not so bold with the  Azores

 

Edited October 10, 2016 by knocker

[fergieweather]

1 hour ago, bluearmy said:

All the extended ensemble modelling show a marked upper ridge on the other side of the NH in two weeks. A high height anomoly showing all the way up at 10hpa on the gefs mean at the same locale. 

I have a feeling that this projected upper ridge is going to play quite a role in the development of the NH winter, helping to continue the neg AO we have seen thus far with the consequential Siberian cold T2m anomoly and Arctic Ocean high one. 

Taking a hemispheric view of the modelling is always worth the effort at this time of year. 

 

Indeed. Interesting how this evening's ECMWF Monthly leans towards +ve heights establishing to N; a NE flow to close-out Oct, followed (albeit with an inevitably weakening signal) by something more northerly into 1st week of Nov, with 850hPa temp plumes gradually on a slide. 

[Polar Maritime]

The GFS this morning shows a Northerly shot into Wk2. Cold enough for some Wintry showers at elevation for parts in the North with -7 850's shown over the UK, And ground frosts to boot..

Edited October 11, 2016 by Polar Maritime

[knocker]

Today and tomorrow

With the HP still to the NE the easterly winds remain and perhaps strengthening. Ergo a continuation of the showers and perhaps longer periods of rain in the east which will spread further inland..Feeling quite cool in the wind and not overly pleasant. More sunshine in Wales and the south west.

The GFS this morning

Friday continues to see the reinforcement of the upper low from the NW and thus initiating the surface low domination over the weekend. Having said that with the surface feature setting up shop to the west most of the precipitation is confined to the west of the UK and with quite a long southerly fetch to the streamline it could become quite warm in places, Of course this is very dependent on the precise position of the surface low.

After that more of a transition to a westerly upper flow with a quite strong jet and troughs emanating from Canada and it continues to look quite unsettled next week. It's all looking pretty mobile so no ruling out the Azores HP having a hand in the proceedings, particularly in the southern half of the country.

Edited October 11, 2016 by knocker

[I remember Atlantic 252]

2 hours ago, Polar Maritime said:

The GFS this morning shows a Northerly shot into Wk2. Cold enough for some Wintry showers at elevation for parts in the North with -7 850's shown over the UK, And ground frosts to boot..

I liked the 18Z version, hopefully though still up in the air, those charts above are ugly

[Frosty.]

The Gfs 00z op run shows thurs / fri being the coldest days this week as the ESEly winds strengthen which will exacerbate the chill but then turning milder by the weekend, much milder in the south which continues early next week. As well as the temperature fluctuations it becomes increasingly unsettled later this week but then during next week high pressure extends across the south bringing pleasant weather but staying changeable in the north but then we have our first of hopefully many arctic incursions with snow on northern hills and widespread frosts.

Edited October 11, 2016 by Frosty.

[knocker]

The ecm shows early Friday being quite  unpleasant in a strong SE wind, particularly in the north, before the strengthening upper low starts influencing affairs with the surface feature meandering just to the west  Associated fronts push east over the weekend bringing some rain but tend to stall which initiates some brief WAA particularly for East Anglia.where temps could reach the giddy heights of 20C.

From then on it gets quite complicated with a small feature tracking rapidly NE across the UK on Monday before more fronts arrive by Wednesday.and the next major system from the west by Friday. It's all a bit messy and unsettled next week.

Edited October 11, 2016 by knocker

[Grimers]

The GFS model shows a weak low to the SW of the UK giving light SE winds to all parts of the UK on Saturday.

The ECMWF model shows a fairly strong low to the SW of the UK giving moderate S winds to W parts of the UK on Saturday.

The UKMO model shows a weak low to the SW of the UK giving light SE winds to all parts of the UK on Saturday.

Edited October 16, 2016 by Grimers

[Man With Beard]

As so often happens, the GEFS is starting to pick up a signal that it had previously dropped. At around D12, there are a number of GEFS members (about 40%) now going for Atlantic heights or a Greenland High, which allows a northerly to encroach on the UK for a while - with the op and control run included in the cluster. The signal was showing at D16, was dropped over the weekend, but now appears to be back. Some runs, such as the control run, would bring snow to parts of Scotland (certainly on high ground):

The main alternative cluster keeps heights strong over the UK or Europe. It's about 50/50 between these two scenarios, really, with only a few straddlers going for a status quo south-westerly.

[Ravelin]

31 minutes ago, Man With Beard said:

As so often happens, the GEFS is starting to pick up a signal that it had previously dropped. At around D12, there are a number of GEFS members (about 40%) now going for Atlantic heights or a Greenland High, which allows a northerly to encroach on the UK for a while - with the op and control run included in the cluster. The signal was showing at D16, was dropped over the weekend, but now appears to be back. Some runs, such as the control run, would bring snow to parts of Scotland (certainly on high ground):

Does that not sort of tie in timing wise with what Fergieweather said earlier.....

"Indeed. Interesting how this evening's ECMWF Monthly leans towards +ve heights establishing to N; a NE flow to close-out Oct, followed (albeit with an inevitably weakening signal) by something more northerly into 1st week of Nov, with 850hPa temp plumes gradually on a slide."

[knocker]

The EPS has been looking at rising heights to the west and briefly an upper NW flow for a couple of runs now but the pattern is quite mobile and the positive heights end up to the east by the end of the run with the wind backed to SW and temps a little above average.

[jvenge]

21 minutes ago, Ravelin said:

Does that not sort of tie in timing wise with what Fergieweather said earlier.....

"Indeed. Interesting how this evening's ECMWF Monthly leans towards +ve heights establishing to N; a NE flow to close-out Oct, followed (albeit with an inevitably weakening signal) by something more northerly into 1st week of Nov, with 850hPa temp plumes gradually on a slide."

It's current output, but just keep in mind it is T312. You will find all kind of options in the ensembles at that range.

[Man With Beard]

27 minutes ago, Ravelin said:

Does that not sort of tie in timing wise with what Fergieweather said earlier.....

"Indeed. Interesting how this evening's ECMWF Monthly leans towards +ve heights establishing to N; a NE flow to close-out Oct, followed (albeit with an inevitably weakening signal) by something more northerly into 1st week of Nov, with 850hPa temp plumes gradually on a slide."

It would tie-in to some extent - though, as Knocker points out, many of the ensemble northerlies are fairly short-lived.

But Fergie's post would fit one of my personal "weather pattern principles" - if it can happen once, it may well happen again soon after!

Jvenge - yes certainly agreed, and worth not forgetting there is an equally persuasive cluster that goes for a more persistent ridge through western/central Europe for that time frame.

Edited October 11, 2016 by Man With Beard

[Frosty.]

3 hours ago, Frosty. said:

 

I like the Gfs 6z trend, looking at developments to the nw / n / ne

a bit of fine tuning would deliver our first Arctic maritime incursion of the season!.

Edited October 11, 2016 by Frosty.

[Frosty.]

5 hours ago, Frosty. said:

 

Looking through the GEFS 6z perturbations shows a sprinkling of potential arctic / polar maritime incursions which is similar to the operational but better. I like to keep an eye on developments to the north and east from now on as we head deeper into autumn.

Edited October 11, 2016 by Frosty.