Model Output Discussion - mid Autumn

[damianslaw]

1 hour ago, LRD said:

Yep. Good summary. Wet, rather than especially cold, looks the likely outcome for the rest of this month. That's fine. The cold stuff can wait another 6 weeks. Although a foggy Halloween and frosty bonfire night might be nice

The latter stages of October are often synonymous with predominantly unsettled conditions. Can't recall the last cold settled end to October. More often than not very mild and wet and windy.

Back to the models, all very messy, UK caught between a rather ineffectual atlantic and a continental high that isn't sure of itself.

Fine margins between a chilly continental more settled flow and something quite persistantly wet and not that mild either. 

[Weather-history]

Some big rainfall totals are showing up for some parts

 

 

Scotland on ECM

[IDO]

GFS and backed up by ECM to D10, looking like standard October fare (for London):

A cooler few days, countered by a warmer few days, followed by averaging out. 

Some systems are incoming from the south mid-week  before it turns to a westerly stream later in the D10 period on GFS:

Make the most of the next few dry days.

[knocker]

8 hours ago, damianslaw said:

The latter stages of October are often synonymous with predominantly unsettled conditions. Can't recall the last cold settled end to October. More often than not very mild and wet and windy.

Back to the models, all very messy, UK caught between a rather ineffectual atlantic and a continental high that isn't sure of itself.

Fine margins between a chilly continental more settled flow and something quite persistantly wet and not that mild either. 

I wouldn't say it was ineffectual. The trough development and the strong jet does result in the low SW of the UK tracking NE across the country as the blocking high changes orientation

Edited October 15, 2023 by knocker

[ANYWEATHER]

Better make the most of the next two/three days, looks YUK after that ,with yet more rain, October is going to turn out very wet....

[sheikhy]

Its looking pretty terrible from wednesday onward!!the scandi high and colder drier air has been blown away!!maybe a sign of things to come  for november aswell in regards to any forecasted scandi highs!!

[northwestsnow]

14 minutes ago, sheikhy said:

Its looking pretty terrible from wednesday onward!!the scandi high and colder drier air has been blown away!!maybe a sign of things to come  for november aswell in regards to any forecasted scandi highs!!

Yep.

I began to get that sinking feeling yesterday TBH.

Block can't withstand the Atlantic and the UK gets soaked.

 

[swfc-ocs]

Good morning. Looking at nhp and synoptics on offer heading to late October im struggling to see any concerns are merited atm. Eqbo on the cards, nao app going neutral into november. What is shown on the Mo is subject to huge swings has shown with the retrogression runs towards greendland earliee in the week.

[summer blizzard]

We appear to have concensus now that our E/SE spell will be followed with an Atlantic pattern to day 10. 

Personally i wonder if we are not seeing competing signals for week 4. You can see in the chart below that we have standing waves trying to form in both the west and east Pacific. 

[TSNWK]

6 minutes ago, summer blizzard said:

We appear to have concensus now that our E/SE spell will be followed with an Atlantic pattern to day 10. 

Personally i wonder if we are not seeing competing signals for week 4. You can see in the chart below that we have standing waves trying to form in both the west and east Pacific. 

Still plenty of heights to our north and not sign of the vortex just yet 

[CoventryWeather]

21 minutes ago, summer blizzard said:

We appear to have concensus now that our E/SE spell will be followed with an Atlantic pattern to day 10. 

Personally i wonder if we are not seeing competing signals for week 4. You can see in the chart below that we have standing waves trying to form in both the west and east Pacific. 

Sorry, but what does that chart mean? I'm still learning!

Latest GFS has a rather weak and displaced Polar Vortex, and some sign of some warming near Canada at the end of the run. The ECM zonal wind charts also seem interested in a potentially early SSW, as a cluster has now developed mid Nov. Despite the zonal spell in the next week or two, I doubt there is any need to be concerned - blocking I think will develop before the months out.

Edited October 15, 2023 by CoventryWeather
Added Zonal Wind Charts

[Rain All Night]

The ECM ensemble 0z run suggests troughing affecting the UK through the last third of October. Shown below are days 7, 10, 13 (22nd, 25th, 28th Oct). If you look at both the Z500 and MSLP contours, you can see a suggestion that the troughing shown at day 13 might have a cooler flavour to it.

The GFS ensemble 0z run shows more lingering heights to the north and east offering us some protection from this, especially towards the very end of the month, but the 6z run which is coming out now seems to have moved closer to the ECM.

Edited October 15, 2023 by RainAllNight

[damianslaw]

4 hours ago, knocker said:

I wouldn't say it was ineffectual. The trough development and the strong jet does result in the low SW of the UK tracking NE across the country as the blocking high changes orientation

Yes, perhaps 'ineffectual', the wrong word to use. It does look like the atlantic trough will take hold, but importantly the jet is more southerly, and there is still a signal for heights to linger to the north.. the trough could become rather slow moving - hence a possibly very wet outlook mid week onwards. 

[summer blizzard]

1 hour ago, TSNWK said:

Still plenty of heights to our north and not sign of the vortex just yet 

Basically it illustrates the position (and forecast) of anomolous westerlies (convection) and easterlies (subsidence) in the Pacific, close to the equator. When you have two areas that are competing, this makes things harder to forecast because it's abnormal. 

 

[WYorksWeather]

Going to do an afternoon comparison in case I don't get around to doing one on the 12z runs. I'll use the 06z GFS but offset it to account for the difference between it and the ECM 00z, i.e. compare GFS T+66 to ECM T+72. Both runs are fairly representative of their means.

 

At T+66/72, both models are going down a similar track with the low in the Bay of Biscay. 

 

By T+114/120, both GFS and ECM deepen the low, and it is sat right over the UK. Just looks like generally horrendous weather for Friday - extremely wet and windy. There is a milder interlude on Thursday beforehand, but probably associated with a fair amount of wet weather.

 

Not much improvement by T+162/168 either, still lows sat over the country. GFS has a separate trough over the UK, whilst ECM has low pressure moving in from the Atlantic. Both charts show a Scandinavian high but the wind never really gets into a proper easterly on a consistent basis - it varies from SW to E. The blocking is also there over Greenland, but it just doesn't really do much other than slow down troughs of low pressure so they linger over the UK.

 

Pressure tries to rise a bit, but nothing much comes of it, and here's the situation at T+234/240 with more low pressure centred over us. ECM even has another powerful low situated to the south of Greenland, and another low on the bottom left of the chart. The Scandinavian high has completely disappeared.

 

Not even going to bother posting the extended GFS - it's mostly more of the same right out to the end of the run. Brief attempts at ridging, but nothing too useful.

Here's the GFS accumulated rain totals at T+234 and at T+384 at the end of the run. Over 100mm for parts of Scotland in the next 10 days. By T+384 it just looks horrendous, with over 100mm for most of central and northern England and large parts of Scotland.

 

Here's ECM at T+240, which looks arguably worse than GFS!

We could be in the running for an extremely wet second half to October if this is right. Temperatures probably about average.

[Guest]

GFS 12z op seems to be on its own for next weekend as UKMO and GEM show troughing extending further into Europe:

Edited October 15, 2023 by Guest

[sheikhy]

Wow!!!back to strong scandi high further west and cold air into the uk from the ukmo 12z!!!!you couldnt make this up!!!!

[sheikhy]

@northwestsnow you seen that ukmo!!!we back in the game lol!!!literally from the brink of defeat!!!and if ecm follows it then i dont see anyway back now for the delugeof earlier runs!!!but ecm has to follow ukmo first lol!which i doubt!

[I remember Atlantic 252]

Horrid I'd say, but we all like different weather, 6 degrees and rain/gales is horrid to me, but maybe not others

[sheikhy]

Just now, I remember Atlantic 252 said:

Horrid I'd say, but we all like different weather, 6 degrees and rain/gales is horrid to me, but maybe not others

Totally agree but i just want it to feel cold and seasonal at the very least which i think is what that chart shows!dont want mild southwesterlies anymore!dont worry buddy we gona have our december 2017 event very soon again hang in there!!!

[Howie]

ECM built a huge scandi block and then sinks it back south east lol

[Jacob]

1 hour ago, I remember Atlantic 252 said:

Horrid I'd say, but we all like different weather, 6 degrees and rain/gales is horrid to me, but maybe not others

If it was 7 degrees colder I’d be very excited but cold, rainy, windy weather is definitely my least favourite type 

[alexisj9]

2 hours ago, sheikhy said:

Wow!!!back to strong scandi high further west and cold air into the uk from the ukmo 12z!!!!you couldnt make this up!!!!

All depends on the low coming up, if it stays south stronger high, if it goes north high is further east.

[sheikhy]

Just now, alexisj9 said:

All depends on the low coming up, if it stays south stronger high, if it goes north high is further east.

Ecm was much improved early on but then lifts the low north from 168 hours!!!

[Mike Poole]

27 minutes ago, sheikhy said:

Ecm was much improved early on but then lifts the low north from 168 hours!!!

It may be that this scandi block might take more shifting than the models give credit for.  Mind you, the pattern at T240 on the ECM is not without interest either:

Heights building over Greenland, and the developing vortex far from where it would like to be.