Model output discussion-mid Autumn and beyond

[mb018538]

Whatever the outcome.....autumn 2018 has been pretty much devoid of the usual zonal train that we normally endure. Nothing in the upcoming models and forecasts to suggest this changing any time soon either.

[BlueHedgehog074]

Looks like a couple more generally bright and settled days to come, mostly over Southern areas, with models showing High Pressure being invasive over the South-Western areas of the UK. Knocker and some of the others go in great detail regarding the weather for next few days, so will keep it brief.

Today does indeed seem to be the warmest day (feels very mild right now), according to the GFS UK Maximum Temperature charts:

The warm temperatures reserved for South and Eastern areas of the U.K. Best to make what you can of today and possibly tomorrow, as the very mild temperatures for South and Eastern parts are going to get snatched away.

You can see on those 06Z GFS 500mb and Sea Level Pressure charts, lower pressure and lower heights will dig down from the North. This squeezes the Western/South-Western UK High Pressure out further West with it amplifying in the Atlantic.

A chillier flow floods down from the Arctic on Friday with sunshine and showers for places. Wintry I suspect over the Northern hills.

All the models in brill agreement for this Northerly now and does look certain. This is what the various operational models show for Saturday.

06Z GFS:

00Z ECMWF:

00Z GEM:

06Z ICON:

00Z NAVGEM:

All show a cold plunge from the North with the Atlantic High Pressure ridge poking into Eastern Greenland. They do all show very minor differences from one another as you would expect at that sort of time-frame. The Atlantic ridge, for example, seems the most amplified on both 00Z NAVGEM and 00Z ECMWF runs. 

For some reason, the 00Z UKMO completely disagrees and thinks everywhere could be covered in snow...

The UKMO must have had too many drinks at the pub with the 18Z GFS last night and didn’t get a good night’s sleep. 

Most likeky just a glitch as to how it came out at 72 hours on Wetterzentrale for that particular run.

Main thing, however, is support for an Arctic blast looks rock-solid for this weekend with a transformation in the weather; cold nights, frosty mornings, a chilly, blustery, Northerly wind and a chance for some wintry weather in places. Mostly of sleet and snow over high ground, but some heavier showers could drag the sleet and snow line to down lower levels at times. Low level sleet and snow probably most likely just for Northern areas of the UK, which would see the coldest conditions. Away from the showers, it could be bright and sunny at times, particularly over in-land areas of the U.K away from Eastern and Western coastel areas (this Friday, though, would probably see rain and hail showers streaming through the Midlands from the Cheshire Gap via a North-Westerly flow). Be quite a change from what we’ve been used to.

[Cheshire Freeze]

3 hours ago, bluearmy said:

From the coldies perspective this is a decent evolution with WAA being pumped into the arctic to our NNE - better to have this set up in early November than a wishy washy early season northerly ...... 

Couldn't agree more. October into November is ALL about getting the correct synoptics to force a disorganised trop vortex come December... 

[knocker]

Still a complex scenario next week. On Tuesday the ecm is tracking the next upper trough SSE from the Denmark Strait west of Ireland as high pressure ridges strongly in the western Atlantic and Europe north through Scandinavia.

As the trough continues en route towards Iberia the previous trough now swings north up the North Sea but struggling along the western flank of the ridge, In fact the amplifying of both ridges effectively cause the troughs to swivel around each other

The upshot of all this, if it actually verified which is very unlikely vis detail, would be some very wet and windy in the north, and particularly the north east coast, on Tuesday.

[Summer Sun]

The colder air shouldn't hang around too long temps on the up slowly from around Wednesday

[damianslaw]

Models showing a squeeze on the trough as it settles itself between two areas of rising pressure, one to the NE and one to the west, thus a weaker less defined feature than shown yesterday, the upshot is that we would likely see a messy scenario as we move into November, with the colder air probably holding firm, and less in the way of continental air from the south getting in on the mix. A shallow low development could easily form in situ over the UK and result in chilly rain or showers for many. 

Longer term - heights do look likely to hold firm to the NE, so a colder drier continental theme may be the eventual route, but not before further trough disruption invades the UK.

The models in my view today are showing a holding cold pattern.

[knocker]

By Tuesday the ecm does as expected taking the Atlantic trough south east to Iberia and the developing wave around SE France north into the North Sea.which would produce some very wet and windy conditions over the eastern half of England and Scotland. It then tracks rapidly north east, filling en route, leaving the UK im a slack area of low pressure with temps still tad below average with maybe the odd shower around in the south west and south

After that probably becoming more unsettled with a strong jet swinging around the high pressure in mid Atlantic but this is getting a bit far ahead

 

[knocker]

The quite impressive low in mid Atlantic by day 10 of this morning's ecm is currently weal TS 95L at 21N 40W. It wanders around for a while before picking  up the jet around half way through the run and then gains momentum in the second half.

[Polar Maritime]

The GFS showing a W/N/W flow off the Atlantic taking over by the end of next week keeping temps cool but wetter.

 

Edited October 25, 2018 by Polar Maritime

[knocker]

The ecm brings the low tracking into the North Sea next Wednesday further east than the gfs so would impact eastern regions and later swings a low round the ridge on a strong jet which really struggles against the block to the east.

[Summer Sun]

The 7-day trend shows the chance of something milder towards the south and SE still on the chilly side further north

 

[Summer Sun]

GEM 12z also showing a very different second half to next week as the cold blip retreats and milder air moves further north again through Europe

[Summer Sun]

ECM shows the 2nd half of next week could be very different to the 1st as milder air sweeps across Europe 

Edited October 25, 2018 by Summer Sun

[knocker]

2 hours ago, knocker said:

The ecm brings the low tracking into the North Sea next Wednesday further east than the gfs so would impact eastern regions and later swings a low round the ridge on a strong jet which really struggles against the block to the east.

That should read "further west than the gfs"

[knocker]

The evolution next week remains problematic.The ecm takes the North Sea low north of Scotland by Wednesday with a slack area of low pressure over the south west approaches which drifts north east over the next 24 hours over the whole of the UK. Thus light winds, showers and sunny intervals with temps not far off average

Meanwhile in the west a couple of troughs have phased over NE N. America and the surface low has deepened rapidly and tracked towards the Denmark Straits with the associated front approaching Ireland by Friday with TS 95L tagging along for the ride,

.

Edited October 26, 2018 by knocker

[Man With Beard]

A little look further ahead to D12 (Nov 7th): Tricky. The past three sets of EC clusters indicate heights remaining biased towards our NE or ENE, but the balance between the Atlantic going over the top or under the block does not look resolved to me:

    

I think the most likely scenario is a trough stuck close by to our west with fairly mild but wet periods for the UK - but also a dangling possibility of troughing remaining more to our SW and a drier flow anywhere from a southerly source (warm again) to an easterly source (this would not likely be an exceptionally cold one just yet, but may increase the likelihood of frosts). Maybe, just a maybe, the block would be sufficient for the jet to go south?

[knocker]

The difference between this morning's ecm and the 06 gfs at only T120 is stark, After that it's downhill

Edited October 26, 2018 by knocker

[ItNeverSnowsInWindsor]

GFS 6z is garbage outside the reliable.

[Summer Sun]

GFS looks like reverting back to a more typical pattern of rain and fairly mild with occasional short-lived settled cooler periods

[Summer Sun]

The cold runs on the 7-day trend didn't last long.

Normal service resumes

 

Edited October 26, 2018 by Summer Sun

[Always a red]

1 hour ago, Summer Sun said:

The cold runs on the 7-day trend didn't last long.

Normal service resumes

 

Quite right Summer Sun, but what is `normal`?

Its that time of year again when looking at who likes which posts tells you all you need to know about the current outlook, saves hours!!

Choo Choo! all aboard again 

[knocker]

10 minutes ago, Always a red said:

Quite right Summer Sun, but what is `normal`?

Its that time of year again when looking at who likes which posts tells you all you need to know about the current outlook, saves hours!!

Choo Choo! all aboard again 

Quite so. If you look at the EPS the forecast is still below average.

[Purga]

2 hours ago, Summer Sun said:

The cold runs on the 7-day trend didn't last long.

Normal service resumes

 

You off to the Balkans then SS?

Looks chilly over here

[Mike Poole]

I've detected from just a few posters a waning of enthusiasm for a front loaded cold winter, so I'd like to take stock just before this brief northerly and unseasonal blast hits this weekend. 

It matters not a jot whether this persists or is replaced by milder wetter weather, as far as the bigger picture of early winter is concerned.  

The models still point to a disconnect between the trop and strat vortexes, with the strat vortex organised and modelled to become less so, and the trop vortex disorganised and not modelled to become more aligned with the strat. GEFS zonal mean zonal wind in the strat  as follows:

Last months Met Office contingency planners noted an unfavourable SST pattern for UK cold, but it has dissipated since then, pattern today first v last month:

SST profileS look to me to be neutral-ish re UK winter weather now.  Having viewed the GloSea5 output earlier, on balance I would expect the next 3 month MO output due Monday? will slightly tilt in favour  of cold, but not massively so, baby steps...

Finally people mention the CFS, it is meaningless to study one run from this model, so for a balanced view here are the last 8 runs starting yesterday's 18z, for sea level pressure mean anomaly during December:

Only the last one looks horrendous, maybe this model is coming on board.  interesting times ahead for sure!

 

Edited October 26, 2018 by Mike Poole

[Summer Sun]

This weekend sees temps struggling to get above 9c for the majority next weekend some parts could be in the mid-teens!