Model output discussion - 1st December onwards

[Captain Shortwave]

This afternoons GFS does develop a chillier and more settled weekend with a few exceptions.

The exceptions being some wintry showers in the north and maybe some rain across the south as a shallow low slides under the developing high, large uncertainty here.

Unfortunately developments after this are pretty much in line with the GEFs I posted earlier (Euro/Atlantic pattern though the refusal to remove the Greenland lobe of the tropospheric PV is a surprise), the ridge builds back with south to south west winds returning for the following week. Still a large amount of time to develop something different mind you.

 

The UKMO now making much more of the low shown on the GFS at day 6 as opposed to previous runs.

The result here looking fairly similar to the GFS potentially??? (we don't get to see day 7)

To be honest some drier sunnier weather for all would be much welcomed, especially for those in the north west where there have been some insane rainfall amounts and frankly until the end of next week the outlook looks very wet indeed.

GFS rainfall predictions

Dire for the north west unfortunately. 

Edited December 5, 2015 by Captain Shortwave

[Mucka]

11 minutes ago, Ali1977 said:

No comments on the 12z pretty much sums it up, cooler spell next weekend then back to stormy spells.

Yes nothing to get excited about there but nothing to get us too downbeat about either.

When GFS comes up with two consecutive runs that actually resemble each other upstream I will pay more attention.

UKMO finally decides that it will develop the low off the Eastern seaboard but much more amplified than GFS upstream otherwise.

All eyes on ECM really which has been more consistent and more accurate but clearly all models struggling with the period leading up to mid month.

[marksiwnc]

What has been shocking is that the met office failed to provide a red weather warning for us in nw Wales even tho 179mm has fallen in the area!  Surely there should have been a amber or even red warning for that. Hundreds of roads are closed in my area 

[Eskimo]

1 minute ago, marksiwnc said:

What has been shocking is that the met office failed to provide a red weather warning for us in nw Wales even tho 179mm has fallen in the area!  Surely there should have been a amber or even red warning for that. Hundreds of roads are closed in my area 

Remember that a red warning is issued if there is imminent danger to life. Road closures are bad, but it isn't necessary severe. 

[Methuselah]

2 minutes ago, marksiwnc said:

What has been shocking is that the met office failed to provide a red weather warning for us in nw Wales even tho 179mm has fallen in the area!  Surely there should have been a amber or even red warning for that. Hundreds of roads are closed in my area 

Can we please stick to the topic?

[Mucka]

 

Control run has a stab at something close to an Icelandic high, nearly a very good winter chart which is consistent with the 06z output.

 

 

Otherwise thought he ensembles are a bit of a mess with no pattern dominating, a mixed bag of weather much in line with MetO forecast. There is some support for attempts to build sceuro high as mentioned by other posters but being in FI the pattern is largely overrun. Non the wiser basically

[Captain Shortwave]

5 minutes ago, Mucka said:

 

Control run has a stab at something close to an Icelandic high, nearly a very good winter chart which is consistent with the 06z output.

 

 

Otherwise thought he ensembles are a bit of a mess with no pattern dominating, a mixed bag of weather much in line with MetO forecast. There is some support for attempts to build sceuro high as mentioned by other posters but being in FI the pattern is largely overrun. Non the wiser basically

The GEFs playing around with that high to the east, heck maybe we will get lucky....

If we can dig the southern arm of the jet into southern Europe we could develop something which doesn't involve Cumbria becoming the new Atlantis. I think any potent northerly is looking increasingly slim but this anomaly offers hope of something from the continent in terms of colder conditions.

Just for the point of saying it, the GEM operational is absolutely dreadful.

Its alternative view of Friday is something none of us wants to come off....

Edited December 5, 2015 by Captain Shortwave

[Polar Maritime]

Can we please stick to discussing the Models in here please. There is a thread open for today's severe weather and NWeather have had warnings in force for the past 24hrs being emended when needed.

Edited December 5, 2015 by Polar Maritime

[Polar Maritime]

Link here; https://forum.netweather.tv/topic/84572-atlantic-storm-4-desmond/?page=12#comment-3297185 

On with Model Discussion now please.

Edited December 5, 2015 by Polar Maritime

[Nouska]

By the time this month is finished, I wonder just what staggering rainfall totals can be accumulated for Ireland and the north west of the UK.

That's up to another 20 cms forecast for the parts now under the most severe conditions.

[Tom Jarvis]

Interesting end to the ECM with heights trying to build into Scadi area 

[SMU]

Eve all

Just a quick one as xmas party beckens-

i disagree with comments regarding the concept that there is no pattern change ahead- whether whats being touted is sustainable & leads to very cold weather down the line can be questioned-

but there is a pattern change on the way

take T0 ECM then follow it up with the 9 day ECM at 216 shows a distinct pattern change over the pole from a concentrate  fast vortex to a weaker more broken profile

allowing high pressure to start making inroads into 70N...

pattern change - YES

sustainable pattern change - MAYBE....

 

 

[Frosty.]

The Ecm 12z shows the current exceptionally mild tropical maritime airmass across the south of the uk being replaced by a relatively much colder polar maritime airflow later next week with the transition day being thursday with wintry showers then pushing in from the northwest for a time and then becoming more settled for a few days with widespread night frosts. In the meantime, Storm Desmond is still doing it's worst with another 12 hours of torrential rain / gales and continued severe flooding  in parts of the northwest (especially cumbria) but in the week ahead, although there will be more rain at times, it won't be as persistent or as torrential as it is now. 

[Duane S.]

8 hours ago, s4lancia said:

So  whilst a PM airflow looks to be the most likely of the  colder outcomes for the mid month period, we could perhaps squeeze a decent mid lat high pressure out of this, bringing in more seasonal continental airflow for that period to the southern areas.

The Control run along my lines of thinking...

Mid Strat coming under a bit of pressure towards the end of FI, one to watch...

I'm surprised actually there aren't a few more posts following the 12z suite. All in all very decent output and bags of potential, all things considered!

[Duane S.]

7 minutes ago, THE CHOSEN ONE said:

pattern change - YES

sustainable pattern change - MAYBE....

 

+1

[nick sussex]

Given the lack of posts I thought I had access to a different ECM run!

Pretty chaotic but interesting best sums up the ECM, the T240hrs looks very likely to develop high pressure to the north/ne past that point.

The overall NH pattern is quite complicated because its a bit of a spin of the roulette wheel in terms of where the dig of troughing will occur, any time you get low pressure digging that far south as shown in the ECM T240hrs you hit the code red for possible Scandi/east Greenland high, the reaction down stream to that digging trough is pressure rising ahead of it .

The issue of course is getting to whats shown by the T240hrs.

The NH pattern is undergoing some changes and that's normally when chaos ensues in the NWP.

Just looking at the De Bilt short ensembles, it looks likely the control run cuts low pressure east under a ridge to the north and develops a Scandi high within T240hrs. The operational run is towards the top end of members days 8 to 10. The control and operational run are close together until day 8, then we see them diverge.

 

Edited December 5, 2015 by nick sussex

[knocker]

Again the outputs are very much a dogs dinner. Later in the run the ecm develops a low way down east of Florida and deepens and runs it NE to mid Atlantic. What's going on here? well looking at the anomalies at T240 both the GEFS and ecm have developed a trough mid Atlantic running way south but the ECM trough is positively tilted which could provide some sort of simplistic explanation for the aforementioned depression. Anyway apart from anything else the trough causes the flow to back a tad over the UK dragging some air in from a warmer source.

Further afield  at the end of the ext period the ecm is back to basics with the trough more neutrally centred in mid Atlantic and the UK in the unsettled regime. The upstream characteristics remain the same.

http://www.tropicaltidbits.com/

 

Edited December 5, 2015 by knocker

[bluearmy]

Knocker, the ECM eps mean /anomolys stink of undercut days 10-12. it then reverts  to type but this post day 10 period is lower res so this may need to have an eye kept on it as it gets within the 10 day timeframe

 

Edited December 5, 2015 by bluearmy

[Ali1977]

This could be a very tasty FI, high pressure building above Labrador - maybe Northerly followed by a block!!! No doubt I'll be made to look stupid in about 10 minutes......again

forget that, 1 more frame and I know I'm wrong!!!

Edited December 5, 2015 by Ali1977

[Mucka]

I think this new GFS needs a holiday already.

Hairdryer

 

 

And just to emphasise the point, the control goes for a Beasterly

 

 

Ensembles.

Op and control heading in opposite directions does not inspire confidence.

 

 

Edited December 5, 2015 by Mucka

[BlueHedgehog074]

Just a look at the various models and it does look as though there will be some active and wild weather to come up for places. Today, for example, there has been (and continues to be) some powerful gusts of wind for places thanks to a fickle Low Pressure system to the East of Iceland driving in gales from the Atlantic. The tightly packed isobars over the UK from the Low over Eastern Iceland combined with a strong North-Western UK Jet stream seems to be the cause of some disruptive conditions for places today (Saturday). More so towards North-Western parts of the UK with places, such as Cumbria, facing the worst of this:

The charts above illustrate the stormy weather well with some particularly strong gusts and heavy downpours over North-Western parts. Some continued problems with flooding too, but the rain does look as though it will ease during the night and become patchier and lighter as in sinks South:

 

This, I'm sure, will be great news for those affected by the manic weather conditions. And the strong gusts of wind should slacken off a bit into Sunday as we lose the strong South-Westerly gales (these strong gusts of wind retreating South-Eastwards into the North Sea):

Though will still be quite windy for places.

The next few days will continue a similar sort of theme as the models show ridges of High Pressure getting dragged East or North-East into Mainland Europe keeping heights to the East/South-East of the UK strong. This seemingly due to some further deep and intense Low Pressure systems out West in the Atlantic pumping up ridges into the nearby continent. These Atlantic Lows spiralling around the trough of low 500mb heights around the Iceland and mid-Atlantic area bringing further strong South-Westerly to Southerly winds over the UK at times with spells of heavy rain and showers for places, particularly for North-Western parts of the UK where flooding could continue to be a problem in that part:

The above 500hpa and Sea Level Pressure charts from the 12Z GFS above, though, do show some ridging of High Pressure being close enough to influence South-Eastern areas of the UK at times with these parts seeing the best of some drier brighter, weather between the bands of rain. 

...but nowhere looks to escape from the wet and blustery weather. Especially from Cold Fronts tracking East across the UK as in the example below using the Met Office FAX chart for next Tuesday. (Cold Front marked by the black line with spikes)...

...this being thanks to some cooler/less mild air trying to tuck in behind the weather fronts. Though North-Western UK areas would see the most influence from the cooler (and, at times, showery) Polar Maritime interludes from the North behind the weather systems.

But because of the general South-Westerly or Southerly flow for the next few days, the temperatures, for this type of set-up, look to generally be on the mild side. The below charts, though, do show cooler air clinging on over Northern UK areas at times with the South-East seeing the best of the mildest conditions; particularly so in sunnier or brighter spells. South-Eastern areas also mostly being more under influence from Tropical Maritime air from the South-West.

Some nights will be on the chilly side, too, for places. Again, especially so for North-Western areas. But not exclusively so:

Note: this is just a general view of the outlook for the next few days (upto next Thursday) and the chances are the weather won't pan out exactly like this. Some little adjustments to the positioning of the Low and High Pressure systems, as an example, could have some fairly big affects as to the concentration of unsettled and disturbed weather conditions for the UK. As an overall theme, the idea of more wet, windy and stormy weather from the Atlantic with the European block keeping pressure higher towards South-Eastern UK at times seems very likely. 

Out to 144 hours - next Friday - and the GFS, ECMWF and UKMO generally agree with a chillier, showery, Westerly, flow taking over as the trough of Atlantic Lows, along with some low 500mb heights, move further Eastwards to be more positioned directly to the North of the UK. Maybe a chance for showers to become wintry over North-Western UK hills

This pushes the European block further away to the East or South-East with more of West to East tracking Jetstream* through Southern UK. (*GFS used as an idea) 

You'll notice that the Jetstream coming out of the Eastern Canada/Northern America area to our West is more fragmented and more Southerly tracking compared to the Jetstream chart of today (Saturday), below:

This not only allows chillier air to get further South across the UK for next Friday, bringing some lower heights over us, but it also appears to draw in some weakish Tropical Lows tracking South beneath an amplified ridge of High Pressure coming out of Eastern Canada. 

Black circle showing the weakish Tropical Low sliding beneath the narrow ridge of High Pressure above it coming out of Eastern Canada (as shown with the blue circle and blue arrow). 

This is one of the aspects that seems to lead to some increased meridional (amplified) patterns later on in some of the model runs, which I'll go onto in a bit.

There is one opposition against the chillier, Westerly, flow for next Friday - the 12Z GEM!

Has more of a milder, South-Westerly flow influencing the UK with what would seem to be a cold front over Northern UK. Another thing to note is it had one of the Low Pressure systems from the area of Tropical Lows trapped under the Atlantic ridge linking up with the main Atlantic trough over North-Western/Northern UK. The other models keep the Tropical Low(s) as separate features during that period. It's an additional aspect that delays the cooler air coming down from the West/North-West. To be fair, as a general pattern, it's not too far off from the other operational models at 144 hours - just that the GEM is a bit slower progressing the Atlantic Low Eastwards. Since it doesn't have much support from the other operational models, it's possible the GEM is being a bit slow with its evolution, and being too eager to merge one of its two little Tropical Lows with those Northern UK low heights. But interestingly, the 12Z ECMWF ensemble mean shows more of a South-Westerly influence over the UK:

Would perhaps be reasonable to say, though, that it would be more of a cool, Polar Maritime, sort of influence since the 850hpa temperatures for much of the UK are below 0*C. Plus, at that time range, the ensemble mean will blend out some of solutions from its ensemble members masking some detail of the surfaces features. Doesn't really show how cut-off that weakish Tropical/Azores Low to the South-West of the UK would be, whereas almost all operational models at that time-frame easily show the Tropical Low(s) being a cut-off feature.

I think overall, though, some kind of Polar Martime (or some kind of cool down) is possible towards the end of next week with some pretty good support for it. How far East the Atlantic Lows progress and the amount it pushes the European ridging away further East (if it really does) is still a little uncertain. And also whether any Tropical Lows to our South-West link up with Lows to our North. Some situations of which could have some bearings as to what happens further down the line. 

Focusing a little on the patterns further ahead (192 to 240 hours) and there are some varied solutions on offer. One aspect that perhaps seems evident is the possibility of a more amplified and/or blocked patterns occurring (as mentioned as a possible outcome further up in this post). As to whether any true Mid-Latitude or High-Latitude blocking occurs will probably in some ways depend on the behaviour of those Tropical Lows to our South-West and how it behaves with the Lows over Northern UK as well as (possibly) the strength of the Vortex to our North-West towards Greenland. What would probably appear to help as well is seeing the Tropical/South-Western UK lows attempting to undercut any of the ridges of High Pressure that get pushed to our East and help prop the highs further North to provide the cold weather fans with an Easterly flow. 

For up to 240 hours the GEM seems to be one of the worst solutions for those looking for more blocked and/or cooler solutions as it merges the Tropical Low too far West with the Low heights over Greenland, pushing the ridge to the West of the UK to our South into Europe drawing in a mild flow from the South-West. One of the better solutions, though, seems to be the 12Z ECMWF where the Tropical Low remains cut-off as it tracks to the North-East of the UK while sustaining some kind of Atlantic ridge to our West. Doesn't end on a cold note admittedly, but does at least show more of a meridional pattern and help provide a break to constant West to East travel of Atlantic Lows. In a way, breaks up the Westerly drivern Atlantic pattern. 

Something else to notice about the charts below is the Polar Vortex is generally disorganised with the ECMWF and GEM, in particular, showing the main chunks way out to our North-East around the Russia/Siberia area. I think as some talked about in the last few days is how it's important to see as much of the Vortex as possible getting knocked over to our East/North-East without much of the Vortex/very low 500mb heights getting stuck to our North-West over Greenland/Canada (if Westerly Atlantic drivern weather ain't your thing) as it could still pump further Atlantic Lows our way and try to flatten any ridges of High Pressure to our West. Not to mention trying to add fuel to the Jet Stream coming out of Canada/Northern America. The more the pieces of the Vortex clear away from Greenland/Canada (unless it's not too intrusive or is far enough West into Canada to not be of much bother to the UK), the more room it can leave for height rises to occur to our West. Which could then lead to some blocked and/or chillier conditions down the line.

Using the GEM as an example again, it shows how having a chunk of the Vortex left to over Greenland leads to a solution that would make some of the cold weather enthusiasts want to shut there eyes. Essentially quite a flat pattern over the UK towards the end of the run.

12Z GFS

 

12Z ECMWF

 

12Z GEM

For the time being, would say the solutions offered by models towards the end of next week and beyond look quite messy with a few things to sort out. Have probably rambled on too much regarding model solutions in the dreamland zone. Some of my ideas I admit probably are quite inaccurate in places as there are others who have better experience with using those Northern Hemisphere charts above and have better understandings of the behaviour of the Jetstream. For the next ten days at least, though, none of the models this evening and tonight are showing any real cold spell (even if some show more of an amplified pattern that may lead to something more favourable for chilly/blocked conditions further down the line, or some that show undercutting Low Pressure possibilities). 

Tonight's 6 to 10 day NOAA 500 mean chart backs up the idea of nothing too cold occurring by showing higher than average heights to our South-East over Europe and lower than average heights over the UK/Western UK, which could suggest further troughs of further cyclonic activity affecting us, especially Northern UK. Nothing too mild or too cold with an upper flow from the West. As such, any upper ridges of High Pressure towards, and over, the UK would have to be very brief, especially over Northern UK, to prevent the mean chart from registering higher than average heights over the UK.

Nothing particularly blocked on the above chart, and despite the higher than average heights the chart shows over Eastern Canada, the 8 to 14 day mean chart keeps those positive heights locked up over Eastern/North-Eastern Canada. 

Little too far West really to benefit those wanting to see some much colder conditions. 

The NAEFS 12Z 500mb mean chart at 240 hours not showing a particularly clear signal, though, but perhaps suggesting some ridging to continue hanging about to the East/South-East of the UK with the odd areas of slightly below average heights to our South-West and over Greenland to promote some further outbreaks of cyclonic weather. Though neither the lower or higher anomalies are that invasive over the UK, so could just be a mixture of anything really. The chart does however, show, some strong higher than average heights towards Eastern Canada and does bear some similarities to the NOAA charts above.

Personally wouldn't say the confidence beyond next week (with perhaps some little uncertainties near the end of next week) is terribly high (even though there always is going to be some doubts for what the weather does beyond the next few days). In some ways, I feel until the models get a better handle on how those tropical Lows and how the ridging coming out of Canada behaves as well as how these Lows could interact with features to the North of the UK, while perhaps also monitoring the strength of the Vortex to our North or North-West, then would be weary some of the solutions the outputs show for now. Considering the accuracy of the mean charts, like those from the NOAA, would tend to side a little more towards them.

Maybe, though, should models such as the GFS (and the 18Z run in fact does this) show the Tropical Lows to our South-West being able to undercut the Canadian and Atlantic ridge as it gets knocked over the UK, without those Lows linking up with Lows further North, then some little surprises like this aren't out of the question:

A channel Low idea that is able to bring a flow in from the East over the South of the UK and something that could provide some wintry surprises on its Northern flank over Southern UK. This is just an example, however.

Think there's still a fair bit to sort out, though, and let's face it, in average Winter, the UK doesn't see prolonged cold spells with constant Northern blocking and I think sometimes it can be easy to expect too much. At the same time, I can sympathise with the cold weather admirers in the South who haven't seen any (proper) snow in a while. Hopefully, something will turn up soon. Lots of time for snowy opportunities still.

[damianslaw]

Detailed post above - but I wouldn't take the charts literally at that sort of range. Best to look at the overall trend and theme and that is simply a cooler but still unsettled flow from the NW.

[BlueHedgehog074]

4 minutes ago, damianslaw said:

Detailed post above - but I wouldn't take the charts literally at that sort of range. Best to look at the overall trend and theme and that is simply a cooler but still unsettled flow from the NW.

A good point! There is always a risk of just over-analysing things and paying too much attention to the fantasy outcomes each of the operational models show (lol). And I think the problem with that is it could lead to over-thinking trying to figure out what the general outcome the models are showing, even when you've the anomaly charts to compare to. Think some people have always mentioned it's best anyway to focus on what the longwave pattern is doing and to not focus too much on little surface features which may not affect the overall patterns that much.

[Duane S.]

Wow the 18z Control run has certainly been to the Xmas party! Still liking the idea of the formation of a mid lat sceuro type block, part courtesy of some upstream trough disruption. We would need to roll a double 6 and some to get quite this lucky though...

However, albeit unlikely, it is at least feasible, the window of opportunity for this period well and truly open.

[knocker]

Last night's 18z GEFS anomaly dabbles again with height rises over Scandinavia before dropping them later. Tends to drag warmer air in from the south.

 

Edited December 6, 2015 by knocker