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Model Output Discussions 12z 08/03/17

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The models have a fair bit of trouble sorting out the evolution for this week and onwards so not much confidence at the moment although this week seems finally to be coming together. Of course I'm saying that without a view of this morning's ecm  So to the gfs

After the weak front traverses the country on Tuesday the amplification of the Azores high pressure gets underway accompanied by a simultaneous movement south of the upper trough which by 12z Thursday has a shallow surface low just north west of Ireland

gfs_z500a_natl_19.thumb.png.932945ddc8f30fc6ab59cfd7d10502e3.pnggfs_ptype_slp_eur3_19.thumb.png.844a93b055ff1dc01488df7964f895d8.png

In the next 48 hours this low slowly tracks south and fills whilst the high pressure ridges NE/E (perhaps the ecm wasn't so daft after all). This introduces a showery regime over most of the UK but with little wind and temps in general around average it could well be quite pleasant where sunshine is prevalent. Impossible to pin down any detail on this at this range.

gfs_ptype_slp_eur3_23.thumb.png.c0a6fc5d8c806661b0f13de32e53a92a.pnggfs_ptype_slp_eur3_27.thumb.png.463588a32e0045760c94b997a8122f20.png

Thereafter the gfs is sticking with the idea of the cut off upper low created by the earlier amplification drifting into the southern North Sea and developing a nice surface low that could impact the eastern side of the UK. This is mainly academic, although not without interest, at the moment

gfs_t2maf_slp_eur3_35.thumb.png.b3b05c99244b81f10335cc5363727da8.png

Edited by knocker
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Well okay more or less until T144 but then the ecm diverges from the gfs quite drastically. At T144 it does have the shallow low NW of Ireland but then it casts the Atlantic ridge asunder and tracks a new depression in from the SW which by the end of the run is centred over Cornwall. The amount of ducking and diving the ecm is doing is quite stark and if nothing else highlights once again why it is exceptionally unwise to take day ten charts at face value without a fair bit of supporting evidence.

ecm_mslp_uv850_natl_8.thumb.png.f0eac857d58918d08f4c429f7b4191d0.pngecm_mslp_uv850_natl_9.thumb.png.1757c17314e7b44b7e5ec5e32fcd4467.png

Edited by knocker
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5 minutes ago, summer blizzard said:

It's summer folks.......

ECMOPEU00_216_1.png

Indeed SB, just look at all that blocking where heat lovers dont want it.That said im not overly concerned wrt June at the moment, i can handle the crud now if the worm turns in a few weeks time. :-)

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Not much change on the models for the upcoming week, tuesday looks the warmest day with 23C/24C possible in the SE, cooler/unsettled further northwest though, thereafter a cooling trend with temps back into the teens with scattered showers though with a risk of a pulse of heavy rain moving into Central/SE England on Wednesday afternoon.

Next weekend onwards we have the ominous looking slow moving/stalling low pressure system, high pressure to our northwest/northeast pattern, a pattern very hard to get out of.

 

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Afternoon all :)

@Tamara:

Thank you for a fascinating post which I won't repeat in full for grounds of brevity and clarity for the forum readers.

We spoke about the two scenarios - Scenario A, where the LP sets up in the Atlantic and encourages ridging over or to the east of the British Isles and Scenario B where instead of a trough we saw a ridge in the Atlantic and that left the British isles under the trough.

2 hours ago, Tamara said:

But taking the overall evidence at hand, it is utterly pointless and futile expressing angst at any short to medium term UK troughing pattern and extrapolating that as some kind of a given for weeks and weeks ahead. Or, if cool, unsettled and soggy weather happens to be your preference for the coming season, celebrating prematurely that another summer like 2007 is coming

Set against the background ENSO factors, despite the very vulnerable arctic sea ice (but no imminent down-welling to the surface of an easterly QBO wave to help engage a high latitude tropospheric response such as happened in 2007) and assuming steady eastwards progress of the tropical signal and propagation through to the extra tropics via frictional and mountain torque mechanisms, then crucially seasonal wavelength changes will help assist removal of the Atlantic ridge/UK trough pattern solution and there is good reason to expect to see a steadily improving picture timed quite nicely for the approach of summer.

My view on the models last week was that Scenario B was the short-term favourite and we would have to enjoy/endure (delete as appropriate) a spell of unsettled weather (with some much needed rain to be fair) before a more summer-like evolution came into view. 

I think it may be early June before Scenario A occurs (if it happens). I'd also be keeping a close eye on the long-overdue development of the easterly QBO and I just wonder if 2017 may be a summer of two distinct halves - a warm and sunny first half and then a wetter more unsettled period later on.

Plenty of interesting chart analysis to come as always..

 

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On ‎13‎/‎05‎/‎2017 at 12:16, Gael_Force said:

It doesn't show much signal for precipitation but it didn't in the previous very wet summers. I remember Gavin Partridge saying, in a video, these small patches of trapped low pressure were very difficult for the long range models to pick up. Supposedly a low solar signal and low ice pattern ... we have both at the moment.

Great post, exactly long range models as well as ensembles for just 10 days ahead find it difficult to pick up small scale features for the UK, there is an over reliance of basing expectations on long range models for our small patch of the northern hemisphere. 

 

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3 hours ago, summer blizzard said:

It's summer folks.......

ECMOPEU00_216_1.png

 

Actually, that chart is still spring :p

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4 hours ago, summer blizzard said:

It's summer folks.......

ECMOPEU00_216_1.png

 

 

Meanwhile this week back in 1976 there was talk of writing of the summer.....     the rest is history 

awful summer.gif

Edited by 40*C
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Ummm very interestingly Gavin P's best analogue for this Summer is 1957's which had a very good first half followed by a poor second half, a summer of two halves, i think this summer will be similar but the halves could be reversed. :) 

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After a pretty wet and quite windy couple of days the ecm this evening has the transition beginning on Wednesday with the ridge building in mid Atlantic and the main Atlantic trough starting to slip south east towards the UK. Thus some unsettled showery conditions on Thursday, and not forgetting a belt of more concentrated rain tracking up from the SW affecting southern England. The low continues to track SE until Saturday when it's over the UK and so the unsettled showery conditions continue. During all of this the temps generally but one suspects there will be a fair bit of geographical variation.

I'm not going to attempt to analyse the rest of the run. Suffice it say a state if inertia takes over.

ecm_mslp_uv850_natl_5.thumb.png.f46a25e559173c2f331901934762d476.pngecm_mslp_uv850_natl_7.thumb.png.eb765633bf4a3c8f3f096ef2f1251fde.png

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Not much to get excited about in the 12z....trough parked over the uk. Expect plenty of big showers or longer spells of rain.

 

IMG_4384.thumb.GIF.fc6d61f4712d137f59607d923b1efa89.GIF

 

This tells you everything. Wet.

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The anomalies this evening are not terrible informative although the ecm and NOAA on the same page. The problem, one suspects, is that there is nothing very dynamic going on. Sticking to general comment and the ecm we have a weak area of high pressure to the west and a filling trough over the UK. towards the end of the period the trough has filled and a weak ridge is orientated NE from the UK towards Iceland. All of this points to a very quiet period vis weather with temps perhaps a little above average but one suspects this a fair way from being nailed down.

ecm_eps_z500a_5d_nh_11.thumb.png.23273aa9fb58ad03ee3ba85ac8802523.pnggefs_z500a_5d_nh_41.thumb.png.bd40b0a62aa7229381e62c3255189655.png610day_03.thumb.gif.17aafca80833a9ce060d807551311cf3.gif

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The gfs this morning.

Midday Wednesday sees a general area of low pressure to the north west thus  a wsw flow over most of Britain, the exception being the far south which is under the influence of a slack area of low pressure and a front which will bring more general rain for a time. Whilst at the same time the Azores high is starting to ridge north in mid Atlantic.

PPVK89.thumb.gif.f204a50a4e51198eb950f85ba5433506.gif

From this point the high pressure continues to amplify and the upper  trough sinks south east and the corresponding surface feature is over south west Ireland by 12z Friday which brings showery conditions, and perhaps spells of more general rain, into the UK with temps around the average. This really sets the tone for the evolution over the next few days.

gfs_z500a_natl_19.thumb.png.380c915acc5b4893f501752960cff81c.pnggfs_ptype_slp_eur3_19.thumb.png.b3b0f501317ce52b6e482bed766478d1.png

The surface low continues to wander around the UK over the weekend, albeit generally tracking north east, thus showery and unsettled for most areas. But the upper trough that has been sitting between the ridges to the west and east gets some reinforcement from energy tracking east and popping down between the ridges which reinvigorates the surface feature which by 12z Monday is 996mb over Thurso bringing rain showers, particularly to the north, in a brisk NW wind. The latter also introduces some cooler air with temps dropping a little below average.

gfs_ptype_slp_eur3_25.thumb.png.6aa1e3917989cf2bf996a557d1caf13c.pnggfs_ptype_slp_eur3_31.thumb.png.6afc55faa7a200ad75f64d90d45b0852.png

So in a nutshell from Thursday to Tuesday of the following week the UK is under the Influence of low pressure and thus showers, some outbreaks of more persistent rain and temps around average. Of course this only the gospel according to the gfs. I have no doubt the ecm will differ.

No raging argument, in general,  from this morning's GEFS vis  this interpretation but that's not unexpected

gefs_z500a_5d_nh_35.thumb.png.e0b24a84ec1df7954580a819ebe35496.png

Edited by knocker
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Very broadly speaking the ecm is in the same ball park as the gfs although not surprisingly the detail of the low pressure next weekend  is somewhat different and it brings the next Atlantic low in a bit quicker. Still an unsettled showery weekend likely but may need a run or two to harden up on the details.

ecm_mslp_uv850_natl_6.thumb.png.6717d419e17fa1a50d94e1bfb33823de.pngecm_mslp_uv850_natl_9.thumb.png.1d027125204d9fb095f44615b1e62590.png

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As is always the case with these low pressure systems, the detail is quite hard to pin down. Generally looks to be staying unsettled for the next week at least.

gefsens850london0.png

Perhaps a crumb of encouragement there, with a small number of warmer runs starting to appear after the 25th May. Far away in FI though, and there are also cooler solutions at the same time. I'll keen an eye out though.

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1 hour ago, mb018538 said:

As is always the case with these low pressure systems, the detail is quite hard to pin down. Generally looks to be staying unsettled for the next week at least.

gefsens850london0.png

Perhaps a crumb of encouragement there, with a small number of warmer runs starting to appear after the 25th May. Far away in FI though, and there are also cooler solutions at the same time. I'll keen an eye out though.

Indeed and as I've argued in my commentary on the In Depth Thread (shameless plug as always), all options from a washout to a spell of warm/hot conditions are on the table this morning.

So much depends on whether the LP drops anchor in the Atlantic or whether it gets displaced further east or south by heights building from the north. If you like, this is a variation on the A and B Scenarios I've discussed before. If you want the possibility of warm/hot weather, you need to keep the LP to the west to draw up heights and/or southerly winds. If the LP shifts too far south or east, it either ends up over the British Isles or the flow comes from the east which would be pleasant for many but not the heatopia some would like.

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Well the south east should get some rain on Wednesday

gfs_ptype_slp_eur3_10.thumb.png.0da88f5b96503807e9c4749d9e528b0b.pngPPVK89.thumb.gif.5b891cd1bf7a1c40bd1142c384246f6a.gif

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GFS 12Z not what you want to see over the late May bank holiday weekend that's for sure, northerly winds and LP from the SW engaging that very cool air with single figure max's in northern uk.

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2 minutes ago, Eugene said:

GFS 12Z not what you want to see over the late May bank holiday weekend that's for sure, northerly winds and LP from the SW engaging that very cool air with single figure max's in northern uk.

You have to say, the 12z GFS looks like 2007 on steroids. 

gfsnh-0-276.png?12

Means nothing this early on though. Still suspect we'll see an improvement in the modelling as summer proper approaches.

 

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4 minutes ago, CreweCold said:

You have to say, the 12z GFS looks like 2007 on steroids. 

gfsnh-0-276.png?12

Means nothing this early on though. Still suspect we'll see an improvement in the modelling as summer proper approaches.

 

Yes a long way away and an extreme of what could happen but the building blocks for some disappointing weather in late May start this weekend with stalling LP and HP building to our north, looks pretty cool from this friday.

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Lets not forget @Tamarasaid we might have to see two to three weeks of disappointing weather before we see a marked improvement.

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27 minutes ago, CreweCold said:

You have to say, the 12z GFS looks like 2007 on steroids. 

gfsnh-0-276.png?12

Means nothing this early on though. Still suspect we'll see an improvement in the modelling as summer proper approaches.

 

Very representative of the ice destroying dipole anomaly of that year. The long rangers have a big positive anomaly where the blue is over Scandinavia so we can expect a turnaround, all being well.

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