Model Output Discussion 12z 20/04/13

[NeilN]

This is a joke right? Cant we burn away this low pressure?

[Frosty.]

This is a joke right? Cant we burn away this low pressure?

It's a low that doesn't exist and may never exist so not worth worrying about, i'm confident in the met office update further outlook and the latest ens mean charts which all point to a prolonged anticyclonic spell beginning towards the end of next week and going from strength to strength.

[NeilN]

Frosty, thanks.

I am new to this, so its interesting picking at the charts. I am more of a heat lover here.

[SP1986]

Looking at the 12z my initial reaction was bin the 12z as it is very unlikely we will see -5C at 850hPa expanding geographically.. as someone who has watched the charts for numerous years, I find this scenario pretty unlikely going into May. I would certainly push this run to the side, and see if the 12z tomorrow continues with it, or bins it. I suspect this will be an outlier however, in terms of cold. 

 

That said, I don't think there's any widespread or prolonged warmth (or any warmth for that matter), after Friday, but that is not something that is surprising... we are on a roll of below average month and who says it's necessarily just going to end? At the end of the day we'll see eventually, but it could be a long wait!

Edited April 24, 2013 by SP1986

[Frosty.]

I think this evening's ukmo 12z is very encouraging because the trough is much further east compared to the 00z output and by T+144 hours it suggests a much faster improvement than the met office update talked about today, hopefully this will be a trend which gathers momentum and the ecm carries it forward tonight.

[SP1986]

I think this evening's ukmo 12z is very encouraging because the trough is much further east compared to the 00z output and by T+144 hours it suggests a much faster improvement than the met office update talked about today, hopefully this will be a trend which gathers momentum and the ecm carries it forward tonight.

 

yes this is more encouraging, I think even though this scenario would not necessarily be a warm one, it's far more realistic than the GFS ever expanding cold air scenario (something you'd be be more accustomed to seeing in October!).. so UKMO gets my vote I suppose, well for todays runs anyway.

[Carlrg]

10th May is the best straw clutch I can find showing signs of waning 850 temps decent warmth and slack easterly flow. Deep deep into FI though.

 

 

http://176.31.229.228/modeles/gfs/archives/2013042406/gfs-0-384.png

 

 

http://176.31.229.228/modeles/gfs/archives/2013042406/gfsnh-1-384.png

Edited April 24, 2013 by Carlrg

[Summer Sun]

10th May is the best straw clutch I can find showing signs of waning 850 temps decent warmth and slack easterly flow. Deep deep into FI though.

 

 

http://176.31.229.228/modeles/gfs/archives/2013042406/gfs-0-384.png

 

 

http://176.31.229.228/modeles/gfs/archives/2013042406/gfsnh-1-384.png

 

Thats the 06z run 12z is a bit better

 

[Frosty.]

We have more good news here from the latest GEFS 12z mean, the gradual trend to a very anticyclonic outlook is looking solid once the troublesome trough to the northwest of the uk fills and drifts away northwestwards towards iceland/greenland, the south and east would be the first to improve with a nice pressure rise, the northwest would take longer so it would appear to be a northwest-southeast split we are heading towards from around the middle of next week but by the following week the whole of the uk will hopefully be settling into a prolonged spell of high pressure and slowly warming up with the risk of frost reducing as we go deeper into may. 

[Carlrg]

Would there be a few problems once again with fret in the East/North East from that setup in the latter stages?

[chionomaniac]

 

 

So, in the shorter term, our baseline summer pattern with that Sceuro type trough dominating proceedings for the UK (though the chance of course of a temporary ridge of high pressure once again towards next weekend). Beyond that the American currently pointing towards some sort of Euro pressure build, though this should be taken with a pinch of salt for a few days yet until we see a stronger anomaly signal develop, or indeed see the ECM start to become interested - GFS/ECM combo is pretty useful at such range, where as disparity breeds uncertainty

 

SK

I see a Euro High pressure build as the natural evolution following the Scandi trough. And it is not without some tentative support.

 

The MJO is currently forecast to enter phase 1, which allowing for seasonal wavelength changes hint at a Scandi trough - hence the northerly and building euro high.

 

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/clivar_wh.shtml

 

 

 

This is likely to be followed by a progression to MJO phase 2 where the euro high migrates further north - certainly the UK looks to be in a favourable position where this to occur.

 

 

Looking at the latest NH strat profile we can see the influence that the delayed return of the increased mean  westerly zonal winds is having on the polar vortex since mid April, and this should work in tandem with the MJO for the month of May once the phase 1 has cleared.

 

 

My bet here would be for a dry settled month after a cold start with a tendency for some much warmer interudes.

 

Ps I wrote this an hour and a half ago but then experienced a power cut before being able to post - the updated ECM shows a likely May scenario by the end of the run.

 

[Gibby]

Good evening. Here is the report on the 12 noon output from GFS, UKMO, GEM, NAVGEM and ECM for today Wednesday April 24th 2013.

All models show a slack West or SW flow across England and Wales with a trough embedded over the North of England. A wave is shown to run along the front West to East overnight bringing rainfall across Central parts. A colder showery regime affects Scotland through the next 24 hours before it moves SE behind the front to reach all areas by midnight tomorrow night. Friday and Saturday will feel very much colder in Southern areas with sunshine and heavy showers before a ridge moves South on Saturday to be settled over Southern areas for Sunday giving a fine and dry day before the North clouds over late in the day.

GFS shows a cold front crossing slowly East over the UK on Monday with a band of rain in tow followed by generally slack winds with bright or sunny intervals and scattered showers in association with Low pressure to the east ad west of the UK. FI tonight shows a milder SW flow for a time with rain at times in the NW before High pressure builds across the UK and moves North to set up an easterly flow over the UK. Northern and Western areas would then see some dry and rather warm conditions while Southern and Eastern areas would likely be plagued by a chilly ENE breeze under extensive low cloud moving across most parts from the North Sea.

The GFS Ensembles show an unsettled spell with heavy showers for a time over the period of this weekend until later next week. Thereafter things settle down as high pressure builds and uppers exceed normal values, however, conditions at the surface could be different if an onshore wind develops from the East.

The Jet Stream shows the flow currently moving West to East across the UK steadily weakening over the next week, probably breaking down entirely over the Atlantic later next week.

UKMO tonight shows a complex pattern over the UK between low pressure over Northern Scandinavia and Spain and a slack if large area of High pressure in the Atlantic. There would be some scattered showers around but a fair amount of dry weather too in a rather chilly spell of weather.

GEM shows a rather cold and showery period for much of next week with winds from a Northerly quarter for much of the time. Towards the end of the run the flow backs more Westerly as milder air feeds East though with a trough of Low pressure bringing rain West to East too.

NAVGEM opens the isobars out over the UK as we go through next week with light winds in a Northerly bias and with cool uppers showers are expected to continue, though in any sunny spells with light winds it will feel quite pleasant.

ECM tonight shows a more coherent showery spell with just Sunday offering a respite from the showers as a ridge slips South over Britain. Through next week the weather looks set to remain showery as a weak and slack Northerly flow takes the while weak to weaken sufficiently to allow longer sunny spells and slightly warmer conditions to leave the end of the run with the UK under a developing high pressure with a dry spell likely thereafter.

In Summary there are still mixed messages from the output tonight with all models showing different outcomes when looking at a time point late next week. With a weak jet profile at this time synoptics are hard to be agreed upon with such slack weather features meandering about. the most likely scenario that I can see tonight is a showery week next week with temperatures gradually recovering to near normal by the end of the week and with a bit of luck High pressure may come on to the scene in time for the Bank Holiday weekend.

[Frosty.]

Would there be a few problems once again with fret in the East/North East from that setup in the latter stages?

At this stage I would just be happy to see the current trend from the ens mean and met office experts continue to firm up, there would be that risk you mention but that's a long way down the line and the high could remain in a better position to avoid that issue spoiling things.

[phil nw.]

Yes agree there C.

Good ens support for the jet gradually easing north as thicknesses rise from the south.

The ECM Op showing the way supported by the GFS mean in week 2.

http://modeles.meteociel.fr/modeles/gens/run/gensnh-21-1-300.png?12

Certainly a generally dry prospect after the showery interlude to come with a gradual warm up into May.

http://modeles.meteociel.fr/modeles/gens/graphe_ens3.php?x=263&ext=1&y=99&run=12&runpara=0

Looking promising for a nice spell of May weather with just a caveat for some coastal mist /low cloud depending on placement of the surface features and the direction of any onshore breeze.

[chionomaniac]

 

 

Yes agree there C.

Good ens support for the jet gradually easing north as thicknesses rise from the south.

The ECM Op showing the way supported by the GFS mean in week 2.

http://modeles.meteociel.fr/modeles/gens/run/gensnh-21-1-300.png?12

Certainly a generally dry prospect after the showery interlude to come with a gradual warm up into May.

http://modeles.meteociel.fr/modeles/gens/graphe_ens3.php?x=263&ext=1&y=99&run=12&runpara=0

Looking promising for a nice spell of May weather with just a caveat for some coastal mist /low cloud depending on placement of the surface features and the direction of any onshore breeze.

Phil look at the links to the positive mean zonal wind anomalies that I have posted in the strat thread. Incredible values for this time of year and this is likely to influence May's pattern.

Edited April 24, 2013 by chionomaniac

[phil nw.]

Phil look at the links to the positive mean zonal wind anomalies that I have posted in the strat thread. Incredible values for this time of year and this is likely to influence May's pattern.

Yes almost like a rebound from those negative values earlier in the year.

As you suggest Ed will encourage mid-latitude blocking -at least for a while we should eventually end up on the warmer side of the mean jet.It would be nice to see it more towards Iceland -until the end of Summer.

[chionomaniac]

Yes almost like a rebound from those negative values earlier in the year.

As you suggest Ed will encourage mid-latitude blocking -at least for a while we should eventually end up on the warmer side of the mean jet.It would be nice to see it more towards Iceland -until the end of Summer.

We can but hope, Phil.

[NeilN]

You never know! It's looking promising though with the outlook. The weekend, how low is the drop going to be? It's been around 12-15C in Weston-super-mare. 9-11C would do me OK even if it's a bit ropey.

[Summer Sun]

So next week its looking like we'll see a mixture of sunshine and showers with a gradual rise in temperatures as the week goes on towards next weekend there are now increasing signs that pressure will rise giving us all a settled period for how long? who knows how much sunshine they'll be all depends on where the high places its self

 

Next Thursday sees the first signs of a change as the high builds to the west

 

 

By Friday it continues to drift eastwards

 

 

And by the Saturday its in charge

 

 

 

 

 

[Frosty.]

A very encouraging Ecm 12z by the later stages, especially from T+192 hours onwards, much less impact from the trough to the northwest of the uk as it's further out of harms way for northwestern areas, this ecm run goes from strength to strength and by T+240 hours it's looking like a prolonged anticyclonic spell is locked and loaded to persist for a couple of weeks at least but there is no gain without pain and the ecm is showing a cold and showery spell for the first half of next week with colder air filtering south with widespread frosts and a lot of shower activity with hail and thunder with wintry ppn on northern hills, from midweek the approaching ridge from the west would start to reduce the potency of the showers and then kill them off completely as pressure continues to rise. As for the near future, tomorrow will be the last warm day in the south for a little while as a cold front brings a band of rain southeastwards later tomorrow and we will all be in the cold air by friday, coldest in northern britain with wintry showers, and showers breaking out all over the uk during friday with hail and thunder but with some sunshine too. The weekend is an improving story, especially sunday with southern britain under relatively higher pressure so a fine and fairly sunny day and also less cool than saturday after an early frost, rain spreading out of scotland and n.ireland into northern england on sunday afternoon, colder. windier and showery weather spreading into nw scotland during sunday.

 

 

[snowking]

I see a Euro High pressure build as the natural evolution following the Scandi trough. And it is not without some tentative support.

 

The MJO is currently forecast to enter phase 1, which allowing for seasonal wavelength changes hint at a Scandi trough - hence the northerly and building euro high.

 

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/clivar_wh.shtml

 

 

MayPhase1500mb.gif

 

This is likely to be followed by a progression to MJO phase 2 where the euro high migrates further north - certainly the UK looks to be in a favourable position where this to occur.

 

MayPhase2500mb.gif

 

 

It will certainly prove an interesting test for the various NWP MJO outputs.

 

ECM currently the only one hugely keen on phase 2:

 

 

Meanwhile GFS, GEM and UKMO tend to stick with a weak phase 1 projection:

 

 

And just to offer some balance....the JMA goes off on its own merry way:

 

 

But it does throw up another outcome to look at - the ECMWF projection keeps us in phase 2 for around 5 days, before pushing into phase 3 territory, and phase 3 has us back to something less settled looking:

 

MayPhase3500mb.gif

 

So it could prove an early season chance for us to see which model to look at in the coming months for MJO projection - the ECM projection of phase 2 would do very nicely!

 

Sk

Edited April 24, 2013 by snowking

[Cloud 10]

Certainly a strong signal from the CFS (usual caveats) for a dry May across Northern Europe

and especially the UK.

 

[Purga]

Trough sticking over the UK in the 6-10 day range

 

Whilst there is a slack very nondescript regime further out so no strong warm anticylconic signal as far as I can see.

 

Average at best.

[SP1986]

Certainly a strong signal from the CFS (usual caveats) for a dry May across Northern Europe

and especially the UK.

 

euPrecMonInd1.gif

 

This would suggest a southeasterly, with low pressure around Iberia, which would give Iberia wetter weather, and here potentially warmer, drier weather.. but who knows..

[chionomaniac]

It will certainly prove an interesting test for the various NWP MJO outputs.

 

ECM currently the only one hugely keen on phase 2:

 

 

Meanwhile GFS, GEM and UKMO tend to stick with a weak phase 1 projection:

 

 

And just to offer some balance....the JMA goes off on its own merry way:

 

 

But it does throw up another outcome to look at - the ECMWF projection keeps us in phase 2 for around 5 days, before pushing into phase 3 territory, and phase 3 has us back to something less settled looking:

 

MayPhase3500mb.gif

 

So it could prove an early season chance for us to see which model to look at in the coming months for MJO projection - the ECM projection of phase 2 would do very nicely!

 

Sk

We could do a lot worse than phase 3 - the main trough centre would be towards Iceland. Funny enough, I analysed earlier this evening, years where we had a similar above average zonal mean wind stratospheric conditions in April and forwarded it to May and constructed a H500 composite.

 

Here it is and it does look similar to the phase 3 MJO:

 

 

I think that the phase 3 composite suggests more unsettled in the far north - but far more settled towards the south.