Model Output Discussion 12z 20/04/13

[johnholmes]

yes the 3 anomaly charts, NOAA, ECMWF and GFS have all backed away over the last 2-3 days from all that much change from what we currently have-interesting to see how about 7 May actually looks compared to the charts I showed from, I think, about 5 days ago for NOAA, and what is showing now.

[phil nw.]

yes the 3 anomaly charts, NOAA, ECMWF and GFS have all backed away over the last 2-3 days from all that much change from what we currently have-interesting to see how about 7 May actually looks compared to the charts I showed from, I think, about 5 days ago for NOAA, and what is showing now.

Yes the more settled conditions for week 2 perhaps now a day or 2 later.

Looking at the 00z anomaly charts John i get the impression that the May bank holiday period is when we finally see the UK trough fill with the next one held out into the Atlantic.

This corresponds fairly well with a weak MJO phase 1 forecast as we go into May

Heights building around Europe with a mid-Atlantic trough should warm things up again eventually as the ens have been showing for a few runs now.

http://modeles.meteociel.fr/modeles/gens/graphe_ens3.php?x=261&ext=1&y=98&run=0&runpara=0

Looking mixed until then with some showers and rather cool but having said that rainfall amounts are forecasted to be still quite low during the next week or 2 according to the Ens. graph.

[Milhouse]

GFS 6z is an upgrade on the 0z building high pressure more strongly over Europe keeping low pressure at bay out in the Atlantic. Not saying a change to warmer conditions has now become more likely but the indications are still there. Infact temperatures reach average again as early as Wednesday next week on the 6z and its a warming trend from there but low pressure would be close enough to bring unsettled conditions for a time late on next week for western parts. The ensembles still trend below average until next weekend but under high pressure and sunshine temperatures would still reach expected values for early May.

 

ECM op is overdoing the low pressure over the UK when compared to the mean. UKMO has a very bizzare T+144 with high pressure affecting the UK on 3 sides with Scotland under the cool air mass to the north and Southern England under the influence of warmer continental air.

[snowking]

Just to give you all an idea of why I don't presently buy into a long, settled spell for May.

 

Heres a few of the composites from my initial summer forecast research for May (showing 500mb anomaly):

 

First of all, based around the strongest QBO index value years:

 

 

Then with strong ENSO matches added:

 

 

And finally, with the two strongest composite years in terms of QBO and ENSO at the same time:

 

 

It will be interesting to see how long any sort of positive euro height anomaly can be maintained, because the expectation from me is that the Sceuro type trough is likely to become dominant.

 

In fact, the best chance of the summer for a long settled dry spell for me looks likely to be very late May or early June.

 

Only one run, but the subtle changes from the GFS ensembles in the 1-15 day time range is noticeable vs previous outputs

 

Yesterdays 12z:

 

 

Todays 0z:

 

 

You need more than one run to create a trend obviously though, so some tense viewing of future ensemble outputs will ensue I suspect!

 

SK

[Frosty.]

The Azores High has a big influence on the Gfs 06z in FI as it tries to take control, the good news if the az high does ridge in like that is we could expect a warm spell which could turn into a very warm spell. Next week also looks better, at least for southern parts with high pressure ridging northeast across the south but the north of the uk generally controlled by low pressure, so a northwest-southeast split appears to be more likely with pressure gradually rising to the south & east with anticyclonic conditions over the near continent but pressure remaining generally low to the northwest of the uk for the next few weeks with limited fine weather for nw britain, as things stand. So, the northwest to continue cool and changeable/unsettled, the south and east slowly improving but with a few unsettled blips along the way and temps rising during FI.

[Purga]

The bad news for warm /dry lovers is that the 06z GFS is the worst verifying run.

 

...or so I am led to believe.

[Alexis]

True! There must be a signal coming from somewhere that causes the Azore High to inflate so strongly though. I take pretty much any GFS run as plausible though if it shows something other than a vague continuation of the status quo or flabby highs and filling lows, which it often does.

Edited April 26, 2013 by Alexis

[Summer Sun]

The latest from Matt Hugo on twitter for May

 

 

Latest update of the EC32 is not good for May, despite a signal for higher pressure, it is in the wrong place which brings below avg temps.

 

Certainly a clear signal for a drier than average month, but a cooler than average one as well.

 

 

So the way Matt see's things this morning he's going for a drier than average, settled & cool month

 

The Met office are still going for an improvement during the first full week of May with it perhaps becoming warm at times towards the east and southeast.

 

UK Outlook for Wednesday 1 May 2013 to Friday 10 May 2013:

 

An unsettled start to May is expected in many central and northern areas with some longer spells of rain and even hill snow in the far north. Some southeastern areas will probably be mainly dry at this stage with some sunny spells, but even here there is a risk of some cloudier spells with more patchy rain. Temperatures will be generally rather cold with overnight ground frosts still likely. However daytime temperatures may reach close to average in any sunnier interludes in the southeast. Heading into the first full week of May there is an increasing likelihood of drier and more settled conditions spreading to many parts of the UK, with daytime temperatures perhaps becoming warm at times towards the east and southeast.

 

Edited April 26, 2013 by Gavin.

[Frosty.]

The Ecm 00z ensemble mean is very encouraging, gradually improving from the south and east, the northwest of the uk the last to improve but the persistent trough to the northwest of the BI does eventually show signs of weakening and drifting away nw with high pressure gaining control by T+240 hours, if the ecm verified at that range, the uk would be settling into a fine and increasingly warm spell, similar to the near continent.

[bluearmy]

looking at the extended london ecm ens, it seem there is a 75/25 split in favour of a warmish dry trend heading through week 2 rather than a cool dry one. (prob nw/se). no doubt the ecm 32 dayer must take the blocking to a less favourable position re wamth.

[AWD]

With plenty of suggestions about where we could be heading way out in FI, in 8-10+ days time, let's see what the remainder of April holds weather-wise for those interested.

Tomorrow looks like a day of sunshine and scattered showers. As ever with a showery regime, some places will miss them and have a pleasent, sunny day whilst others could see a fair number of showers;

With weak vertical instability aloft, along with minimal CAPE, cloud tops will remain relatively low, inhibiting further enhancement of shower cells into storms, thundery showers etc.

Although with low ELT values, especially further south, hail (probably soft) will be a distinct possibility.

The showers looking more frequent the further south you are I think, with the north seeing them rather more scattered. Temperatures tomorrow maxing out below average for many of us, with a good part of the north possibily failing to reach double figures;

As the remaining showers decay over the south tomorrow evening, skies will clear over England tomorrow night;

allowing temperatures to drop away for much of England;

with the risk of a ground frost for many of us, and indeed away from towns and cities, an air frost too. Further north and west however there is expected to be much more cloudcover, this preventing temperatures dropping away too much and keeping the risk of a frost minimal;

The cloudcover is associated with an occlusion to the NW of Scotland, wrapped in a deep depression over the GIN corridor;

On Sunday that occlusion is expected to sweep slowly SE;

Bringing a spell of rain to most of us at some point throughout Sunday;

Nothing too heavy is forecast though, with the south possibly seeing only a few mm's from it as it slowly decays on it's journey. A little more for the north west though. Behind this rainband will be a mixture of sunny spells and squally showers in a strengthening W/WNW wind;

Again, at this stage I can't see anything more than just "shower" activity due to limited instability aloft although a better look at this tomorrow might be better. Temperatures similiar to Saturdays values, on the cool side for many;

Monday again looks like a day of sunshine and scattered showers, the showers possible anywhere. They could again be heavy, frequent in places and blustery in a gusty north westerly wind;

Haven't looked to see if any thundery element could be associated with them yet, will leave that until the weekend. Temperatures slowly recovering to nearer average values on Monday;

Things look like settling down somewhat by Tuesday, with the showers becoming fewer and further between;

As a weak ridge of pressure forms;

giving what looks like could be a rather sunny and pleasent day with lengthy sunny periods inbetween patchy fairweather cloud;

Although due to the cooler upper air brought down by the weekends low;

Temperatures struggle to respond too much, with around average values at best likely, broadly speaking;

That's the next few days anyway, and the more commonly thought reliable timeframe prognosis. Further out towards next weekend and things, IMO, remain a tad unclear to have a good degree of confidence on. One thing that has been consistent however is a continuation of lower than average rainfall amounts, thus indicating higher than average pressure influencing the UK through the beginning of May. It's where this sets up that's unclear to me this morning, and this of course as a big effect on conditions felt on the ground, be it warm, cool, cloudy, sunny etc.

[Milhouse]

The met office are predicting it may becore warm at times across the south and east during the first 3rd of May. That would lead me to assume that they are predicting high pressure to be sat more or less over the UK or just to the south to get warmth in those areas. I assume the ECM 32day predicts high pressure more to the north or the UK feeding in cool easterlies bringing the best of the warmth to western parts.

 

Conflicting outlooks there from the UKMO and ECM.

[Milhouse]

GFS 12z looking increasingly unsettled late next week and into next weekend. Still a settled and increasingly mild spell to come mid week before low pressure edges in bringing the threat of some slow moving heavy showers. Temperatures remaining fairly respectable in the mid to high teens.

 

UKMO settled out to T+144.

[Frosty.]

One thing that is starting to look clear next week from  the 12z runs so far is it's better to be in the south of the uk than the north, northern britain looks increasingly like remaining cold and showery next week with below average temps and overnight frosts with some of the showers being heavy with hail & thunder and cold enough for snow on the higher hills and scottish mountains. Southern britain looks less unsettled, indeed it looks like high pressure will be ridging across the south for much of next week bringing a lot of dry and fairly sunny weather and not as cool as further north but still cold enough for a touch of overnight frost, towards the end of next week the gfs 12z shows the unsettled weather spreading east and south to all areas and the synoptics look very messy by the end of next week with small highs and troughs drifting around in a very depressed pattern. Beyond that, some brief atlantic mobility with windier and more unsettled weather spreading from the west but high pressure starts to build from the south and the jet is forced gradually to the north, northern uk remains unsettled for most of the next few weeks but there continues to be a strong signal in FI for an anticyclonic further outlook for the whole of the uk which is also what the ecm 00z ens mean shows and also what the met office are sticking with so our patience will be rewarded.

[Milhouse]

ECM looking good so far with a quiet and mild start to May.

 

[shaky]

ECM looking good so far with a quiet and mild start to May.

Am actually quite surprised!!the ecm looks way better than the ukmo and gfs at the same time frame!!and the ecm 12z looks better than the 00z!

[Frosty.]

Well what a GREAT run from the ECM 12z compared to the gfs run, high pressure across the south for most of next week and then an atlantic ridge spreading into the northwest and a large anticyclone forming over the uk , it looks a lot less complicated than the gfs 12z run, the gfs run becomes very messy and directionless for a while but the ecm cuts through all that and just displaces the troughing to the north with a big fat high. This would mean that most of next week would actually be fine with sunny spells in southern britain (as per gfs) and temps recovering in the strong sunshine, almost reaching average but cold nights with ground frosts, northern britain has a more unsettled week but then becomes settled, so, the ecm 12z has cut the unsettled spell  in half for northern uk compared to gfs 12z with a prolonged settled spell taking control for all areas.

Edited April 26, 2013 by Frosty039

[Gibby]

Good evening. Here is the report of the 12 noon output of GFS, UKMO< GEM, NAVGEM and ECM for tonight Friday April 26th 2013.

All models show a cold and showery Northerly flow over the UK tomorrow with a ridge of High pressure moving down from the NW later. Over Saturday night the ridge moves on down over the South too with a fine and in places frosty night while Northern areas cloud over later with rain into the North and west before Sunday morning. the attendant cold front crosses further SE down over the rest of Britain through the day with cloudy weather with light rain in places. It will be a rather cold day. Monday sees the cold front having cleared away SE leaving a blustery and chilly NW flow with scattered showers on Monday restricted to the far North by Tuesday as pressure builds slowly from the SW.

GFS then shows the midweek period with a North/South split developing with the North staying breezy and more cloudy with occasional rain while the South sees drier and brighter conditions with temperatures recovering to nearer to average for late April and early May. Then as we move towards and over the Bank holiday weekend the weather turns slightly more unsettled with shallow Low pressure increasing the risk of showers in temperatures close to average. Through the second week unsettled conditions become confined to the North with High pressure building from the South, eventually to all areas bringing a spell of fine and warm weather with sunny spells.

The GFS Ensembles show a steady rise in uppers to levels near to average and eventually somewhat above as the cool and unsettled conditions gradually give way to more High pressure based weather with sunny spells and warmer temperatures by week 2.

The Jet Stream shows the flow over the Atlantic and down over the UK weakening by next week as a second weak arm is shown to blow across a more Southern position in the North Atlantic and on across North Africa.

UKMO for the period later next week shows slack pressure over the UK with a lot of dry weather for many with the risk of a few showers here and there. Temperatures should recover a little by day but there could still be a touch of overnight frost.

GEM shows a changeable week next week with some rain or showers for all for a time before the trend towards drier and warmer conditions begins over the holiday weekend.

NAVGEM shows slack pressure over the UK later next week with the risk of a shower almost anywhere prior to the Bank Holiday weekend.

ECM finally shows a lot of dry weather next week with the odd scattered shower especially towards the start of the Bank Holiday weekend. Through the weekend itself things look very promising tonight as High pressure builds strongly over the weekend with increasingly dry and warmer weather with sunny spells developing over most areas setting us up for what looks like a spell of sustained fine and warm weather for the UK.

In Summary the long term prospects look fairly good as a spell of fine and warm weather looks very possible from the Bank Holiday weekend onward. In the week to come things may be a little more 'iffy' for many with rain or showers possible at times almost anywhere but probably more likely in the North. With regard to temperatures they should slowly recover by day though frost at night may be a feature early in the week the risk should be removed before the Bank Holiday weekend begins with the prospect of some pleasant late Spring weather thereafter.

 

Looking too busy to post my report on this forum tomorrow. Website only I'm afraid.

[phil nw.]

Yes Frosty the UK trough looks like it will start warming out around the middle of next week.

The mean rise of GFS 500hPa temps underline this

http://modeles.meteociel.fr/modeles/gens/graphe_ens3.php?x=263&ext=1&y=100&run=12&runpara=0

A more promising outlook for some fine weather for the BH weekend looking more widespread as those heights really build.

The surface high may show up slightly differently in future runs but the general pattern is well supported by the means and anomaly charts.

[Summer Sun]

Fantastic output from ECM tonight which results in something unusual for a bank holiday in the UK yes high pressure and pleasantly warm

 

 

Looks quite a dominant high which could last a while

 

All over to the ensemble run in around 40 minutes to see what support it has

 

Edited April 26, 2013 by Gavin.

[Methuselah]

Fantastic output from ECM tonight which results in something unusual for a bank holiday in the UK yes high pressure and pleasantly warm

 

 

Looks quite a dominant high which could last a while

 

All over to the ensemble run in around 40 minutes to see what support it has

 

That's what I like to see, Gav; no ghastly NE flow, so allowing any haar to burn back to the coast...

[Summer Sun]

Good new folks the ensembles back the Op tonight for ECM's bank holiday weekend pressure rise

 

 

[NeilN]

Great news!! Can get the second part of my decorating done on the Sunday, and some time on the beach on BH Monday.

[Milhouse]

Good new folks the ensembles back the Op tonight for ECM's bank holiday weekend pressure rise

 

 

 That is solid support for a pronounced rise in pressure to the east of the UK albeit in FI. Also for much of the latter half of the run high pressure remains on the right side of the UK for warmth so no indication on the mean for a momentary plunge in temperatures like the op shows at T+192.

[Milhouse]

Great news!! Can get the second part of my decorating done on the Sunday, and some time on the beach on BH Monday.

 

North Somerset and Devon would be favoured for some pleasant warmth given the early indications of high pressure to the east of the UK.