Model Output Discussion 01/06/2012

[Scorcher]

The thing is GFS has stuck to its guns on this and is still not backing down, will be interesting to see what happens with the next runs as it appears ECM is coming closer to GFS rather than the other way round.

[Lincs Observation]

Its a pretty good ECM 12z in the way that it prolongs the dry and settled conditions throughout next week. Temperatures wont be all that great if those charts verified but its July now so we are reaching the peak of possible warmth. Therefore temperatures will be around average which means 18-22c which should feel very pleasant.

This is not strictly true, Even though the longest day falls on the 21st June, it takes a fair while for the earth to warm up. The fact that the days are slowly getting shorter does not mean the summer is over, the fact is according to the Met office the warmth is more likely to be in July and August due to warming of the northern Hemisphere. However the caveat to that is that if the NH is cool it is likely to take longer meaning that it never reaches its potential before autumn comes a knocking. LO

[johnholmes]

Quote

There is a corresponding signal for less sunshine than we see on average in July. Similarly, whilst temperature levels are quite uncertain, the chances of very warm conditions prevailing over the period as a whole are considered very low.

why that is a brave call seems a rather odd statement to make?

the part in bold makes it pretty clear that for the whole month it is unlikely and looking at the 500mb anomaly charts into the middle of the month (July) then I cannot see anything other than the odd day or two where very warm would apply generally.

Whatever the 4x or 2x daily outputs show until the upper air pattern is predicted to change substantially from its current pattern, of the last few weeks, then not much change in surface weather from the last 2-3 weeks is likely.

[bluearmy]

Unfortunetly the ECM looks like its being considered as an Outlier tonight:

Quick point, the ECWMF model is such a huge change from the 00Z run, the 12Z run is most likely an outlier

The ECWMF ensembles signal little risk of such extensive high pressure next week, a more unsettled theme is likely at the moment...

That was the comment made by Matt Hugo

The 12z naefs anomolys look more akin to the 00z ECM op then the 12z. However, the mean and spreads do not look as amplified with the trough as the 00z op did so I'd say neither op from ECM post day six is reliable today.

[Summer Sun]

ECM 00z has stuck to it guns and keeps high pressure building next week

http://www.jp2webdes...o.uk/ds/ecm.htm

GFS on the other hand has taken a step back and is now following ECM's route from a few days back and brings another low back

UKMO is also unsettled

http://www.null/ds/ukmo.htm

So like this time yesterday its 2 - 1 in favor of unsettled weather but this time from GFS and UKMO, a lot of uncertainty for next week but if I was a betting man i'd say low pressure would be my bet

[Scorcher]

GFS ensembles are indicating a pressure rise next week which goes against the 00z run so could it perhaps be an outlier? It looks like next week will be mixed but certainly still better than most of June with none of them showing a total washout. As is traditionally the case it looks like it could be drier the further south and east you go.

[shedhead]

This 2-1 split remins me so much of Winter, very frustrating, but all things considered the overall trend still continue to look a little better.... little being the operative word.

[bluearmy]

as gfs trends away from an extended settled period for parts of the uk, ecm heads in the opposite direction. the ens mean and spreads from ecm looking fairly reasonable if not as settled as the op run. i'd say that beyond the general rise in pressure following the departure of the weekend depression, any output should be treated with extreme caution until we get cross model agreement with some consistency.

[Weather Boy]

ECM 00z has stuck to it guns and keeps high pressure building next week

http://www.jp2webdes...o.uk/ds/ecm.htm

GFS on the other hand has taken a step back and is now following ECM's route from a few days back and brings another low back

So like this time yesterday its 2 - 1 in favor of unsettled weather but this time from GFS and UKMO, a lot of uncertainty for next week but if I was a betting man i'd say low pressure would be my bet

Generally so far this summer the ECM has (has it not?) outperformed the GFS. However, I do not know whether it follows that we should prefer the ECM because they are computers only and I am not sure it is logical to say that because X model has been better than Y model in the recent past, it follows that X is a better indicator at the moment.

[shedhead]

No change on the 06 GFS for next week, which maintains LP and generally unsettled conditions, especially the farther north and west you go. ECM paints a very different picture at T+168hrs, so clearly one of the big two is going to be wrong, but with UKMO rather more in line with GFS I think it will be ECM that unfortunately gets dragged into line this time.

[Summer Sun]

GFS 06z sticking to its guns for next week in sending more lows our way

http://www.null/ds/gfs.htm

[bluearmy]

as gfs trends away from an extended settled period for parts of the uk, ecm heads in the opposite direction. the ens mean and spreads from ecm looking fairly reasonable if not as settled as the op run. i'd say that beyond the general rise in pressure following the departure of the weekend depression, any output should be treated with extreme caution until we get cross model agreement with some consistency.

note that the dutch ens are wet for week 2 - moreso than the past few days output have been.

[SP1986]

Yes I have to agree with the above posts, while not definitive, it would seem the unsettled GFS/UKMO combination is the most likely outcome. From what I can see this would either lead to a prolonged period of cool, northerly type weather ultimately, or a short period of cool, unsettled weather followed by something a little closer to average.

I do think the best we can hope for July is around average if I look at the broad situation, but average is somehow better than it could be..

Hot weather in summer definitely seems to be a thing of the past at the moment.

[Summer Sun]

Todays update from the met office supports todays UKMO and GFS updates

Tuesday 3rd July 2012 to Thursday 12th July 2012:

The rest of the week looks showery with the risk of some heavy downpours by day, easing overnight, with perhaps some longer spells of rain in the northwest. It may be windy at times, particularly on exposed western coasts and hills. Changeable weather is set to continue for all areas through the weekend and into next week.

ECM's update has little support it would appear

Edited June 28, 2012 by Summer Sun

[Glacier Point]

A quick scan through posting and models today might suggest the two main global forecasting models are miles apart for the 6-10 day timeframe. However, in reality, the two ensemble means are not a million miles apart, but the modelling of longwave features in our locale is likely to cause some problems.

The GFS H5 ensemble mean height anomaly puts the UK in another trough (albeit much weaker than those experienced in June) next week, c/o an amplified pattern in the Atlantic. This trough is largely intact in our area.

The ECM H5 ensemble mean height anomaly however suggests a cut off low to be the more likely scenario, with some uncertainty as to how far south any such feature might be (and consequenlty where if any the build of high pressure over the top). The DeBilt ensembles reflect the potential for cut off low and enhanced rainfall signal for week 2.

In so far as the basic signal - ridge in the Atlantic c/o low angular momentum, we can be reasonably confident. The key variables, which will likely bounce around in the coming days, how much flow over the top tilting the ridge towards northern UK and tied into this where angular momentum goes in this timeframe. If we see a rapid increase in tendency of relative anguar momentum coming out of Asia, expect to see the ECM version the more likley to verify which would see more convective potential to the south of the UK and mainland Europe rather than the north.

[Summer Sun]

GFS 12z builds pressure later next week but before that there is another low to deal with

http://www.jp2webdes...o.uk/ds/gfs.htm

[Methuselah]

True enough, SS. But those lows are much farther north than many of the recent ones?

[William of Walworth]

Something to cling to perhaps, a possibly more Northerly tracking of lows (ETA : for those of living further South in the UK anyway!)

But so much chopping and changing from run to run. As several have said, it's very frustrating for summer preferrers ...

For now!

Edited June 28, 2012 by William of Walworth

[Summer Sun]

True enough, SS. But those lows are much farther north than many of the recent ones?

Not sure tbh more areas further south are prone to rain next week which they weren't a few days back

UKMO also keeps low pressure over the UK

http://www.jp2webdes....uk/ds/ukmo.htm

ECM also on board now with low pressure heading our way once more

http://www.jp2webdes...o.uk/ds/ecm.htm

Its looking odds on now for low pressure to continue into next week

Edited June 28, 2012 by Summer Sun

[Methuselah]

Therein lies the problem, SS. Lows (and highs) change their positions on each and every run and on each and every model...

[Milhouse]

I'm not suprised the nationwide setled spell has almost vanished. We just cant seem to get rid of that endless barrage of lows crashing into the UK. Having said that i can see Monday and Tuesday being mostly dry and warm the further south east you go. From Wednesday onwards the ECM has the low weakening and sliding south allowing an easterly to develop which would deliver some warm and settled weather to western Britain at last. So certainly not a writeoff, but next week was looking much better a few days ago.

Some signs from other models that next weeks low will be a rather weak affair and could end up pulling in a warm easterly off the continent.

Edited June 28, 2012 by Milhouse

[WhiteFox]

True enough, SS. But those lows are much farther north than many of the recent ones?

There does seem to have been a slight shift over the past week or so. The lows were crashing straight through the UK and exiting over the North Sea. The last two (of which I include the current one) seem to have been deflected somewhat and are tracking more to the North East. The result is that the last two systems have delivered much less in the way of rain to the South East compared to previous ones, and there are signs that this trend is continuing. This week, initial forecasts suggested that the South East would be in the firing line for heavy rain today; however, we only had a relatively short spell of rain overnight on Wednesday. The models seem to be indicating that the next system may also fail to make it too far east which means the South East only gets a few hours of frontal rainfall with the main rain being further North and West.

The 12z GFS shows the next system passing to the North West of Scotland, just that bit further out than the current one which crossed over Northern Ireland, so I think there are hints of the main storm path heading out to sea a little...

[Sunny Android]

Slightly further ahead Milhouse (192hrs) and GFS and ECM show signs of depressions forming around Spain and pushing north.

Modelling more humid weather for us .... perhaps

[Sunny Android]

Also, do agree White Fox,

the Atlantic depressions are more northerly but the spanish plumes may show their hand !

[WhiteFox]

Also, do agree White Fox,

the Atlantic depressions are more northerly but the spanish plumes may show their hand !

Maybe. The Azores high seems reluctant to push too far East with any strength so it could leave a door open for the Spanish to enter! If nothing else, the weather seems set to turn warmer and perhaps humid if not settled.