Model Output Discussion 31/07/14 onwards.

[Milhouse]

The chance of something warmer pushing into southern england for a time early next week as shown on the GEFS mean. But it will be accompanied by generally unsettled conditions.

 

 

Saturday not looking too bad the further south you go. A chance for getting out and about enjoying some pleasant average summer temperatures.

 

[Milhouse]

ECM 12z mean more keen on a cooler push of northerlies early next week before pressure builds later on.

 

 

 

[Captain Shortwave]

Very little on offer for those who have enjoyed the summer so far. Saturday looks the nicest day of the lot from across the model suite. The south may stay dry on Sunday until late on so there is a chance of a decent weekend for some. It looks like rain will spread south from the north in association with low pressure moving ESE from Iceland before clearing towards Scandinavia.

 

There is decent agreement on low pressure developing towards our south west, this will likely spread ENE towards the UK, depending on the track some areas could get a soaking, if anywhere gets south of this low then there is a chance of conditions turning briefly warmer and more humid before the low clears to fresher northerly winds. This will take some time to resolve, the low may not exist come verification if the cut off low remains just that.

 

With the bank holiday weekend now starting to loom in the model outputs, there is a sniff of hope for something better.

A fine weekend then would definitely make up for what would be a poor August in relation to June and July.

Edited August 12, 2014 by Captain shortwave

[William of Walworth]

Well, I refuse to be too disheartended (and I'm actually more focussed on the upcoming weekend than Bank Holiday time).

 

Far from a washout on these latest outputs for this weekend, at least not in Devon (where we'll be). Even with such a shortage of summer in current forecasts/output, Friday and Saturday in particular look they may end up pretty pleasant. Just need a modest improvement with HP lingering a little longer (and yes I know that would be temporary) to keep Sunday a bit drier, delaying rain until Monday maybe? and I'd BANK given the trough dominated scenarios we're looking at now in general. 

Edited August 12, 2014 by William of Walworth

[knocker]

The anomalies for next week show little change with NOAA, GFS and ind ECM in agreement.

 

Thus surface analysis remains unsettled with temps below average and in places well below. The exact distribution of temps at this stage is impossible because obviously much depends on the synoptic set up and whether some areas, such as the south, will be in the path of a somewhat modified airmass

 

 

[bluearmy]

The gefs diagram for London has generally indicated an improvement for the last week of the month. The ECM extended precip totals are now more encouraging for an improvement.

I note matt Taylor on the 10pm N24 10 day forecast was not optimistic for next week but did say that things were looking more promising for the last week of the month. Surprised he would say that unless there was decent extended ens support for it. August might just save the best till last!

[SteveB]

Weather is still not looking very Summer like, with a continuation of the Autumnal theme... cool and showery.

 

 

 

Weekend looks okay on both Saturday & Sunday, showers around, but hopefully most will miss them.

 

Into next week and more of the same.

[William of Walworth]

On those rainfall charts from SteveB, tomorrow looks closer to a washout for a lot of places than do the subsequent three days (at least in the S).

[SteveB]

William of Walworth, on 13 Aug 2014 - 07:41, said:William of Walworth, on 13 Aug 2014 - 07:41, said:

On those rainfall charts from SteveB, tomorrow looks closer to a washout for a lot of places than do the subsequent three days (at least in the S).

 

I think the main theme over the coming week is just how cool it will feel, especially up North. They are the sort of Temps you could expect mid September, not mid August.

Edited August 13, 2014 by SteveB

[IDO]

Saturday looks OK for most as the ridge gives us a glancing blow: 

 

We then get 3-4 days of a cool N/NE flow with cool uppers as a LP develops over Iceland and heads east over the northern half of the UK. Good agreement on this inter and cross models:

 

 

That when the models have some divergence. GEM as it has a tendency to do of late builds a weak ridge from the west as it cuts off the trough and upper low. This gives a window of opportunity for a few days of settled milder weather (especially for the south) before the trough reconnects with the low:

 

 

GEFS has 33% support for this so no long shot but the other 66% keep us in the trough with these members split between developing the low or just extending the trough, like the Control:

 

 

The more rigorous LP system include: 

 

After D10 the GEFS are showing no real trend but no clear signal of a return to higher pressure though there is a cluster heading that way: 

 

 Control ends: 

 

ECM up to D7 is now aligned to GFS and we see some cold uppers coming down from the north: 

 

ECM after this goes with the upper low linking with the trough but doesn’t develop the low,

 

D8:   D9: 

 

So best day in the next 7 is Saturday, the other days no real washouts just changeable with average temps for the south and cooler further north. Next 8 days rain totals: 

 

 

Not too bad then, though we were spoilt in June/July so compared to those months disappointing. Potential in week 2 for a continuation of this or a wetter period with also a (smaller) chance of  a warmer few days.

Edited August 13, 2014 by i'm dreaming of...

[Captain Shortwave]

I think the main theme over the coming week is just how cool it will feel, especially up North. They are the sort of Temps you could expect mid September, not mid August.

The GFS is probably the lesser of two evils, the ECM is cool and unsettled to at least day 10 this morning with low after low being pushed down from the North/North west. Temperatures might reach average on the south coast but below elsewhere with showers or longer spells of rain.

 

GEM is a little better with the Atlantic ridge nosing in from time to time to give a few decent days but otherwise the theme of strong heights to the west and low heights to the east is the theme. 

[Frosty.]

The GEFS 00z mean shows a definate improvement beyond T+240 hours with a return to summery conditions at least for the south with +10 T850 hPa flirting with the far south and southeast meaning temperatures into the mid 20's celsius during late august with a more continental flavour to the weather, actually the mean shows a taste of that warmer, muggier feel early next week across the south for a short time. Looking at the bigger picture, the uk looks like being dominated by a deep trough to the north east for most of next week with average temperatures at best but feeling cooler due to the strength of the winds at times, temperatures should still reach 20-21 celsius across southern uk but nearer mid to high teens celsius further north but as time goes on, the influence of the scandi trough weakens and the azores anticyclone then edges closer to the uk, however, the emphasis of the most unsettled weather then switches to the north west of the uk due to increasingly lower heights in that region. So eventually we get a nw / se split with the south & east having warm / very warm fine spells and just occasional unsettled intervals with the north west of the BI becoming the most unsettled. 

Edited August 13, 2014 by Frosty.

[draztik]

Days 5-10 temp anom.

Next week looking decidedly chilly, according to the ecm ens.

[Man With Beard]

Excellent agreement this morning on the ops - a couple of drier days on Friday and Saturday before a low moves across the north on Sunday:

 

With troughs moving from Iceland down to the North Sea, though, I think the ops eventually move the trough slightly NE 7 times out of 10 - a bit like the GFS mean for T120:

Not much difference for the North and East, but puts the south-west closer to more settled conditions. Though even if this did happen, the Atlantic trough looks set to pounce - one possibility:

Quite a few ens members go for something warmer by D7 (perhaps 33%?), demonstrating that the impact of the Atlantic low is yet to be resolved:

Edited August 13, 2014 by rjbw

[Frosty.]

Days 5-10 temp anom.

Next week looking decidedly chilly, according to the ecm ens.

The GEFS 0z mean is warmer with +5 T850 hPa across the southern half of the uk meaning 20 c 68 f is realistic, feeling warm out of the wind and in the sunshine, cooler in the wind and rain. :-)

[Staffordshire]

Getting mixed signals as to what sort of temps we can expect in the West Mids this weekend, ideally i need it warm and dry, some models telling me 20-21, some models showing 16-17?

 

Can anyone shed some light please?

[knocker]

The GEFS, GEM and ECM anomalies are all singing from the same hymn book. I won't witter as it's self evident.

 

All giving below average temps with the ECM being quite dire but as I've mentioned before temps will vary according to the exact synoptic set up. They sure hope so in northern Scotland.

ECM

GEFS

GEM

 

[phil nw.]

I have moved 3 posts to the model banter thread here-

http://forum.netweather.tv/topic/79882-model-banter-moans-and-ramps-springsummer-2014/

 

where they were more suited.

 

Only posts containing your views on the models in here please all.

 

Thank you.

Edited August 13, 2014 by phil nw.

[Tamara]

At the present time, only this mornings London ECM ensemble suite is available to peruse for the medium/longer term temperature trends, but the parameter boundary extents of this data solidly support average to above average temperatures throughout the coming 10 days and beyond and there is not scope for sufficient deviation in this data to alter the mean trend to anything less than sub 20 to 25C for some time to come.

 

 

The first ten days, at least for the south of the UK, have verified reasonably well in terms of these expectations. However, self evidently, a very unpredictable seasonal ex tropical storm system coming into the equation towards the end of this ten day timeframe, and just at a time that patterns upstream have been significantly changing, has certainly cut short the possibilities apparent at the start of the month that the warmer than average summer conditions (certainly as seemed apparent for the south with some hopes for further north at times too) might prevail up towards mid month.

 

We cannot always account for tropical storm/hurricane developments and tracks, especially this far downstream from them as we are, and this is true of late summer in many years - its nothing new at all. Some years the tracks of these systems can favourably augment patterns this side of the NH hemisphere, so the glass can be as half full as half empty

 

What we can do though is look at the overall pressure and jetstream patterns that underpin the H500 anomaly charts often discussed on this thread to get an idea why they suggest what they do, and what might evolve with time in forecasting terms.

 

I've referred to the PNA forecasts a few times this summer and attempted to match our prevailing weather patterns (and expected associated surface conditions) against what these indices and forecasts suggest upstream over the Pacific, and which invariably go on to influence our weather downstream up to a few days later.

 

We have seen periods in June whereby troughing has set up in the altlantic to our west with downstream ridging eastwards ahead of this, over, and to our east. The trough has set up in the atlantic in association with High pressure over circa the spine of mainland US with, further upstream still, a trough in the Eastern Pacific, close to the US west coast. This pattern  (a -PNA) repeated, more notably in terms of surface conditions for the UK, during July and led to the peak heatwave and thundery conditions during the mid to last third of July as the trough was slow to advance eastward and break the plume down.

 

We have also seen the opposite pressure profile (a +PNA), with pressure high in the Eastern Pacific, low over mainland US and high again downstream in the western/central atlantic - and the Azores High, as a consequence of this arrangement, retracted westwards away from us in the UK. This happened briefly later in June, and is occuring more significantly now.

 

At this point its worth re-posting the PNA current analysis and forecast map to remind us of all this as described above over the summer so far as a whole, and as evidence in terms of the solidly +PNA spike that is occuring at this time (and which is likely to prevail for the coming 7 to 10 day period) and solidly underpins the relatively cool and unsettled spell advertised across the models.

 

 

 

So no surprise in the here and now that the attempted eastward ridging this coming weekend to settle things down again is very transient and thwarted, and there is full model support for a further downstream trough to be aligned over us and into Europe/Scandinavia and allow 'cold' (cool) air advection from the north to spread over the UK next week. The pattern this time being quite pronounced and sustaining, allowing CAA to penetrate further south across the whole of the UK

 

With the pattern so amplified in the atlantic in association with the retrogressed High towards southern Greenland, it fully supports the UK being in a polar air sandwich between the retrogressed High and the downstream trough extending into Scandinavia. Classic winter charts for many cold and snow enthusiasts amongst us, but at the same time, pretty useless and much less welcome for many of us at this time of year when we might still want to make the most of the longer days of late summer.

 

The MJO is mentioned fairly often on this thread in terms of its forecasted movements and how it might change fortunes in weather patterns for the UK. But, being obviously just one factor of many, and just used in this way by just posting forecasted movements across the tropical equator it doesn't necessarily tell us what it is, why its movements affect pressure patterns across the NH, and how and why it might change things in future forecasts. 

 

The MJO is a measure of eastward moving progress of tropical convection precipitation pulses, close to the equator, that typically recurs each month. Its worth being completely simplistic here and identifying this as an obvious weaker, lower pressure anomaly - especially when the tropical convection wave gets stuck in place over any one region. This is the case currently, with such activity rooted over the equatorial Indian ocean.

 

This map shows the MJO wave in terms of its suggested position by precipitation anomaly charts. Clearly the enhanced blue areas in the western Indian Ocean show where the greatest intensity of this rainfall is suggested to lie accordingly. Furthermore, the orange shaded dry anomalies gives good indication for the presence of High pressure further eastward and northward into the Pacific - which underpins that +PNA forecast. It is only towards the end of the 10 day period that the +PNA signal starts to properly wane as the precipitation signal is suggested to edge a little eastwards as it weakens.

 

 

These precipitation anomaly forecasts give just one knock-on illustratration of how stuck and slow to change the pattern far upstream over the western hemisphere and Pacific is expected to be. We should not expect any change in our fortunes all this way downstream within the next 10 days, with the pressure amplified over the atlantic accordingly, and the downstream trough fixed in position into Scandinavia.

 

Its a case of watching over coming days for consolidation of any hints beyond the 7 to 10 day period for the atlantic to de-amplify in accordance of relaxation of the prevailing pattern.  A modest warming trend is still indicated in the longer term London ECM ensembles to reflect the possible background changes as discussed further out (and as illustrated previously by others in the thread, this is reflected by GFS data)

 

http://www.weathercast.co.uk/meteo/eps/ensemble-tt6-london.gif

 

 

At least there are some hints that the last period of August may well produce something of a return of more settled summer weather with temperatures returning from slightly below average to closer to average and perhaps slighly above as the Azores high is allowed to ridge eastwards, eventually, from its retracted and amplified westward position. Taking into account the first 10 days of August (which, although increasingly changeable, was reasonably acceptable and quite warm for many up to the arrival of Betha this weekend) then an improved last week or so of the month would put August into a positive context as not being by any means a write-off or wash out month and nothing comparable with, say, 2012 - albeit a step back from the upward momentum through and into the mid part of summer

[carinthian]

A great post again from Tamara with added in depth knowledge that seems reasonable in its conclusion to my mind. Strange summer across much of Europe, UK fairing well so far, particularly in the south. Scandinavia, a cold June and hot July, Germany in the north and east of the country having one of the warmest summers for a decade. The Alps fairly cool and cloudy. Plenty of thunderstorms from France to Sweden. A great summer for weather fans all over the continent. Let hope the winter delivers proper cold this coming winter season.

[Summer Sun]

UKMO continues to show some Autumnal charts this afternoon with low pressure centered to our east dragging down some cooler air from the north, the east coast could be looking at some gale force winds at times next week day time temperatures are likely to be lower than average for the time of year with some chilly nights

 

 

So after a couple of calmer days it looks like next week will be similar to this week minus an ex hurricane

[phil nw.]

The charts show a very good example of a blocking high out in the Atlantic which in effect splits the jet stream.Most of the energy going north across Greenland and then back down towards NW Europe which sharpens the downstream upper trough over the coming days.

 

The situation at T96hrs

 

 

The next low coming from the Iceland area with more unsettled conditions spreading south east by Sunday followed by a cool showery period into next week with those winds from the north west.

 

[Mucka]

Some very nice winter synoptics appearing in the 5 to 10 day range - shame it is August. 

 

[summer blizzard]

Very low thickness values for the time of year even at day 8.

 

[Summer Sun]

ECM hinting at something more settled developing around the BH weekend the 00z ensemble showed this as well

 

 

00z ens

 

 

Would be good timing if it did arrive a long way to go yet though