Model Output Discussion 26/08/2012

[Milhouse]

ECM 12z going down a similar route as this mornings 0z. Dry and pleasant for the most part with warmth building later on in the week and into the weekend asociated with a push of very warm uppers from the south.

[Summer Sun]

ECM 12z going down a similar route as this mornings 0z. Dry and pleasant for the most part with warmth building later on in the week and into the weekend asociated with a push of very warm uppers from the south.

ECM looks lovely again tonight it will feel very pleasant in the sun mid 20s is possible for the south with high teens low 20's further north I would think

[Milhouse]

ECM looks lovely again tonight it will feel very pleasant in the sun mid 20s is possible for the south with high teens low 20's further north I would think

The run ends with low pressure encroaching into western parts brining the threat of rain here. However, for the bulk of the UK it serves to maintain the southerly flow and associated warm temperatures.

[Summer Sun]

The run ends with low pressure encroaching into western parts brining the threat of rain here. However, for the bulk of the UK it serves to maintain the southerly flow and associated warm temperatures.

Yep a warm southwesterly flow If I'm looking at that correctly, yes it will often be cloudy and or wet but temperatures would certainly be anything but cold but before that next week is certainly looking like a decent one for many at some point

[Frosty.]

Another settled outlook from the Ecm 12z and with very warm T850's wafting northwards from the continent in FI, not so pleased with the ukmo 12z at T+144 as it shows the anticyclone splitting as a low heads southeast towards nw britain but the ecm looks settled apart from the potential for a few heavy showers if we do end up with a very warm and humid southerly flow towards T+216 hours.

[Gibby]

Here’s my take on the 12zs from GFS UKMO and ECM taking in the GFS Ensembles and Jet Stream Forecast along the way.

All models show a basic pattern of High pressure down to the SW between now and Wednesday before it moves over the UK late next week. The net result will be a lot of fine weather for all areas but the period between now and Tuesday sees some more unsettled weather for Northern areas as troughs pass East from the Atlantic while Southern areas see a couple of weak fronts cross SE too tomorrow and Tuesday. From Wednesday on the weather becomes fine and warm for all areas with sunny spells and temperatures well above normal.

GFS then gradually returns more unsettled weather for the North from next weekend which gradually extends to all areas over the course of FI

The GFS Ensembles show a fine spell for Southern locations with 850’s gradually falling off as we approach mid month. Rainfall too is shown to increase by the end of the run for London. Further North the ensembles show much indecision after the first week with some widely different outcomes between the members with rainfall here more common through the run.

The Jet Stream continues to blow on a more Northerly track close to Northern Scotland for the next few days and moving still further North next week as the High pressure moves over the UK.

UKMO shows High pressure over Germany next Friday with a ridge west over Southern Britain. A trough is threatening the West later though the weather would continue fine and warm for most areas with an increase of cloud for the North and West late in the day.

ECM gradually moves the High pressure away slowly Eastwards late in its run with a deep Low in mid Atlantic pushing a trough NE and increasing the instability of the air in a SW flow. After a dry, sunny and warm weekend the weather would slowly deteriorate as we move into the second week.

In Summary there is good agreement now on a fine and warm spell from midweek and it looks like the North could share in some of this too. The longer term trend taken from tonight’s output is that things look like they will gradually turn cooler after next weekend with the chances of more unsettled weather moving into many areas on the increase.

[A Winter's Tale]

Tonight, the rainfall in the NW will move further SE but it'll become lighter and patchy as it does so. Some patchy rain may continue to affect the NW Highlands but largely dry in the rest of Scotland and Ireland with a few clear spells - the best of the clear skies likely the nearer you are to the north sea. More overcast across large parts of England as the remnants of the rain over Scotland move further south down the country and it could be drizzly for a while in the Welsh hills. Early morning clear skies should vanish in the SE as cloud increases from the NW. And, tomorrow morning, for a time some persistent and at times heavy rain could affect the SW of England and Wales. Ireland and the northern half of the British Isles should have a very decent morning with plenty of sunny intervals for most away from some of the western coastal areas where cloud cover could be be possible at times. By lunchtime there could still be some patchy light drizzle in very southern areas of England and skies could still be overcast as far north as Manchester and Hull. Sunshine may become even more unspoilt and widespread in the north and parts of Ireland, again always more likely to be cloudy at times on the western coasts. Through the rest of the afternoon, cloud cover may still hang on to the southern third of England with widespread sunshine for many areas but cloud cover should increase in the NW of Scotland as a front may bring some rain to the Islands and parts of the highlands.. Overall, maximum temperatures should be at around 18-20C for most. Into the night, some rain may hang on to western areas of Scotland with some showers near the coasts and one or two spots elsewhere in Scotland. Largely dry away from Scotland but little in the way of completely clear skies - minima at 13-16C.

Monday is a reminder of how September is one of the warmest months of the year despite it now being part of the official summer as defined by the met office. You can see in the chart below that temperatures are widely above 20C across a good deal of England and Wales and some pleasant temperatures across parts of Ireland and Scotland. Temperatures could even reach 25C or more in the far south.

However, sunshine on Monday is likely to be quite short-lived at times and hardly widespread at all and in the NW, skies here should be overcast as another front arrives and bringing rain with it to Ireland and Scotland. The rain should clear leaving a drier night with some light showers near the coasts on the NW and the Lake District. Again, it'll be hard to find widespread clear skies but clear patches should be expected although in Ireland and western Scotland skies are more likely to stay overcast. Quite mild, with lows of 14-16C.

Tuesday at the moment looks like a dry day other than the odd shower in the NW but good spells of sunshine are expected to be illusive for most of us - in other words, Tuesday is likely to be a cloudy day. Slightly cooler than Monday with highs of 16-21C. Light rain and showers could become a little more widespread and persistent in western Scotland during the night but the south of England could have a better night for clear skies and observing the stars. A cooler night too with lows of 10-13C.

Wednesday is looking like another dry and cloudy day, temperatures could max at 16-20C. And the picture at the moment is similar for the night - a cool night too with lows of 9-11C - but there are signs that there could be a threat of rain for far NW areas from a front.

High pressure near the SW could expand to influence the British Isles beyond with some warmth and the threat of rain in the NW at times but beyond next week remains uncertain. But my guess at the moment is that high pressure to the SW may be a feature for the first half of the month with some wet periods associated with low pressure systmes and occasional blips of colder air from the north at times and I'm looking forward as to how the models map out the outlook for September in the coming days and weeks.

[Gavin Hannah]

Having looked at the GFS output this morning... Run show high pressure dominating for the next two weeks. North being more slightly more unsettled. The depression out in FI, if it materialists could have some interesting influences on the weather beyond two weeks.

[Frosty.]

I really don't think there could be a better example of a nw/se split than what is showing on this mornings GFS 00z operational run, it's a classic and shows a prolonged very warm and settled FI for the southeast quarter of the BI with a continental Anticyclone in control. The week ahead is looking pretty good for the southern half/third of the uk with high pressure dominating and temps into the high 60's to low 70's although occasionally with more cloud and the odd patch of rain as weak fronts drift southeast into the high but it's a very different story for the far northwest and north where it will be generally cooler with a wet spell tomorrow and with more rain on thursday and again next saturday, also some drizzly patches on other days but some drier and sunnier intervals but then into FI it's a very unsettled pattern with low pressure close to nw scotland so the rainfall totals would be large although it more than makes up for the very dry first half of the summer up there. It could not be more different for the southeast with barely a trace of rainfall until beyond T+300 hours.

[mushymanrob]

looks like an early autumn warm/hot spell is likely by next weekend, the only thing in disagreement is the timing. the fax, ecm, ukmo, all suggest warm settled high pressure dominance by next weekend whilst the gfs gets there eventually, lagging by a few days. either way its looking good for a widespread warm, dry, eventually sunny period.

[Frosty.]

Another good ecm run for warm and settled weather, a strong anticyclonic continental block which would stop atlantic depressions from making many inroads into the uk, with mainly just the northwest of the uk affected by low pressure but the anticyclonic block holding firm to the southeast and this pattern persisting well into this month, it's a better run for the north than the gfs 00z with more in the way of warmth and sunshine further east but nw scotland still looks fairly changeable/unsettled, especially early and then again towards the end.

Edited September 2, 2012 by Frosty039

[Frosty.]

Ecm 00z looking very settled towards the south and east of the uk for the duration although signs of a change to perhaps a more mobile atlantic regime from mid month.

Edited September 2, 2012 by Frosty039

[TonyH]

Weather guide blog for the coming week only for Wales and the Midlands though:

http://forum.netweather.tv/blog/309/entry-4472-weather-guide-monday-3rd-to-sunday-9th-september-2012-west-wales-and-the-midlands/

[mushymanrob]

.... and now the 06z gfs is in agreement with the ecm and ukmo, looking like a heatwave next by weekend for a good chunk of the uk.

Edited September 2, 2012 by mushymanrob

[AWD]

.... and now the 06z gfs is in agreement with the ecm and ukmo, looking like a heatwave next weekend!

Yep, looking good for some very warm temps for September next weekend.

Then around the 10th/11th with the warm air still in place and pressure dropping ( both the ECM & GFS show this now ), perhaps some thunderstorms could break out too, so something for convective fans to watch, albeit a long way off yet!

[Summer Sun]

Settled and warm this week FI is interesting however for storm fans

[Dorsetbred]

Settled and warm this week FI is interesting however for storm fans

Could you drop it 75miles south please?

[Iceberg]

A lot of uncertainty regarding that low which is ex hurricane Leslie according to the models, it will def. be in our part of the Atlantic but its speed, direction and strength have a wide range of possibilities.

[MP-R]

The GFS seems to have been pretty consistent the last few days showing a very settled outlooks for the first week of September with the high that builds midweek, eventually transferring eastwards with the Atlantic returning around the 10th-12th of the month. Every now and again it looks like a possible thundery breakdown could occur but that will all depend on the alignment of the isobars and antecedent temperature/sunshine.

FI continues to show a more unsettled outlooks with a significant Atlantic storm still showing for the 14th/15th.

From a personal point of view, I'd certainly be game for the last few model runs if there was a likelihood that the Atlantic returns the week after next.

[SMU]

I would tend to agree with Stewart although with one caveat-

with increased wavelengths of mid lattitude highs developing towards the pole - due to the reduced snow cover & arctic ice cover I think that the 500 MB anomaly for Sept + OCt looks a lot like the second one above-

However because the polar cell will be expanding erratically south through a meridional jet as opposed to gently south across a sinuous jet I would say the the mean trough & the quasi stationary Euro high with be pushed maybe 5-10 degrees south - especially as we head to Oct -

The net effect of this will be less of an influence from the South & more unsettled influence from the North & NW-

I expect Iceland to be below average as well- I think we could see some early frosts in the extremem North & the polar air escapes South rather that South east- / east from greenland....

S

http://www.meteociel.fr/modeles/jma/runs/2012090212/JN192-21.GIF?02-12

Snow over the mountains

ECM developing similar with the GH

S

[Frosty.]

There are signs of a change to something more unsettled by the end of next weekend onwards on the Gfs 12z but there is a lot of uncertainty because pressure looks like remaining high to the east of the uk and the block could force atlantic lows to stall to the west or southwest or even retreat back west into the atlantic and just help to maintain the feed of warm/humid breezes from between ssw'ly to se'ly. It is not until the gfs develops some major autumn depressions that the stagnant pattern gets a kick and then autumn finally gets into full swing but for the week ahead the models are showing a lovely spell of early autumn weather with plenty of sunshine and light winds with temps well above the seasonal average, still a bit mixed in the far nw and north but the gfs 12 is a better run for these areas too.

[William of Walworth]

A lot of uncertainty regarding that low which is ex hurricane Leslie according to the models, it will def. be in our part of the Atlantic but its speed, direction and strength have a wide range of possibilities.

And location by the time it gets here. Pretty much impossible to nail location as far ahead as 15th or so of September, at this early stage.

Don't forget the possibility (note emphasis!) of anticyclonic displacement of such mega-Low pressure systems.

Edited September 2, 2012 by William of Walworth

[Summer Sun]

ECM is very late tonight only at 48h

Edited September 2, 2012 by Summer Sun

[Gibby]

Good evening. Here is tonight’s look at the 12zs of the big three.

All models show High pressure firmly in control of the weather for most of the UK this week. Its centre drifts over the UK and out to the East by next weekend ensuring plenty of warm and sunny conditions as we move into the second half of the week and away from the weak troughs that will move SE over Tuesday and continue plaguing the far North at times.

GFS then shows a more disturbed pattern emerging as we move into FI with Atlantic depressions and eventually an ex tropical storm all playing a part in unsettled conditions for all as we move into the week after next.

The GFS Ensembles continue to programme 850 uppers above the long term mean for some considerable time to come. A gradual fall off does occur towards the end of the run with rainfall on the increase as we move towards mid month.

The Jet Stream continues to stay well North for the reliable future blowing West to East near Northern Scotland.

UKMO for noon next Saturday shows High pressure sliding away over Europe next Saturday with a weak trough bringing the risk of a little rain towards the NW during the day.

ECM too shows High pressure sliding away next weekend with fine and bright weather giving way to a more unsettled phase early next week. By midweek an ex tropical storm in mid Atlantic pumps up a ridge over the UK bringing back fine and warm conditions at the end of the run.

In Summary the weather is set fair this week with High pressure drifting slowly East across the UK before the weekend. Later in the output an ex tropical storm causes a wobble in the models and it’s the behaviour and placement of this which will determine whether we see more warm sunny weather or if we turn more unsettled and windy or potentially stormy late next week.

Edited September 2, 2012 by Gibby

[Milhouse]

ECM is very late tonight only at 48h

Its fully out on meteocleil. Remaining warm and settled for all until the end of the weekend with the south east squeezing out another warm day on Monday. More unsettled conditions moving down from the north for Tuesday and quite a chilly day to come across Scotland. More settled but cool for day 10.