Model Output Discussion - September Onwards

[J10]

General pattern not changed at the moment, but a trade off between longevity, heat/warmth and sunshine at the moment as highlighted above.

If we are to look at detail at the latest GFS run (00Hz) wind direction is mostly of from a S to SE vector from Wednesday through to Sunday, with a period of more of a SW flow late Wed-early Thursday. ECM/UKMO also tends to agree with this to a certain extent. 850Hpa temps in the range 13-15c for quite a few days. GFS currently gives max temps of 23-25 for much of S and SE England, 21-23c for many other areas. So a few degrees higher than this very possible given GFS prediction history.

Cloud amounts look very low on the high res predictor on WZ for much of England and Wales from Wednesday through to the weekend, however we all know that cloud prediction can be very problematic.

[summer blizzard]

This morning's runs have introduced more of a westerly component to the southerly flow, as well as the GFS/ECM drifting more towards yesterday's UKMO, so for much of Scotland, Ireland and the western side of England and Wales, sunshine and dryness are looking less certain than on yesterday's runs. Central and eastern England are still looking set to be very warm and sunny though, and with a stronger south to south-westerly flow, the GFS shows even higher temperatures late in the week than any of yesterday's runs. .24-25C maxes are shown across a large area on Thursday, and that's before correcting for GFS's tendency to underdo maxima, so some date records may end up under threat.

I am pretty sure that the relevant date records are all from 1895 and around 30C, so unlikely to be beaten.

In regards to the the hot spell itself, the ECWMF models does seem to have moved the centre closer in line with the GFS12z yesterday so i am a little sceptical that we will be able to maintain the very high maxima levels (that said they should still be within 2-3C of the peak). GFS has backed off this senario however. Both would probably yield 27C/28C as peak maxima.

In the longer term and ECWMF and GEM do not break down properly within ten days however GFS breaks down completely at day 11. GFS and ECWMF do both have the high centre west of the UK at day 10.

Edited September 24, 2011 by summer blizzard

[Frosty.]

Typically what the models give one day, they take away the next day..after months of wind and rain across nw britain it appeared yesterday that a fine and warm week was on the way but today it seems we are back to the same old story with the nw / se split, nw britain once again will be exposed to spells of rain & strong ssw'ly winds in the coming week although at least it will be mild and then next weekend there could be a ridge giving a calmer interlude but the main focus is on the sunny and increasingly warm week ahead across southern and eastern england with a blocking high to the east with temps between 25-27c by midweek and through to next weekend. Further into FI shows a gradual erosion of the fine spell with temps dropping closer to average but the north and north west of the uk remaining unsettled but cooler than next week. No sign of any early cold snaps through mid october yet but hopefully we will have a cold spell later in october.

[J10]

Typically what the models give one day, they take away the next day..after months of wind and rain across nw britain it appeared yesterday that a fine and warm week was on the way but today it seems we are back to the same old story with the nw / se split, nw britain once again will be exposed to spells of rain & strong ssw'ly winds in the coming week although at least it will be mild and then next weekend there could be a ridge giving a calmer interlude but the main focus is on the sunny and increasingly warm week ahead across southern and eastern england with a blocking high to the east with temps between 25-27c by midweek and through to next weekend. Further into FI shows a gradual erosion of the fine spell with temps dropping closer to average but the north and north west of the uk remaining unsettled but cooler than next week. No sign of any early cold snaps through mid october yet but hopefully we will have a cold spell later in october.

GFS gives temps of 22-23c for Wakefield for Wed - Saturday next week with cloud levels of 0-20%. seems pretty good to me. (Net Weather 16 day look ahead - GFS 12Hz)

Indeed for much of England and Wales it looks dry, warm/very warm and bright or sunny for the end of next week. A little more cloud for Ireland and Scotland, and perhaps some coastal fringes for the NW of England (worst case scenario), but even here it is set to be turning sunnier on the Friday and Saturday. Of course it can change and nothing is nailed on, but looking promising for most atm.

I can certainly understand caution for some given some recent weather.

[Grimsby Snow Lover]

Having looked through the ensembles from tonights 12z the operational from the GFS seems to be on the high side compared with the bulk of the other runs. There still appears to be a big dip as we head into October. Not sure what to read into this but a more seasonal feel could be on the cards during the first week in October.

[Gibby]

Hi folks. Here's my take on the 12zs tonight.

GFS shows a SW flow over the UK with weak fronts near to the West with attendant cloud and a little rain in places, especially later tomorrow. From Monday on pressure builds further to the East of the UK with Southerly winds pushing North over Britain bringing increasingly warm and sunny conditions. This trend continues through the week and into the weekend with some unseasonably high temperatures in the east and SE. Over the weekend a slow trend to less warm conditions begin as the southerly flow weakens with low pressure close to the SW bringing some rain there for a while. High pressure then re-establishes itself close to the North with a continuation of fine weather though temperatures both by night and day would steadily lower with fog an ever increasing feature nights and on into the mornings.

UKMO tonight shows tomorrow being rather cloudy but on the warm side especially in the East with a trough close to Western Britain intensifying showery rainfall later. Thereafter. the model also shows High pressure building strongly on a slightly more Southerly trajectory than GFS with the resultant tilt of wind towards the SSW keeping Northern and Western regions rather cloudier but still rather warm. Further South and East air floods North from Europe bringing increasingly warm or very warm conditions with sunny skies.

ECM follows UKMO closely for the next few days wth occasional rain in the NW and SW tomorrow close to weak fronts. In the days that follow things warm up quickly with increasingly sunny and very warm conditions for many SE and eastern areas. Further North and West with onshore winds cloud could be more problematic though even here some warm sunny spells are likely. Later in the week and over the weekend the Southerly drift drops out encouraging the formation of overnight fog, slow to clear for some in the mornings with warm and sunny afternoons still. Towards the end of the run pressure falls slowly from the North with firstly an increase of cloud cover over the UK and a slow fall off in temperature and eventually a marked drop in temperature as a cold front sweeps SE late in the run.

In Summary tonight it still looks odds on for a notable late spell of very warm summer weather next week. The intensity of the heat will be concentrated on SE and East England where some late September heat records could be approached if not beaten with the heat modified as you move further West and North from those areas. However, after a little rain tomorrow and occasionally elsewhen in the far NW the weather should remain dry everywhere else. The longevity of the event is still open for debate but on tonights evidence it looks likely that next weekend will see a dip in temperatures with ECM showing Autumn's door opening widely by Day 10.

[J10]

A bit more detail from the ECM on this link recently posted on these forums. (these have 3 hr timeframes)

http://www.wundergro...i=0&ls=0&rad2=0

Click on models on Right Hand Side

[NorthYorksWeather]

Having looked through the ensembles from tonights 12z the operational from the GFS seems to be on the high side compared with the bulk of the other runs. There still appears to be a big dip as we head into October. Not sure what to read into this but a more seasonal feel could be on the cards during the first week in October.

Ecm maybe the first model to clock on to this cooler spell in October. Will feel very autumnal if that run verifys. May change but could be the start of trend, defiantly one to keep an eye on. All eyes on the 18z.

[Grimsby Snow Lover]

Thats exactly what I was thinking, there are a lot of runs shown in the ensembles that could support the ECM 12z ,which showing quite a cool NW wind developing after next weekend. Is it a new trend or just a blip? Time will tell I guess. Lets see what the GFS 18z run suggests.

Edited September 24, 2011 by Grimsby Snow Lover

[snowlover2009]

There is definitely a trend for a pattern change for the following week(october) after the warm spell, it could be a big shock to the system. from 20 to 26c, to 9 to 15c in the first week of October if ECM tonight is to go by. Some gfs runs go below -5 air uppers, which would result in temperatures being below 10c for northern parts in particular, I would imagine. But we will see. I am not a fan of unseasonable weather, so sorry if I seem to by passing the fact.

[bluearmy]

it would be unreasonable for temps to stay in the mid twenties for more than a few days late sept/early oct. so its inevitable that conditions will cool down. just how far they drop is the question and i would suggest that, looking at ecm 12z fi, it is a very progressive run and very unlikely to verify. average temps of low to mid sixties seems to be where we'll settle - in the south we could be a bit higher on occasion, in the north a tad cooler.

[damianslaw]

Thats exactly what I was thinking, there are a lot of runs shown in the ensembles that could support the ECM 12z ,which showing quite a cool NW wind developing after next weekend. Is it a new trend or just a blip? Time will tell I guess. Lets see what the GFS 18z run suggests.

Yes its a long long way off, but ECM is showing a very plausible evolution this evening - i.e. heights moving to our NW and far enough westwards to pull down a cold front and thereafter cold northerlies. Background signals suggest heights are most likely to move to a position to our NW, so a cooldown is inevitable, this isn't July... how cool remains to be seen, it would be highly unusual to maintain next weeks synoptics for any great length of time whatever the time of year and more so now we are entering October.

In the short time - a very quiet spell of weather, all eyes on cloud levels and the flow of air, a SE/S wind would be excellent for the whole country, a southerly good away from the far west and northwest, a S/SW flow only really good for central and eastern areas, western parts especially northwest parts would see lots of high cloud with chance of drizzle/mist on the hills and coasts. Temps above average for everyone, exceptionally so for central, eastern and southeastern parts with many days above 70f, our best spell of weather since late April, can't help but say it is a bit too late in coming, could have done with it about 3/4 weeks ago.

[summer blizzard]

A trend may be emerging, both ECWMF12z and GFS18z have a northerly breakdown, ECWMF at day 10 and GFS at day 13.

[SP1986]

It was at day 12 yesterday on the GFS and day 10 yesterday on ECM so it is a trend but it's one that is being pushed back somewhat.

It will break down though, of course, but really the actual warm spell hasn't occurred yet.

[ZONE 51]

This is an animation(gif) of the GFS 18z surface pressure up to 144hrs from sunday evening.

first and last frame slowed so you know where start and end is!

[ZONE 51]

play once then it would loop better on 2nd run.

[johnholmes]

The 500mb anomaly charts are showing differences and changes now and this lends doubt as to what the actual evolution is going to be from next weekend onwards.

Some of the differences I think stem from the models not being very sure how to deal with a feature in mid Atlantic, ECMWF and GFS show it as a cut off upper low. NOAA 6-10 days shows it but the 8-14 day outlook simply warms it out. Whether this is an ex tropical storm that has migrated well south into the Atlantic is unclear. It will probably take several days before its reasonably clear of the weather pattern post next weekend.

Edited September 25, 2011 by johnholmes

[Thundery wintry showers]

The longer-term is uncertain but there is pretty strong agreement on next week now, with the very warm dry sunny weather extending north and west to most parts of the country by Wednesday/Thursday. Scotland keeps more of a SSW flow which may bring some cloud and rain into the west of Scotland, and Ireland looks set to be rather too far west with some cloudy wet weather likely, but the rest of the country is currently looking odds-on to stay in the clear.

[Gibby]

Good morning.

GFS today continues the theme of a dry and warm week to come and very warm for many. Today and tomorrow will be somewhat cooler and fresher though and many places may even see a little rain in the next 24hrs as a weak trough tracks SE tonight. Tomorrow would see bright weather for many Northern regions though cloud would be quite persistant in the South as the front decays in situ. Things become straightforward then so that between Tuesday and Sunday increasingly warm and sunny conditions spread North across Britain in response to High pressure out east. Temperatures would reach the low 20s for many and in the SE the mid to higher 20s are possible late in the week. After next weekend temperatures leak away as we lose the Southerly flow and pick up a more NE flow around High pressure out to the NW then. Settled weather though would persist but with the ever lowering temperatures by day and night fog and patchy frost could develop in places.

UKMO also shows a fine and increasingly very warm week. It maybe that the highest temperatures occur quite late in the week as a SW flow innitially influences the weather for many Northern and Western areas with further rain in the far NW. By Thursday though this has backed Southerly allowing some of the warm air to advance North through most areas with sunny and very warm conditions likely in the SE pulling temperatures to near record levels there Thursday/Friday.

The Fax Charts show the warm air being sucked Northwards through the week with any troughing restricted to the far NW after Tuesday.

ECM finally follows a similar route through the week with the highest temperatures in the SE by the weekend when things start to cool down slowly for most places as High pressure transfers to the SW of the UK allowing progressively colder air to move steadily South over the UK by the end of the run.

In Summary after the next 24 hours most of the UK can expect an unseasonably warm spell with sunny spells. The highest temperatures look likely in the SE and Eastern England where 27C is possible by Friday before a slow cool down thereafter as pressure patterns change alignment somewhat. In general throughout this morning's output rainfall amounts for the UK look like being well below average for the next 10-14 days.

[minus 9]

The 500mb anomaly charts are showing differences and changes now and this lends doubt as to what the actual evolution is going to be from next weekend onwards.

Some of the differences I think stem from the models not being very sure how to deal with a feature in mid Atlantic, ECMWF and GFS show it as a cut off upper low. NOAA 6-10 days shows it but the 8-14 day outlook simply warms it out. Whether this is an ex tropical storm that has migrated well south into the Atlantic is unclear. It will probably take several days before its reasonably clear of the weather pattern post next weekend.

[SP1986]

After a very warm week ahead, the 6z generally gets cooler beyond next weekend (as you would expect anyhow), as high pressure moves eastwards and introduces a cooler airmass. Not surprising at all, this spell of well above average temperatures will probably 'only' last for 4-5 days, but what is unclear is how dry it will be.. certainly if high pressure maintains its area, then it will be very dry for the forseeable future. This may in turn (in the future) allow the first widespread frosts of Autumn (but that is way way off at the moment)

[J10]

Good charts this morning for warm/very warm weather next week. If this had happened in mid summer, would 31-32c be the most likely maximums in favoured spots in the SE.

[ANYWEATHER]

From Summer Sun to Winter Cold in less than a week!! Gfs 06z run is a stonking run for the heat and cold lovers! You couldnt make it up! What it does go to show ,is that despite this weeks very warm weather ,the cold season in now not too far away and is now building very cold air in and around the Artic...

Edited September 25, 2011 by ANYWEATHER

[Costa Del Fal]

The GFS ensembles tell a slightly different story with regards to the first week of October. Both the Pressure and 850hPa temps are right at the bottom of the rest of the members during the 4th-6th especially. Only the Operational really went for the cool Northerley. The rest kept pressure relatively high and decreasing only very slowly and the same applies to the upper temps. In reality, most of the members do not go for any sudden switch to much cooler weather next week, just a slow cool down on what will be a brilliantly warm week for many of us. The ECM I think paints the most likely outcome with the slow transition of very warm uppers to cooler ones with High pressure building in the N Atlantic/Greenland and opening opportunities for Northerlies as the last ECM frame shows but not at the rapid transition the GFS shows imo.

Edited September 25, 2011 by Blizzards

[SMU]

Ive been following the models daily as we gear up for the ups & downs of WInter-

Hopefully we will see the first retrograde pattern of the season emerging in around 8 days-

If we can get enough westerly retrogession then we will be talking of the first frosts & possible wintry flurries over the scottish mountains-

That seems an awful long way as it stands- with 25c being reached this week-

I will be making the most of the sun, but a growing expectation that winter is closing in- only a shade over 8 weeks away-

Steve