Model Output Discussion - September Onwards

[Weather-history]

Some very warm uppers on ECM 0z

http://www.wetterzentrale.de/pics/Recm2402.gif

[Gibby]

Good morning folks. Here's a look at the outputs of the 00zs from GFS, UKMO, The Fax Charts and ECM.

GFS today would look a dream if it was mid July. Nevertheless, even though its late September there's still room to verify a late taste of summer. The next few days continue with a North/South split with todays light showers in the south and heavy ones in the North dissolving away through the day today. Things would steadily warm up over the weekend with plenty of cloud still about with weak troughs on Saturday and a more active one on Monday bringing the risk of rain to many. It's from Tuesday on that things turn summery as High pressure sets up shop east of Britain with very warm South to Southeast winds wafting up over Britain from the Med with warm sunny spells with temperatures up to around 25-26C each afternoon in the Southeast and near 70F elsewhere away from the far NW. In the outer reaches of FI a breakdown is shown with low pressure from off the Atlantic dislodging the high pressure to bring cooler, wetter and windier conditions to all areas with time.

UKMO brings warmer conditions North over the UK over the weekend with winds from the South or Southwest. There will be plenty of cloud around over the weekend with a little rain here and there but a lot of dry weather too. Into next week and High pressure strengthens to the East with some bright and very warm weather for the SE though rather large cloud amounts elsewhere could restrict very high temperatures with an Atlantic element to the breeze.

The Fax Charts indicate a warm SW airflow developing over the UK in the next 48hrs. With Low pressure passing close to the NW troughs would continue to bring rain and wind at times there while southern areas see the best of the dry and warm conditions. There are weak troughs meandering SE over Southern Britain too over the weekend so its unlikely to be sunny in the timeframe of the fax charts but amounts of rain in the South should be small with high pressure not too far away from the SE.

ECM finally is a dream for anyone looking for a Autumn heatwave. Over the next three or four days the weather will slowly become warmer but stay rather cloudy as weak troughs get caught up in the flow. The last of these on Monday is shown to give a windy day with some rain more widely but thereafter pressure builds strongly just to the east of Britain sucking up very warm and sunny conditions Northwest from Tuesday of next week. Temperatures would soar to 25-26C by day in the South and Southeast and be well into the 70s further North too if these charts verify. The pattern then remains unchanged right out to the end of the run.

In Summary today the charts of the last few days have not indicated highly settled and sunny weather that some members on here have tried to imply but this morning's certainly do. With both GFS and ECM putting High pressure near to Germany orientated in a way to pull very warm air up from the Med if they verify it could easily give most areas a sustained spell of sunny and unseasonably warm weather from Tuesday of next week. With regard to UKMO it is hard to read too much into its evolution in the limited timespan we are able to see and it does look a bit more tentative than the other two but with ECM on board as it is there is a strong chance of a Autumn heatwave next week. GFS does eventually break things down out in FI but ECM looks set fair even at 240hrs to maintain the very warm theme on.

[johnholmes]

All 3 500mb anomaly charts continue to show the settled spell with an upper high over and east of the UK with the upper trough 20w or even further west on the NOAA chart giving 500mb wind flow on all 3 into the UK from between SW and south. As each chart is issued this flow is shown to be backing. So out to 2-5 October then the upper ridge looks like holding and may do further out than that.

[Liam J]

It could only happen in the uk, to little to late imo regarding this settled warm spell being progged next week.

I'm sure it will be nice to have some settled conditions for a time but I'm not a fan of unseasonably warm weather at this time of year. The days are getting much shorter, nature and wildlife are now into there autumn transformations.

I'm sure the models are well over cooking the temps, we are well away from the core summer months now and heading into October the sun is getting very weak and daytime heating is getting less by the day.

[Milhouse]

15C uppers brought 28c on the 21st September 2006 and 1st October 1985 so if anything i think the GFS could be undercooking the max temps. Looking at the models i'm not sure you could get any closer to the ideal synoptics for maximum warmth. Therefore i would say 25/26c is achievable, which has been recorded in past Autumn warm spells

[I remember Atlantic 252]

The GFS this morning seems to continue its "better late than never" summer theme for next week with temps progged to be in low to mid 20's even in the north with Scotland registering temps of 20c. What else is quite nice to see is that GFS is showing this to last a week atleast with night time temps some days remaing around 15-18 degrees counrtry wide and as for any return to an atlantic regime, that is now considered as being way out in FI.

However, one thing I've learnt is that the GFS can over cook temps and 20c can quite easily turn out to be a cool 15c. That said, high pressure influence backing westward over the UK is most certainly within the reliable time frame, so what will this mornings ECM have to say about LP influence? because it was favouring the development of a new LP core to dig in toward the UK from the west and assert itself putting a spanner in the works of any chance of a sustained spell of decent weather lasting more than just a couple of days.

Yeah like I remember last year on 8-9 0ct, very similar setup with SE winds, GFS was saying 20C and higher, and my max was 15C due to staying cloudy, If it stays cloudy max temps could only be 17C even in south

[Weather Boy]

15C uppers brought 28c on the 21st September 2006 and 1st October 1985 so if anything i think the GFS could be undercooking the max temps. Looking at the models i'm not sure you could get any closer to the ideal synoptics for maximum warmth. Therefore i would say 25/26c is achievable, which has been recorded in past Autumn warm spells

Yes, I was a bit baffled by Anyweather's comments about the GFS over-doing the temps as it is notorious for under-doing them both in winter and summer but especially summer. In fact, if you look at the local GFS forecast, in summer, I tend to view the 'feels like' temperature (which in warm spells is higher than the actual) as being the most likely actual, due to the way that the temps are constantly undercooked.

I can'r remember whether it was 1988 or 1985 that got record October temps - but the summer was so poor, that scarily, that was the highest temperature all year in many places!

[ANYWEATHER]

Yes, I was a bit baffled by Anyweather's comments about the GFS over-doing the temps as it is notorious for under-doing them both in winter and summer but especially summer. In fact, if you look at the local GFS forecast, in summer, I tend to view the 'feels like' temperature (which in warm spells is higher than the actual) as being the most likely actual, due to the way that the temps are constantly undercooked.

I can'r remember whether it was 1988 or 1985 that got record October temps - but the summer was so poor, that scarily, that was the highest temperature all year in many places!

The latest output puts more of some weight and support behind the much warmer weather next week....."IF" conditions were right picticularly in the South, with plenty of Sunshine there would be no reason why temperatures in one or two places would not touch the 80f mark, especially if you have high ground to the South Of You. But before we get there ,theres going to be a lot of twists and turns in our weather and in the model outputs!!!

[Frozen Britain]

Just seen this over on accuweather.com:

http://www.accuweather.com/blogs/news/story/55329/europe-to-see-extended-dry-str.asp

Looks like the progged settled spell is pretty much nailed now.

[Isolated Frost]

The HP is also a bit to the east, so even cooler nights are quite unlikely, with us pulling in a humid, southerly flow. Next week will contain some very hot days, nearly the warmest of the whole summer possibly. Highs of 23-26C possible in the Southern England, East Anglia and London. 21-24C in North East England, the Midlands and Wales/South West England, with nearer 20C highs in the North West, Scotland and NI. The Jet stays nearby and some Atlantic weather may still brush the west coast throughout, but the East and South East should stay immune from cloud for quite a while Tuesday onwards - tremendous end to September. Night-time minima should be between 16-19C in the South and East and around 12-15C elsewhere, roughly mid-teens generally, possibly sub-10C in the Highlands, Pennines, and if the Atlantic remains in place, even blowtorch southwesterlies won't be as mild as the warm southerlies, so the Western Isles and Northern Ireland could see some more average low temperatures.

And don't be surprised to see some convection during and after the heatwave, especially the south near the channel. Could be an explosive breakdown, synoptics sound near perfect for it.

[conor123]

The 06z is insane this morning with 850hPa Temps above 10c from next Tuesday right to the end of the run.

I'm not really sure how likely mist/fog is going to be, it will obviously have a big effect on temperatures but it does look a very sunny high to me, and for some reason this approaching

warm spell may well be a good thing, aka getting to enjoy the warmth without the worry of sun damage, I would be surprised if theres much in the way of mist/fog around here

considering its like a dustbowl these days for a start :lol:.

I'm still convinced 25/26c may well be squeezed out of it somewhere especially if the ECM came off and it's increasingly looking like the whole UK may well join in the warm, sunny weather now rather than a NW/SE split.

[Beasterly]

The 06z is insane this morning with 850hPa Temps above 10c from next Tuesday right to the end of the run.

I'm not really sure how likely mist/fog is going to be, it will obviously have a big effect on temperatures but it does look a very sunny high to me, and for some reason this approaching

warm spell may well be a good thing, aka getting to enjoy the warmth without the worry of sun damage, I would be surprised if theres much in the way of mist/fog around here

considering its like a dustbowl these days for a start .

I'm still convinced 25/26c may well be squeezed out of it somewhere especially if the ECM came off and it's increasingly looking like the whole UK may well join in the warm, sunny weather now rather than a NW/SE split.

So...when will the media start ramping up?

[No Balls Like Snow Balls]

From what I can see from the latest ensembles and reading the met office update i cannot see this being more than a 7 day warm spell. Looks like things will start to cool down to around average for October in the middle of the 1st week of October. After that it looks as though we could enter a period of cold frosty nights, looks like we could go from summer nights to winter nights in the space of 2 weeks.

Edited September 22, 2011 by Jimblob

[Summer Sun]

It could only happen in the uk, to little to late imo regarding this settled warm spell being progged next week.

I'm sure it will be nice to have some settled conditions for a time but I'm not a fan of unseasonably warm weather at this time of year. The days are getting much shorter, nature and wildlife are now into there autumn transformations.

I'm sure the models are well over cooking the temps, we are well away from the core summer months now and heading into October the sun is getting very weak and daytime heating is getting less by the day.

Like it or not next week is going to bring some very warm weather 25c will be quite possible in the South, with low 20s just about Nation wide rain fall amounts should be very low.

GFS 06z shows keeps the high pressure, well into the 20s nation wide next week, 25c quite easily in the south later on

http://www.wetterzen...s/Rtavn1081.png

http://www.wetterzen...s/Rtavn1321.png

http://www.wetterzen...s/Rtavn1561.png

http://www.wetterzen...s/Rtavn1801.png

http://www.wetterzen...s/Rtavn2041.png

http://www.wetterzen...s/Rtavn2281.png

This continues right through FI with no sign of a Breakdown what so ever.

[Thundery wintry showers]

The models have moved into near-unanimous agreement that the high pressure will end up in a pretty ideal position for a combination of warmth and sunshine by midweek next week, with dry continental air taking just a short sea track over the English Channel. I agree with those who suggest that GFS is probably undercooking temperatures, given the synoptics and upper air temperatures, and mid twenties is quite feasible in the south. It could well turn out to be a fairly prolonged such spell too, with NOAA's 8-14 day guidance progging a significant anticyclone just to the east of the British Isles.

Some may say it's a case of too little too late, but many of us (myself included) find these bouts of unseasonal weather pretty interesting in themselves- as well as the 1st October 1985, anyone remember 8th October 1995 or 27th October 2005? Those two days were sunny and unusually warm across most of the country despite high pressure being significantly further east than the models are showing for next week, and they also occurred later in the season.

Before that, I think most of us will get a sunny dry day tomorrow but the weekend looks like it may well have rather more cloud associated with the tropical maritime south-westerly type. Sunday continues to look favourable for a fair amount of sunshine coming through in eastern and southern areas.

[Summer of 95]

Sounds like finally some weather to look forward to, just hope it doesn't turn out to be one of those SE-gets-everything setups again.

I remember both 8th Oct 1995 and 27th Oct 2005- for totally different reasons. The first was an amazing cloudless day with temps well into the 20s, the second was an absolute stinker with cloud hanging around here all day, while nearly everywhere else had sunshine and 20C temps.

[Frosty.]

The Gfs is now coming into line with the ecm on a prolonged anticyclonic spell developing next week with a large area of high pressure forming to the east of the uk with low pressure becoming anchored out to the west and the result will be a warm or very warm southerly/southeasterly airflow pushing north across all of the uk although the airflow will initially be much stronger across nw britain until the high moves closer and takes total control. There will be a blip next monday as a new low pushes into nw scotland but thereafter it looks like turning more and more settled across the uk with some very high temps for the time of year, just a hint on the 6z at the end of FI of some cold air spreading down across northern europe but high pressure holding firm across the BI until well into october. This weekend gives a taste of things to come across the southeastern half of england with temps of 22-23c..even warmer as next week progresses with air sourced from southern europe.

[conor123]

Next weeks setup is exactly what all us heatlovers wished for all June, July & August and never got, just like early October last year the right setup just a bit to late :lol:

Still going to be glorious though!! widespread 21-25c seems pretty likely for England & Wales with 17-21c for Scotland & Northern Ireland.

[I remember Atlantic 252]

I have a feeling the high will be further north than models are showing, meaning more of an easterly, with temps around 17°C, it is still FI after all

[Nick F]

The upper flow troughs and ridges are pretty amplified around the northern hemisphere on GFS next week, for once the trough setting up in the right place to bring warm and settled conditions to much of the UK next week:

The deep trough to our west should ensure a long-draw southerly across the UK, which by Wednesday sees 500-1000hPa thicknesses approaching 563dam across southern England with continued WAA - GFS indicates temperatures reaching 24-25C across southern/central/eastern England - perhaps add 1-2 deg C and it will be quite hot for the time of year:

And as others mention, the ridge close to the E and SE doesn't look like budging on the 12z GFS operational, with the trough out west eventually disrupting to allowing the strong ridge to expand west even more. It will certainly be a formidable obstacle against any return of the Atlantic after its domination for what seems like months!

[Matty M]

People may be overlooking a certain little feature expected to race north through Ireland Sunday- Monday

With the speed its moving, and potential intensification, it is of high interest to me.

[Weather-history]

Some of the charts are not far off the September 1895 set-up. That was a remarkable heatwave

[Costa Del Fal]

I have a feeling the high will be further north than models are showing, meaning more of an easterly, with temps around 17°C, it is still FI after all

Given the significant agreement across pretty much all the main models, this looks unlikely. As ever not impossible but it looks pretty firm the High will be just where we want it to deliver the warm and sunny weather. Maybe late next week will be a different story but given the agreement, we are likely to have a great spell of warm weather.

[Cheese Rice]

Yeah the models look pretty much nailed for a significant spell of warm weather, not just for Sep/Oct but also the whole year and the last 20 years.

The cut of point for hot weather is usually around the 22nd of September for the most of the UK. In other words in the last 15 years temperatures haven't risen above the high teens. Here for example between the 25th-30th of September temperatures have never risen above 16.c in the last 15 years. It looks like next week will be low-mid twenties, probably even more significant the further north you go.

I personally can't wait, I live for hot weather.

Edited September 22, 2011 by Cheese Rice

[Geordiesnow]

Given the significant agreement across pretty much all the main models, this looks unlikely. As ever not impossible but it looks pretty firm the High will be just where we want it to deliver the warm and sunny weather. Maybe late next week will be a different story but given the agreement, we are likely to have a great spell of warm weather.

I suppose it depends how long is a "spell" is in your eyes? It could easily be a spell of very warm sunny weather or the high could be shifted further East with each run and we will get more of a cloudier SW'ly but still quite humid. I think thats something people need to keep an eye out for, the models has not hinted at this at the moment but who to say it won't happen? The UKMO perhaps showing some hints and we all know the UKMO is quite an reliable model.

One thing for sure, for the early part of next week, high pressure quickly building on Monday is certainly the trend, how long will it last for is anyone's guess really.