Model Output Discussion 22/07/12 Onwards.

[Frosty.]

Well, the Gfs 00z is looking very unsettled next week but at least we keep the warm S'ly to SE'ly flow until midweek although not as warm as this weekend due to spells of heavy rain and showers spreading north and east across the uk. Wednesday shows a brief window of dry weather but then heavy rain associated with a depression swinging in from the southwest spreads north and then northwest across the uk with rain for all areas and much cooler temps but then pressure rising to the southeast and temps recovering again but the ongoing risk of rain as a trough really sets up home over the north and west of the BI, eventually that trough pushes east and opens the door for a cooler Northerly before high pressure in the atlantic edges east but it's a disappointing outlook for everyone hoping for a fine and very warm end to this poor summer.

[mushymanrob]

There's been more than enough dire predictions on here in last two weeks, which haven' t really materialised so i'll take the latest with a warehouse load of salt.

Not the best summer outlook, granted, but no June/1st half of July that's for certain.

eh?... for most of the last two weeks the focus has been on this nice spell of weather, and the rest has been comments on what the teleconnections are predicting. unfortunately there no real sign of any prolonged dry sunny spell, so a continuation of changeable , whilst not as grim as june/july first half, does seem like more of the same as summer slips away... (daylength is noticably shorter now).

still great uncertainty over what will happen next week, but all models suggest warm, probably humid, and changeable! heavy showers at times, longer spells of rain, some cloud, some sun...detail will be very localised i think.

[Methuselah]

Not a particularly bad outlook suggested by the 00Z...That said, after mid-week things look to complex to predict. My guess, for what it's worth, would be for a continuation of the type of mix we've had of late??

[shedhead]

There's been more than enough dire predictions on here in last two weeks, which haven' t really materialised so i'll take the latest with a warehouse load of salt.

Not the best summer outlook, granted, but no June/1st half of July that's for certain.

If you disagree with those who are calling for an unsettled outlook could you please explain why, preferably with some charts to support you arguement.

[johnholmes]

The colours on the 500hPa charts arent directly related to temperatures but show the thickness of the air. How it feels on the ground is generally dictated by solar input at this time of the year, the effect of mixing air through layers of the atmosphere is generally minor. The thicknesses shown on the charts you mention are essentially the distance in the atmosphere between where the air pressure is 500hPa and 1000hPa. In low thickesses the distance is less (and often the temperature gradiant tighter) and vice versa when thicknesses are higher. As can be seen in spring, it can be -5C at 850hPa level and 12-15C at ground level, but only when a shower arrives does solar input cease and it actually feel cool at the surface.

Just a word of caution here, I'm sure neither you nor Stephen have done this but remember there is a difference between 500mb temperatures and the 1000-500mb 'thickness'. The former simply shows the 500mb temperature NOT thickness?

[East_England_Stormchaser91]

Been looking at the BBC, by their outlook(not always the most reliable) it seems to me that they're talking of a possible spanish plume like feature on Tue night into Wednesday straight up from S to N with most of the country being affected, then it all giving way later on. Heres hoping, but due to the amount of trust that has been eroded from the beeb so far, I'm not going to take a gamble into believing it might actually happen for once!

[UV-RAY]

If you disagree with those who are calling for an unsettled outlook could you please explain why, preferably with some charts to support you arguement.

It's a hopecast chart Shed, nothing more nothing less.

The outlook is an unsettled one albeit not on the lines of early Summer and spring, lot's of interesting weather coming up in the next week or two IMO.

[shedhead]

Have to agree S o N, I'm absolutely mystified by how some appear unable to see the wood for the trees. As I've said before it's all well and good seeing the glass half full, but to call this type of chart anything other than unsettled is just plain wrong imo.... unless you choose to call it very unsettled that is!

Edited August 11, 2012 by shedhead

[Evening thunder]

Where has anyone said it's not an unsettled outlook?, all I've seen anyone suggest is it's perhaps not a 'dire' one, but agreeing it's not the best summer outlook.

Anyway I won't name the poster but several days ago I saw someone describing the outlook containing this current/recent spell described as 'dire', which puzzled me somewhat.

It depends what you are looking for, in terms of temperatures it isn't a 'dire' outlook (GFS possibly underestimating maxima a couple degrees as usual):

On another note there could be some interesting (IMO) weather coming in Wednesday with the GFS developing that deep low which has lots of warm moist air mixed in meaning very heavy possibly thundery rain, this is for 9pm GMT:

What I see on the current models, is some interesting weather, some unsettled and wet weather at times but also some pleasantly warm weather (maybe a bit humid/muggy at times) between rain/showers.

There is the possibility of a couple generally more settled days if the trough gets pulled back west by lows joining it in the Atlantic:

An unsettled outlook for sure, not a 'dire' one for me, but maybe it is for some other people if all they are interested in is whether it will be dry for the next two weeks, though that isn't very common in a UK summer. For me a 'dire' outlook would have to be cool/cold and wet with persistent cloud and frontal rainfall, a bit like some of early-mid summer was.

Edited August 11, 2012 by Stormmad26

[johnholmes]

It's a hopecast chart Shed, nothing more nothing less.

that is the problem there was no chart shown to my knowledge. It will help newcomers if we ALL show the chart causing our comment or a link to it. That way we can all make our own mind up what the chart is showing?

I am as guilty as anyone but hopefully I do try to post objectively!

the type of chart being continually shown by all 3 500mb anomaly charts can not really suggest anything other than an unsettled spell with something of a nw-se splt, more unsettled for the nw and less so for the se. Fairly warm at times also again especially for the se.

Edited August 11, 2012 by johnholmes

[johnholmes]

Looking rather wet at times next week, particularly on Wednesday - 12z ECM precipitation charts:

Atlantic shortwave troughs ejecting NE on the forward side of the upper low/trough to the west of the Uk early/mid week engage warm and rather moist Tm airmass advecting up from the south - so certainly need to keep any eye on the potential for some torrential rainfall events.

hi Nick

Can you drop me the link for these charts please?

many thanks

John

[mushymanrob]

Have to agree S o N, I'm absolutely mystified by how some appear unable to see the wood for the trees. As I've said before it's all well and good seeing the glass half full, but to call this type of chart anything other than unsettled is just plain wrong imo.... unless you choose to call it very unsettled that is!

it IS a setlled chart, settled into an unsettled regime! lol.

[Milhouse]

ECM mean showing a lot of promise for another decent weekend next week. Thursdays low looks to have shifted northwards by Friday to lave a bright showery and breezy day but northing too bad. For the weekend itself the push of warmer uppers is still there and its from a more humid source so we could see a more rapid rise in temperatures than what we've seen during this current spell.

GFS 6z throws in a fly in the ointment in the shape of another low which drifts out into the north sea with a front draped over the UK ruining what on the face if it looks some good charts.

ENS mean still looking good

[Methuselah]

that is the problem there was no chart shown to my knowledge. It will help newcomers if we ALL show the chart causing our comment or a link to it. That way we can all make our own mind up what the chart is showing?

I am as guilty as anyone but hopefully I do try to post objectively!

the type of chart being continually shown by all 3 500mb anomaly charts can not really suggest anything other than an unsettled spell with something of a nw-se splt, more unsettled for the nw and less so for the se. Fairly warm at times also again especially for the se.

Thanks for that, JH. Says much the same as the GFS 06Z does, I think: Unsettled and rather warm? A stark contrast to what we had earlier: freezing cold and soaking wet!

[Thundery wintry showers]

"Unsettled and warm" is a fair description with low pressure dominating to the W and NW and feeding in warm west to south-westerly winds. Although the previous two days were sunnier than some people expected, today has had a fair amount of cloud roll in off the North Sea. Tomorrow this cloud will probably retreat northwards, affecting most of eastern Scotland, while NE England should brighten up with the winds turning southerly.

There are two main areas to watch for thunderstorms tomorrow- south-west England could see some elevated storms coming in off the continent at around 3-9am, and then the Midlands and possibly Lancashire and Yorkshire may see some thundery downpours break out in the afternoon and evening. Many parts of East Anglia, the SE, and the east Midlands and central southern England will probably have a dry sunny day with temperatures in the mid 20s.

With fronts spreading from the west, tomorrow looks set to start off dry, sunny and quite warm in eastern areas, but dull and wet in the west, and then the rain belt will head north-eastwards, perhaps becoming more showery and thundery as it heads into eastern areas. The front looks set to be slow-moving on Tuesday, which will bring pulses of rain and possible thunder to eastern areas while western areas are likely to brighten up with scattered showers.

Thursday's depression is worth watching as the GFS shows a very deep low with some extremely heavy rain spreading in on Wednesday night, though ECMWF and more especially UKMO show a much weaker low which perhaps suggests that GFS is overdeepening it (not for the first time). Extended guidance from the ECMWF shows the mean trough just to the west of Britain promoting a continued changeable but fairly warm outlook.

[Frosty.]

The Ecm 00z and Gfs 06z are showing a much cooler spell around T+240 hours onwards with Northerly winds so it will be interesting to see if it verifies, the chances of it verifying are good because it has been showing in that timeframe for a few days now. The latest models indicate a warmish S'ly to SE'ly airflow for the first half of next week but with some heavy and possibly thundery showers, the showers getting going tonight in the southwest and spreading north into wales but tomorrow spreading further east, the very unsettled spell around next wed/thurs is still on track but I have noticed the low seems to be a bit further west but thereafter it looks like warming up as pressure rises towards the southeast although a trough becomes a likely feature for the north and west with showers and longer spells of rain and temps closer to average or slightly below, then a cool n'ly plunge developing before pressure rises from the west, but that is a long way off.

[Methuselah]

I can't find much wrong with that synopsis, Ian. Some long-needed realism!

[johnholmes]

Predicting rainfall totals more than 24 even 12 hours ahead is fraught with difficulty. However given that all 3 main models are showing a very similar set up at the surface and in the upper air, pulling in high levels of humidity and other indicators for heavy rainfall. I would think it prdent for most parts of England and Wales to be aware that falls, by Thursday, could exceed 1 inch over quite wide areas.The link below gives the 'feel' for what the models are suggesting, and note the comment from Nick F(Senior Forecaster) in his post this morning.

I am sure both Nick and Paul are keeping a beady eye on this possibility for issuing warnings as appropriate.

http://www.wetterzen.../fsgfsmeur.html

Edited August 11, 2012 by johnholmes

[lorenzo]

@John

Looks like the Iceland chaps have moved bookmarks around. Think the data is from ECM.

Precipitation http://en.vedur.is/weather/forecasts/atlantic/#type=prec

850s http://en.vedur.is/weather/forecasts/atlantic/#type=temp

Wind http://en.vedur.is/weather/forecasts/atlantic/

[Frosty.]

Well..the latest meto update was quite a sobering experience to read, little chance of a return to the current very warm and settled weather for the rest of august or even into the first 10 days of autumn, this basically ties in with the latest gfs/ecm modelling which look cooler in the outlook and mainly changeable after the warm and unsettled (thundery) spell ahead, although it looks like turning cooler in the north and west later next week but remaining warmish in the far south and southeast throughout the next 10 days.

Edited August 11, 2012 by Frosty039

[johnholmes]

@John

Looks like the Iceland chaps have moved bookmarks around. Think the data is from ECM.

Precipitation http://en.vedur.is/w...ntic/#type=prec

850s http://en.vedur.is/w...ntic/#type=temp

Wind http://en.vedur.is/w...casts/atlantic/

many thanks for that-I did wonder if it was an output from Iceland-thanks again

[Bobby]

Looks like quite a washout next week, flooding concerns I would think

NAEFS doesn't show much sign of a proper settled spell

Edited August 11, 2012 by Barb-

[Frosty.]

Looks like quite a washout next week, flooding concerns I would think

NAEFS doesn't show much sign of a proper settled spell

Agreed, flooding concerns as cool air and warm air mix together next wed/thursday but still a little bit of uncertainty regarding the track of the low as it swings northeast into the BI, the models then show a cooler trend for most areas with a Northerly now looking likely in FI.

[I Cumbria Marra I]

[AWD]

A very deep LP for August being shown on the 12z.

Widespread very heavy rain with gales to the South West. Something that needs watching closely IMO, especially as I was planning on going to Weymouth Carnival that day.