Model Output Discussion 18z 28/07/13

[Tamara]

There is very good agreement for the week ahead now and right up to next weekend...if we discount for a moment the UKMO at day 6.  The suggestions of the last day or so of that deeper trough towards next weekend digging south into the UK look to have been overdone, as suspected, and the somewhat split pattern we have seen sustained for a while is very likely to continue into the medium term.

 

In terms of that UKMO output - can we discount it? I think that we can take a view that it seems very much the minority scenario at this time and the modelling in general has moved away from that evolution. The EPS members this morning as depicted below show little support for the trough being that far south and also the UKMO has been quite inconsistent in its 'FI output' of late switching from trough to anticylonic solutions on intra day modelling. Nationwide, the changeable westerly pattern continues into the medium term, but with southern UK being fortunate to get a good deal of fair and quite warm weather

 

 

However, beyond this, the suggested trend for the split scenario to continue to keep adjusting northwards to allow the greater part of the UK to enjoy late summer conditions shouldn't really be too much of a surprise and has some credence. The background factors suggest that the atmosphere continues through the rest of August to behave quite cyclically as it has done since the later part of June and so it is quite conceivable that we could arrive back with a similar pattern to how we began July.

 

The difference being that with the days rather shorter and the sun less intense than in July, the upside of that could be that the heat is tempered nicely to be out and about in. So temperatures attaining , say, 25 to 28C may well be more easily tolerated by those who struggle with higher temperatures. 

 

However, it is a long way off and subject to the usual caveats - but temperatures may be higher than this eventually if the pattern evolves as the long term suggests. 

 

The operational ECM this morning fully supports and reflects the pattern evolution as suggested by the NAEFS height anomalies and therefore has credibiltity in terms of the constant signal these have been giving

 

 

The NAEFS anomalies have been very consistent over the last day or two for High pressure over the continent to adjust its influence further north west and the upper trough to back further away from the North of Scotland and towards Iceland and Greenland.  This implies late summer warmth becoming more extensive beyond day 10, and on the basis that we know that even late September can bring pretty high temperatures with air sourced from southern Europe, then it is not hard to imagine what some 4 weeks or so earlier may achieve.

 

[Milhouse]

Its pointless looking at the GFS in FI and picking charts from individual runs which show/do not show hot conditions because they change so much from run to run. At the moment the best place to look is the ensemble means which at this early stage do indeed point towards a drier and warmer spell to end the month. I'm not getting pulled into this heatwave talk as its still way out in FI. All i'm going to accept now is that the mean outputs are showing a trend for pressure to rise from the south starting in about 9 days time. Noone can deny that is what the models are showing but it would also be foolish to mention a heatwave. But i dont think its unreasonable for some to be talking about the building blocks for a potential hot spell. After all, in late June any heatwave talk was played down and look what happened. It may happen, it may not but we will find out in due course.

[mushymanrob]

heatwave ? i referred to a possible hot spell which isnt the same as a heatwave and there is growing support for something like that evolving. ok it is along way off, and might not happen, but this is me..mr negetive talking, and in this case there are tentative reasons for cautious optimism.

[shedhead]

heatwave? i see no sign yet of a real 'heatwave'.  becoming more settled over time though with the following caveat - shallow troughs moving west to east cannot be discounted (as looks to be the case next weekend). the anomoly, building initially from the se then seems to become established to the east/northeast thru week 2. that then allows for temps to build but currently the spreads out to two weeks not showing this. week 2 maxes 26/27 in the south and dropping slowly as you head north. if we do get a decent block to our east then clearly that allows for a whole gammut of scenarios including thundery incursions form the sw. certainly a decent outlook considering there was plenty of doom and gloom painted once the july spell had ended.

There was also more than enough hype about an immediate return to heatwave conditions at the time ba, the cooler spell was touted by many as nothing more than a blip, despite little or no support whatsoever for that assertion from the models. Any possible heat (and that's all it is right now) remains deep, deep in FI and even that looks very tenuous too me, with the 06 GFS effectively having none of it. 

[bluearmy]

shed - i'll take the x model extended ens over the 06z gfs fi op every time. infact, the gfs op post T192 doesnt even get a look in when i browse the output. (i rely on the gefs diagram to see the trend of the outlier op which it invariably is). not saying it doesnt ever have the right solution but the swings back and forth make it pretty difficult to use as a forecasting tool.

 

oh and rob, you quoted a post with only the relevant word 'heatwave' and then posted three charts with the quote, 'here, here and here' against them followed by some prose with 'hot spell'.  forgive me for thinking you felt we might be on the cusp of a 'heatwave'! 

 

Edited August 11, 2013 by bluearmy

[Captain Shortwave]

We find ourselves in pretty much the same position as we did at the very end of June, a strong signal from both GFS and ECM for high pressure to build in 9-10 days time. The GEM model also doing something very similar and being a little later to the party but again this morning shows the Azores high building in. 

How warm and how extensive any heat is a still up for debate and the true specific evolution is still to be worked out by the models, but the broad trend is there for all to see.

On the output this morning, I think the ECM might be pretty close to the correct evolution for days 9 and 10, but that's just my opinion.

UKMO T144 chart? It really can't help itself at the moment 

[Methuselah]

There was also more than enough hype about an immediate return to heatwave conditions at the time ba, the cooler spell was touted by many as nothing more than a blip, despite little or no support whatsoever for that assertion from the models. Any possible heat (and that's all it is right now) remains deep, deep in FI and even that looks very tenuous too me, with the 06 GFS effectively having none of it. 

Aye, but only in the newspapers...

[Tamara]

Looking at individual GFS outputs in isolation and taking them at face value is not the most reliable guide at any time of year. I am sure that most will agree on that I don't think anyone is suggesting record threatening heat is on the way, but there are signals there, beyond the enchanting quirks and nuances of individual GFS outputs, for summer to head towards a close on a distinctly above average note temperature-wise and it will be interesting to see how the pattern evolves over the days to come.

[Frosty.]

The Gfs 06z shows good weather from midweek for most of the southern half of the uk and more especially for the southeast, temperatures on the rise, into the mid 20's celsius, mid to high 70's F and possibly nudging into the low 80's F for london & se generally, the further north and west you are from the southeast, temperatures are a few degrees lower but still feeling pleasantly warm, around the mid august average with 21-22c being a general figure, but lower than that for northwestern britain where the most unsettled weather will be, occasionally the unsettled weather across the northwest extends further southeast but weakens as it moves into the higher pressure. There is also a real chance of the uk tapping into some serious continental heat during the next few weeks if we get lucky, the heat is not far from the uk, occasionally flirting with the southeast on this run so it wouldn't take much of a change synoptically for a hot spell later in the month.

[Bristawl Si]

If temps get up to mid 20s, say 25/26c i'll consider that a heatwave for 2nd half of August.

[Frosty.]

If temps get up to mid 20s, say 25/26c i'll consider that a heatwave for 2nd half of August.

ditto, it's good enough for me.

[Milhouse]

[Frosty.]

The GEFS 06z mean is continuing the trend towards a warmer and more anticyclonic outlook which is also what the Ecm 00z ensemble mean is showing (see the Ecm 00z mean charts on my earlier post) it's a progressively more summery pattern towards the back end of the month which could persist through early september, the PFJ is forced further and further northwest, retreating right back to greenland and the arctic as high pressure builds northeastwards across the uk, we get a little taste of it for the second half of next week, at least the southeastern half of england will, this is followed by a brief dip in pressure and temperatures before the tide really turns and then a set fair and much warmer last 10 days of august should be nationwide.

Edited August 11, 2013 by Frosty039

[Methuselah]

I do hope so, Karl...I'd imagine that, what with charts like those, the Daily Express's hacks will be upping the ante?? 50 centigrade killer heatwave to strike UK next week! You read it here first! 

[Frosty.]

I do hope so, Karl...I'd imagine that, what with charts like those, the Daily Express's hacks will be upping the ante?? 50 centigrade killer heatwave to strike UK next week! You read it here first! 

or the Daily Mail..or both

[William of Walworth]

Frodty, I personally could do with those rainfall charts for Thursday and Saturday that you posted, NOT verifying -- semi-washout in SW risked there unless matters improve ...

 

Will catch up properly tomorrow.

[DTHFCJ]

Frodty, I personally could do with those rainfall charts for Thursday and Saturday that you posted, NOT verifying -- semi-washout in SW risked there unless matters improve ...

 

Will catch up properly tomorrow.

yes William looks like we are in the firing line for some of the wet stuff,check out the weather for the week ahead on the BBC site...tues weds and fri looks damp i wouldnt say washout though

 

Thanks again to Tamara for a top post and Frosty great input guys....ive still got me L plates on

[Frosty.]

Lots of high pressure showing on the GEFS 06Z CONTROL, especially through the second half of the run which shows anticyclonic dominance, it just strengthens the backing this upcoming pattern has from other model output today and recently, especially the Ecm 00z ens mean, a settled and increasingly warm further outlook is looking more and more like the form horse for late august and early september, yesterday I posted a chart with an atlantic high that looked like the painting, the scream, with these charts we will require plenty of sun cream.

[TootyFruity]

yes William looks like we are in the firing line for some of the wet stuff,check out the weather for the week ahead on the BBC site...tues weds and fri looks damp i wouldnt say washout though

Thanks again to Tamara for a top post and Frosty great input guys....ive still got me L plates on

[TootyFruity]

I totally agree Tamara does do great posts that you can actually understand herself and Frosty are not biased towards heat or cold and they just post what the charts are showing .

Also have to sneak in captain shortwave does make me giggle great posts and he takes no crap from anyone !!!

Cheers guys

[mushymanrob]

shed - i'll take the x model extended ens over the 06z gfs fi op every time. infact, the gfs op post T192 doesnt even get a look in when i browse the output. (i rely on the gefs diagram to see the trend of the outlier op which it invariably is). not saying it doesnt ever have the right solution but the swings back and forth make it pretty difficult to use as a forecasting tool. oh and rob, you quoted a post with only the relevant word 'heatwave' and then posted three charts with the quote, 'here, here and here' against them followed by some prose with 'hot spell'.  forgive me for thinking you felt we might be on the cusp of a 'heatwave'!

true, but i was quoting someone else, me, i think we might get a hotspell, how long it lasts and how hot, if at all, will make the difference between hot spell and heatwave. i too will be happy with a few days of 25c, anything hotter will be a bonus.i do think theres going to be a pressure rise and plume as depicted but it might not hit us, it just might get shunted to our east.

[draztik]

Kudos to the MetO, it seems they were onto something with their t144 output, as the gfs is now moving in that direction, with the deep low nesting the NW!

[Milhouse]

Heres the UKMO 12z at T+144. Still a menacing looking low pressure but it would be far from unsettled everywhere. A north south split i reckon with the SE warm and settled if a bit breezy. A different story in the north west with strong winds and rain.

 

 

The GFS has low pressure clearing northwards next weekend to be followed by westerlies bringing more average temperatures and quite a bit of dry weather. Very pleasant stuff with still no sign of a resumption of very unsettled pattern of the last 6 summers.

 

[draztik]

Gfs 12z wants to give us a settled second week, with temperatures comfortable to warm, perfect

[Captain Shortwave]

For balance, the UKMO delays the low by at least 12 hours and it is taking a more northerly course, if we continues it would probably clatter the Shetland Isles instead of going through Scotland

Have to admit it looks unusually vicious for the time of year so will probably be toned down a bit in future runs.

GFS also has a deeper low. Must say low resolution is fantastic, not overly hot but would I feel bring conditions the vast majority would enjoy.