Big divergence between ECM & GFS at 144H this morning which has the trough really digging in and forcing the high away with the jet strengthening and heading south. Wonderful ECM charts though  

Let's see if the very positive Meto update continues today,

Could be some good model watching coming up over the next few days.

If the GFS was being upgraded a week earlier this would have been the 00z op run.

Early days Tim. Will it! won't it model drama for a little while yet. I'll take 72h at a time for sanity...

struggling to build in - But gradually getting there. That low pressure over southern Norway is a real pain. There is a high pressure behind it as well.

Yep, if you went by the St. Swithin's Day legend rather than the models, you would say that it's not looking good for the rest of the summer in this part of the world with rain forecast for here during tomorrow. On the other hand, the outlook would be really good for the rest of the summer in those areas which are forecast to stay dry tomorrow if you went by that.

Met/o and GFS 00z generally unsettled, where's the ECM turns briefly unsettled and cooler but the AH ridge builds in, in fi along with the warmth.

I would say at the moment the ECM is more realistic as its the pattern we're had for most of this summer so far.

The cyclonic output in the 06z GFS rather worryingly is backed up by 13 ensemble members which all have a low over the UK at T196. Looks like cold air leaking south of Greenland is really going to scupper the heat staying after the middle of next week.

I'm off to Lake Garda on 22nd July, I may have picked a good week to get away from the British weather!

Couple that with the GEM and we now have considerable uncertainty.

I'm favouring a more blended solution now whereby an area of low pressure moves NE'wards to the west of Scotland with a gentle rise in pressure from the Azores thereafter. Southern UK largely unscathed with temps remaining in the warm category throughout. 

Things have gone downhill though in the last 36 hours of model watching. From looking how hot we could have got we are now faced with looking how close and how deep the offending low pressure system will get.

Well, we sure have been treated poorly by most of the operational models these past 48 hours now haven't we?

Talk about small-scale details throwing spanners into the broader-scale pattern (Azores High extending NE to Scandinavia)! Essentially we have GFS in particular looking to wedge a cut-off low in between Azores and Scandinavian highs such that the broad picture is almost as it would have been anyway, but with a small region being markedly different... a region containing the UK, because how could it not  be that in the mid-range GFS output? 

So I find myself looking for what we need to happen in the shorter-term in order to score something akin to the ECM 00z run instead.

Here are the 'Big Three' arranged side-by-side.

What we see is that GFS and UKMO have the small low west of the UK in an elongated shape such that it more or less resembles an extension of the deeper trough near Iceland, but ECM has this low as a distinctly separate feature - pretty much cut-off from the main Atlantic jet stream.

This is crucial because the cut-off means interaction between the low and the deeper trough to the north doesn't occur over the following 24 hours, which is when the latter is well-positioned to not only exploit the resulting enhanced temperature gradient (it has cool polar maritime air on its side, while the small low has some tropical continental; much warmer) and intensify, but also guide that thermal gradient such that it pumps up a section of the jet stream running NW-SE and passing a little way SW of the UK. This means that the strengthened low is driven SE and over the UK. At this point, upstream developments cause the main Atlantic jet stream to resume a SW-NE orientation and, like a meander in a river being severed, this leaves the aforementioned low wandering aimlessly around the UK in the case of GFS. This did seem particularly bad though, with GEM showing a plausible alternative in which the low soon drifts south into Europe while blocking becomes strong between the mid-Atlantic and Scandinavia.

With the interaction delayed to the following day as per the ECM 00z, the low is not as well-placed to deepen, and the fact that it's further northeast means that even if it does move SE, it misses the UK, leaving the door open for the Azores High to build in. The realignment of the Atlantic jet as mentioned above then works in our favour rather than against.

So the main point to take away from all that is - we need that little low to be as far south and independent from the Atlantic trough as possible in the 3-4 day range. All eyes on the 12z in hope of seeing such amendments from GFS, GEM and UKMO so that we may escape the extraordinary misfortune that their 00z runs suggested! 

Dry and fair with sunny breaks and partial cloud and a very comfortable 22.7 C, just a bit of a north west breeze keeping humidity levels at 40%.

I really couldn't have picked a better day to extend my back yard. I've adopted a long since abandoned and closed off pathway which has never been touched by anyone - including the council - for two decades so I might as well have it, especially as I paid to have a sycamore tree cut down from there. It's only a metre wide but might as well make use of that wasted space to put a new weather station there.

Ian invest in a Davis.  I get irritable reading syndrome (irs) when your  Maplin does its thing.

Well, if anything it's adjusted the low a bit further north so the best we can hope for from this run now is the main low staying west of the UK. Ideally northwest. It does have more in the way of westward extent than on previous runs so that suggests there's a chance, at least.

Wonderful news ! 

Remember when you used to get loads of running commentaries on model runs?

I think it was a time known as 'winter' 

Anyway - the main low has set up further west as hoped so we're in a fairly slack sunshine and showers setup. Question is, will the low be a good fella and stay west? Given this is the GFS, I'm not getting my hopes up .

UKMO 12z at 144 for comparison:

That's better perhaps only a 2 day unsettled blip. Gfs though is still being a %@#$ . Fascinating output at the moment though models all over the place.

To be truthful, I'd be more concerned about things if the GFS chart looked the better one and the UKMO was more unsettled.

Maybe it's just me, but I have always been very reluctant to trust GFS on its own. Too many let-downs with it in the past and all that.

GEM at 144 pretty similar to GFS. Interesting that it's the first time in a while with such a difference between UKMO at 144 and the other Ops. We'll see what ECM brings us.

A big relief to see it siding with the ECM 00z in terms of the general progression, given how far GFS managed to go wrong anyway despite the low starting off less nearby than on preceding runs. Both it and GEM seem obsessed with keeping lows in our vicinity for some reason .

Here's hoping ECM sticks to its guns tonight for a good old Euro v. N. America standoff