Model Output Discussion

[Pennine Ten Foot Drifts]

As has been the case on many occasions already this year, the final resolution of lots of 'interesting' weather which has appeared on all the models at mid-range, (T120-T168), has been a watered down middle-ground version, and I see no reason to think this will change now. So in other words there will almost certainly be a depression headed our way later this week and into the weekend, but it won't be anything dramatic or unusual, and will fit well with what we have had so far - a pretty standard normal average UK summer................

[Alex]

As has been the case on many occasions already this year, the final resolution of lots of 'interesting' weather which has appeared on all the models at mid-range, (T120-T168), has been a watered down middle-ground version, and I see no reason to think this will change now. So in other words there will almost certainly be a depression headed our way later this week and into the weekend, but it won't be anything dramatic or unusual, and will fit well with what we have had so far - a pretty standard normal average UK summer................

In terms of normal, It's how you look at it: June just gone was the coolest since 92 and rainfall exceeded the avg in most places. The CET is running avg or slightly above so far for this summer. Sunshine is a touch above.

We certainly have had a bit of everything but the main point is that so far we have had a wetter summer than normal and the temps although generally avg, it's been the coolest in nearly 20years and as I can only remember about 20 summers, I would call this summer so far poor but we have had more nicer straight forward days than 07/08. Others may remember worst and call the summer average or better.

I think central areas so far have had some of the best weather so maybe a slightly better opinion here.

Onto the models and the 06z is pretty dire with an unusually deep low possibly feeding in for Sunday.

[Downpour]

CR : I thoroughly agree -- West Wales has seen some very sunny and at times warm weather. Even last week, very far from summery and very LP dominated synoptically, managed to include some lovely conditions at times.

As for Electric SnowStorm's snapshot for next Saturday -- a Low of that intensity simply won't verify. And I'm prepared to lay money on that.

Indeed. Anyone who has been model watching for any length of time will know that forecasting monster lows at 6-7 day range is a fool's errand. I recall a couple of them being "nailed on" by the models in winter as short as T60 and then either disappearing into thin air or else tracking off into some maritime wilderness and dumping their goods in the middle of the sea.

[Summer Sun]

GFS has as expected downgraded and come into line with ECM in developing the unseasonable low, looks like a spell of wet and windy weather will be on the way before this changes to sunshine and showers then high pressure looks like it will slowly build fro the south.

[Thundery wintry showers]

This high pressure seems to have been squeezed somewhat for this week- tomorrow and Wednesday may well be quite cool and cloudy in the east due to that pronouonced north-easterly flow, though it will be sunny and fairly warm with a few showers in the west. We will lose the north-easterly flow by Thursday, and Thursday and Friday look like being quite warm and bright with a scattering of showers due to the high pressure fading away.

I agree that the big low for the weekend currently looks like bringing windy weather with a band of rain followed by sunshine and showers, but there are strong hints of a far more mobile jet which introduces an increased chances of shortwaves turning up at short notice and giving longer outbreaks of rain. Not sure about the high pressure building from the south afterwards- it's way too far out to have much confidence there, while in the meantime I note that even the much sought-after pressure drop over Greenland is no longer evident on the outputs. I have a feeling that we may start to see rather cloudier and windier conditions than most of us have been used to recently.

[Snow Queen one]

I have a question. just looked at the jet charts and was wondering why it is so messy it has loads of gaps in it. is this why we are so unsettled. I know about the jet needing to move north and all that. thanks for the info.

[Richie V]

This high pressure seems to have been squeezed somewhat for this week- tomorrow and Wednesday may well be quite cool and cloudy in the east due to that pronouonced north-easterly flow, though it will be sunny and fairly warm with a few showers in the west. We will lose the north-easterly flow by Thursday, and Thursday and Friday look like being quite warm and bright with a scattering of showers due to the high pressure fading away.

I agree that the big low for the weekend currently looks like bringing windy weather with a band of rain followed by sunshine and showers, but there are strong hints of a far more mobile jet which introduces an increased chances of shortwaves turning up at short notice and giving longer outbreaks of rain. Not sure about the high pressure building from the south afterwards- it's way too far out to have much confidence there, while in the meantime I note that even the much sought-after pressure drop over Greenland is no longer evident on the outputs. I have a feeling that we may start to see rather cloudier and windier conditions than most of us have been used to recently.

Sweet music to my ears, I surely hope that saturday progged low holds true though I'm sure it will be reduced in intensity somewhat. Cool suits me fine, I melt with anything much over 24C!

[Thundery wintry showers]

The jet is pretty weak and sinusoidal at the moment (unusually so for July), which is why it appears so messy, and also why we're getting slack highs and slow moving areas of low pressure rather than a full-on Atlantic onslaught.

I think, particularly for northern areas, there's more to it than simply looking for the jet to move north (meteorology around the British Isles is very rarely simple!). The stronger a northerly tracking jet is, the more likely it is that we'll end up with a north-south split with many regions having cloudy westerlies and weak frontal systems on the northern flank of ridges from the Azores High, while a weaker jet would allow high pressure to periodically build further north. I tend to think of a jet aligned SW-NE or WSW-ENE across the eastern Atlantic to be most favourable for hot sunny weather as it allows high pressure to become displaced generally into western Europe allowing an anticyclonic/southerly regime to prevail over the British Isles.

[ohno]

The jet is pretty weak and sinusoidal at the moment (unusually so for July)

Hello again

You say its unusal for July? I would like to add that its not..And the previous Julys have proven this?... We are lucky in the UK if the Jet stream pushes that far north for long enough to give us a good a summer.. But the Usual weather in the summer is a mixture of everything..

[Thundery wintry showers]

Hello again

You say its unusal for July? I would like to add that its not..And the previous Julys have proven this?... We are lucky in the UK if the Jet stream pushes that far north for long enough to give us a good a summer.. But the Usual weather in the summer is a mixture of everything..

I mean that it's relatively unusual to get a weak jet in July with alternating slack highs and slow moving lows (though of course not unknown). Traditionally the westerlies are at their weakest during spring and early June, and increase substantially in frequency as we head through June, which is why north-western Britain is traditionally somewhat drier and sunnier during May and June than during July and August. Thus when the jet is more or less "overhead" during July and August the result tends to be a continued train of low pressure systems bringing rain belts and extensive cloud cover, with occasional attempts at ridges into the south from the Azores High.

What's interesting here is that the jet did crank up a few notches around mid-June as often happens at that time of year, and then slackened off again towards the end of the month, giving rise to that southerly incursion and then this slow-moving sinusoidal jet pattern that I would more often associate with spring or early summer. Of course it isn't a hard and fast rule- for instance August 2004 was a very wet, cyclonic month but westerlies were largely absent during the first two-thirds of the month, with slow moving low pressure being typical.

I think the "north-south split" issue with a strong northerly tracking jet also contributes to northern and western regions becoming cloudier and wetter on average during July and August as it's mainly the south and east that feels the full effect of any highs that extend north and east from the Azores. That said, there are exceptions, e.g. during the record-breaking August of 1995, the jet took such a sharp left turn as it crossed the Atlantic that the westerlies and fronts largely stayed to the north of even northern Scotland:

http://www.wetterzentrale.de/archive/ra/1995/Rrea00119950818.gif

But for that sort of thing it would have to get a long way further north in the vicinity of the British Isles than it is at present- I think a strengthening and modest shift north would most likely leave most of us in westerlies.

[Summer Sun]

GFS Is changing more times than enough,

http://www.wetterzen...s/Rtavn1261.png

We have high pressure moving in by Sunday now

http://www.wetterzen...s/Rtavn1501.png

http://www.wetterzen...s/Rtavn1741.png

http://www.wetterzen...s/Rtavn1921.png

GFS has a new LP system around the 20th, no doubt it will be totally different again this time tomorrow

http://www.wetterzen...s/Rtavn2161.png

I wonder what ECM will offer later, GFS isn't keen to follow ECM.

GFS FI still teasing us with High pressure and temps of around 25c for the south from the 23rd onwards

Edited July 11, 2011 by Gavin D

[Uncle_Barty]

GFS Is changing more times than enough,

http://www.wetterzen...s/Rtavn1261.png

We have high pressure moving in by Sunday now

http://www.wetterzen...s/Rtavn1501.png

http://www.wetterzen...s/Rtavn1741.png

http://www.wetterzen...s/Rtavn1921.png

GFS has a new LP system around the 20th, no doubt it will be totally different again this time tomorrow

http://www.wetterzen...s/Rtavn2161.png

I wonder what ECM will offer later, GFS isn't keen to follow ECM.

GFS FI still teasing us with High pressure and temps of around 25c for the south from the 23rd onwards

I'm not sure about high pressure for Sunday - the isobaric curvature is still cyclonic on every chart you link to, bar Monday.

Looks like Monday only gives a respite before the next low moves in on Tuesday.

Long way off though!

[UV-RAY]

Looking grim from the weekend onwards, I very much doubt that low will be that deep, but an unsettled and cool/average outlook remains the form horse.

[bluearmy]

the shortwave moving through the north sea on sunday is right where the ecm spreads stuck it this morning. given that GFS and UKMO now place it there aswell, one has to hope that something changes over the next 24 hours or it would be a big surprise to see it not verify.

i'm struggling to find any straws if you're looking for a sustained settled spell. i really wouldnt make too much of the MJO - until it escapes the clutches of low amplitude, we are unlikely to see the composites relate to anything we see over here. and even if it does make progress away from the centre, there is no guarantee that the composities will verify. otherwise, forecasting would be quite straightforward.

the only positive spin i can make at the moment is that the past two troughs have shortened in their modelled duration as verification has approached. the only problem with this one is that it looks much deeper than the past few did at the same timescale. glass half full would say that its progged to come in further to the east than the past couple. hence, an eastward correction as we often get with a 'northerly' could well see the west escape the worst. next two days will give us the answers on this.

[snowlover2009]

GFS Is changing more times than enough,

http://www.wetterzen...s/Rtavn1261.png

We have high pressure moving in by Sunday now

http://www.wetterzen...s/Rtavn1501.png

http://www.wetterzen...s/Rtavn1741.png

http://www.wetterzen...s/Rtavn1921.png

GFS has a new LP system around the 20th, no doubt it will be totally different again this time tomorrow

http://www.wetterzen...s/Rtavn2161.png

I wonder what ECM will offer later, GFS isn't keen to follow ECM.

GFS FI still teasing us with High pressure and temps of around 25c for the south from the 23rd onwards

There is nothing there to suggest any dry weather or it sticking around, it is going to get unsettled through the weekend and likely hood to stay like that most of next week. As for excuses that gfs is changing, well it is out on a lim anyway, with all the other models showing something different to it anyway, but even I can see gfs looking pretty unsettled. High pressure does not build in like you say, it clips us and a new low pressure spawns in the northwest, I think your clutching at straws again or trying to build up the assumption that something good will come out in all this by picking at charts that shows a little bit of high pressure, but from the weekend and next week it is not brilliant at all. There is no proper high pressure building into the uk, like the one from a few week ago when we had the mini heatwave.

Like you say, gfs is chopping and chnaging, so I don't see how the 'teasers' in FI can be relied on too much yet. I don't see how the fact that the gfs is changing, has any impact on what it could be like next week, the overall pattern is the same for the weekend.

Edited July 11, 2011 by snowlover2009

[shedhead]

A very unsettled look to things across the weekend and into next week IF the 12GFS is to be believed, with a distinctly cool feel likely too, especially in any wind and rain. Indeed it probably wouldn't be

much of a stretch to suggest it will feel autumnal at times across northern and western areas in particular, with little, if any tangible sign of anything settle quite yet.

[Thundery wintry showers]

the only positive spin i can make at the moment is that the past two troughs have shortened in their modelled duration as verification has approached. the only problem with this one is that it looks much deeper than the past few did at the same timescale. glass half full would say that its progged to come in further to the east than the past couple. hence, an eastward correction as we often get with a 'northerly' could well see the west escape the worst. next two days will give us the answers on this.

As I see it, the main feature of note is the associated changes in the atmospheric profile- the jet looks set to become somewhat stronger and this implies a rapid succession of low pressure systems, a much larger emphasis on frontal rainfall, more extensive cloud cover, cooler days, warmer nights, and higher winds generally (indeed, "more autumnal" wouldn't be an exaggeration). It's true that the models have often been too progressive in FI before, but this change looks far more convincing than earlier projections (and if anything the models have moved towards a more mobile jet over the last few sets of runs, hence the deep low moving further east more quickly).

For the same reason I think an eastward correction could easily result in the next Atlantic system in the sequence getting further east more quickly. The GFS even brings fronts into most areas on Friday now, though UKMO still has them holding off until Saturday.

Once such a mobile jet gets in place on that sort of trajectory the only way out is via a further pattern change, with the jet slowing down and/or shifting position. The charts that Gavin D posted with high pressure ridging into the SW don't have the high anywhere near close enough to hinder the moist Atlantic influences. The longer-range 500hPa anomalies from NOAA suggest that we may see a shift towards a mid-Atlantic ridge and an anomalous incidence of northerlies at days 8-14. However, still some warm sunshine to come in the west over the next couple of days and more widely on Thursday.

[William of Walworth]

Writing off July yet then folks?

I agreee the coming weekend, Saturday especially, is looking pretty unsummery on current output, but I also still cling to the hope that the Low will not be so intense/deep as current models are showing.

It's still only Monday, and it's far from unknown for massively deep lows shown 5-6 days ahead to end up weakening or even tracking along a significantly different path than first predicted ...

Also, as for next week, TWS's earlier talk of weak Highs alternating with slack Lows still seems valid to me, but never discount the possibility that one of those Highs just might end up intensifying and building much more strongly in the end (maybe late July) even if there's not too many signs of that just yet. Such can even happen at quite short notice at this time of year.

Hopecasting? Yes, guilty but also I'm being suitably cautious about assuming (as some writer offers fear!) that the worst model output will definitely verify and last longer term. Into and beyond next week, there's still plenty to play for.

[ re the upcoming weekend Low] At this range it's still possible that the models could be overblowing that low.

Very sensible caution there! Although that post was earlier, and TWS post just above is less positive really. Probably rightly ....

One summer, just one in my life, I'd like to see my least favourite words 'Southerly Tracking Jet' never needing to be mentioned for long periods of the summer ...

Edited July 11, 2011 by William of Walworth

[Downpour]

My hunch based on what's happened so far this summer is that you can take a carving knife to any progged rain totals and sprinkle in some extra sunshine for good measure - at least in the SE. So I am sceptical of this monster low delivering, just as I am sceptical of big events in the winter. Not saying it won't happen, purely speculating that the models are likely to be overbooking it massively and that it's too far out to be anything more than a vague possibility.

[Staffordshire]

Well I am preety lookin forward to an unsetteled period! Love strong winds and heavy rain, just a shame I live here- would love to get a ticket to Scotland

[Interitus]

Got to love the 12h control run of the GEFS with yet another pesky low swinging in from the northwest at 192h-240h but this time re-invigorating over Germany and heading back westwards to give us another blast, brilliant.

[January Snowstorm]

The high pressure spell this week has now almost been totally eroded.

More like an avg couple of days followed by very unsettled wkd and next week

As I said last night we were only an upgrade away from a warm sunny spell.

This hasn't happened though so it's deja vu really!!

Ah well it's only the weather

[Summer Sun]

ECM has the low over all the UK for Saturday,

http://www.wetterzentrale.de/pics/Recm1201.gif

Plenty of Rain for Saturday, before it slowly edges into the North sea,

http://www.wetterzentrale.de/pics/Recm1441.gif

Looks like a wet weekend is instore, more like Autum then Summer.

[sparky1972]

ECM has the low over all the UK for Saturday,

http://www.wetterzentrale.de/pics/Recm1201.gif

Plenty of Rain for Saturday, before it slowly edges into the North sea,

http://www.wetterzentrale.de/pics/Recm1441.gif

Looks like a wet weekend is instore, more like Autum then Summer.

out of the whole year i want one dry day, that day is saturday and it looks like its going to be the wettest day we have had for a while. bugger, 11 kids camping out in the garden as its daughters birthday, dont want 11 kids in my house. lol

[Staffordshire]

Is this low forecast to go from SW (Cornwall) to NE (Northumberland)

Or...

NW (Scotland) and go SE to London?