Model Output Discussion 22/07/12 Onwards.

[Panayiotis]

Doesnt look like that low can go anywhere unfortunately, also that last chart looks like pressure is rising over greenland

[Summer Sun]

If ECM is right this low hardly moves for 6 days

[OldMetMan]

Looking at the GEFS ensembles they have toned down the precip amounts for London for Friday, quite a few do have that miracle dry gap. It really is touch and go, the timing of the front moving se is still open for revision and those thunderstorms over France do get quite close to the se.

I find it increasingly curious the way the models are trending at the moment, especially with regard to Friday and these mysterious dry gaps. Given that these "plume" events are notoriously difficult to predict, at the risk of sounding like a conspiracy theorist, I can't help but wonder if the Met O is being leaned on to minimise the potential threat the models are showing.

As I see it now, the models are showing the distinct possibility of a significant thundery event. Increasing heat over the UK and France with falling pressure, plus a slow-moving cold front moving SE, followed by a developing LP and accompanying sharpening trough to the NW and W is, in my experience a receipe for severe storms.

As you rightly point out, Nick, the location of any such trough line is very difficult to determine this far out. Yet, not even a hint of any warning from the Met even though it's within the range of its advance warning system, so I would have thought a vague yellow warning would be appropriate at this stage.

Yesterday's 120 hrs UKMet FAX shows the threat very clearly:

With this arrangement, the LP to the NW usually sinks SE as the developing LP over France heads NW and the area of major thundery activity forms ahead of the greatest air mass contrast. It is somewhat complicated by the presence of 2 cold fronts in this case but the most likely area for thie storm line if this chart were actualised would be the Midlands and E Anglia.

However, areas of thunderstorms also form within the developing LP over France, travelling N and then NE across the SE of England ahead of the upper trough. The trough line shown over France on the above chart suggests this, although the actual situation would no doubt be more complicated.

I think this developing synoptic pattern needs careful watching.

[stewfox]

yes it does look terrible for most after this week,worse summer of all time?

Please we are half way through the summer and its forcast to be 84f here tomorrow.

I still don't believe in T396, and my great great great grandfather use to say 1816 was real crap

[nick sussex]

The limpet trough returns and with it its equally hideous companion the Greenland high.

This all culminates in unsettled conditions returning for the whole UK by Friday and not going anywhere fast. Any low pressure at the moment looks slack so showers will be slow moving, with some sunshine between the deluges.

If only that high pressure would weaken to the north this troughing may edge a little further north and theres still a small chance that we could see the odd weakish ridge thrown ne towards southern areas to bring the odd dry day for the Olympics.

Apart from that it looks a poor excuse for proper summer weather, still some time before the athletics start so we live in hope that there might be some changes but unfortunately this pattern looks very entrenched.

[nick sussex]

Lol ! I'm not sure that Met Office operatives have infiltrated the data inputs yet OMM but there does seem to be little mention of the weather for the Opening Ceremony and you are right regarding some potentially heavy precip.

I think that front moving se would intensify but perhaps high cloud ahead of it could reduce convection, those storms from France may well graze the se but I think the flow changes later as that other front approaches so maybe this is where the miracle dry gap comes into its own to save the Opening Ceremony!

[tinybill]

Lol ! I'm not sure that Met Office operatives have infiltrated the data inputs yet OMM but there does seem to be little mention of the weather for the Opening Ceremony and you are right regarding some potentially heavy precip.

I think that front moving se would intensify but perhaps high cloud ahead of it could reduce convection, those storms from France may well graze the se but I think the flow changes later as that other front approaches so maybe this is where the miracle dry gap comes into its own to save the Opening Ceremony!

the gods might be with them if they are very lucky

[OldMetMan]

Nick, I was thinking more along the lines of a convergence zone forming ahead of the frontal zone, somewhat similar to the situation we saw in late June when that line of severe storms formed, rather than heat storms, although that would be a distinct possibility given the increasing heat, humidity and falling pressure.

I agree with you regarding the return of the limpet upper low, there seems no real end in sight for its re-occurence to finally end.

I think a lot depends on how quickly the upper trough/low develops and the surface LP deepens, which in turn will be influenced by what happens upstream, specifically whether the meridionality is marked enough.

I also think it is worth noting that the GFS in the last few days has been showing a significant LP actually tracking N and then NE right across England but it has backed off that idea today. Interesting situation.

[johnholmes]

I find it increasingly curious the way the models are trending at the moment, especially with regard to Friday and these mysterious dry gaps. Given that these "plume" events are notoriously difficult to predict, at the risk of sounding like a conspiracy theorist, I can't help but wonder if the Met O is being leaned on to minimise the potential threat the models are showing.

come on as an ex metman do you seriously think that is even a remote possibility?

As an ex forecaster I see nothing odd in the way the models are coping, none of them have a very good track record for predicting precip even in summer let alone with the infinitely more difficult situation in winter. Rainfall totals ending 00z Saturday for the London area have varied over the last 4-5 runs from as little as 2mm to as much as 11mm. Even that is considerably less than variations at this time scale on past rainfall events.Prior to that and even greater totals were showing on GFS.

A week ago it looked like a fine reasonably pleasant evening now its looking much less likely but it may still occur but not due to any 'leaning' on any met staff that is for sure.

Edited July 23, 2012 by johnholmes

[legritter]

even all ,im sure the miracle dry gap will be shown in variouse locations over the next few days . and that the MET ,and bbc will come up trumps nearer this weekend . the synoptic situation going by current data and charts is a very complex one and we all know by pAST EXPERIENCES WHAT COULD HAPPEN COME THE TIME . IM SURE THAT BY WED ,WE WILL KNOW MORE WITH REGARDS THE FRONT HEADING SOUTH AND SOUTHEAST AND THE MAKEUP OF IT . I EXPECT ANYTHING THUNDERY COMING OUT OF FRANCE WILL TAKE A WHILE AND THE EXACT TRACK COULD BE ANYWHERE ACROSS SOUTH BRITAIN EVEN CLIPPING THE S.E .TODAYS gfs IS ALL OVER THE PLACE SIMILAR TO AN EVENT WHEN I WAS OVER CANADA BACK AT THE END OF JUNE , IT WAS NEARER THE EVENTUAL EVENT AT 5 DAYS THAN IT WAS AT 3DAYS . MY MAIN CONCENTRATION NOW WILL BE MET FAX , BUT ALL SAID AND DONE ,FRI SAT LOOKING VERY INTERESTING .

[Timmytour]

Personally I can't see any storms coming up from France. When the models show it happening, it rarely happens to the extent they model it and it never happens when they don't! So taking the average position I would say that they will struggle to make it much beyond the French shore.

[shedhead]

come on as an ex metman do you seriously think that is even a remote possibility?

As an ex forecaster I see nothing odd in the way the models are coping, none of them have a very good track record for predicting precip even in summer let alone with the infinitely more difficult situation in winter. Rainfall totals ending 00z Saturday for the London area have varied over the last 4-5 runs from as little as 2mm to as much as 11mm. Even that is considerably less than variations at this time scale on past rainfall events.Prior to that and even greater totals were showing on GFS.

A week ago it looked like a fine reasonably pleasant evening now its looking much less likely but it may still occur but not due to any 'leaning' on any met staff that is for sure.

I never knew that.... No offence JH, just desperately trying to lighten the mood.

[Upgrade]

The troughing looks too weak to bring anything significant up from France. With any luck it will be a dryish "breakdown" from the North.

[johnholmes]

I thought it an idea to show how much the GFS outputs have changed over the past 5 days or so - copied into the Olympic thread as well

GFS and the Olympic opening ceremony predictions.pdf

[OldMetMan]

come on as an ex metman do you seriously think that is even a remote possibility?

Hi John I am not suggesting that the data has somehow been tweaked, merely that the threat shown by the models at this point should merit at least, as I said, a vague yellow advance warning. Goodness knows, the Met has been issuing warnings left, right and centre throughout the summer, with some considerable success I should say, but they have erred on the side of caution consistently, even 5 days out, so why stop now?

It has been widely reported in the press for some time that the Met has been "requested" to put a positive spin on forecasts at various times for various reasons, such as "public morale". But it is the timing of all this that makes me suspicious, i.e. had it not been the Opening Ceremony, I am sure a warning would have appeared by now.

I agree with what you say regarding the variability of the model output and the difficulties of forecasting with this kind of set up. It will be what it will regardless, yes, but let's see how the forecasts develop in the next couple of days.

[bluearmy]

no need for warnings 4 days away. thats absurd in my view, especially whilst uncertainty remains. the trend is to take the thundery plume to our se, possibly clipping kent and east sussex. maybe it will trend back nw again but i doubt it. i'm more intrigued by the 12z output which seems to be swinging the pendulum a tad back towards a shallower trough next week which will do less damage, precip wise. noaa cpc looks pretty grim on its 6/10 day output - i'm wondering whether just as we saw a trough appear from nowhere on the ops at the end of last week, its feasible that we could see next weeks troughing become unexpectantly less prevalent on subsequent model runs

[OldMetMan]

Out of interest, I have included the GEM output for Friday. This model doesn't get that much attention but, in my view, it has proved accurate in the past in some tricky forecasting situations and I tend to look at it more closely than the GFS for the 5 day period when in such a situation.

It is basically showing a thundery LP getting pulled NE across England in association with the developing LP to our NW. Note the amplitude of the 500mb trough to the west, much sharper than shown elsewhere and thus more likely to bring any thundery activity to our shores.

We'll see!

[OldMetMan]

Spot on. I spoke of this last week....big concern IMO for start of olympics. The air masses could bring fireworks......

Summer begins according to MetO................ok

BFTP

Thanks BFTP, guess we're in the minority at the moment. I'm looking forward to the Met O FAX later on, might clarify things a bit.

OMM

[Glacier Point]

no need for warnings 4 days away. thats absurd in my view, especially whilst uncertainty remains. the trend is to take the thundery plume to our se, possibly clipping kent and east sussex. maybe it will trend back nw again but i doubt it. i'm more intrigued by the 12z output which seems to be swinging the pendulum a tad back towards a shallower trough next week which will do less damage, precip wise. noaa cpc looks pretty grim on its 6/10 day output - i'm wondering whether just as we saw a trough appear from nowhere on the ops at the end of last week, its feasible that we could see next weeks troughing become unexpectantly less prevalent on subsequent model runs

I suspect so Nick given where angular momentum is heading right now.

[Glacier Point]

Is this a changed prognosis from your earlier thoughts some days back of the mean atlantic ridge edging slowly east in early august, whereby the mean ridge lies across the British Isles. My thoughts are that as the Summer Greenland high fades in autumn as the atlantic charges up, we well see a Euro High close to southern Scandinavia build feeding in some unusually warm weather from the second week of September or thereabouts.

Yes, very much so. Although we were just starting to sniff another little coup, and the ensemble means were swinging 'our' way, along came freaky friday and the whole pattern got yanked back a thousand miles and set us on course for next weeks upper trough. The ensemble mean products have us a sharp trough days 6 through 10, steadily lifting out thereafter.

If there is one area I would look at the longer range offerings tonight, it would probably be around Scandinavia - heights not high enough in the models if we begin to see angular momentum shifting us towards a weak El Nino state.

[Jason T]

Yes, very much so. Although we were just starting to sniff another little coup, and the ensemble means were swinging 'our' way, along came freaky friday and the whole pattern got yanked back a thousand miles and set us on course for next weeks upper trough. The ensemble mean products have us a sharp trough days 6 through 10, steadily lifting out thereafter.

If there is one area I would look at the longer range offerings tonight, it would probably be around Scandinavia - heights not high enough in the models if we begin to see angular momentum shifting us towards a weak El Nino state.

Stu, Don't mean to sound rude but could you put that in laymen terms for us lesser. Thank you.

Jason

[Upgrade]

Stu, Don't mean to sound rude but could you put that in laymen terms for us lesser. Thank you.

Jason

The weather's not going to be too bad.

[Glacier Point]

Showery next week, the focus of the showery activity possibly a touch further north than was anticipated yesterday. Longer term, slow changes - possibility that we may see pressure rise to our east and north-east and troughing shift south-west in the Atlantic alllowing for an improvement, drier and warmer conditions to take root in the SE, extending further east and north - but this only a theory at the moment and not substantiated by any model as far as they go.

[DTHFCJ]

Yes, very much so. Although we were just starting to sniff another little coup, and the ensemble means were swinging 'our' way, along came freaky friday and the whole pattern got yanked back a thousand miles and set us on course for next weeks upper trough. The ensemble mean products have us a sharp trough days 6 through 10, steadily lifting out thereafter.

If there is one area I would look at the longer range offerings tonight, it would probably be around Scandinavia - heights not high enough in the models if we begin to see angular momentum shifting us towards a weak El Nino state.

Sorry for going slightly off topic but thanks GP for your honesty...at least you admit things when they dont go to plan(which of course is no fault of yours)...keep up the good work

[Jason T]

Showery next week, the focus of the showery activity possibly a touch further north than was anticipated yesterday. Longer term, slow changes - possibility that we may see pressure rise to our east and north-east and troughing shift south-west in the Atlantic alllowing for an improvement, drier and warmer conditions to take root in the SE, extending further east and north - but this only a theory at the moment and not substantiated by any model as far as they go.

I'M Not sure how to take this .The fact you posted laymen terms or you replied,Bugger the weather THANK YOU.Cheers GP.