Model Output Discussion 22/07/12 Onwards.

[Catacol]

Maybe there will be thunder around but after the uk's luck with thunder over the past years who knows

You should have been in the SW last night. Heavy thunderstorms for hours... kept me up until after 2am watching relentless lightning and torrential rain...

[Evening thunder]

Hi SM. In contrast to my earlier postings, it would look like many parts of the UK (but with a southern/southeastern UK bias at the moment) is at risk of thunderstorms during the period in question, as high low-level moisture surges across the country. The GFS is also modeling strong vertical ascent in the region around the frontal boundary, so would likely see storms firing with ease.

Thanks for that, looks like an interesting period then Maybe I shouldn't be too greedy as had some nice lightning last night, be nice to see others that havnen't seen much getting some.

Better post something model related myself, some models still suggest some warmer uppers drawn up from the south at times after Wednesday too, in this overall unsettled pattern, though not like yesterdays 12Z GFS. Quite possibly more of a SSW flow shifting storms further east on current charts I'd guess, but still some potential for those that want very warm temps (though probably brief and in the east more) or thundery activity still I'd guess. UKMO looks slightly better than others for this at T+144 I'd think: (though it could well come into line with other models instead)

Edited August 12, 2012 by Stormmad26

[bluearmy]

The latest 500mb anom chart still shows troughing across the UK as we enter the final week of Aug, with, you guessed it, HP over Greenland...

not really shed, that euro high anomy is new for this summer and keeps the worst effects of any troughing further north. The low anomoly is also less severe for the uk than we've seen on deep fi naefs charts over the past few months.

[Cloud 10]

A few runs from the GFS now wanting to develop deep troughing near Scandinavia and the 06z

is no exception.

Somebody tell me that's not snow forecast for northern scandi?

[Milhouse]

not really shed, that euro high anomy is new for this summer and keeps the worst effects of any troughing further north. The low anomoly is also less severe for the uk than we've seen on deep fi naefs charts over the past few months.

To be fair that chart has updated since it was first posted and it originally did show a greater low pressure anomaly over the UK. But it has changed, which doesnt make this current one any more accurate, but it does serve to highlight the uncertainty. It does seem that its only the poor charts that get posted.

[Gavin P]

Hi all,

Here's todays model based video: Soaking Rain On Wednesday: http://www.gavsweathervids.com/

Quite an unusual event to say the least (if it comes off as progged) with 15c+ 850's fueling an intense area of low pressure just to the south-west approaches

Edited August 12, 2012 by Gavin P

[phil nw.]

Certainly some unstable weather looking more likely as we go into the new week with the approach of very moist TM air coming up against the warmth of the last few days.

The developing extensive upper trough over the Siberian side of the Arctic looks like a notable feature for the next 10days or so locking in the heights over Europe and holding the core of the Atlantic trough just to our west.

Here the height anomls. at T192hrs from the mean 00z outputs.

All pretty much show the same pattern as described above.

For the UK we do have a cooler week ahead of us with some rain and possible thundery outbreaks but later on towards the weekend those thickness look like rising further south and east as the influence of the Euro. high shows it`s hand..

We can see this from the 2 thickness images from the ECM means at T72hrs and then at T192hrs.

the Atlantic trough losing it`s sharpness and filling.

Of course details of day to day conditions can`t be ascertained beyond the next 2-3 days but the way the sypnotics are shapiing up we should see things gradually settling down somewhat further south with the more unsettled weather retreating to the north west in week 2.

Edited August 12, 2012 by phil n.warks.

[Frosty.]

As phil just said, it looks like improving by the end of the week in the south and east of england as the euro high becomes more of an influence but some very unsettled weather to come for all areas in the week ahead, the models show bands of heavy rain spreading north and east early in the week with wednesday currently shown to bring torrential rain northwards, gradually thinning out by the time it reaches the far north of the uk on thursday but after that, the main focus of the bad weather switches to nw britain with the southeast becoming dry and warmer.

Edited August 12, 2012 by Frosty039

[Gavin P]

I think it will settle (at least in the south) for the final week or ten days of the month, but I'm also thinking it will become cooler - GFS ensembles keep showing a notable slide in temperature for the final ten days of the month;

http://www.wetterzen..._London_ens.png

Maybe dry and bright with temps around 20c by day and 10c by night? Would be quite a nice spell of late summer/early autumn weather

Edited August 12, 2012 by Gavin P

[DTHFCJ]

Certainly some unstable weather looking more likely as we go into the new week with the approach of very moist TM air coming up against the warmth of the last few days.

The developing extensive upper trough over the Siberian side of the Arctic looks like a notable feature for the next 10days or so locking in the heights over Europe and holding the core of the Atlantic trough just to our west.

Here the height anomls. at T192hrs from the mean 00z outputs.

All pretty much show the same pattern as described above.

For the UK we do have a cooler week ahead of us with some rain and possible thundery outbreaks but later on towards the weekend those thickness look like rising further south and east as the influence of the Euro. high shows it`s hand..

We can see this from the 2 thickness images from the ECM means at T72hrs and then at T192hrs.

the Atlantic trough losing it`s sharpness and filling.

Of course details of day to day conditions can`t be ascertained beyond the next 2-3 days but the way the sypnotics are shapiing up we should see things gradually settling down somewhat further south with the more unsettled weather retreating to the north west in week 2.

excellent post there Phil,also looking at the NAEFS all summer like Nick has said they are better than they have been,also the 500mbr height anomaly charts dont look to bad compared to what we have seen

[mushymanrob]

The UK's past 'luck' with thunderstorms has no bearing at all on what will happen next Wednesday. Besides, the UK as a whole has seen quite a few thunderstorms just in this year alone, so far. In fact, it's been one of the more notable years in relatively recent times for convective weather, given the supercell(s) that affected Oxon in May and the severe thunderstorm outbreak of June 28th.

Re. the GFS's storm risk charts, ditch them. They are of little use. Just to give one example, earlier this year the GFS was progging fairly high SBCAPE over many parts of the country over a period of a few days...but under a robust ridge aloft. Clearly thunderstorm development would be a struggle. Nevertheless, the model calculated a rather high storm risk because of the CAPE values that were progged.

Had some interested/excited, the same were disappointed when little happened.

personally my definition of a 'storm' isnt the same as 'shower'. whilst ive seen many thundery showers, some heavy, but a couple of rumbles of thunder does not a storm make in my book.

[TonyH]

Model related guide to the week ahead (for some of us):

http://forum.netweather.tv/blog/309/entry-4463-weather-guide-monday-13th-to-sunday-19th-august-2012-west-wales-and-the-midlands/

[AWD]

The 12z run from the GFS continues to paint quite a picture for Wednesday. I think there is the potential for a significant event of a different sort than to what others are perhaps thinking. This isn't simply your autumn-like heavy dynamic rain and strong winds depression. The convective potential associated with this low looks like being well within the 'notable' category, perhaps even matching June 28th.

A good supply of warm, moist air at low levels looks to surge north and east during the period, with strong forcing for ascent from the CF - which looks to cruise by during the day. With the sort of moisture return being progged combined with an impressive shear environment, it's a favourable setup for organised/severe convective weather.

In other words, I'm thinking squall line MCS mode possibilities.

Careful, to us storm lovers, that could be considered a RAMP. Lol.

[Milhouse]

Very interesting model viewing at the moment. It looks like a lot of warm, tropical air will be sent northwards during this week and into the weekend. GFS 12z has the makings of a potentially hot spell for the beginning of next week but the rest of the 12z is yet to come out.

[johnholmes]

To be fair that chart has updated since it was first posted and it originally did show a greater low pressure anomaly over the UK. But it has changed, which doesnt make this current one any more accurate, but it does serve to highlight the uncertainty. It does seem that its only the poor charts that get posted.

It does illustrate the knee jerk type of reaction to a chart, from whatever source and describing whatever weather phenomena. Whatever we use it has to be based on SEVERAL ouputs from whichever model you are using. That refers to the 4x daily GFS the 2x ECMWF, the longer range outputs, 500mb charts, NAO, AO, MJO etc etc.

Consistency is what forecasters look for.

[Cheese Rice]

Outlook has a very tropical edge to it, plenty of warm uppers and heavy rain. Wednesday looks very interesting with a high risk of severe storms affecting the UK with a pool of 10 850s ahead of the front, we are sure to see dramatic convection with large temperature swings in-between the storms. A sure chance of seeing a super cell considering it's these kinds of synoptics that brought those storms earlier this summer.

BBC going for severe weather on Wednesday with many areas showing the lightning symbol.

[William of Walworth]

It's after Wednesday (15th) that I'm (personally/selfishly) interested in, and for Thursday onwards I'm struggling to predict. Do people still agree that uncertainty should remain the watchword after Weds?

Edited August 12, 2012 by William of Walworth

[Weather-history]

The UKMO 72hr precipt chart shows a really intense area of rain

http://www.meteociel.fr/modeles/ukmo/precipitations/72h.htm

[Methuselah]

Aye, I think Wednesday could be very interesting indeed. Frequent lightning perhaps, if the models have got it right?

[AWD]

Aye, I think Wednesday could be very interesting indeed. Frequent lightning perhaps, if the models have got it right?

Not just lightning either.

Eeeeeeeek!

[Summer Sun]

Warm and stormy for wednesday

Towards the end of ECM things improve and it turns hot at the end

Wonderfull chart below

The latest short term outlook from the met office to Thursday suggest's it will often be breezy with heavy and persistent rain or showers at times mixed with drier and brighter periods. Near normal temperatures by day and humid by night.

http://www.metoffice...00&locId=351164

Edited August 12, 2012 by Summer Sun

[Milhouse]

And to finish it off:

Amazing! 30c for sure.

[SP1986]

The first two thirds of August looks like it will be warm, and wet, probably similar to summer 2004 in terms of weather type (not necessarily synoptics). This is definitely a different pattern now that's for sure; if it wasn't then the cool, southerly driven jet would have resumed. I have to say I like the outlook, it paints more of a traditional summer picture; a battle between high and low pressure, with some very warm spells in between more average periods with some rain events in between sunshine.

[DTHFCJ]

wish i could post the 500mbr height anomaly charts...they look pretty good to me regarding fine decent weather...i know they are just one tool but ive been looking at these for some time , just wondered the opinion of more experienced posters?

[AWD]

wish i could post the 500mbr height anomaly charts...they look pretty good to me regarding fine decent weather...i know they are just one tool but ive been looking at these for some time , just wondered the opinion of more experienced posters?

Yes, definetly looking like settling down towards the end of August. The Euro High coming closer to our shores, influencing the South more than the north as you would expect. Deep trouging over Scandi should take LP systems from the Atlanctic to our north, away from most of England and Wales.

Edited August 12, 2012 by Active Weather Dude