Model Output Discussion 18z 28/07/13

[Frosty.]

The good news on this run (Gfs 12z) through the low res is the azores/atlantic anticyclone which continues to build into the south of the uk which is where most of the fine and warm weather would be, it's showing a north-south split, the northern half of the uk being progressively more unsettled with a broadly westerly pattern off the atlantic with spells of wet and breezy weather interspersed with sunshine and showers and temperatures generally around average, the occasional warmer drier day here and there. For the southern half and particularly from wales, the midlands, east anglia & south/se it would be fine and warm the majority of the time with relatively higher pressure as ridging continues to build across and temperatures in the low to mid 20's celsius range, it's only at the end of FI when the gfs decides we should have some cool unsettled weather but for most of the next few weeks, the PFJ ( polar front jet) remains well to the north of the BI.

 

So, in summary, warming up, especially after midweek, becoming sunnier and as we draw in air from france, it will become increasingly humid and by the weekend the pressure slowly leaks away and the threat of heavy showers and storms breaking out increases but staying very warm & sultry through the weekend and into the start of next week.

Edited August 19, 2013 by Frosty039

[Captain Shortwave]

Again the GEM looks pretty decent with a breakdown on Saturday and high pressure re-establishing

 

I find it rather amusing that it still disagrees with the other models even at 3-4 days out.

[Frosty.]

No wonder the bbc forecasts are making very little of this warm spell, if they are using the ukmo 12z as their template, it's much more progressive than the gfs 6z & 12z and not as warm either, mid 20's celsius at best, hopefully the gfs is on to something.

[Man With Beard]

No wonder the bbc forecasts are making very little of this warm spell, if they are using the ukmo 12z as their template, it's much more progressive than the gfs 6z & 12z and not as warm either, mid 20's celsius at best, hopefully the gfs is on to something.

Mind you the UKMO looks reasonably sunny for Sunday and a better chance of HP building in next week?

[Frosty.]

Mind you the UKMO looks reasonably sunny for Sunday and a better chance of HP building in next week?

True

[J10]

I think we should all take a step back, the inter run uncertainty is getting more than a little silly.

 

Perhaps tomorrow we can finally get a concensus,

[draztik]

The gfs ensembles have nosedived this evening, with below average temps shown from the 26th of August thru to end of its run, particularly for Aberdeen & Manchester. Rain spikes have also increased for all areas.

http://www.netweather.tv/index.cgi?action=charts;type=ens;sess=

the precipitation chart illustrates where the highest rainfall amounts are likely; mostly in the north west. Just a couple of days ago the same chart was showing no rainfall for these areas, so obviously taking into consideration the change in the models.

http://wxmaps.org/pix/prec4.html

[Captain Shortwave]

Well the GEM solution has gone from least likely to most likely in one model suite, ECM backing the GEM

Has anyone ever seen a lower respected model completely trump the big 3, because we could be looking at it happening here.

Edited August 19, 2013 by Captain shortwave

[Costa Del Fal]

The gfs ensembles have nosedived this evening, with below average temps shown from the 26th of August thru to end of its run, particularly for Aberdeen & Manchester. Rain spikes have also increased for all areas.

http://www.netweather.tv/index.cgi?action=charts;type=ens;sess=

the precipitation chart illustrates where the highest rainfall amounts are likely; mostly in the north west. Just a couple of days ago the same chart was showing no rainfall for these areas, so obviously taking into consideration the change in the models.

http://wxmaps.org/pix/prec4.html

Below average? Looks like its tanking very close to the mean actually. But given all these changes youd suggest there will be more to come right. Certainly nothing certain for the weekend onwards yet. I recommend you highlight such uncertainties in your post.

[draztik]

Below average? Looks like its tanking very close to the mean actually. But given all these changes youd suggest there will be more to come right. Certainly nothing certain for the weekend onwards yet. I recommend you highlight such uncertainties in your post.

the ensembles were showing a very different scenario just a couple of days ago, nosedived is an appropriate statement in this case. No idea if a trend for lower temps has been set. As ever, i only analyse what the models appear to suggest.

[draztik]

Big difference at T144 between the ecm and gfs

[Captain Shortwave]

If it's one consolation, the ECM looks pretty decent over the bank holiday weekend, no heat but certainly usable weather

[summer blizzard]

While the next week or so looks respectable in terms of temperature i don't think that we can escape the breakdown to a westerly pattern at the weekend.

 

By day 5 the jet is blocked resulting in amplification and allowing the low to move over the UK...

 

http://www.tropicaltidbits.com/analysis/models/gfs/2013081912/gfs_mslpa_atl_41.png

 

Afterward there is something of a stalemate where the Atlantic tries to flatten the high but on the particular run the high eventually tries to amplify again.

 

http://www.tropicaltidbits.com/analysis/models/gfs/2013081912/gfs_mslpa_atl_49.png

 

...

 

All in all my call would be to enjoy this mostly pleasant warm and dry week before a westerly pattern with temperatures average to cool. Rainfall also looks low away from the north west.

[johnholmes]

Possibly the most realistic thing to do might be to follow UK Met Fax charts. The human/machine mix is almost always superior to any model on its own. By lunch time tomorrow the low that seems to be bedevilling model ability for the weekend will be easily seen on sat piccs and one can then follow it using your own ideas on what upper air set up is moving it, does it look correct, and by Friday it will be fairly clear from its position at 12z Friday and its movement/speed etc over the previous 72 hours where it is likely to go. Then one can begin the even more interesting bit, where will it rain, when, how much, will it be frontal or convective or a mix of both.

Lots to look at and perhaps learn from rather than the odd niggles from one or two of you.

just an idea!

[Milhouse]

If it's one consolation, the ECM looks pretty decent over the bank holiday weekend, no heat but certainly usable weather

 

I see high pressure incoming judging by that chart. Even over the weekend its looking half decent with some bright and breezy conditions with nothing notably wet. Although i imagine northern Scotland wont fair too well given Sundays chart.

 

[johnholmes]

I might even do a winter thing, following the low to see how good/bad UK Met are and which model was best in this set up. Depends how much time I have. Perhaps one of you might like to take the lead I'll happily contribute to it.

Basics like

position of low, sat picc, T+24 prediction from Met, and the models to see how they differ(if they do)?

Edited August 19, 2013 by johnholmes

[bradymk]

Much happier with tonight's runs. ECM is much better beyond the weekend with that horrible northerly ditched. GFS is best for weekend but I will take the euros also if HP builds in quickly behind like they are showing. ECM ends with a cracker

Edited August 19, 2013 by bradythemole

[Milhouse]

A rather pleasing chart at T+168. Low pressure on a more northerly track than this mornings 0z allowing the Azores high to influence the UK settling things down. By T+192 the high has not suprisingly being flattened somewhat but it does mean some warmer upper temperatures will make their way over the southern half of the UK warming things up again.

 

[Milhouse]

By T+216 cooler air is slipping south over the UK as high pressure builds northwards to the west of the UK. Remaining mostly fine and settled.

 

[Captain Shortwave]

Back to square 1 in 10 days 

Mind you it's a lot better than this mornings charts

Though I don't know whether I have the mental capacity to chase another high pressure cell haha

Edited August 19, 2013 by Captain shortwave

[Frosty.]

Back to square 1 in 10 days 

Mind you it's a lot better than this mornings charts

Though I don't know whether I have the mental capacity to chase another high pressure cell haha

rinse and repeat is the way forward.

[Cloud 10]

Possibly the most realistic thing to do might be to follow UK Met Fax charts. The human/machine mix is almost always superior to any model on its own. By lunch time tomorrow the low that seems to be bedevilling model ability for the weekend will be easily seen on sat piccs and one can then follow it using your own ideas on what upper air set up is moving it, does it look correct, and by Friday it will be fairly clear from its position at 12z Friday and its movement/speed etc over the previous 72 hours where it is likely to go. Then one can begin the even more interesting bit, where will it rain, when, how much, will it be frontal or convective or a mix of both.

Lots to look at and perhaps learn from rather than the odd niggles from one or two of you.

just an idea!

 

Forecasting how much rain and where for  midweek  looks to be a tricky

exercise with that small low seemingly dying a slow death across the country.

 

 

 

As for the bank holiday weekend,almost anything is still on the table at the moment!

[Polar Maritime]

Autumn could start on a chilly note.. 

 

Edited August 19, 2013 by Polar Maritime

[Frosty.]

Let's do a direct comparison between this morning's Ecm 00z & this evening's 12z, it's clear the 12z is much better with a more pleasantly warm and generally settled pattern for the south of the uk and even the north does rather better, the 00z became cool, showery and windy, the 12z stays warmer. The latest ecm run also has similar features to the gfs 12z next week with high pressure ridging into the south.

 

So, in summary, turning sunnier warmer and more humid through this week *cloudier blip on wednesday and wet in the far northwest* the pinnacle of the warmth and sunshine being thursday and friday with widespread mid 20's celsius and nearer 27-29c for the southeast corner, the heat could trigger some late thundery showers, then a band of rain pushing in from the west on saturday followed by cooler/fresher and sunnier weather with a few showers dotted around, then becoming fine and warm across southern uk and slowly improving further north, a nice anticyclone in control by T+240 hours.

Edited August 19, 2013 by Frosty039

[legritter]

Evening all ,a little bit of a nip out there this evening but looking forward to this weeks increasing sun and heat .a good possibility of somewhere possibly hitting high twentys and an increasing chance of some thundery weather later ,but at this range still a hard call for followig week but high pressure does look like being in the frame especially for southern parts .lets grab it while we can as i noticed tonight how much further west from my view that sun is setting ,at the 240hr range on tonights ECM it wouldnt need much to put us in a very good end to a much better summer ,of course tomorrow, runs could totally change especially if mid atlantic becomes more active as things further west kick off ,but thats way in the much longer range .