Model Output Discussion 18z 28/07/13

[johnholmes]

That's all well and good but in a few hours time the anomaly charts might be completely different, especially if the GFS/ECM agree which they now do

 

T

The anomaly charts very rarely make sudden changes and need to be watched over a 3 day period for comparison, ie NOAA and the ECMWF-GFS, when they all 3 show a similar upper air pattern over that time scale it is rare in my experience that the following upper air pattern is much different. Overall at day 10 they are correct 70% or more of the time, much better than the chopping and changing that the synoptic type shows. That then gives a general guide, not detail at day 10, as to what type of weather to expect on the surface.

[snowking]

Its GFS vs ECM again into the medium range

 

These two charts may only look to be showing subtle differences:

 

 

But in reality we are seeing quite a big difference at the surface, with the ECM mean keener on a trough solution (consistent with its upper forecast), whilst the GEFS suggests something flatter with the azores high influencing things quite a lot more in around 10 days time.

 

The 8-10 day mean charts today could be rather deceptive in terms of their absolute suggestion of an upper trough across the UK, with days 8 and 9, when separated from the mean, in reality exhibiting something more akin to the GEFS mean day 10 output with some influence from the azores high.

 

I still agree overall with the sentiment in here of a general continuation of the status quo, but always best to be a little cautious with calling the pattern out towards day 10 when we have the unusual situation of the ECM being the more keen of the two on a slight trough solution!

 

I would still back the ECM mean every day of the week over the GEFS, but perhaps just a glimmer of hope for further temporary ridging at times - I think it will be restricted to just temporary spells though - amongst the less settled pattern that looks set to dominate.

 

SK

[shedhead]

I too agree with the general sentiment so far today in so much as the period overall still appears fairly close to average for the vast majority, perhaps a little above in the S/SE and a little below in the N/NW.  Rainfall looks to be lightest over southwestern areas, which is good news after the deluges suffered there yesterday, but with the Azores ridge always flirting with the UK nowhere is expected to be anomolously wet across the reliable timeframe. 

 

So all in all not bad looking prosects through until mid month; plenty of usable weather, with no need for heavy duty waterproofs or aircon - which will probably do very nicely for most on here. 

Edited August 6, 2013 by Paul

[Captain Shortwave]

The anomaly charts very rarely make sudden changes and need to be watched over a 3 day period for comparison, ie NOAA and the ECMWF-GFS, when they all 3 show a similar upper air pattern over that time scale it is rare in my experience that the following upper air pattern is much different. Overall at day 10 they are correct 70% or more of the time, much better than the chopping and changing that the synoptic type shows. That then gives a general guide, not detail at day 10, as to what type of weather to expect on the surface.

That is absolutely correct but as snowkings post shows, such little tweaks (say a shift of 50-100miles) which is perfectly acceptable error in any chart could mean a difference between nationwide cool and wet conditions and more favourable conditions where temperatures are warm and at times very warm with mostly dry conditions. Hence why I felt the need to at least provide a rebuttal to some posts saying that conditions will be cool and unsettled for the foreseeable. Sorry if I kind of touched a nerve there.

Anyway GFS 06z, again pretty good with the Azores high always having some form of influence and temperatures in the South remaining in the low-mid twenties. Around average elsewhere.

 

 

[Frosty.]

The further south by southeast you are, specifically the southeastern half of england, the Gfs 06z is an above average run with temperatures frequently in the 24-26 celsius range, 75-79F and not only that, this also looks the driest and sunniest part of the uk for the next few weeks on this run with frequent incursions of azores/atlantic ridging with only a few showers and hardly any persistent rain at all. As we expand further to the north and west, the temperatures look closer to average, more like the low 20's celsius which is still pleasantly warm but with a greater risk of scattered showers and the occasional heavier burst of rain but with a lot of dry and sunny weather too, especially this weekend and into the first half of next week. The final area which is n.ireland, cumbria, northumberland and the whole of scotland looks rather more changeable than further south with low pressure to the northwest holding the upper hand more often than not with more of a mix of weather with showers and longer periods of rain but with some drier, sunnier and warmer intervals but overall, near average temperatures, but for the southeast of the uk and especially southeast england, it's a generally good run.

[TootyFruity]

Hi Frosty

Thankyou so very much for your posts I come on daily to check thevmodels and always look for your posts Captain Shortwave and summer sun as I find them the easiest to understand .

Heading to yorkshire Scarborough on the 12th any thoughts on what the models or weather is going to go ? I fully understand that it's FI but and heads up would be great .

Thankyou

[johnholmes]

Sorry if I kind of touched a nerve there.

 

No nerve touched Cs

Best I make clear what can and what cannot be prdicted using the 500mb anomaly charts and this in no way detracts from your post.

The 'general' weather pattern at 6-15 days can be deduced NOT any specifics, althoug an idea of temperature levels is usually clear enough in the terms of cold, average, mild/hot or whatever is the correct terminology for the time of year. An idea of settled dry or unsettled and even how unsettled or changeable is usually possible and with a lot of practice experience some other variables, wind strengths, how unsettled, how frequent any weather systems. The detail is always down to the synoptic models at closer time scales. If its precipitation details you want then as we often see the models can really struggle even 24 hours ahead sometimes even less for when/where/how much, of rain let alone of snow. For details below 6 days then check each model and compare it with the other 2 main ones, whichever is your preference, look for contiuity with them, as the time decreases the predictions of wind strength, temperatures and when/where areas of precipitation are most likely will become higher. Don't expect too much from them even at fairly short time scales. Following this advice would certainly decrease the roller coaster, toys out of prams syndrome that regularly afflicts this thread in winter. But then some of you quite like this or say you do!

[Frosty.]

Hi Frosty

Thankyou so very much for your posts I come on daily to check thevmodels and always look for your posts Captain Shortwave and summer sun as I find them the easiest to understand .

Heading to yorkshire Scarborough on the 12th any thoughts on what the models or weather is going to go ? I fully understand that it's FI but and heads up would be great .

Thankyou

Hi TootyFruity, firstly, thanks for your kind comments, Yes it's tricky at this range to predict the local conditions for Scarborough but based on the Ecm 00z and Gfs 06z, there is a good chance it will be mainly dry with a moderate westerly or northwesterly breeze with sunny spells as an atlantic ridge of high pressure builds into the uk, temperatures around normal, say 20c or possibly into the low 70's F, overall, I think the weather will be sunniest and warmest this coming weekend, temps nearer average early next week and then warming up again midweek, hope that is helpful.

Edited August 6, 2013 by Frosty039

[mushymanrob]

indeed as has been mentioned, the 06z gfs does look better then other recent runs, trouble is yet again i dont think it has any support from the anomaly charts which suggest, and have broadly done so for a while now, the upper air pattern will be westerly, even north of west, and im guessing (and will stand corrected if im wrong on this) with the lines tightly packed (are they isobars on those charts? sorry, still learning), itll be brisk and windy.. the southern warmth progged by the 06z gfs is dependant on a ridge from the azh, but is that even possible with these charts?

 

please, john, anyone, if im interpreting this incorrectly feel free to correct me

 

 

[johnholmes]

not isobars mushy, they are called contour lines and represent the heights of the 500mb charts, numbers like 5460 DM 5280DM 5640DM are the heights of the 500mb; in technical terms the height of the 500mb isobaric surface as opposed to the height of the 1000mb or surface shown as isobars, say 1032mb or 984mb. It can get very very complex so best to just think of the 500mb numbers as contour lines which is what they are.

Hopefully when I eventually get round to doing the notes on 500mb contour charts I might take it to a stage where we can talk about this.

 

Much as in isobars at the surface though their closeness signifies the relative speed of the air at 500mb. Usually when they suggest a strong flow is when we tend to get an unsettled or changeable pattern of weather. This is because the weather systems are then moved fairly quickly in a very approximate direction shown by the contour lines. Beware though, as always, where ridges and troughs occur life becomes pretty complicated so don't worry away from where the lines are relatively parallel to one another.

Edited August 6, 2013 by johnholmes

[mushymanrob]

not isobars mushy, they are called contour lines and represent the heights of the 500mb charts, numbers like 5460 DM 5280DM 5640DM are the heights of the 500mb; in technical terms the height of the 500mb isobaric surface as opposed to the height of the 1000mb or surface shown as isobars, say 1032mb or 984mb. It can get very very complex so best to just think of the 500mb numbers as contour lines which is what they are.

Hopefully when I eventually get round to doing the notes on 500mb contour charts I might take it to a stage where we can talk about this.

 

Much as in isobars at the surface though their closeness signifies the relative speed of the air at 500mb. Usually when they suggest a strong flow is when we tend to get an unsettled or changeable pattern of weather. This is because the weather system are then moved fairly quickly in a very approximate direction shown by the contour lines. Beware though, as always, where ridges and troughs occur life becomes pretty complicated so don't worry outside where the lines are relatively parallel to one another.

 

thanks john .

[The PIT]

One or two chilly nights shown by the GFS 12 oz. If they are correct there may be the odd ground frost around. Otherwise not too bad overall. The further north you go the more unsettled while the South east is a bit too close for comfort to the Low coming up from France midweek.

[draztik]

The MetO and GFS both showing a more significant pressure rise, for Friday thru next week... That's a big change from what the MetO were showing last night.

will be interesting to see where the ECM takes us.

Edited August 6, 2013 by draztik

[TootyFruity]

Hi TootyFruity, firstly, thanks for your kind comments, Yes it's tricky at this range to predict the local conditions for Scarborough but based on the Ecm 00z and Gfs 06z, there is a good chance it will be mainly dry with a moderate westerly or northwesterly breeze with sunny spells as an atlantic ridge of high pressure builds into the uk, temperatures around normal, say 20c or possibly into the low 70's F, overall, I think the weather will be sunniest and warmest this coming weekend, temps nearer average early next week and then warming up again midweek, hope that is helpful.

Thanks Frosty

[Summer Sun]

The MetO and GFS both showing a more significant pressure rise, for Friday thru next week... That's a big change from what the MetO were showing last night.

will be interesting to see where the ECM takes us.

 

Indeed it would be mega warm at first with NW'ly winds but they wouldn't last too long if the high built in

 

Edited August 6, 2013 by Summer Sun

[Frosty.]

The Gfs 12z shows a lot of normal August weather with spells of sunshine but also scattered showers and occasional longer spells of rain with temperatures into the low 20's celsius across the southern half of the uk but nearer the high teens celsius for n.ireland, scotland and the far north of england. The next few days bring an increased risk of showers, some heavy with thunder, I think tomorrow the heaviest showers will be across scotland but on thursday they are more likely further south and east but there will also be sunny periods in most areas but with partly cloudy skies and feeling pleasantly warm. Friday brings a weakening occluded front southeastwards across the uk with a few showery bursts of rain on that but becoming fine behind it with pressure trending higher from the southwest as we head into the weekend, the azores/atlantic anticyclone building a ridge across the south with a mainly dry and warm weekend on the whole although the ridge pulling southwest as pressure falls to the north, saturday looks the nicer of the days for a larger area, the fine weather tending to become squashed further south on sunday, with the ridge pulling back, it will allow fronts to brush around the top of it and bring outbreaks of rain and showers to the west and north, the southeast staying mostly fine for longest. Early next week, the atlantic ridge tries to build into the uk again but is thwarted by low pressure pushing in from the northwest but southern britain looks fine and pleasantly warm on monday, further north there is a risk of rain and showers with temperatures struggling in the 16-19c range. The good news on this run is a large anticyclone builds in during FI and intensifies over the top of the uk, this would bring a return to widespread fine and warm weather with temperatures widely into the low to mid 20's celsius, it would be a lovely mid August if it occures.

 

PS. hope it's fine for TootyFruity in scarborough next week, gfs 12z looks a bit dodgy for the northern half of the uk, hope it's being over progressive, hoping the atlantic ridge will build in stronger through next week.

[TootyFruity]

Hi Frosty thanks again great post I'm also hoping the GFS is being too progressive ... Hoping tonights ECM is a cracker

[Frosty.]

Tonight's Ecm 12z creates a Battleground across the uk between low pressure pushing east from greenland/iceland and disrupting the weather across northern britain and the Azores/Atlantic Anticyclone trying desperately to build northeastwards across the south of the uk, what this run shows is the further south you are, the better the weather will be overall with fine and pleasantly warm weather having the upper hand, certainly from wales, the midlands and east anglia southwards, it may well be that we can include the southern half of northern england in generally drier, brighter and relatively warmer conditions but with the PFJ rippling across northern britain at times, most of scotland and probably northern ireland will be in a more changeable oceanic airmass for the majority of the time with temperatures in the mid to high teens celsius, occasionally nudging into the low 20's celsius. For most of england & wales though, good sunny spells at times, some cloudier days with a few showery bursts of rain, such as friday for example as a weakening occluded front pushes southeast and fragments with brighter, drier weather following, pressure then rising from the southwest as the azores anticyclone ridges across the south, saturday looks like being a fine and warm day for most of the uk apart from the northwest corner and temperatures should reach the mid 20's celsius across the south/se and generally 22-24c but nearer 19c for the north of the uk, sunday trends more unsettled in the north as a trough swings southeast from iceland but southern britain should be fine and warm again despite the atlantic ridge pulling further back to the southwest in response to the trough further north, then early next week once the spoiler trough has cleared off into scandinavia, the azores/atlantic anticyclone has another opportunity to ridge into the uk but there is a risk of the ridge being at least partially flattened by the next area of low pressure heading towards northwest scotland, so a north/south split  trending more northwest-southeast eventually seems likely, the north more changeable with average temperatures for most of the time but with occasional sunnier & warmer interludes, and for the southern half and especially the southern third of the uk looking generally drier and brighter with only an occasional risk of a shower with longer sunny spells and pleasantly warm as a result, possibly rather warm or very warm from time to time across the eastern half or southeastern quarter of england.

[ANYWEATHER]

Quite simply a changeable to unsettled week ahead depending on where you live from the models tonight with some incursions of rpm air. Best in the south ,more unsettled in the north.....and if you go deeper into FI not a lot changing!   

[Milhouse]

Very good summery there Frosty. Temperature wise, the outlook is about as average as it gets with no sign of any heat or very cool weather over the next 10 days. temperatures always in the range 18-22c north to south. As is often the case with weather fronts moving down from the NW, It should be fairly dry in the SE with the rain tending to fizzle out.

[J10]

A definite SW/NE split to the weather into the weekend and for the start of next week, the best of the weather to the sunnier SW, and the worst of the weather to the NE, but not too bad even there to be honest. 

 

If this is unsettled, I'd take it anyday.

 

This very much reminds me of the pattern at the start of this summer, wasn't too bad the either.

 

Interesting to see how much of an improvement there is in the FAX chart for Saturday compared to last night's version. 

Edited August 6, 2013 by J10

[ANYWEATHER]

Hi Frosty thanks again great post I'm also hoping the GFS is being too progressive ... Hoping tonights ECM is a cracker

Certainly is a cracker!   

[TootyFruity]

Certainly is a cracker!

Very funny !!!

[William of Walworth]

Edited on reflection -- last night's silliness removed.

 

Have hopes now that Captain S (below) and GFS really are onto something.

Edited August 7, 2013 by William of Walworth

[Captain Shortwave]

Much stronger building of the Azores high next week from the GFS

 

 

One hopes this is a trend which will continue in the morning.