Model Output Discussions 12z 03/05/2016

[B87]

1 minute ago, coldcomfort said:

Yes, but under a heavy shower, especially a prolonged one I think the temps could easily get dragged down by 4 or 5 degrees. That said, there would still be some parts like the south coasts of England and Wales that wouldn't fair to badly out of this setup, especially the further west you go and here it could still feel pleasant in any lengthy spells of sunshine, but these really aren't the kind of synoptics most of want to see as we start to close out this very indifferent summer! 

I think the record coldest max for August here is around 14 or 15c, so that could be under threat?

[coldcomfort]

1 minute ago, B87 said:

I think the record coldest max for August here is around 14 or 15c, so that could be under threat?

Well it all has to verify yet, but a cold, clear night followed by a cloudy, showery day could conceivably see temps pegged back in that sort of range imo...certainly not out of the question if all the pieces fall into place, which you kind of know they will at this time of year!

[mb018538]

Looks pretty bad really - though not quite as bad as the June gloom we got here - one day was around 11c all day with incessant rain.

Northerlies can be quite pleasant at times - lower humidity, sharp blue skies. Unfortunately in midsummer with all the solar input it's inevitably going to brew some beefy showers up. It'll certainly feel like autumn in the mornings under clear skies!

[coldcomfort]

10 minutes ago, mb018538 said:

Looks pretty bad really - though not quite as bad as the June gloom we got here - one day was around 11c all day with incessant rain.

Northerlies can be quite pleasant at times - lower humidity, sharp blue skies. Unfortunately in midsummer with all the solar input it's inevitably going to brew some beefy showers up. It'll certainly feel like autumn in the mornings under clear skies!

Especially for any early risers who could be scraping their windscreens....

[Scorcher]

No chance of maxes below 15C for most of England without extensive cloud cover. Of course maxes around 13C are possible under heavy cloud and rain but in a northerly that seems extremely unlikely to me.

There were some very cool upper air temperatures in August 2014 (probably cooler than what is coming next week in fact) after Bertha passed through but the temperature in Manchester only failed to reach 16C on two occasions in the entire month and there was no maximum below 15C.

At this time of year you only need a bit of sunshine to lift the temperature easily into the mid teens- even with 0C uppers, which most of us probably won't quite get.

Edited August 3, 2016 by Scorcher

[Man With Beard]

1 hour ago, summer blizzard said:

Cracker of a potent cold shot (for August) in terms of how potent it could be..

That has to be the most depressing August chart I have ever seen. Would it be colder than December 2015?

Good news is the ensembles for both ECM and GFS - both much, much more seasonal than their ops for the end of next week:

  

though not particularly warm. Look at that GEFS one - the 8C line close to the Med - so it won't just be us in jumpers!!

  

[MP-R]

The best one can hope for supposing the models don't backtrack again, is a slack northerly or northwesterly, with lighter winds. Nights would still be chilly but days would be sunnier and those further east wouldn't feel the punch quite so much. I've warned my Spanish friend who's visiting next week that it'll be cold by his standards, coming from 35C in Zaragoza!

[Nouska]

The 192 hour mean does not look like there is much scope for improvement.

H500           spread

T850  

MSLP spread at +360 hours - hope that is not indicative of the green blobby shown on the GFS in low-res.

[Matthew.]

1 hour ago, Nouska said:

The 192 hour mean does not look like there is much scope for improvement.

H500           spread

T850  

MSLP spread at +360 hours - hope that is not indicative of the green blobby shown on the GFS in low-res.

I always knew I was risking it booking a holiday in Scotland for August next week but this is outrageous! Opposite to a trip in July 2013. Might need the old log fire on, night times looking around 5c locally. Thanks to all for the advice early though

Edited August 3, 2016 by Matthew Wilson

[cheeky_monkey]

5 hours ago, Man With Beard said:

That has to be the most depressing August chart I have ever seen. Would it be colder than December 2015?

Good news is the ensembles for both ECM and GFS - both much, much more seasonal than their ops for the end of next week:

  

though not particularly warm. Look at that GEFS one - the 8C line close to the Med - so it won't just be us in jumpers!!

  

Not sure how this is the most depressing chart August chart ever ??...looks refreshing..dont see banks of cloud and lots of wind and rain..dry and cool..seen far far worse!

[Weather-history]

6 minutes ago, cheeky_monkey said:

Not sure how this is the most depressing chart August chart ever ??...looks refreshing..dont see banks of cloud and lots of wind and rain..dry and cool..seen far far worse!

Anyone should take a look at the 26th August 1986 chart and the days that followed it. Now that was depressing. That was cool, and I don't mean in the awesome sense. 

Edited August 3, 2016 by Weather-history
.

[Man With Beard]

33 minutes ago, cheeky_monkey said:

Not sure how this is the most depressing chart August chart ever ??...looks refreshing..dont see banks of cloud and lots of wind and rain..dry and cool..seen far far worse!

ok that's another way of looking at it!!

By the way, the 06Z ensemble swings even further from the trough scenario by next Friday - a very decent 1025mb mean pressure nudging in

- in fact, by Saturday (T240), 12 out of 21 members have already progressed well beyond the mean chart and have high pressure either over us, or to our south, or east - wouldn't be long before a warm up after that. 

Mind you, the GFS 06Z does have a reputation for being the most progressive...

[bradymk]

Don't think the northerly will be as potent as some are thinking. A below average temp trend as next week goes on nevertheless but do think models will now trend towards a less potent northerly with the high closer to the UK as next week moves into a more reliable timeframe. 

UKMO 144 a lot better than expected!

Edited August 3, 2016 by bradythemole

[northwestsnow]

Well i think we can safely assume from fri sat and sun are going to be fine warm and settled for the majority, after that gfs wants to bring a northerly while ukmo seems less keen.More runs needed..

[Man With Beard]

20 minutes ago, bradythemole said:

Don't think the northerly will be as potent as some are thinking. A below average temp trend as next week goes on nevertheless but do think models will now trend towards a less potent northerly with the high closer to the UK as next week moves into a more reliable timeframe. 

UKMO 144 a lot better than expected!

Yes real surprise this one, UKMO warm and sunny on Tuesday

GFS nearer to this idea than it was, though more of a northerly

GEM has the cool snap but by Thursday High Pressure is back in charge

 

 

Edited August 3, 2016 by Man With Beard

[Wildswimmer Pete]

1 hour ago, Weather-history said:

Anyone should take a look at the 26th August 1986 chart and the days that followed it. Now that was depressing. That was cool, and I don't mean in the awesome sense. 

Here's the chart.  That blob of green snot is the mortal remains of Hurricane Charley however it didn't crawl into its grave, instead it "bombed" just as it approached the British Isles.  The result? Driving, very cold rain, gales and very dark all day. If I remember correctly, we just about made 48F (9C) - I was moaning at the time about experiencing such low daytime temps for summer.   All of summer '86 was very showery however there were a few fine days during the continual procession of lows. 

Edited August 3, 2016 by Wildswimmer Pete

[Frosty.]

The Ecm 12z shows quite a noteworthy cool down next week with temps falling below average, even in the south as time goes on, the night's look like becoming unseasonably cold with slight frosts in rural northern areas and it looks like sunshine and showers, the east and north most showery but by T+240 high pressure is slowly drifting in from the west and normal Atlantic weather is well and truly blocked. This weekend looks like becoming very warm and sunny across the south with the most unsettled weather across the far northwest / north but next week looks like feeling more like Autumn than summer with a brisk Northerly flow, coolest in scotland with a chance of wintry ppn on the highest mountains. 

[Singularity]

 

There is a troubling difference between ECM and GFS at just 48 hours range; look at the 850 hPA temperatures to the SE of the incoming storm system. ECM has them significantly higher than GFS, which in turn leads to a stronger jet stream during the weekend, with the system tracking further south and developing more efficiently as it heads to Scandinavia (hence we see a single storm of unusually large size and intensity early-mid next week, whereas GFS has one compact, strong storm followed closely by a weaker secondary system).

I've long suspected that ECM tends to advect warm airmasses with less modification than GFS, but not until now have I had such clear evidence.

In other news, UKMO dangles the carrot for those hoping the ridge tries to hold on more into next week:

Perhaps just delaying the inevitable, though.

[Frosty.]

The Ecm 12z ens mean charts lack detail but you can still see what's coming next week, a much cooler spell with a Northerly airflow setting in as high pressure retrogresses well into the atlantic. The main weather type looks like sunshine and showers, especially further east and north, some heavy and thundery which could merge into longer spells of rain and really chilly nights for the time of year where skies clear, even a risk of ground frosts / slight air frosts in rural northern uk and possibly cold enough for the showers to turn a touch wintry at munro level (3,000 feet +) in the scottish mountains...Brrr

On the other hand, the met office currently say the south looks largely dry and bright after a spell of rain early next week with the north of the uk catching most of the unsettled weather but the Ecm indicates a noteworthy cool spell developing next week, especially the operational. Unfortunately most of the mean charts were unavailable, including the T850s so I'm mainly expanding on what the Ecm 12z op run shows which is frankly autumnal, especially up North.

Edited August 3, 2016 by Karl.

[William of Walworth]

Thanks for the updates all.

Personally, I continue to sense possibilities, from some output, that the likely Northerly blast next week won't end up quite as extreme, or end up quite as dominant, as some all-year-round cold-celebrators (I mean objective Model Output Discussion observers here!!! Ahem ... ), seem to assume is completely nailed-on .

 

Form horse in these extreme-in-FI-looking synoptic scenarios is surely a midway compromise.

 

I'll stick my neck out, but only a bit, and gamble on more HP influence than predicted on some output for next w/e (that of Sat 13th), but (realism!) not particularly warm either.

 

I also sense few signs of a washout next week  (for most places anyway).

Edited August 3, 2016 by William of Walworth

[Frosty.]

I agree William, it's not nailed on but I think the trend next week is for cooler weather to spread from the north but just how cool and how unsettled is still unclear, I was basing my comments on the Ecm 12z operational run but if the worst happens, scotland will feel it most, as you would expect from a Northerly.

[Man With Beard]

46 minutes ago, Singularity said:

 

There is a troubling difference between ECM and GFS at just 48 hours range; look at the 850 hPA temperatures to the SE of the incoming storm system. ECM has them significantly higher than GFS, which in turn leads to a stronger jet stream during the weekend, with the system tracking further south and developing more efficiently as it heads to Scandinavia (hence we see a single storm of unusually large size and intensity early-mid next week, whereas GFS has one compact, strong storm followed closely by a weaker secondary system).

I've long suspected that ECM tends to advect warm airmasses with less modification than GFS, but not until now have I had such clear evidence.

Let me get this straight ... are you suggesting the ECM is wrong??

[Frosty.]

1 minute ago, Man With Beard said:

.. are you suggesting the ECM is wrong??

It has been known..often

[Man With Beard]

11 minutes ago, William of Walworth said:

Thanks for the updates all.

Personally, I continue to sense possibilities, from some output, that the likely Northerly blast next week won't end up quite as extreme, or end up quite as dominant, as some all-year-round cold-celebrators (I mean objective Model Output Discussion observers here!!! Ahem ... ), seem to assume is completely nailed-on .

 

Form horse in these extreme-in-FI-looking synoptic scenarios is surely a midway compromise.

 

I'll stick my neck out, but only a bit, and gamble on more HP influence than predicted on some output for next w/e (that of Sat 13th), but (realism!) not particularly warm either.

 

I also sense few signs of a washout next week  (for most places anyway).

Completely agree William - looks to me like things will improve rapidly by the end of next week - starting cool but would warm up quickly if a HP cell gets reasonably close, it's early August after all!

[Frosty.]

The Ecm 12z ens mean charts have now updated and its not as bad as the op shows, northern scotland bears the brunt of the cool unsettled weather and in any case, the cool air supply is cut off later next week by a ridge with winds backing through nwly / wly as the ridge of high pressure builds in further south..so yes it does turn cooler from the north for a time next week but it doesn't amount to much or last long before things return to something more normal, it's more of a glancing blow for the south.