Model Output Discussions 12z 03/05/2016

[knocker]

The ecm also has the fronts from the next low arriving in the south west early Friday and has the centre of the low over northern England 992mb by midday Saturday. So a wet and windy couple of days with possible gales in the south. The low clears away east and there is brief ridging behind it before fronts from the next low traverse the country on Monday. The ecm runs this low further north before tracking it east which allows the Azores to impose itself and bringing some fair weather in England before the next system arrives on Thursday.

Edited August 16, 2016 by knocker

[Weather Boy]

11 hours ago, William of Walworth said:

From those charts above from knocker : Utter weekend washout for many parts. Probably a Glasto-level (?) mudbath in the SW (near Exeter) -- where we'll be at our penmulitmiate van/festival outing this season.

I see little if any chance right now of those fronts tracking further North. Is my pessimism for a writeoff weekend nailed on, more or less, by now?

 

Or are 'further runs needed'??

For you, maybe, if you take those charts at face value.  However, it's worth noting that (again taking those charts at face value) the country, aside from Wales and the SW, avoid the rain as the front stalls in, er, Wales and the SW.  Perhaps not the washout weekend for most that many are predicting?  Indeed, presumably there would be quite a draw of warm air ahead of the front leading to rather high temperatures in any sunshine, particularly on Saturday when cloud from the system seems less likely to have an effect on the benefitting areas of the country.  Better in the east for the same reason, perhaps?

I looked at the BBC charts and thought we were in for a bit of a horror show weekend but, from a IMBY perspective, I'm not so sure looking at Knocker's charts.

I'd be very hesitant to look beyond the weekend at the moment.  Models are often mistaken (sometimes over-progressive) in slow moving or stalled systems and I'd suggest that pretty much anything could happen - always fun looking at the scenarios though.  35C for EA maybe??

[coldcomfort]

No real point in attempting to put lipstick on a pig, the 06 GFS is an absolute out and out stinker, effectively writing off the final fortnight of meteorological summer IF proven even close to being correct. August is currently looking a classic game of two halves, the 1st being considerably better than the 2nd!!

Edited August 16, 2016 by coldcomfort

[Yarmy]

5 minutes ago, coldcomfort said:

No real point in attempting to put lipstick on a pig, the 06 GFS is an absolute out and out stinker, effectively writing off the final fortnight of meteorological summer IF proven even close to being correct. August is currently looking a classic game of two halves, the 1st being considerably better than the 2nd!!

Certainly not great, but not without interest (in the south anyway):

 

30C+ although it doesn't last.

[No Balls Like Snow Balls]

55 minutes ago, coldcomfort said:

No real point in attempting to put lipstick on a pig, the 06 GFS is an absolute out and out stinker, effectively writing off the final fortnight of meteorological summer IF proven even close to being correct. August is currently looking a classic game of two halves, the 1st being considerably better than the 2nd!!

 

 

Some of us like pigs lol :-). Personally looking forward to some  autumnal rain and gales.

Edited August 16, 2016 by No Balls Like Snow Balls

[fine wine]

It's good to see a more settled and warmer spell shown on the 06z compared to the 0z early next week after this weekends brief but much needed rain in the south. Just compare the charts and you will see.Certainly a more positive picture for those looking for a warmer end to August. 

[coldcomfort]

1 hour ago, No Balls Like Snow Balls said:

Some of us like pigs lol :-). Personally looking forward to some  autumnal rain and gales.

Risky admission...Anyway to each their own - fine, dry and warm means I make money, unsettled with rain or showers means I lose money....so it's a no brainer for me!

[Summer Sun]

Just for fun

[William Grimsley]

7 minutes ago, Summer Sun said:

Just for fun

Never say never!

[Mark.C]

Would that temperature actually be possible to achieve late August given the correct set up?

[NO LONGER POSTING]

2 minutes ago, mark blackpool said:

Would that temperature actually be possible to achieve late August given the correct set up?

Possibly, you would need some serious mechanics to get it though and crystal clear skies from the word go.

It's not Un heard of to have some proper heat mid to late August as the sun is still very strong.. In fact until mid September the sun is cooking.

The 06z is toying with us and would expect it to dull down a little.

At this stage though it's a rinse and repeat. The rinse being the weekend. But any rain is very very welcome down here in the parched south!

[Summer Sun]

5 minutes ago, mark blackpool said:

Would that temperature actually be possible to achieve late August given the correct set up?

It's possible but as said above we need sunshine for the word go we got 30c at the start of October a few year back I think so the mid to high 30's in late August is certainly achievable if everything was right

[Tamara]

 

3 hours ago, coldcomfort said:

No real point in attempting to put lipstick on a pig, the 06 GFS is an absolute out and out stinker, effectively writing off the final fortnight of meteorological summer IF proven even close to being correct. August is currently looking a classic game of two halves, the 1st being considerably better than the 2nd!!

Sitting on the patio in the sun as I have been, and typing this over a very late lunch, its good that most can draw comfort from the fact that the first half of August has been better than the unduly negative slant and assumptions that you have put on many of your posts in that time, whatever the model ups and downs might have appeared to show at various points.  

 

On ‎12‎/‎08‎/‎2016 at 13:18, Tamara said:

However, the further we had towards the end of August and official end of summer, the more likely it seems to me that unsettled conditions may establish more widely once more as angular momentum falls, and the pattern upstream retrogresses once more..

Not quite large scale attractive end of summer expectations for everyone, but within the restricted possibilities that this summer offers to the nation as a whole, its better to be glass half full than empty one might suppose

Taking into account the main talking points of my own previous post just above, I think that the general (not the precise face value) gist of GFS 06z just happens to offer a realistic way forward. Albeit the reasoning and perspective comes from a very different angle and approach to the post under original reply - and also draws quite different interpretations of what is suggested by that output. 

Obviously not interpretations or conclusions based on the GFS 06z alone, or the rest of NWP for that matter. The task is rather to try and question NWP output and evolution, based on the GSDM modelling - and it is from there that some objective assessment is hopefully attempted.

As reasoned why in the last post, we have benefitted from a fine spell which some of the UK will have enjoyed for at least a full week or more by the time it breaks down late this week. It doesn't make a great summer on its own - but it is highly welcome and enjoyable while it is here.

However atmospheric angular momentum tendency is on the slide once more - as positive frictional torques recede back into -ve territory, as they have been most of the summer and leading mountain torque more negative. 

 

These developments support the return of the mobile pattern - with strengthened Azores High to the SW and the long-wave trough extending towards Scandinavia beyond the 5 day period -  following a cyclonic and poor weekends weather that will certainly contrast last weekend and much of this week.

However, that mostly gets the negatives out of the way.

We have the wildcard of seasonal hurricane development within an environment of an enhanced sub tropical jet flow and continued tropical convection signal in the Pacific. That is plenty enough to ponder over and discourage any sweeping generalisations on detail for the next 10 days, let alone the rest of the month.

The tropical convective signal looks to continue to prop up atmospheric angular momentum sufficiently in the medium term to prevent it falling into Global Wind Oscillation Phase 1/2 (at least for now) and that should prevent the Azores High retrogressing too much - before the end period of the month anyway.  A low signal from the extra tropical Global Wind Oscillation, leaves tropical forcing developments in the 10 to 15 day period as the leading player.

It will be the end of the present tropical convective cycle that will shift angular momentum more decisively downwards and the GWO onwards - and it might well be that which creates a more amplified Atlantic ridge to our west late in the month and suggest more of a polar maritime influence. At least for a time. More of that possibility in the foreseeable future - when events and timings become clearer.

So, to translate all that synoptically, whilst we are returned to a feed of depressions from the Atlantic, it will take little amplification within the sequence of these lows to push some hot humid air northwards, courtesy of sub tropic flow, and provide further brief heat spikes.  These can't ever be guaranteed, but such amplification is quite conceivable because with the pattern not yet fully retrogressed there is band width for the Azores High to ridge eastward and sufficiently far northwards for at least some transitory very warm air advection to occur downstream ahead of any deepening and slowing Atlantic lows..

On that basis, whilst the extent of the intense plume as shown on the ECM 12z last night is questionable, the re-appearance of a similar overall type of synoptic on the GFS 06z to whatever lesser degree, is not just coincidence.  Whilst it doesn't represent another country wide settled spell (the outlook is certainly back to a changeable one and suggests something of a NW/SE split instead beyond the unsettled conditions of the weekend and start of next week)  there remains plenty of opportunity for interest in glimpses of summer before the new autumn season officially begins. Also, until the pattern further retrogresses (watch the tropical signal for that), it will be very hard to achieve temperatures below the seasonal average - even if it feels cool in the more unsettled and blustery interludes such as it may well do this weekend.

With the re-emergence of the amplified mid Atlantic ridge in mind, any modelled synoptic that plays around with the ridge toppling over a cut off low entrapped with hot humid air is quite conceivable also - before any polar maritime influence eventually arrives from the west.

Enjoy the rest of the glorious weather before anything from the weekend and beyond arrives.

Edited August 16, 2016 by Tamara

[johnholmes]

This comment in the post above by Tamara is very valid, and probably so for a good few weeks to come

We have the wildcard of seasonal hurricane development within an environment of an enhanced sub tropical jet flow and continued tropical convection signal in the Pacific. That is plenty enough to ponder over and discourage any sweeping generalisations on detail for the next 10 days, let alone the rest of the month

Whenever a Tropical Storm or Hurricane get into the Atlantic then every model, short or longer term struggles to cope with the enormous amounts of moisture and energy they put into the northern hemisphere area. Forecast acuracy at any length becomes almost woeful at times. But it does make for interesting model watching whichever model type any of us spend most time with. For the anomaly charts then when this happens I just take a break from trying to predict 6-14 days ahead!

Edited August 16, 2016 by johnholmes

[Methuselah]

1 hour ago, mark blackpool said:

Would that temperature actually be possible to achieve late August given the correct set up?

There was a time, I believe (I'm almost sure I read it somewhere) when 32C was far more common in early September than it is nowadays...As to why such temps, at that time of year, no longer seem to occur, I have absolutely no idea whatsoever...Anyone else?

[Man With Beard]

Despite the recent trend to better Septembers recently, I have a feeling that there is also a trend from the traditional end-of-season plume to miss us. This current little teaser is trending the same way - compare the ensembles for London and Paris, and you'll see the latter is far more likely to swelter while we might reach for the jumper (if the cooler cluster is right).

  

The uncertainty in where this plume is going is summed up in the spreads - a green colour for 850s means a high uncertainty over what the ensemble mean predicts (a pretty similar picture between GEFS and ECM given the timeframe)

      

Meaning France in particular could be much hotter or much cooler, with the far SE of England perhaps also in the big swing-zone too.

So charts like this seem within the bounds of expectation

but this one doesn't at the moment

Still - at T216, most of the op runs and ensembles were quite a way out for this week's (eventually quite feeble) plume. So while the ensembles throw up these situations, who knows?? The clear trend is to lower heights towards Biscay next week, and that puts us in the game for a plume, with details to follow by, oh, about T96?

Lastly one for Knocker, remember the ECM predicting 22C for Barnstaple? Nowhere near: http://www.weatheronline.co.uk/weather/maps/current?R=310&LEVEL=140&ART=temperatur&WMO=03707&LANG=en&SI=mph&CEL=C

 

 

[Faronstream]

Still looks rainy and humid in long range ECMWF,  it has been only 2-3 days with sun from the morning until late evening in August, last year was much better for almost whole west Europé this time of the year. Still the chances of a couple of days with temperatures above 25 degrees are 40-45% so i wish for a big high pressure as we go into September

[knocker]

I thought it was Croydon. It was the figure for Croydon high street that I gave you.

Edited August 16, 2016 by knocker

[Scorcher]

2 hours ago, mark blackpool said:

Would that temperature actually be possible to achieve late August given the correct set up?

Although it will not happen, it's basically just as feasible as it is on August 10th, when it happened in 2003. With the right synoptics it's definitely possible- it's getting them that's the issue and what makes it so unlikely. 35C+ has been recorded in September before and as we saw in 2011, 30C is possible right into the start of October.

The 850 hPa temperatures are the crucial factor- the strength of the sun is secondary to this. There is still a lot of heat around on the Continent and the Med well into September and often beyond in most years.

[knocker]

Plume alert as upper trough sinks south

 

Edited August 16, 2016 by knocker

[Man With Beard]

38 minutes ago, knocker said:

I thought it was Croydon. It was the figure for Croydon high street that I gave you.

It was Croyde, not Croydon! You know, north Devon.

Now to stop expectations rocketing unrealistically like perhaps I was partly responsible for last week, I have decided not to post more than one ridiculously hot chart per day if they are for FI (T120 +)

 

(...oops, sorry, my finger slipped)

[knocker]

See you can't be trusted

[coldcomfort]

Still no real point in attempting to put lipstick on a pig, the 12 GFS is another out and out stinker bar a rogue and very unlikely plume, so IF it verifies we can pretty much write off the final fortnight of meteorological summer...or am I simply guilty of putting another unduly negative slant on things?

[Gael_Force]

2 hours ago, johnholmes said:

Whenever a Tropical Storm or Hurricane get into the Atlantic then every model, short or longer term struggles to cope with the enormous amounts of moisture and energy they put into the northern hemisphere area. Forecast acuracy at any length becomes almost woeful at times. But it does make for interesting model watching whichever model type any of us spend most time with. For the anomaly charts then when this happens I just take a break from trying to predict 6-14 days ahead!

Maybe time for the feet up and a cuppa then.GFS has two huricanes in the Atlantic from about 7 days on. Do you reckon the modelling is messed up by the virtual appearance or is it only when the hurricane is actually formed that the models struggle?

[The PIT]

I wouldn't right anything off as yet. The speed the hot spell disappeared shows that what the models show isn't down in concrete at within the T96 time period is still good time point to get excited or unexcited depending on what you like. Add in hurricanes and the reliable time frame may drop well below T96.