Model Output Discussion 31/07/14 onwards.

[Frosty.]

The Gfs 00z op run shows an increasingly cool week ahead with sunshine and showers, overnight it turns colder with minimum temperatures dipping to mid single digits celsius in towns and cities but closer to freezing point in rural areas with a touch of frost, the rural ground frost risk increases next week as the cool, strong N'ly airflow moderates as the week goes on. Taking a snapshot of next wednesday, temperatures down south don't look bad, pretty close to normal actually and feeling pleasant in the sunny spells with 19 celsius for southern / southeast england, actually, folk down south may wonder what all the fuss is about! it's the northern half of scotland which will bear the brunt of this upcoming very cool, windy and unsettled spell, as they will have Northerly gales and frequent showers for most of next week and temps around 12 celsius..but we will all notice the overnight chill.

 

Looking further ahead, it's the south which has occasional anticyclonic influence with spells of warm sunshine alternating with cooler and unsettled weather but it's the north and west which looks predominantly unsettled but at least temperatures recovering closer to the seasonal average, the run ends on a much more optimistic note with a stronger push from the azores high which would go on to bring a summery early september for most of the uk.

Edited August 16, 2014 by Frosty.

[knocker]

Just as we saw the modelled less settled weather being shortened and in some cases not occurring at all through June and July, so the pendulum has swung the other way and we now seem to be in a period where the promise of higher heights is one that fails to materialise or is very transient. strange to say that summer is over, but given how good it was for large parts of June and July, methinks that's pretty well it for warmth this season, apart from the odd day of two. it doesn't look like there is a chance of a flip back. anyone care to make a call on what changed! Was it really just down to the energy in Bertha being able to get the mean lw trough to our east? Surely not.

 

I frankly have no idea but the situation of standing waves is quite interesting. It was discussed briefly in the banter thread. We had this situation in the summer personified by the weather in the US and Siberia and a static evolution over Europe leading as it happens to a pretty good summer here. Perhaps a subsequent breakdown of these waves leading to a more dynamic tropospheric circulation. Again perhaps tied in with summer coming to an end in the Arctic. Just a thought.

Edited August 16, 2014 by knocker

[bluearmy]

The MJO was in fairly low amplitude through July so I can't accept that as an explanation. standing waves is ok knocker but if so, what was the catalyst for that to break down? The arctic summer coming to a close is not something I can buy into in this regard.

Edited August 16, 2014 by bluearmy

[Captain Shortwave]

The ECM would still probably give a decent Bank holiday weekend.

Maybe some showers in the east on Saturday

Sunday looks fine for most

Could turn very warm in the east before a cold front moves through during Monday night into Tuesday. The 12C isotherm gets into the UK.

 

Would need some support from the other models though. Both GFS and GEM look flatter though still giving a brief drier and warmer spell.

[Polar Maritime]

I have had to delete some posts, Can we please only discuss the Model Output. Let's not get to carried away with the up-coming Winter, It's not even Autumn yet!

 

Many Thanks, PM.

[ANYWEATHER]

The ECM would still probably give a decent Bank holiday weekend.

Maybe some showers in the east on Saturday

Sunday looks fine for most

Could turn very warm in the east before a cold front moves through during Monday night into Tuesday. The 12C isotherm gets into the UK.

 

Would need some support from the other models though. Both GFS and GEM look flatter though still giving a brief drier and warmer spell.

In all fairness, Ecm has been the poorer model against the gfs. Ecm has now sided with the gfs and really shows little in the way of ridging as we move towards the Bank holiday weekend. All a long way off, but very unsummer like conditions in the week ahead....

[phil nw.]

The MJO was in fairly low amplitude through July so I can't accept that as an explanation. standing waves is ok knocker but if so, what was the catalyst for that to break down? The arctic summer coming to a close is not something I can buy into in this regard.

My view on this is that tropical storm developments upstream would seem to be the key to the change in the pattern since the start of the month.

Looking through the charts since the start of August and we can see the previously persistent Scandi ridge coming under more pressure from the gradually increasing jet.

It looks to me that Bertha re- invigorated the Atlantic trough as it tracked across from the tropics flattening those heights further east.

 

Some charts showing the eventual breakdown of the Scandinavian block which kept us on the warm side of the Atlantic setup through a good part of Summer.

 

 

Comparing the track of the jet before Bertha and now.

 

 

the block to our east gone with the jet now cutting further south and well into Europe.

[Cloud 10]

Just as we saw the modelled less settled weather being shortened and in some cases not occurring at all through June and July, so the pendulum has swung the other way and we now seem to be in a period where the promise of higher heights is one that fails to materialise or is very transient. strange to say that summer is over, but given how good it was for large parts of June and July, methinks that's pretty well it for warmth this season, apart from the odd day of two. it doesn't look like there is a chance of a flip back. anyone care to make a call on what changed! Was it really just down to the energy in Bertha being able to get the mean lw trough to our east? Surely not.

 

Comparing the anomalies for the first week of August (which looks very familiar this summer) and then for the 13th of August,maybe bertha was indeed the straw that broke the camel's back,the camel being the scandi high.

 

[IDO]

Just as we saw the modelled less settled weather being shortened and in some cases not occurring at all through June and July, so the pendulum has swung the other way and we now seem to be in a period where the promise of higher heights is one that fails to materialise or is very transient. strange to say that summer is over, but given how good it was for large parts of June and July, methinks that's pretty well it for warmth this season, apart from the odd day of two. it doesn't look like there is a chance of a flip back. anyone care to make a call on what changed! Was it really just down to the energy in Bertha being able to get the mean lw trough to our east? Surely not.

 

 

I suspect it was several factors that gave the UK a warm June-July but it looks a good bet IMO that Bertha has disrupted our mid-latitude and moved us out of the pre-Bertha pattern. The block to our east, once our benefactor, acted as a wall when the energy from Bertha arrived. So for the last 5 days it has been in situ to the NE slowly edging heights to our east further east, building an Atlantic ridge in the wake of the trough. The jet now split, with the main arm now coming from Greenland it was only a matter of time before further energy was sent SE from Greenland which is the upcoming flow. This just deepens the trough and another static trough dominated 5-7 days awaits as this low fills.

 

Aided by this flow, the Atlantic ridge during the next week builds into Greenland and cuts off the feed of lower heights and by next week the jet has found another route and broken through the other arm (normal route), giving us a more zonal flow. This should de-amplify our part of the NH till we see what happens to the PV; at the moment the op settles it in Greenland:

 

 

ECM D10 mean again like last night and matches the GEFS mean: 

 

The NOAA 8-14 day also in line with the above: 

 

Interestingly the D5 ensembles for ECM this morning has one cluster:http://old.ecmwf.int/samples/d/inspect/teasers/samplers/banner/mean_sea_level_pressure_and_temperature_at_850hpa!120!pop!od!enfo!enplot!2014081600!!/  As strong a signal for the next 5-7 days as you could get.

[Gael_Force]

The MJO was in fairly low amplitude through July so I can't accept that as an explanation. standing waves is ok knocker but if so, what was the catalyst for that to break down? The arctic summer coming to a close is not something I can buy into in this regard.

 

Have a read of this post by Michael Ventrice ....

 

http://www.wsi.com/blog/energy/sub-seasonal-u-s-temperature-outlook-for-september/

 

A lot of changes took place, far from where Bertha was, during late July.

 

He mentions AAM and MJO but no reference to the QBO which switched to easterly with the biggest two monthly drop in the record.

[johnholmes]

I hope this post is acceptable in the model thread although I do not show any charts.

 

It is very interesting as to what caused the change in upper air pattern that in turn leads to quite different temperature levels at the surface both now and being predicted.

 

To me Bertha had a part in it, but, the marked trough into which the ex hurricane moved and then deepened in its left exit had been predicted even before Bertha had been a largish ‘blob’ of convection off the West African coast. The 500mb anomaly charts had been coming to this conclusion over 5-10 days prior to the arrival of Bertha off the N American coast. The trough had been there (predicted) for quite some time. What changed was that they began to show the ridge and +ve heights E/NE of the UK being dropped to favour a less blocked set up to our east. As just above, how much Bertha accentuated this I have no idea. It has to be said though that the arrival of these systems into the North Atlantic almost always causes model problems.

 

What we don’t know of course is if ‘she’ had not come along whether the predicted change in upper air pattern would have been quite so marked. As has been posted, would it have been sufficient to edge the upper block to our E/NE away as has happened. Myself I suspect it would but others may disagree.

 

A final comment is, given the above, just how long temperatures here have taken to drop from their ‘high’ values to around or a touch below normal. Only 3 days, prior to today, have maximum temperatures failed to reach 21C or more this month with July showing an average Maximum of 25.1C. The average maximum up to yesterday for August stood at 22.6C.

 

Certainly an interesting period in weather watching.

[Frosty.]

The GEFS 00z mean shows the pattern eventually flattening out with lower heights to the north west / north and high pressure to the south of the uk which ridges across the south at times, this means the warmest temperatures, driest and sunniest weather is more likely across the south, especially southern england but with occasional unsettled and less warm intervals too, it looks progressively more unsettled further north but at least temperatures recover to average after the autumnal blast next week.

Edited August 16, 2014 by Frosty.

[lorenzo]

Have a read of this post by Michael Ventrice ....

 

http://www.wsi.com/blog/energy/sub-seasonal-u-s-temperature-outlook-for-september/

 

A lot of changes took place, far from where Bertha was, during late July.

 

He mentions AAM and MJO but no reference to the QBO which switched to easterly with the biggest two monthly drop in the record.

 

This is a great blog, it's a pity the maps didn't cut out our bit of the world and leave us filling in the gaps, will be interesting to see where the next kick off in West Pacific typhoon activity takes things.

 

The re-analysis shows the AAM state changes pretty clearly, will try and plot a GWO August forecast once I get a new FTP sorted.

 

June / July / August to date

[Gael_Force]

This is a great blog, it's a pity the maps didn't cut out our bit of the world and leave us filling in the gaps, will be interesting to see where the next kick off in West Pacific typhoon activity takes things.

 

The re-analysis shows the AAM state changes pretty clearly, will try and plot a GWO August forecast once I get a new FTP sorted.

 

June / July / August to date

http:////f1.nwstatic.co.uk/forum/public/style_images/master/attachicon.gifJune 2014.gifhttp:////f1.nwstatic.co.uk/forum/public/style_images/master/attachicon.gifJuly 2014.gifhttp:////f1.nwstatic.co.uk/forum/public/style_images/master/attachicon.gifAugust 2014 so far.gif

 

Have you seen the research page from Nicolas Schiraldi - hes has GWO composites and forecasts.

 

http://www.atmos.albany.edu/student/nschiral/comp.html

 

[Frosty.]

I'm BANKING the Gfs 12z op run because it shows a pleasant Bank Holiday weekend with a ridge of high pressure building in from the west and bringing a fine and gradually warmer spell across the south and east which lasts well into the following week, more unsettled across north western areas. The fine BH weekend is just the starter dish because following another unsettled blip, the end of august into early september is shaping up to become increasingly summery with high pressure taking control bringing warm and sunny conditions to most of the uk, mid 20'c for the south.

 

Looking at the week ahead, becoming cooler and breezier with sunshine and showers, especially further east, then watch out for a risk of ground frosts when the winds drop, at least in rural northern uk.

 

If we all pray hard enough, this run might verify

Edited August 16, 2014 by Frosty.

[IDO]

Not much change this evening; 6-7 days of uppers around 5c on the GEFS and cooler further north: 

 

Surface temps look like being 2-3c below average for S/SE. Relatively dry in the south, more unsettled further north.

 

GEM has changed its 12z to reflect other model's morning output with a brief ridge Friday-Saturday next week:

 

The GFS op conversely is more like this morning's GEM with the transient ridge a slower moving feature; however the control, like this morning's GFS op is more in line with the mean:

 

T204 op:  Control:  Mean: 

 

Though the op does have cluster support within the ens.

 

ECM is in between: D7:   D8: 

 

That will be resolved in due course though we can conclude the ridge is transient. The net result is that Bank Holiday Monday could go anyway:

 

GEM is the most unsettled:   :  

 

ECM looks OK for the south after the front clears Sunday and should be warmer: 

 

GFS is the best for temps for the south: 

 

Into GEFS FI and about 33% of members at D16 showing pressure building, the rest keep the westerly flow (though variations within that cluster).

 

 

 

[ANYWEATHER]

Still a very cool outlook for next week, some interesting temps next week with regarding low temperatures, after that the Bank holiday weather is rather messy!But it does look like we will swap the cold maritime air with something rather warmer from a tropical maritime airmass for a time just after the bank holiday....But staying unsettled......

Edited August 16, 2014 by ANYWEATHER

[Man With Beard]

This would suggest an eventual return to the pattern from early August, except the mean trough to our west rather than north-west. Potentially still wet, but possibly warmer as the winds may be largely from a SWly direction. 

[knocker]

The anomaly charts are in broad agreement for the BH.

 

Surface wise the GFS has very brief transient ridge before low pressure resumes and the ECM remains with the low pressure. Temps below average. The position of the jet rather confirms the unsettled Atlantic westerly flow.

 

 

[Frosty.]

Tonight's Ecm 12z ensemble mean looks rather good for the Bank Holiday weekend, at least across the south & east with temperatures recovering and a ridge of high pressure killing off any remaining showers near the east coast, winds fall lighter, more in the way of sunshine but chilly nights on the way. So this really could be a BH weekend we can bank on to stay dry. Looking further ahead, shallow trough to the north west, high pressure to the south east, warming up with temperatures back into the low 20's celsius, possibly mid 20's c for the southeast..this looks realistic since this autumnal blast will only reduce the max temps to 18c in the south / se more like 19-20c and perhaps 22c by the weekend nearer low to mid teens c for scotland but a bit higher later. Following week looks rather warm and showery but with decent sunny spells too, especially for the south and east, winds generally from south of west.

Edited August 16, 2014 by Frosty.

[knocker]

A brief look at the GFS ens for the BH and just after.

 

The anomaly chart quite familiar with the trough SW/NE over the UK.

 

A brief transient ridge Sat/Sunday before the low pressure moves in so relatively settled weather initially. Temps lower than average intially but becoming around average as the cold air is kicked into touch by the westerly flow.

 

[IDO]

As expected this morning's GFS op moves more in line with its mean after yesterday's 12z. So for BH Monday the three main models:

 

GFS:   GEM:  ECM: 

 

Compared to yesterday it has moved into the wetter territory.

 

GFS in FI is Atlantic driven till around the 30th when it tries to ridge from the Azores. HP never really establishes but the UK is influenced by the ridge:

 

 

 

The control is similar, with a battle between the Azores and lower heights to Scandi: 

 

GEM keeps it unsettled at D10: 

 

The GEFS like yesterday has the Azores ridge scenario at around 33% but interesting that the hi-res runs are playing with it now. The rest continue with the westerly flow with transient short wave ridges for the south.

 

So as a whole a continuation for the rest of August of average to cooler weather with the potential in early week 2 for some wetter few days, that coincides with a return to more average uppers; London ensembles:

 

 

 

After that a westerly flow for around 3-4 days at least.

Edited August 17, 2014 by i'm dreaming of...

[Frosty.]

BH weekend starts to warm up by day and night with the southeastern half of england reaching 22-23 c  72-73 f..perhaps a notch higher in london and overnight down to 13 c, a brief ridge of high pressure nosing in from the south finally shunting the remains of that pesky trough out of the way BUT it's only a brief respite as by BH monday it looks thoroughly miserable with rain just about everywhere, then it stays v unsettled, cooler and windier as a low tracks across the uk but at least high pressure tries to build into the south later in low res,  Gfs 00z op run this morning is a bit of a roller coaster..at least next sat/sun look better for the southeast...not so good further north and west.

[tinybill]

morning all  looking at the  gfs  this  morning  its looking  like  our summer coming  to an end .  and  its going  to a unsettled Atlantic westerly flow. 

 

http://www.meteociel.fr/modeles/gfse_cartes.php?mode=2&ech=6

 

 

http://www.meteociel.fr/modeles/gfse_cartes.php?mode=2&ech=204

[mushymanrob]

This would suggest an eventual return to the pattern from early August, except the mean trough to our west rather than north-west. Potentially still wet, but possibly warmer as the winds may be largely from a SWly direction. 

 

lol.. you stole my thunder!

 

yep i was going to highlight this chart, which basically rules out (if it variefies) any widespread return to settled summery conditions. yes some favoured southeastern areas might get some very pleasant days, but the bulk of the country wont.

i think the troubles with model watching is picking which set of data to believe, of course the more skilled view all sets of data and draws a conclusion based on that. others, like myself for eg, tend to pick a 'favourite', and my favourite is the noaa 500mb anomaly charts. they have (as john holmes championed) been the most accurate in predicting the most likely upper air pattern .... hence my scepticism over other scources that suggested a settled spell to end summer/august.  the anomaly charts gave no signal really that there was likely to be any decent period of settled weather.

of course after a cool week, we are likely to get a fine sat/sun as a transient ridge builds/crosses the uk between 2 areas of low pressure. but by bank holiday monday all runs suggest a vigourous low hitting the uk , after which, as the chat above suggests, an unsettled atlantic driven regime is pretty likely to see the rest of summer/august out.

will we get a settled warm sunny spell in september?... flip a coin, its anyones guess, but september/autumn looks like starting unsettled.