Model Output Discussion 06Z, 13 Sep. 2013 ---->

[phil nw.]

Good evening everyone.

I thought it time to look in after a break enjoying some of our recent warm Summer weather.

A much more Autumn like feel has gradually developed since the early days of this month with our first deep Atlantic low of the season now on our doorstep.

Looking at the T72hrs fax and 850hPa charts we can see much cooler Arctic sourced air coming south in the strong north west winds behind the cold front as the low moves across to the north of Scotland affecting all areas by Monday.

 

 

so a windy and wet spell through late Saturday through Sunday with this brisk and cool westerly regime continuing through next week by the looks.

GFS T144 ens mean

 

the mean jet position on the move further south in the next few days with rain or showers never far away for many of us.

 

[Frosty.]

I wonder what the Ecm will do next, the operational output has been chopping and changing during the last few days but mostly looking very cool and unsettled with a persistent trough to the northeast of the BI.... this is a major upgrade, similar to what the gfs 12z op is showing and more in line with the ensemble mean output which despite the very autumnal looking 00z op run, doesn't look too shabby at all. The mean has continually been showing the spoiler trough slowly drifting away east towards the end of next week and then enabling pressure to rise from the azores, it's pin the tail on the donkey time,,what will the 00z show?

Edited September 13, 2013 by Frosty.

[Summer Sun]

Latest from Gibby on the models high pressure could be moving back in from next weekend

 

Good evening. Here is tonight's account of the 12 noon outputs from the midday outputs of GFS, UKMO, GEM, NAVGEM and ECM for today Friday September 13th 2013.

 

All models show a rippled front across Southern Britain will move away East overnight with it's heavy rain clearing away East with it. The North already rather drier and fresher than further South and these conditions extend South to Southern areas too tomorrow with some sunshine and light winds. On Sunday all models show a deep depression crossing East to the North of Scotland with a spell of rain and strong winds sweeping East across the UK through the day with gales in the North. By Monday clearer and more showery weather will have swept across all of Britain with some heavy and squally showers for all with hail and thunder possible through the day. On Tuesday another disturbance looks like crossing Southern Britain with another spell of heavy rain and the chance of strong winds before all of the UK return to a more showery regime midweek as Low pressure slips SE down the North Sea.

 

GFS then shows a steady improvement developing from the SW as High pressure builds in later next week though a complication from an ex tropical storm could return unsettled and wet weather briefly at the weekend as this feature passes across the UK. Thereafter the South sees a lot of dry and bright weather close to High pressure to the South. However, further North and West depressions and fronts passing close by could maintain some spells of cloud and rain at times. It should become somewhat warmer as winds back more towards the SW.

 

The GFS Ensembles look somewhat different to this morning with considerable variation from day to day. There is alternating cool and warmer phases shown tonight with the operational a particularly prime example showing as a warm outlier towards the end. Rainfall amounts as far as Southern Britain are concerned are lower too than was shown this morning.

 

The Jet Stream continues to show a strong jet flow across the Atlantic and down over the British Isles from the NW over the coming week or more.

 

UKMO shows a changeable weather pattern across the UK in the middle of next week with Westerly winds and occasional rain as troughs pass East in the flow but lighter winds by then and probably a little less cool.

 

GEM tonight also shows changeable weather continuing throughout next week. The cool and windy theme of the beginning of the week does lessen in the second half of the week as the cool flow is eventually cut off as winds back West. GEM also shows the remnants of an ex tropical storm move East over the UK next weekend.

 

NAVGEM continues to show the Low held up over the North Sea next week with cool and showery weather for all before winds decrease and back towards the West next weekend with less in the way of rainfall in the South for a time.

 

ECM looks much better too tonight as High pressure is programmed to build from the SW to replace the cool and unsettled spell next week with a much better weekend especially in the South.

 

In Summary tonight the pendulum has swung back towards a shorter unsettled spell with quiet and standard High pressure based Autumn fayre more likely from next weekend as High pressure is shown with some cross model support to build up from the South or SW with temperatures returning to normal if not a little above in the South. The North though looks like maintaining a more unsettled feel though even here improvements are shown over this morning's output.

 

http://www.norton-radstockweather.co.uk/Model-Analysis%282859336%29.htm

 

[johnholmes]

I think this is the thread?

 

http://forum.netweather.tv/topic/72606-checking-the-500mb-anomaly-charts-against-the-actual-one/

 

thanks for that I will try and save it somewhere that my addled brain can remember

[johnholmes]

Picking up on the Humberto thread again

Now at T+168 from T+192 last night

 

Humberto - 2- from T+192 down to T+00.pdf

 

I am unable to copy single charts of my own pdf! hence resorting to the way I've done it this evening, this time saved to my pc as word document so I can use it as the count goes down to T+00

 

[bluearmy]

ecm 12z ens suite appears to be setting up the nw/se flow of energy that some are expecting to verify. given the strong blocking well to our ne, the continuation of troughing to our se seems a reasonable bet.  it would be fair to say that the extended ens output has done a good job of picking up this weekends deep low but a poor job re a settled period. naefs was very keen on blocking post the 20th and ecm extended for london was always quite dry. reality has been anything but that with most of the rainfall non convective so it should have been shown on the graph.

[Gaz1985]

Pressure rising from the west, I think that ex-hurricane will just scrape Scotland probably into next weekend but the rest of us will be controlled by high pressure. 

 

Edited September 13, 2013 by Gaz1985

[Gaz1985]

If you compare Humberto here: 

 

 

 

And then to below it seems to have weakened some what, and we all know GFS over exaggerates low pressure so who knows it may be a non-event with high pressure instead being the form horse.

 

 

 

 

And then pressure builds over the UK

 

 

Edited September 13, 2013 by Gaz1985

[Scorcher]

Things certainly looking up this evening if it's settled conditions you're after with the ECM, GFS and UKMO all showing pressure building after this deep low has cleared away to the east. It also looks likely that it will warm up after a very cool start to the week. It certainly should feel warmer from midweek onwards for most, especially for England and Wales.

[No Balls Like Snow Balls]

Defo a ridge of HP moving over the UK at T120 on the GFS and UKMO on the 00Z run. ECM 00Z not as convincing.

Latest anomolies still show a Westerly flow coming into the UK so in any ridge of HP temperatures only going back up to around average, and mild rather than cool.

No idea how long any HP would last even if it verifies at all. Plenty of LP close to the UK to scupper any chances of sustained HP spell.

And of course not forgetting what Humberto is gonna do.

Edited September 14, 2013 by No balls like Snow Balls

[johnholmes]

If the 500mb anomaly charts are anywhere near the mark then surface high pressure is going to come and go, not to be a major feature of several days I suspect. Also more in evidence in the SW quarter of the UK than the northern quarter?

[MR EXTREMES]

intresting seeing heights move into Europe to hope this is not a feature that will stick around no uncle bartty surely now.

although as john said its not really sustained heights.

[Summer Sun]

Looking at ECM it looks like the further south you are the better the weather will be once this low ease's away mid week

 

 

At t168 the Azores gets its act together forcing lows north of the UK introducing a north south split

 

 

UKMO moving to the settled route as well, just after they changed there update to an unsettled outlook

 

Edited September 14, 2013 by Summer Sun

[Summer Sun]

Latest from Gibby

Good morning. Here's how I see weather events over the coming two weeks as seen through the eyes of this morning's outputs of GFS, UKMO, GEM, NAVGEM and ECM for today Saturday September 14th 2013.
 
All models including the Fax Charts show a general consensus of agreement for the weather type between now and the end of the coming working week. A weak ridge of High pressure is shown crossing the UK with fine and dry weather for most following the slow clearance of rain and cloud from the SE later today. Winds freshen from the SW later today and tonight across the NW as a deepening Low advances towards an area North of Scotland by tomorrow. After a cool night in the South and East, fronts will bring heavy rain and gales already in the North to all areas by the end of the day with the clearance of a cold front later the precursor to a period of cool and very showery weather over the UK at the start of next week as the parent Low slowly fills and drifts slowly SE down the North Sea. There is still a risk of a more prolonged period of heavy rain for a time towards midweek in the South though this looks less certain this morning with the showery theme equally possible of continuing. Later in the week the trend is shown for all models to point to somewhat less settled conditions to develop over the South as a weak ridge tentatively builds into these regions with the North maintaining changeable weather with rain at times. It is likely that most areas would become less cool by the end of the week.
 
GFS then shows the remains of an ex tropical feature running NE towards the NW of Britain with rain and strong winds here next weekend but with less windy and fair conditions looking more likely over the South. This process is repeated at the beginning of the second week before High pressure affects most of Britain for a time with dry and bright days and misty nights before somewhat changeable conditions with slack winds develop for all by the end of the run.
 
The GFS Ensembles today show a very mixed bag trending just above average overall once the surge of cool air early next week dissolves. Some rain at times is shown for all but more especially for Northern locations.
 
The Jet Flow currently surging across the Atlantic strengthens further over the next few days across the UK where it is maintained for a fair amount of next week slowly easing Northwards across the UK by the end of the reliable period.
 
UKMO shows a slack Westerly flow at the end of its run across the UK with occasional rain from weak fronts crossing East, most active in the North.
 
GEM shows a somewhat more changeable theme again towards the end of the run with a moist SW flow carrying ex tropical air with occasional rain across the UK in rather warmer air than of late.
 
NAVGEM too shows a less windy and less cool end to the week as a weak ridge crosses over giving a drier period before Westerly winds bring a series of fronts, fairly weak in the South with rain at times for all.
 
ECM shows a similar scenario with next weekend looking OK for the South while northern areas see windier and more changeable weather with some rain. This then looks like edging South to more areas early the following week though the extreme South possibly staying drier. It would become less cool than next week.
 
In Summary details are sketchy but the theme is a common one this morning that after a windy and cool Autumnal week next week conditions look like improving to some degree, especially across the South. It's to what extent such an improvement is likely this morning as the Atlantic will maintain more than enough energy to keep the North mostly quite breezy and unsettled while the South has the best chance of seeing fairly lengthy dry spells between short spells of cloudier and damper conditions. The one common denominator between all the output this morning is that beyond next week temperatures would recover closer to average with temperatures rising even a little above average in the South at times, especially by day.

 

http://www.norton-radstockweather.co.uk/Model-Analysis%282859336%29.htm

Edited September 14, 2013 by Summer Sun

[Frosty.]

The Ecm 00z ensemble mean shows an improvement from T+120 hours which is most noteworthy across the southern half of england and wales as the azores anticyclone gradually extends ridging northeastwards across the southwest and then the south/se with increasingly fine and sunny weather with temperatures recovering back to average or a little above which would make it feel pleasantly warm relative to the upcoming cool, windy and unsettled spell which arrives tomorrow and continues until around midweek, by thursday, a weak atlantic ridge pushes east and diverts the PFJ around the far north of the BI with winds easing and with a few chilly nights later in the week with a touch of frost and fog patches but later on the ecm mean the PFJ slowly begins to encroach south again with an increasingly amplified pattern turning the weather very unsettled across the north of the uk but the further south you are, the drier, brighter and warmer the weather becomes, at least for a while.

[William of Walworth]

I'd say BANK** to the above for next w/e, there've been considerably less usable runs recently for those of us who'll be outdoors ...

 

**Unless a trend is building for further HP encroachment in a week's timke, but that's foolish talk!

[Iceaxecrampon]

  Winters here....

 

UKMO LAKE DISTRICT Monday

Severe gale to storm force winds will continue on Monday, with frequent heavy showers affecting the park. The freezing level may fall to around 800m during any heavier showers before dawn, bringing the risk of sleet or snow and a severe chill effect. Sunny spells may develop through the day during larger gaps between showers.

 

Thats 2400ft enough for some wet ppn on the very highest! 

 

Edit: Chart verification at t48

 

 

IAC

 

 

Edited September 14, 2013 by Iceaxecrampon

[No Balls Like Snow Balls]

The 06 GFS would bring some very chilly nights / mornings later next week if it were to verify.

 

 

 

 

 

 

[Scorcher]

The 06 GFS would bring some very chilly nights / mornings later next week if it were to verify.

 

Rtavn14417.png

 

Rtavn16817.png

 

No mention of the warmer temperatures by day though? That setup would bring high teens to low 20s for many which is much better than we will be getting at the start of the week. Looking increasingly likely that temperatures by day will recover to at least average levels for many from midweek onwards.

[Summer Sun]

The 06 GFS would bring some very chilly nights / mornings later next week if it were to verify.

 

Rtavn14417.png

 

Rtavn16817.png

 

No word on the warm temps by day though pushing above 20c for the south given time

 

Edited September 14, 2013 by Summer Sun

[Scorcher]

No word on the warm temps by day though pushing close to 20c for the south

 

 

Seems like those temperatures are potentially bit undercooked as well to me, especially for Friday- I don't think there would be a huge amount of cloud in that setup. Saturday would be a cracking day as well for England and Wales if that came off.

Edited September 14, 2013 by Scorcher

[No Balls Like Snow Balls]

No mention of the warmer temperatures by day though? That setup would bring high teens to low 20s for many which is much better than we will be getting at the start of the week. Looking increasingly likely that temperatures by day will recover to at least average levels for many from midweek onwards.

 

Correct no mention - yawn

[Captain Shortwave]

Not a bad mean chart for a weeks time, especially given we were starring down the barrel of persistent troughing near the UK a few runs back

As soon as there were signs of the jet tilting NW/SE, the models have changed track and are now offering at worst a flat W/E jet (ECM) or maybe even a more SW/NE tilt.

Day 7

Day 8

 

 

Edited September 14, 2013 by Captain shortwave

[No Balls Like Snow Balls]

GFS 06z T2 ensembles show temps mostly slightly below average for the entire run. Only on a very few days  do we see average temps and daytime temps never rise above 20c.

 

 

 

 

 

 

[Tamara]

I think that the underlying pattern is on a definitively cooler pattern now with the jet stream primed on its way south - and with the interesting height anomalies appearing to our north and north east which have been the focus of recent conversations in terms of longer term seasonal prognosis.

 

What is also interesting though in the much shorter term is that the unpredictable behaviour of Humberto could serve to align the jet stream back SW-NE, albeit temporarily, as it influences our weather patterns in this part of the Northern Hemisphere. Hence why todays output has shown the pendulum swing back at least some way towards the *possibilities* of a slightly quieter and less cool interlude of weather in the south at least late next week and into the weekend. However looking to stay more unsettled further north still.

 

With this tropical feature being as unpredictable as it is, and as they usually are at this time of year, we cannot rely on the modelling becoming less erratic however and any improvement *should it occur* further south is most likely temporary and regarded as a reflection of ridging extending from the atlantic for a time as a downstream response to Humberto taking control of the jet stream further north as it curves *somewhere* in the vicinity of the NE atlantic and *probably* to the north west of the UK. The EPS members show resonable support for this to happen based on the current suggestions by day 7

 

 

But taking any FI model output into account, there is a suspicion that the height anomalies to the NE are more likely to steer the jet stream angle back more NW-SE as Humberto is processed out of the system and a more widely cooler and more changeable scenario takes over again. Its worth bearing in mind that the modelling will  try and remove this blocking signal prematurely and thus it is not worth reading into both operational AND ensemble suggestion at this range.

 

Thereafter however, all that said, there is still the possibility of further seasonal tropical features  providing further interruptions to the cooler, mobile and unsettled theme. However, the prevailing theme from here on in will be one of late seasonal warmth steadily being eroded further and further back into southern europe, and becoming dependant on significant amplification of the jet stream ahead of any more major systems that enter the western and central atlantic that slow and *might* serve to pump up a ridge over the nearby continent or towards the Baltic and return some of the perimeters of this warmth northwards again for a time. But this is obviously based entirely on conjecture atm.

 

Clearly then, any prognosis from the end of next week is 'work in progress' and liable to revision and alteration in the days ahead . In the immediate term, the second half of this weekend with its first major low pressure salvo and then the majority of the coming week look distinctly autumnal, blustery and cool, with temperatures below average in the main and showers rattling through with a few longer spells of rain too.

Edited September 14, 2013 by Tamara Road