Model Output Discussion 26/08/2012

[Frosty.]

After the generally shocking summer we had, with all the flooding misery etc.. this chart from the gfs 12z makes a pleasant change, and some nice warmth on the way.

Edited September 2, 2012 by Frosty039

[Summer Sun]

Its fully out on meteocleil. Remaining warm and settled for all until the end of the weekend with the south east squeezing out another warm day on Monday. More unsettled conditions moving down from the north for Tuesday and quite a chilly day to come across Scotland. More settled but cool for day 10.

Wetterzentral is stuck at 48h

http://www.wetterzentrale.de/topkarten/fsecmeur.html

[johnholmes]

http://www.meteociel...92-21.GIF?02-12

Snow over the mountains

ECM developing similar with the GH

S

thanks Steve!

To those new to model watching you have been watching, via Steve, what is called 'cherry picking' of charts to suit your own agenda!

There are 5 or 6 models that go out to T+192 or beyond. Of these Steve has managed to pick one of 2 that at T+192 on this ONE run show a possible northerly which could give snow on some of the higher mountains of Scotland.

On the other hand someone with a mild preference might choose one of the other models that shows gradient winds coming from about 180 degrees opposite direction.

Its a feature we see daily through the winter half of the year.

Be aware of this phenomena!

Edited September 2, 2012 by johnholmes

[Glacier Point]

Actually two subtley different ones I'd say...

June 1 - July 19 H5 anomaly. Note the position of the mean trough directly over the UK.

July 20 - present H5 anomaly. Note the position of the mean trough to the south and west of the UK.

That's a big difference in the mean trough position for the UK, the one that turns around a significantly below average temperature regime to one that is around or just above average. The earlier period was characterised by a strong gradient in the atmospheric profile fuelled by sharp downwelling signal in the Arctic during the spring and early summer - this is no longer present and we're likely to see more of the charts we're seeing now rather than those for the first half of the summer, but still with the mean trough to our west drawing up mild SW'lys.

... back at ya Steve..

GEFS mean H5 height anomalies days 6-10 and 11-15...

I would broadly go along with this evolution given the state of tendency in relative angular momentum right now, and weakness in the polar field.

Looks like the remnants of Leslie will drop into a mean upper trough anchored to our west and south. With the upstream ridge centred over NE Canada, the trough can't get enough umph to make it past the eastern North Atlantic. Net result, potential reloading of Euro Highs.

[bluearmy]

Looks like the remnants of Leslie will drop into a mean upper trough anchored to our west and south. With the upstream ridge centred over NE Canada, the trough can't get enough umph to make it past the eastern North Atlantic. Net result, potential reloading of Euro Highs.

the spreads are headed this way but its possible the mean trough could get close enough to leave us in the 'messy middle' between the euro heights and atlantic trough. maybe, given time, the spread on the trough will back west a bit. thats been the trend for the past few weeks.

[Geordiesnow]

With high pressure near by, it does look like for the majority, this week will be quite settled and at times quite warm with tomorrow perhaps going to be the warmest day of the week ahead. There is some complications with a cold front sweeping South-eastwards introducing some cooler air and the strong winds for parts of Northern Scotland tomorrow evening but in general, a quiet settled week ahead.

[Milhouse]

Saturday is looking like a very warm day with 15c upper temperatures not that far off the south coast.

And the mean at day 10 suggesting low pressure likely to be situated to the west of the UK with a warm southwesterly flow

[Chris W]

Just a quick note on the ex-tropical storm potentially arriving next Friday - I am racking my brains to think of a lower pressure reading that I have seen before and I cannot remember one, it looks like this one could come in around the 960mb mark according to GFS. Is this correct and if so is it one of the most intense depressions we have ever (potentially) seen over the UK? Thanks.

[bluearmy]

Just a quick note on the ex-tropical storm potentially arriving next Friday - I am racking my brains to think of a lower pressure reading that I have seen before and I cannot remember one, it looks like this one could come in around the 960mb mark according to GFS. Is this correct and if so is it one of the most intense depressions we have ever (potentially) seen over the UK? Thanks.

not sure what the answer is chris (kev will probably know) , but an op run for a week on friday isn't worth such analysis. the question re the lowest pressure reading is a valid question and will doubtless receive an answer.

[Cloud 10]

Just a quick note on the ex-tropical storm potentially arriving next Friday - I am racking my brains to think of a lower pressure reading that I have seen before and I cannot remember one, it looks like this one could come in around the 960mb mark according to GFS. Is this correct and if so is it one of the most intense depressions we have ever (potentially) seen over the UK? Thanks.

The lowest pressure reading recorded in the UK - Historic Weather - Netweather Community Forums

[Chris W]

Goodness me that is low! Many thanks for the information.

[Panayiotis]

http://www.meteociel.fr/modeles/cfse_cartes.php?ech=1044&mode=0&carte=0&run=10 That's an extremely low, low pressure thankfully its out at 1044h

[Summer Sun]

Just a quick note on the ex-tropical storm potentially arriving next Friday - I am racking my brains to think of a lower pressure reading that I have seen before and I cannot remember one, it looks like this one could come in around the 960mb mark according to GFS. Is this correct and if so is it one of the most intense depressions we have ever (potentially) seen over the UK? Thanks.

There was a low showing up late last year it was around 940mb at the start of it come the day it was showing to arrive it ended up crossing northern europe and only the far south caught the edge of it

[Gibby]

Here’s my take on the 00zs from GFS UKMO and ECM taking in the GFS Ensembles and Jet Stream Forecast along the way.

All models show a settled spell to come for Southern areas as High pressure drifts slowly East over Southern Britain later in the week. This will be less apparent for the far North as a Westerly drift will bring weak troughs across from the West to give cloudier skies with patchy light rain and drizzle at times here.

GFS then shows a slow decline in conditions over next week as High pressure recedes East with the atlantic pulling in some depressions and an ex tropical storm later in its run to gradually turn things more unsettled for all, albeit very slowly for the SE. By the end of the run rain at times would be likely everywhere on a SW breeze. It would never feel cool though with temperatures on the warm side of normal under South or Southwest winds.

The GFS Ensembles show a lot of agreement between members as we move through the next week or so before some fluctuations occur. Some wildly chilly options are thrown into the mix by a few members but overall uppers should average above normal throughout. Rainfall is negligible in the South until we approach mid month with not much either for the North in the next week.

The Jet Stream continues to keep to its programmed course of a position near Northern Scotland for the foreseeable with a weakening and breakup of the flow next week.

UKMO for Sunday shows very slack if relatively High pressure conditions over the South on Sunday with a Westerly flow over Scotland giving cloud and occasional rain later to these areas as a trough moves East from the West later in the day.

ECM shows things becoming a lot more mobile out to the NW with a deep depression NW of Britain pulling a trough and attendant rain across most areas over Sunday and towards the middle of next week. In between High pressure close to the SE should bring some decent fine weather with some sunshine while the North continues in an unsettled and windy spell.

In Summary this week looks OK for most as High pressure drifts slowly East. The far north will see more cloud and a little rain while longer term the trend looks to be for a gradual cool off in this week’s warm weather to levels just slightly above normal as the risk of cloud, wind and rain increase as we move deeper into next week.

Edited September 3, 2012 by Gibby

[Scorcher]

I know it's still a fair way off but the ECM 00z chart for Sunday is showing a fairly similar setup to the 30th September 2011 when temperatures got close to 30C in some areas. The 15C isotherm is stretching over much of England and Wales. High 20s possible if it came off perhaps?

[OldMetMan]

I've been sitting back for a while to see how things would start to shape up now we are officially out of summer and, as I mentioned some weeks ago, the long overdue HP has finally arrived on our doorstep. The Atlantic hurricane season is currently working in our favour with the remains of Hurricane Kirk pushing very warm air over and to the W of the UK.

At long last the 500mb flow has shifted enough to replace the persistent upper low that has been over the US and Canadian NE and the one to our W with upper low emphasis now to our immediate NW and a cut-off upper low over southern Europe.

The models are showing consistency in maintaining HP for a while with rebuilds occuring behind cold fronts.

I am most interested in the handling of Tropical Storm Leslie, notably by the GFS, as it seems set, as others have mentioned, to become a very intense extra-tropical LP. The big question is where will it track. The latest GFS shows it on a much more southerly path but earlier runs have taken it to the NE. In any event, it is likely to disrupt the upper pattern, at least for a while, to break down the HP here.

The tropical storms this year have shown a marked tendency to recurve well to the E of the US, with the notable exception of Hurricane Isaac, so there is a distinct possibility of further storms getting picked up by the Atlantic jet as the month progresses.

Meanwhile, let's enjoy a bit of late summer and keep an eye on TS Leslie!

[shedhead]

I know it's still a fair way off but the ECM 00z chart for Sunday is showing a fairly similar setup to the 30th September 2011 when temperatures got close to 30C in some areas. The 15C isotherm is stretching over much of England and Wales. High 20s possible if it came off perhaps?

Very much so Scorcher, mid to high 20's very possible IF those charts verify. Also signs on GFS that we might start to pump up some very warm, humid air into next week, so plenty for 'heat' fans to look forward too across England and Wales in particular well into mid month.

PS: Despite a much better month, members should be aware of the following...

The governmental department in charge of Political Correctness has decreed that as of today our climate can no longer be called 'typical British weather' - not even in the Model Output Disscussion thread!

To save offending ever larger portions of the population, the climate will from here on be called 'typical Muslim weather' - i.e partly Sunni, but mainly Shi'ite...

Edited September 3, 2012 by shedhead

[Alex]

Very much so Scorcher, mid to high 20's very possible IF those charts verify. Also signs on GFS that we might start to pump up some very warm, humid air into next week, so plenty for 'heat' fans to look forward too across England and Wales in particular well into mid month.

PS: Despite a much better month, members should be aware of the following...

The governmental department in charge of Political Correctness has decreed that as of today our climate can no longer be called 'typical British weather' - not even in the Model Output Disscussion thread!

To save offending ever larger portions of the population, the climate will from here on be called 'typical Muslim weather' - i.e partly Sunni, but mainly Shi'ite...

Ha ha brilliant! The models are summed up perfectly.

[Robbie Garrett]

I know it's still a fair way off but the ECM 00z chart for Sunday is showing a fairly similar setup to the 30th September 2011 when temperatures got close to 30C in some areas. The 15C isotherm is stretching over much of England and Wales. High 20s possible if it came off perhaps?

The Sun is still fairly strong at this time of the year, during the October spell the sun provided most of the energy under clear skies, this was built up over 2 weeks and 31*C was reached in places. Give or take I reckon we can probably get hottest day of year or equal during this warm spell, possibly even more.

[Frosty.]

The latest models are still showing a warm (locally very warm) and settled week ahead for most of the uk apart from the nw corner and far north where it will be windier and more changeable. High pressure further south looks persistent and only very slowly edging away southeastwards with plenty of sunshine and light winds but overnight and early mornings look chilly with some mist and fog patches but these soon burning off by mid morning time and then more or less unbroken sunshine, however, tomorrow is the exception with the remnants of a front pushing southeast across the uk but no more than an annoying band of cloud by tomorrow afternoon across the southeast quarter. The gfs ensemble mean indicates a nw/se split by day 7 with low pressure to the nw and pressure remaining high to the southeast and east, the ecm ensemble mean has the low to the nw rather further east but still with high pressure across the south/se so basically the same result. The latest meto update was like a run through of the gfs 06z and the further extended outlook is very much in line with the latest cfs runs which indicate some very unsettled/stormy spells through late sept and through into october, the southeast of the uk always looks favoured in the next 2-4 weeks to be drier and warmer even when the general pattern reverts to more typical autumn weather so a nw/se split looks applicable for weeks to come although the southeast will also see some unsettled spells beyond the next 7-10 days.

Edited September 3, 2012 by Frosty039

[Milhouse]

The date maximum records for the 13th and 14th are only in the high 20s so if the warm spell was to last beyond the weekend we could have seen these challenged. The maximum for the 9th is 32.2c and for the 8th its a whopping 34.6c. I predict 28c will be the top temperature on Sunday so falling short of 30c. If the 15c isotherm can make its way north to the UK then 30c might be possible.

[Alex]

Although some daily records may fall I doubt 32.4c which is the highest temp so far this year will be beaten, we had a stronger sun and a 17/18c 850hpa line across the southeast, this time a 15c line with slightly less strong sun can and may push temps upto 30c.

[East_England_Stormchaser91]

From what I'm seeing, hurricane Leslie is going to promote the shift of central saharan air Northwards over NorthWest Europe in the coming week or two. She looks like she'll become part of a huge stretch of a low pressure system from Greenland all the way down past the Canaries, which on its Eastern flank, will give some very warm or maybe hot conditions next week as far North as us! We'll have to watch this space folks.

[Summer Sun]

A warm weekend remains on the cards tonight from GFS

However a breakdown is shown to occur on Monday

And this set's up an unsettled week next week

UKMO however isn't as positive for the weekend

[Gibby]

Good evening. Here is my take on the 12zs tonight.

All models support High pressure drifting slowly East over Southern Britain over the next few days before moving further East by the weekend setting up a warm Southerly flow over the UK. The weather will be basically a fine and settled setup with sunny spells by day and chilly misty nights in the South. The far North will see more cloud and a little rain on occasion while a weak cold front pushing SE across the South tomorrow brings a cloudier zone with a little light rain here and there.

GFS then takes us into the second half of it's run with a return to more unsettled conditions as depressions move East close to Northern Scotland delivering SW winds and rain at times for all areas though with a few dry brighter days as transient ridges pass over.

The GFS Ensembles show the current warmer weather lasting through this week before the 11th looks like a key day of change to cooler and more changeable conditions as rainfall events increase in frequency. There is plenty of spread between the members from the 11th on.

The Jet Stream is forecast to remain well North of its recent location near to Northern Scotland. As we move into next week it looks like it becomes more distorted for a while before setting up closer to Southern Britain late next week.

UKMO shows High pressure having declined away SE by noon next Sunday with a slack flow over most of Britain. Low pressure lies well to the North with some shallow frontal activity close to Western Britain threatening showery rain by the end of the day.

ECM shows a trough having moved East over Britain next Sunday having brought a little rain as it goes. Thereafter, a South or Southwest flow develops with some warm and humid air pumping North over Britain. The East and South will be warm and bright while the North and West gradually becomes more unsettled with some heavy bursts of rain at times.

In Summary the weather is set fair this week and for much of the weekend as High pressure drifts East over the South. As we move into next week a slow decline in conditions looks likely with the risk of some rain in the South and East and rather more than a risk in the North and West. With winds developing next week from the South temperatures will continue to be above normal especially in the drier SE.

Edited September 3, 2012 by Gibby