Model Output Discussion 26/08/2012

[chionomaniac]

Again ECM's ensemble run has the depression less deep for next Tuesday

980mb over Northern Scotland

But the ensemble run has it at 1000mb

And its the same for Wednesday

980mb this time centered over Ireland

And again the ensemble run has pressure much higher at 1000mb

The ensembles are always going to dampen down any feature at this timeframe though, SS - whether it is extremes of high or low pressure. The 50 ensembles could keep the depression at the same depth, but differences in the positioning and timing of the trough would come out in the average ensemble as a more shallow feature and one should be wary of this when posting such charts.

( Without checking all 50 ensembles individually one wouldn't know)

Edit as it seems that I am copying MarkF's thoughts!

Edited September 20, 2012 by chionomaniac

[valiant]

I personally don't regard the weather being settled and warm in the South this September thus far (and I live in the South). Yes it has been far less wet than recent months but the weather has continued to be driven by an Atlantic feed rather than an Anticyclone centred over Britain. So while there have been many dry and bright days in the South, no temperature records have been broken and night times have been jolly chilly at times for this early on in the season. Sorry mods for the off topic post.

Your post proves the original point. I've travelled in the opposite direction from N. Staffs, spending a week around the Lea Valley (Essex/Herts) I'm staggered at the parched grass and cracks in the ground. You have no idea how lucky you all are in the south. You'd slash your wrists after a week in Cumbria. SAD syndrome must be rife north of Birmingham.

[Summer Sun]

GFS 06z has the center of the low pressure further south this morning, the wind doesn't look like been any concern its the rain which could be

Into Wednesday pressure begins to rise

Edited September 20, 2012 by Summer Sun

[AWD]

GFS 06z has the center of the low pressure further south this morning, the wind doesn't look like been any concern its the rain which could be

Into Wednesday pressure begins to rise

Might be worth posting Mondays charts mate when the LP is at its deepest. Wind certainly is notable in areas on Mondays charts.

I'm on phone, so can't yet.

Edited September 20, 2012 by AWD

[Summer Sun]

Monday sees the low pressure at its deepest this morning

It is also shown to be the windiest day

As the day moves on the winds ease for most of inland areas of the UK though coastal areas remain windy

[pyrotech]

On the floodwarn forum and facebook page this has been the expected outcome for this weekend since sept 12th . I can not add pictures today to show reasons as on mobile phone, but have expected the plume of moist tropical air from ts nadine to move over Uk and remnants of ts nadine to follow next week. Models thought until recently that Nadine would move west and anticlockwise around the mid atlantic high. Although Gfs did show current most likely track about 10 days ago and dropped the idea. Gfs has done this regular where it get fi right but drops it and brings it back again. I expect the week end low to be joined bt nadine next week giving a large rainfall to some areas. I again apologise for no images as on phone.

Please also feel free to comment on this on floodwarn facebook page ect as to keep this om model discussion on topic

[Gavin P]

Here's today's model based video exploring the possibility of Stormy Sunday;

http://gavsweathervids.com/

Models seem to agree on the broad pattern, but still a highly uncertain situation.

Edited September 20, 2012 by Gavin P

[shedhead]

Certainly a very different looking week to come next week, with plenty of wind and rain on the cards from Sunday, especially across England and Wales. However this still looks set to be something of a blip imo (albeit a protracted one!) with fine weather returning once again to close out what has been a comparatively decent month.

Edited September 20, 2012 by shedhead

[mushymanrob]

It has so far been a very dry month for many so in a way you were correct.

thats kind of you but no, i didnt predict a dry sept, but an anticyclonic dominated one with sunshine and warmth. the dryness to date is a bonus.

[Geordiesnow]

Wow, still some differences between the UKMO/GFS 12Z runs regarding the low, the GFS still insists on developing the low a bit further and once with us, it will stay on our shores for a while, whilst the UKMO think it will be a more flabby affair and the low from Iceland will come into play which could potentially leave us with a colder shot from the North.

Its fair to say as we go into next week, low pressure will be nearby but getting the specifics right is difficult at the moment but the ECM's idea of pressure being higher in previous runs is way off the mark and the GFS is more closer to what the reality will be. The big question will be, how will it all play out.

Rather the UKMO 12Z run than the GFS's, proper autumnal weather in terms of temperature but it should also be brighter with coolish air coming down from the North, whereas the GFS run is milder but cloudier and wetter.

[Zenarcher]

At just 72 hours some disagreement occurs already between where the low will be placed. Below is a comparison between the 12z runs of the GFS, GME and UKMO.

At 96 hours both the GFS and UKMO go different ways the UKMO sends a weak low pressure over Europe but the GFS shows something a lot more different with the low getting caught up over the UK.

It will be interesting to see what the ECM does tonight.

EDIT: A little more info on what the GFS is currently saying found HERE.

Edited September 20, 2012 by weathermaster

[Summer Sun]

Monday continues to look like been the windiest day of the week but nothing more than we are use to

Into Tuesday and things begin to settled down for all but the far south west

And that sets up the rest of the week with high pressure slowly building

So unsettled at first, then high pressure builds later to the south with Scotland remaining unsettled

Edited September 20, 2012 by Summer Sun

[phil nw.]

At just 72 hours some disagreement occurs already between where the low will be placed. Below is a comparison between the 12z runs of the GFS, GME and UKMO.

At 96 hours both the GFS and UKMO go different ways the UKMO sends a weak low pressure over Europe but the GFS shows something a lot more different with the low getting caught up over the UK.

It will be interesting to see what the ECM does tonight.

EDIT: A little more info on what the GFS is currently saying found HERE.

Yes it`s fairly unusual to have these differences at such a short range.

The GEM models a shallower and more southerly tracking low moving east into the continent-similar to the UKMO.

The main rainband therefore affecting just the more southern coastal districts later on Sunday compared to the more widespread rain on the GFS.

However by Monday it looks pretty wet in many areas as the low moves in from the north west on the GEM/UKMO outputs.

So relatively minor differences at the outset but generally all the models then going for a rather cool and unsettled week with rain or showers quite widely.

[simon29]

Could this low throw a few more spanners in the works and turn out like the great storm of 1987

[Mapantz]

Could this low throw a few more spanners in the works and turn out like the great storm of 1987

Not too many disimilarities either.

Really juicy charts to get stuck in to over the coming days.

[AWD]

ECM 12z Op still going for a notable depression similiar to the GFS 12z Op, with wet and windy weather for all. The worse of the winds in the North, the worse of the rain in the south.

[NUT]

ECM 12z Op still going for a notable depression similiar to the GFS 12z Op, with wet and windy weather for all. The worse of the winds in the North, the worse of the rain in the south.

What's that I see down near the Azores? Surely that won't hit either.

[Summer Sun]

Tonight's UKMO has pressure much higher than GFS and ECM tonight

ECM

[AWD]

What's that I see down near the Azores? Surely that won't hit either.

That has been there around the last week or so, just doing the "Azores Dance"!

[lorenzo]

What's that I see down near the Azores? Surely that won't hit either.

That would be Nadine, who is doing a spot of fishing before heading towards Portugal for her holidays.

[Summer Sun]

A closer look at the models tonight shows that there is a big disagreement at just 96h

GFS and UKMO both go for pressure as low as 985mb

But then when we look at UKMO we have a different option with pressure some 20mb higher at 1005mb

Taking a look at other models we see them taking the same route as UKMO

GEM

This mornings NOGAPS also took the same route as tonight's UKMO (this will update to the 12z automatically shortly)

The next 48 hours should see things become more clear as to which way things will go if things take UKMO's path then we would see nothing more than a normal Autumn day if it went the way of GFS then some areas would see some fairly strong winds and rain

[simon29]

could it intensify a lot and all the models could be wrong.

[Summer Sun]

could it intensify a lot and all the models could be wrong.

It could things could go either way it could intensify or it could go the way of UKMO and end up been nothing other than a wet day for some the next 48 hours will be crucial

Edited September 20, 2012 by Summer Sun

[Gibby]

Good evening folks. Here is the evening look at the 12z output from GFS, UKMO and ECM.

All models are only in unison until Sunday tonight. The current front over Northern Britain will slip South over Southern Britain tomorrow followed by High pressure building down from the North for Saturday. By Sunday changes are under way from the Biscay area while the North look like staying under the influence of High pressure still.

GFS shows Low pressure moving up towards Cornwall in the second half of Sunday with rain and strong winds developing. By Monday an intense Low sits over Southern Scotland with Westerly gales and frequent and prolonged showers likely for England and Wales while Scotland see lighter winds but persistent rain. The Low slides SW then South to a position South of Britain midweek where it is joined by further Low pressure maintaining very unsettled conditions over the UK, worst in the South. By the end of the week and over the weekend the Lows fill up and pressure builds from the Azores over Southern Britain bringing drier and less chilly conditions to all for a while. Late in the run Low pressure re-establishes from the NW bringing fronts carrying rain over Britain once more.

The GFS Ensembles show a very unsettled week to come with copious rainfall shown at times. Longer term rainfall amounts reduce as uppers rise and by the end of the run a lot of dry weather develops and with above average uppers High pressure to the Southeast looks the favoured option. The operational was a warmer outlier for a while towards the end of the run in the South.

The Jet Stream troughs deeply to the SW of Britain aiding the development of the weekend Low before streaming NE over Southern Britain and Northern France. Longer term the flow to the South weakens and disrupts as a new arm blows way North of the British isles towards the end of next week.

UKMO for noon on Wednesday shows a shallow Low pressure over all of NW Europe. Cool and unsettled weather would result with rain and showers in cool NE winds as we go through the midweek period.

ECM shows a deep Low pressure having moved SW from Scotland to Ireland then South of Britain (similar to GFS). Once South of Britain the Low reinvigorates and moves North over the UK once more, finally moving towards the North but opening the door to further troughs and Low pressure to slide SE from the Greenland area as the run closes.

In Summary we are no clearer to a guaranteed solution tonight. GFS and ECM play similar cards in the development and movement of Low pressure over and up to the North of Britain early next week. UKMO takes the Low pressure to the South while we gradually become influenced by a weaker Low pressure area from the NW. Which one is right is hard to call and being it's UKMO that's the odd one out you can't discount it at that range. Longer term things look like staying unsettled for at least a while although the GFS ensembles show a strong signal for warmer and drier conditions in the South in the second week.

[simon29]

Im fascinated by the weather and have been following this forum for a few years now tho im a novice its so interesting.If the track of the low was to go to the west of england and up the irish sea would it become a deeper low than if it travelled further east.