Model Output Discussion 26/08/2012

[AWD]

There is no support for a depression that deep tonight

GFS

UKMO

It would appear ECM has gone off on one tonight

Ummmmmm........... Why? Have you already seen the Ensembles?

Until a couple of runs ago, when the UKMO first picked up on this depression, there was no support for a depression at all. The UKMO picked up on this, and now the ECM and GFS have followed. This mornings ECM Ensembles made nothing of the depression, now we have an Op run with quite a big depression.

Whilst the GFS & UKMO don't show the depresssion that deep, they do still show the depression, so its looking increasingly likely that a depression will come up from the SW sometime late in the weekend now.

I'm not saying the ECM is right, it could well be over doing it, but in difficult forecasting conditions like this, I wouldn't just simply rule it out, it is however possible as Cloud 10 posted above with the reasons.

[Summer Sun]

Calmer by Thursday and Friday

[AWD]

Here are a couple of GFS Ensemble runs that do support a depression similiar to the ECM.

Admittedly there are many runs which show less of a depression too, but this shows that if nothing else, it is definetly something to watch!

[Summer Sun]

Ummmmmm........... Why? Have you already seen the Ensembles?

Until a couple of runs ago, when the UKMO first picked up on this depression, there was no support for a depression at all. The UKMO picked up on this, and now the ECM and GFS have followed. This mornings ECM Ensembles made nothing of the depression, now we have an Op run with quite a big depression.

Whilst the GFS & UKMO don't show the depresssion that deep, they do still show the depression, so its looking increasingly likely that a depression will come up from the SW sometime late in the weekend now.

I'm not saying the ECM is right, it could well be over doing it, but in difficult forecasting conditions like this, I wouldn't just simply rule it out, it is however possible as Cloud 10 posted above with the reasons.

This was ECM's run this morning

And this was its ensemble run

What ECM has tonight is one hell of a change in 12 hours or so from nothing more than a wet and breezy day this morning to a Major storm tonight the ensemble run later on will be interesting

[AWD]

This was ECM's run this morning

And this was its ensemble run

What ECM has tonight is one hell of a change in 12 hours or so from nothing more than a wet and breezy day this morning to a Major storm tonight the ensemble run later on will be interesting

Exactly, it has now moved over to a scenario similiar to what the GFS is showing and what the UKMO has been showing in its last couple of runs. ECM is just more vigorous. This is what ex TS's do to model output this time of year.

Not saying it will happen like the ECM is showing, just saying don't completely write it off. There is a steep temperature gradient somewhere close to our shores at the end of the weekend!

[Summer Sun]

So tonight all of the models agree of an unsettled Tuesday now the question is will it be nothing more than a wet and breezy day or like ECM shows tonight the first Major storm of Autumn 2012

All the runs are at 144h

GFS

UKMO

ECM has the depression the deepest this mornings ensemble run wasn't so deep, 00z ensemble on the right this will update to the 12z run later tonight

NOGAPS goes half way between GFS and UKMO, GEM on the right has the worst of the storm further north

[Gibby]

Good evening folks. Here's how the 12zs handle events over the coming few weeks.

All models are firming up slowly on events at the end of the weekend. In the mean time the weather remains comparatively benign though with a frontal trough crossing Central regions tomorrow with rain through the Central third of the UK. By Friday this band of rain slips South and weakens clearing the South Coast late on Friday. Saturday sees a ridge of High pressure bringing a dry and very pleasant day for many with some warm sunny spells. Sunday sees things sliding steadily downhill as Low pressure advances from the SW with an increase in SE winds later in the day.

GFS then takes us through the entire run under the domination of Low pressure very close to or over the UK with periods of rain and strong winds at times. A window of drier weather is indicated at the end of FI.

The GFS Ensembles show a very wet week next week followed by a drier trend in the second week. 850's are close to the long term mean through the run with a lot more togetherness between the members for the first time for a while tonight.

The Jet Stream currently blowing Se over the UK dips sharply South to the West of the UK in a few days time engaging Low pressure and sweeping NE and East over Southern Britain by the end of the weekend.

UKMO for noon on Tuesday shows Low pressure centred over Northern England with unsettled and windy conditions for all in rather cool air.

ECM too shows a depression over Ireland at the same time point before it tracks South, East then North into the Southern North Sea by the end of the run with very unsettled conditions for all with rain and showers in quite windy conditions.

In Summary the models are slowly coming into line tonight. There are variances on the location of the Low at various times but the message is the same from all in that the weather will turn wet and windy at times next week and possibly beyond in rather cool temperatures.

[Zenarcher]

This is what the ECM is saying what the wind speeds would be if the low for late Monday and early Tuesday was to come off,

Ireland and Northern Scotland 50mph gusts over 60mph.

Wales and Northern England 40mph gusts 55mph.

Rest of England 35mph gusts 50mph.

Most of Scotland 30mph gusts 40mph.

Nothing too serious you could argue that the rainfall is probably more of a concern though.

Edited September 19, 2012 by weathermaster

[BLAST FROM THE PAST]

As some have mentioned above and as I have been highlighting over previous days, period of interest/concern. That is some gale. 25 years ago Oct 16 we had similar LP get sucked up from Bay of Biscay...this could be very tricky.

BFTP

[Summer Sun]

This is what the ECM is saying what the wind speeds would be if the low for late Monday and early Tuesday was to come off,

Ireland and Northern Scotland 50mph gusts over 60mph.

Wales and Northern England 40mph gusts 55mph.

Rest of England 35mph gusts 50mph.

Most of Scotland 30mph gusts 40mph.

Nothing too serious you could argue that the rainfall is probably more of a concern though.

Yes the rainfall would be a big concern there could even be flooding in some areas weather-online are going for flooding in southern and eastern parts of England

Tuesday 25/9/12

Low pressure across Ireland on Tuesday. This is likely to be bringing more periods of rain. Most of the rain is over southern and eastern parts of England and there is a chance of some significant rainfall totals with localized flooding. Further west it should be drier with sunny spells, although a few showers. Highs at 12 to 18C.

[legritter]

I realy like the way the modells are working out lately ,it seems to be that quite often now that what they predict as the generall pattern at 240/288 hrs quite often does pan out ,but it can be severall days different .as for next weeks potential i honestly thought this event would have started about now .i like the way the low pressure next week just casually takes a tour around our shores ,and of course all the other features that will probably pop up to join the party ,very interesting times ahead .im looking forward to tonights Met office fax .some low DAM figures showing up in northern latitudes ,bring it on ,cheers Legritter .

[William of Walworth]

Very interestingly fluctuating op models, and fluctuating charts posted here too, over a recent few runs, from what I've managed to catch up with .... plenty of differences of positioning!

From an entirely selfish POV, the increasing likelihood that the worst of the winds and rain seem likely to hit the N and E of England mostly beyond Sunday rather than during, could possibly end up making a big difference on the ground. If any of this from the general NetW homepage forecast this morning remains valid, then the w/e itself may not be too bad for the wind n rain-averse like me

For the weekend, although the weather models have been showing the threat of wet and windy weather for Sunday these last few days, it's now not looking too bad this morning. A ridge of high pressure building in on Saturday looks to hang around for much of the weekend, bringing mostly dry and settled weather. Though there is a risk of rain clipping SW England Saturday night and wet and windy weather does look to spread in from the west across Scotland and Northern Ireland on Sunday.

Will be off to great outdoors of York/Lincolnshire tomorrow morning and thus will be offline for some time, but good luck with the interpretations ...

[Summer Sun]

ECM's ensemble is out and its more in line with UKMO so at this stage its nothing more than a wet and breezy day for most of England and wales the rain would be more of a concern than the wind

Edited September 19, 2012 by Summer Sun

[Gibby]

One way or another tonight's late faxes set us up for a very wet period as we move into next week.

http://www.meteociel.fr/modeles/ukmo2.php?ech=96&carte=2000

http://www.meteociel.fr/modeles/ukmo2.php?ech=120&carte=2000

[Pennine Ten Foot Drifts]

Given the 'storm' is at T144 there are only two things which are fairly certain - 1. It isn't going to be summery next week, and 2. It isn't going to happen like it's currently showing, because a T144 chart never verifies exactly................... Discussions about windspeeds and levels/locations of rainfall might have some validity at T48, but at T144 it's utter conjecture.

[peterf]

i'm ready for it, onions are in the tunnel and well dried.

[AWD]

The GFS 0z also has a notable depression coming up from the SW and then mixing out slowly over Ireland. Whilst the winds wouldn't be nothing exceptional for Autumn, compared to the relatively benign weather we have had over most of the UK so far this month, it would be fairly noticable none the less:

Plenty of rain throughout the UK though. The UKMO has it more towards the SE though, so if this run verified, the heaviest rain and winds would be further SE.

And again the ECM blows up a fairly potent depression at T120, although a tad further north compared to its 12z output last night.

That's the 3 main models now forecasting what would be the first Autumnal LP of the season for many. Detail like exact position and intensity still to be decided as usual, but wet & windy just about sums up the start of next week.

Interesting model watching. Tentative situation.

Edited September 20, 2012 by AWD

[mushymanrob]

well .... those of us (me especially) who blandly predicted a warm settled september (just because summer was poor) have been proven wrong. whilst after long periods of wet or dry, a following opposite regime does often seem to happen, its obviously not a rule. if anything september is shaping up to be rather cool as a whole and the predicted stormy week next week wont help that. never mind, its autumn, so typical autumnal weather (which is what the models depict) has to be expected.

[TonyH]

well .... those of us (me especially) who blandly predicted a warm settled september (just because summer was poor) have been proven wrong. whilst after long periods of wet or dry, a following opposite regime does often seem to happen, its obviously not a rule. if anything september is shaping up to be rather cool as a whole and the predicted stormy week next week wont help that. never mind, its autumn, so typical autumnal weather (which is what the models depict) has to be expected.

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

[Gibby]

Good morning. Here is the report of the 00z output from GFS, UKMO and ECM for today Thursday September 20th.

All models are gradually simplifying the events of late in the weekend and beyond. The currently light Westerly flow is carrying a frontal trough East across Northern England and Southern Scotland with rain for these areas. Over the next 24 hours this front slips South to clear the South coast on Friday evening as a weak feature by then. Pressure then builds over the Uk for Saturday before falling pressure from the SW Saturday night brings an increase of wind and rain up from the SW on Sunday as a developing depression moves towards the South. By Monday a deep Low complex is centred somewhere over the UK with wet and windy conditions for all.

GFS then shows the remainder of next week with deep low pressure meandering about near the West of Britain with much rain, wind and showers for all, eventually slipping South then East as a weakening feature late in the week. Through the following weekend the unsettled theme continues towards the South while the north cheers up a bit. However, the pattern remains changeable in FI though gradually High pressure builds slowly to bring a settled and Autumnally quiet spell at the end of the run.

The GFS Ensembles show a wet and windy week next week with average uppers. At the surface it will feel cool. through the second half of the run the weather remains changeable with rain at times in normal temperatures though the trend for less in the way of rain in the second week remains.

The Jet Stream is troughing South through the Atlantic. It later engages with spores from ex Tropical storm Nadine and drives a depression across southern Britain over the weekend blowing thereafter generally to the South of Britain across Northern France and the English Channel.

UKMO for midnight on Wednesday shows Low pressure over Southern Britain with areas of rain circulating around over the whole of the UK. Winds will be cyclonic and strong at times in cool conditions at the surface.

ECM has Low pressure over Scotland moving South in the subsequent days with further disturbances running north on it's Eastern Flank. Eventually it fills a little and moves first East over the English Channel then North up the North sea opening the door to further disturbances running down from the NW at the end of the run. The weather would be distinctly unsettled and cool feeling with heavy rain and showers abundant at times throughout the term.

In Summary today the pattern has simplified at last though the exact positioning of Low pressure and it's deepness remains to be decided. Nevertheless, confidence is high now for next week to see a period of sustained unsettled weather with showers or longer spells of rain for all in rather cool conditions at the surface. Further out and GFS does offer tentative signs of an improvement in it's operational model but the more likely scenario remains a changeable pattern to be maintained with Low pressure from the West or Northwest persisting over Britain.

[snow drift]

well .... those of us (me especially) who blandly predicted a warm settled september (just because summer was poor) have been proven wrong. whilst after long periods of wet or dry, a following opposite regime does often seem to happen, its obviously not a rule. if anything september is shaping up to be rather cool as a whole and the predicted stormy week next week wont help that. never mind, its autumn, so typical autumnal weather (which is what the models depict) has to be expected.

Location is key to the statement you have made. September for the South has been mainly warm and dry. Still 10 days or so to go and the models would suggest more unsettled weather but as has happened for much of the month thus far, this may miss our area and affect places further north.

Regards

S D

[Gibby]

Location is key to the statement you have made. September for the South has been mainly warm and dry. Still 10 days or so to go and the models would suggest more unsettled weather but as has happened for much of the month thus far, this may miss our area and affect places further north.

Regards

S D

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.

Edited September 20, 2012 by Gibby

[Summer Sun]

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

[MisfitDog3]

ECM has an interesting little feature rolling up the channel in a weeks time! Borderline FI I know but worth keeping an eye on if you are based on the south coast or SE of England.

[MarkF]

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

The ensemble run charts are an average across all (50?) ensemble runs, so will always dampen the heights of lows due to the different positioning of the low centres in each run. Same goes for high pressures.