Model Output Discussion 26/08/2012

[Weather-history]

UKMO shows very heavy rain for Monday into Tuesday, shows a really intense pulse across the Borders midnight Monday/Tuesday.

[Gibby]

Good morning. I'm very busy this morning so a shorter than usual rundown of the models today. Should be OK for the 12zs though.

In Summary the models have at last come to agreement on a major Low pressure affecting the weather over all of Britain for the upcoming four or five days. There will be periods of heavy rain then showers with some very strong and gusty winds all combining to make for a very stormy Autumn spell. Later in the week the Low pressure gradually fills up in situ with winds decreasing and rainfall amounts subsiding day by day. By next weekend the trend is for a Westerly flow to set up with the wettest and windiest conditions looking more likely in the North as High pressure nudges ridges temporarily across the South with temperatures on the rise a little at times. Nevertheless, even then all areas are at least at risk of rain in a sometimes cool West or NW wind. The ensembles generally support the above but there is a lot of spread from the middle of the run. There is some very chilly members too towards the end of the run indicating that an early Northerly blast is in the mix especially for the North in FI.

[bluearmy]

I've been watching the model output all week regarding the threatened intense LP for this weekend and I have to say that I do not recall any such development happening before.

Hurricane Nadine has been an enigma since it formed and i know that the National Hurricane Centre in Miami have really been struggling with it's behaviour and forecast all week. In particular, the track has been shown to vary greatly from model to model and run to run and at times, they have not even been sure what sort of beast Nadine is - is it still a tropical storm, a post-tropical depression?

Since Nadine arrived near the Azores, the models have, and continue to have a bewildering variety of solutions as to what to do with Nadine. What I find so intriguing is that, while ex-tropical storms do arrive on our shores from time to time, I cannot remember seeing a LP that has been apparently generated by such a storm. Even more puzzling is the way the models have been maintaining Nadine, even intensifying it in the days to come.

As far as the threatened storm here is concerned, yes there is certainly a large amount of very warm, moist air travelling NE towards the UK that apparently originates with Nadine, and that, together with the presence of the jet, could indeed be a situation to allow a rapidly deepening LP to form. The upper low to the W and NW is sharpening as the surface LP sinks SE. But in recent runs the models have had difficulty in deciding which LP will be dominant. The last 2 runs of the GFS have backed off quite considerably on the new LP's intensity but the ECM has gone quite mad and is showing a very intense system developing.

Meanwhile, the UK Met is sticking to it's guns, as it has for several days now, of developing the LP quite rapidly.

I find it unusual that there is so much model divergence so close to the time. I think it will be most informative in this situation to watch the satellite images very closely over the next 24 hours as LPs such as these have distinct signatures.Interesting few days ahead!

tomorrows depression is spawned by the trough and jet diving south and meeting the moisture and warmth that surrounds nadine. bit like the way these features are often created off the eastern seaboard as cold air heads south and meets the the warmth from the other direction. anyway, what remains fascinating is that nadine continues to have massive variations re her likely movement over the next week or so. the general gist of the ens is for a reasonable period to follow the troughing through this week. (better the further south). can someone recall if the extended ens were into the trough headed se into us or was this just an operational theme beyond 8 days?

[lorenzo]

A run through the Fax charts this morning shows the approaching low messily intertwined with the other from the NW during Monday then painting a target firmly on the UK on Tuesday.

Like this link as it has timestamps for when chart is issued, always manages to confuse me ( not difficult)

Tuesday attached, the lead up from Sunday 36/48/60 is going to be a fun watch !

Will probably link this several times as required, but in case you haven't got it saved - sit back and enjoy..http://www.yr.no/sat..._animasjon.html

Edited September 22, 2012 by lorenzo

[Gavin Hannah]

The 00Z has chucked out an absolute STONKER for FI!

[ICETAB]

The 00Z has chucked out an absolute STONKER for FI!

Id love to see that chart at the end of Nov. Kind of a waste if it came off now

[Gavin Hannah]

Id love to see that chart at the end of Nov. Kind of a waste if it came off now

Id love to see that chart as the main winter pattern...

Edited September 22, 2012 by IBringTheHammer

[Polar Maritime]

Yes some lovely charts out in FI, something to keep an eye on during future run's with a cold Northerly showing for the start of October..

[Rainy]

The 00Z has chucked out an absolute STONKER for FI!

Nice fruit picking weather in Greenland though ....

[Summer Sun]

The met office still only have warnings out for Sunday and Monday so they must feel at the moment Tuesday and Wednesday will be better days

Which goes against there own mode which looks very unsettled certainly for Tuesday and the depression is shown to be just a deep as that of Monday

[Geordiesnow]

I think its a little early to send out warnings/watches for Tuesday and Wednesday to be honest but looking at the UKMO PPN charts, they do look quite impressive in terms of rainfall, of course whether the reality will be like that we have to wait and see.

Personally, I am a little dissapointed that one UKMO run that showed the low being a slider which bought the low from Iceland into play and headed out into the North Sea leading to a NE'ly has not really been picked up, it would more than likely mean a drier but brighter outlook with some showers, instead, this week is now looking dull and very wet and after the initial excitement of some gusty winds on Monday, the low will slowly fill in during the week but with weather fronts being around, it will just mean slow bands of rainfall moving around the UK.

So to some up, a fairly average week temperature wise, strong winds and heavy rain to start off but winds should become less of a feature however with low pressure nearby, any rainfall will become slow moving as the low eventually fills in by Thursday and Friday, don't think there will be much sunshine this week so its most certainly an Autumnal week coming up.

[johnholmes]

A run through the Fax charts this morning shows the approaching low messily intertwined with the other from the NW during Monday then painting a target firmly on the UK on Tuesday.

Like this link as it has timestamps for when chart is issued, always manages to confuse me ( not difficult)

Tuesday attached, the lead up from Sunday 36/48/60 is going to be a fun watch !

Will probably link this several times as required, but in case you haven't got it saved - sit back and enjoy..http://www.yr.no/sat..._animasjon.html

yes the link to the sat sequence is one for most on here I would think to bookmark. It is an excellent sequence to watch at any time of the year when fronts and weather systems are predicted to affect the area shown on it.

For a bit of a lesson in meteorology, look at the Fax charts to see where it all starts, then the Fax charts to see where it is predicted to be at 12 hour intervals, then change to the 500 and 300mb charts, first the actuals to tie in with what the sat picc shows at the start and at the intervals when we get basic data (this will mean copying and pasting charts from previous runs), then play the movement of the upper charts to see how the upper air is directing the movement of the clouds, the development or decay, well worth doing this whenever interesting weather is forecast as it will really help anyone understand how everything is tied together.

Edited September 22, 2012 by johnholmes

[Summer Sun]

Some heavy rain looks likely on Monday there could also be some flooding for parts of Wales over the coming week going by the rainfall totals showing during the week, the wind doesn't look like the main concern for Monday its the rain which looks like been the main concern for some areas with wales taking the brunt of it

Rain totals for 18:00 Monday

Totals for next Saturday

Into the weekend and high pressure is shown to move in

Edited September 22, 2012 by Summer Sun

[Paul]

Specific thread for discussion around 'child of Nadine' now open:

http://forum.netweather.tv/topic/74510-child-of-nadine-severe-weather-discussion/

[andymusic]

The met office still only have warnings out for Sunday and Monday so they must feel at the moment Tuesday and Wednesday will be better days

Which goes against there own mode which looks very unsettled certainly for Tuesday and the depression is shown to be just a deep as that of Monday

Just had an e-mail warning for tuesday now from the met office for heavy rain - so that's three days of heavy rain warnings now - flooding abound

[Bobby]

Just had an e-mail warning for tuesday now from the met office for heavy rain - so that's three days of heavy rain warnings now - flooding abound

Looking at the GFS rainfall totals over the next few days I wouldn't be surprised

Nasty.

[Summer Sun]

This afternoon's UKMO follows its previous runs for Monday

[AWD]

After the stormy start to next week and a showery rest of the week, pressure rises, along with temperatures by next weekend.

And in deep FI, a similiar chart, although not quite as potent, to the GFS 0z run at T384, with rising heights over Greenland and a northerly setting up

Jet stream heads north next weekend, allowing those height rises, especially the further south you are.

GFS Ensembles show a decent scatter in 850's from next weekend onwards, with both cooler and warmer options available. Also, rain is still possible throughout the run, with no significant drier slots.

UKMO a little different to the GFS at T144, with a trough over mainland Europe still having an effect on weather conditions to the south of the UK, so not quite as settled as the GFS, nor as warm. The north would be drier on this output though.

The ECM is different still at T144, with a LP system to the NW of Scotland bringing unsettled conditions here whilst the south is drier and brighter, although with pressure not that high, isolated showers can't be ruled out there either.

So, from what I can gather from the models is that we are in for a wet and windy 72 hours before "Nadine's child" slowly fills to the west/south west of the UK, still though with slow moving rainbands & showers right through the working week. Next weekend is where the models start to diverge, with an option for increasingly drier and warmer weather and also an option for unsettled conditions continuing in either the south or the north.

[Summer Sun]

ECM has Monday's depression at 990mb tonight

Tuesday see's it deepen to 985mb with the center located near the Republic of Ireland

Wednesday see's the depression ease with winds also easing across the north as it heads south

By Thursday pressure is back above 1000mb with winds easing significantly

Next Saturday has a Low pressure system located to the North East of Scotland with a north westerly flow starting to develop

Edited September 22, 2012 by Summer Sun

[Summer Sun]

John Hammond has provided a further update on the wet and windy weather forecast for the UK over the coming days

For the south west tomorrow 50mph gusts are possible with 50mm of rain

Into Monday an area between Birmingham and Edinburgh could see 50mm of rain with strong winds

A video can be found here

[Gibby]

Good evening all. Here's a look at the 12zs from GFS, UKMO and ECM.

All models now show a complex and vigorous area of Low pressure moving up from Biscay mixing with a cold pool moving South to the West of Britain to form a large and deep depression over the UK in the first days of this week which fills slowly in situ by Thursday. All areas will see periods of disruptive rain with strong winds only slowly abating as we move towards midweek and beyond. It will be dry in the North tomorrow though as today's High pressure clings on there. It will generally feel cool through the period.

GFS shows the Low pressure continuing to fill near Southern Britain late in the week before High pressure takes control over the weekend bringing cool but dry conditions which would be a welcome respite from the events of previous days. In FI High pressure features quite strongly with some cool and misty nights mixed with some decent days with some sunshine. The operational does break things down again by the end of the run.

The GFS Ensembles show tight clustering near the long term mean for Southern locations until the final third of the run with rainfall lessening beyond this week. Further North much more scattering is shown in the final half of the run in a very changeable pattern.

The Jet Stream shows a deep troughing as it dives South to the West of the UK. It then picks up a returning flow from the SW driving NE on a location South of Britain as we move through next week. Longer term there is a sign that this arm of the jet weakens and breaks up with hints of a Northern arm setting up between Scotland and Iceland late next week and weekend.

UKMO for noon on Friday shows a cool NE flow over Southern Britain in association with Low pressure to the SE. In the North Low pressure to the North of Scotland throws a trough East over Scotland. The net result would be a ontinuation of unsettled weather with rain at times in rather cool conditions at the surface and under the Northeast flow in the South.

ECM finally shows a cool and unsettled end to the week and weekend with rain at times feeding down from the NW. Late in the run High pressure inches in towards the South with a North/South split developing with rain at times in the North together with Westerly gales and dry if rather cloudy and less cool conditions towards the South.

In Summary the models continue the very wet and potentially stormy theme in the first few days of the run. The trend is then for the weather to slowly improve particularly for the South as Low pressure weakens and high pressure moves in closer towards Southern Britain. This has been a trend in previous GFS runs for a while and it gains some support from the ECM operational tonight.

[damianslaw]

I'm just going to comment on the next 72-96 hours or so, because the immediate outlook is a complex one. Very difficult in such set ups to give an accurate forecast in terms of where the heaviest rain will occur and which parts of the country will see the rain lingering the longest. All the models are now suggesting the low will simply fill in situ taking a long time perhaps not until Thursday, which is likely to mean some places are about to receive some very high rainfall totals in the next 72-96 hours with barely a glimmer of sunshine and consequently temps will be very supressed, low teens at best for many, if not 10's and 11's which is well below average for September.

It is a case of nowcasting... central england could be an area deluged with heavy rain for a very long time....

It is certainly an autumnal outlook, and it will feel more like late october than late september.

[jimbo36]

Latest NAE 48 hr rainfall totals looking impressive for the south. Varies on each run, so still finding it hard to nail down.

[Jason T]

Liking the current output..NH Is creating life.

Looks nothing but has potential,

oooooh really hopping on to something,

Awesome, Loving the 995 and 950 with the Claret Centre. Just wondering if NH is developing a real Winter pattern to deal with.

Guys i apologise,Links not working . MODS please delete this post....Bugger

Edited September 22, 2012 by Jason T

[AWD]

The GFS 0z continuing the theme of showing height rises after the stormy working week to come. However, on this run heights remain low enough over the Southern half of England & Wales next weekend to provide a rather wet weekend before HP ridges in and settles things down for the start of October.