Model Output Discussion 18z 28/07/13

[No Balls Like Snow Balls]

According to the GFS 12Z ensembles there is a chance for 2 days next week where daytime temps may touch 20c, before falling away sharply again and continuing cool. Nothing much exciting happening weather wise lately. Luckily this time of year though with summer like weather gradually disappearing again for another 5 months at least the chances of some exciting weather are greatly increasing. The autumn / winter storm season is just around the corner.

 

Edited September 8, 2013 by No balls like Snow Balls

[Captain Shortwave]

I can't remember the last time we saw an autumn storm. I do remember a lot of grey cloudy weather last Autumn, which is one of the reasons why autumn is my least favourite season and always hope the summer/winter transition is as quick as possible.

Out of the output today the most interesting find was a couple of plumes caused by a helpful tropical storm building heights over Europe. Any northerly at this time of year is pointless as all the cold is moderated by SSTs of 18C.

[I remember Atlantic 252]

I can't remember the last time we saw an autumn storm. I do remember a lot of grey cloudy weather last Autumn, which is one of the reasons why autumn is my least favourite season and always hope the summer/winter transition is as quick as possible.

Out of the output today the most interesting find was a couple of plumes caused by a helpful tropical storm building heights over Europe. Any northerly at this time of year is pointless as all the cold is moderated by SSTs of 18C.

 

Child of Nadine not count? it was horrendous my neck of the woodz, 23-25th Sep last year

[Captain Shortwave]

Child of Nadine not count? it was horrendous my neck of the woodz, 23-25th Sep last year

Can't remember that one, still the triangle of doom avoids everything exciting!!!    

[Gaz1985]

I can't remember the last time we saw an autumn storm. I do remember a lot of grey cloudy weather last Autumn, which is one of the reasons why autumn is my least favourite season and always hope the summer/winter transition is as quick as possible.

Out of the output today the most interesting find was a couple of plumes caused by a helpful tropical storm building heights over Europe. Any northerly at this time of year is pointless as all the cold is moderated by SSTs of 18C.

 

There's definitely been less Autumn/Winter Atlantic storms here the last few years, we used to get slammed by gales and severe gales here often in NW England to the point where big fences and trees were blown down, even cars used to wobble. The lack of these storms seems to have coincided with those colder Winters.

Edited September 8, 2013 by Gaz1985

[MP-R]

I remember the Child of Nadine more for the rain than the wind. The wind kicked up a little later on the 24th and into the 25th but nothing impressive here in the southwest. It was the near 100mm of rain that was the talking point.

[mushymanrob]

Current operational output contradicts this at least to some extent though (see examples from Frosty and Summer Sun above). Are you saying that the anomaly charts etc are contradicting the idea of ongoing HP influence altogether? I'd be interested to see what you think of Tamara's analysis further up, she reckons HP will remain  a significant player as the month goes on, Of course there's likely to be interruptions to this at points, especially in the North, but I'm seeing a fair bit of benign weather on the cards for many. No heatwave of anything, but some perfectly pleasant September weather a reasonable hope at least, surely.

 

well the anomaly charts dont flip flop as much as the ops do... atm theres no sign of anything warm dry and settled within the reliable...its always in fi... and further away then the 3 main ones @ t240. theres nothing this side of t240 this morning (ecm 00z not out yet) that gives us any hope of settled warm dry. (for more then the odd day, although the ukmo is the best this morning)

 

the azh might well continue to be a major player, but if its sitting just to our west we end up in northwesterlies.. which will be quite cloudy (location sensetive of course). theres alot of northwesterly scourced air on the current models and the uppers suggest itll be cool.

 

what i see in the models and what the anoms suggest is pretty normal, average, september weather. theres still the possibility for the gfs's fi settled spell to develop, im not suggesting we wont get another settled anticyclonic spell, just that theres no tangible sign of one as things stand. since the end of july we have been promised several hot settled spells that have been downgraded nearer the time to end up being 24-48 hour affairs, so relying on fi charts suggesting settled/warm spells is frankly, foolhardy.

Edited September 9, 2013 by mushymanrob

[Frosty.]

The latest GEFS 00z mean is continuing to show the longer term trend towards a warm anticyclonic further outlook that the met office have been describing in recent days, however, it's not going to be smooth sailing in the meantime and we must expect some cool and windy unsettled days as well as calmer sunnier days with overnight fog, the more benign conditions during the next 10 days will be the further south you are whereas the further north you are, expect the most unsettled weather, especially later this week and early next week but then once things quieten down in the iceland area, the azores/atlantic anticyclone will have it's chance to build in for a while later in september and bring a nice spell of sunny and warm weather for at least the southern half of the uk.

[Frosty.]

The Ecm 00z operational run really amplifies the upstream pattern, keep an eye on developments up around greenland, it's building an autumn storm which it eventually sends hurtling southeastwards towards the uk, it would bring a very cool and very windy spell with heavy rain followed by squally showers early to mid next week but before then looks rather benign in comparison with some fine and sunny days, overnight fog followed by afternoon warmth but also some bands of rain occasionally pushing south and east, despite all this, beyond T+240 hours still looks like settling down as the azores/atlantic high builds in.

[johnholmes]

Yes the synoptic models are mirroring the variability currently seen in the anomaly charts, they are not steady or consistent in what they suggest for the upper air pattern.

the latest ECMWF-GFS output is below and this morning it is back to an almost meridional type and the trough that was well east of the UK is back, especially on the ec version as playing a significant role in the weather at the surface. GFS less so and both are fairly different from what NOAA showed last evening. No consistency=little confidence in the upper pattern at 6-15 days. The only consistent thing from them all for days now is the +ve heights anomaly shown, usually west of the UK with some indication of ridging again chiefly west of the UK. The trough position is a movable feast one could say!

http://www.meteo.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

below the NOAA last evening outputs for 6-10 and 8-14 for comparison.

http://www.cpc.ncep.noaa.gov/products/predictions/610day/500mb.php

Edited September 9, 2013 by johnholmes

[Yarmy]

The Ecm 00z operational run really amplifies the upstream pattern, keep an eye on developments up around greenland, it's building an autumn storm which it eventually sends hurtling southeastwards towards the uk, it would bring a very cool and very windy spell with heavy rain followed by squally showers early to mid next week but before then looks rather benign in comparison with some fine and sunny days, overnight fog followed by afternoon warmth but also some bands of rain occasionally pushing south and east, despite all this, beyond T+240 hours still looks like settling down as the azores/atlantic high builds in.

 

From memory, the pattern has been for the Greenland-sourced depressions to get pushed further North as the runs go by. 

 

Looking further South, all the models show what I presume is Tropical Depression 09 petering out although the GFS makes a little more of it. I guess these things have some influence on the Azores High and thus create quite a bit of uncertainty in the output for our little target.

[johnholmes]

this link is the US weather bureau take on all things hurricane wise

http://www.nhc.noaa.gov/refresh/graphics_at4+shtml/054339.shtml?tswind120#contents

[No Balls Like Snow Balls]

_{The GFS 06Z ensembles paint a very cool picture. Apart from the odd warm day, cool days far outweigh the warm.}

 

 

_{The 12Z ECM ensembles look cool to.}

 

 

 

 

 

[Summer Sun]

Here is the latest from Gibby something more Autumnal after this week?

 

 

Hi everyone. here is the report on the midnight outputs from GFS, UKMO, GEM, NAVGEM and ECM for today Monday September 9th 2013.

 

All models show a trough of Low pressure easing away slowly to the east of the UK today gradually taking it's rain and heavy showers away East with it. Through tonight and tomorrow Low pressure over Europe is shown to be close enough to Eastern Coastal Counties for cool and cloudy conditions with some rain while Western Britain become largely dry with some bright spells. The West and North will be largely dry, bright but a little cool. Through the remainder of the week a NW flow is shown with occasional fronts moving SE at times giving some rain at times for many though no large amounts look likely especially in the South. nevertheless fronts may well get hung up over the South at times hindering the clearance of rain here prior to the weekend.

 

The Fax Charts show Low pressure off to the East at first this week before a ridge collapses SE on Wednesday followed by a complex array of fronts straddling the UK later in the week slow to clear the south at the start of the weekend.

 

GFS then moves forward showing a NW flow over the weekend with fronts continuing to bring light rain at times before a clearance from the NW behind a cold front brings cool and breezy weather at the start of next week with showers in the North and East. Thereafter Autumnal High pressure builds over the UK with a sustained period of bright days with sunny spells and average temperatures with some very cool and potentially foggy nights and even a touch of frost in prone locations.

 

The GFS Ensembles look somewhat cooler than since I last reported and show a lot of spread between members North and South indicating some uncertainty of conditions. There is no great amounts of precipitation shown overall indicating High pressure quite close by to most areas with it's positioning crucial to the type of conditions felt and experienced at the surface.

 

The Jet Stream currently passing SE over the UK weakens over the coming days and reverts to its course West to East just to the North or over the North of the UK for some time from later this week.

 

UKMO today shows a ridge of High pressure over the South on Saturday slipping away South on Sunday as a cloudier and moister SW flow of winds over the North move South to all areas by the start of next week with some rain in the North.

 

GEM has a cold front slow to clear the South at the start of the weekend with some rain while the North has a dry and bright interlude with sunny spells. Through the weekend a more unsettled spell for all is shown to translate SE across the UK with strong winds and outbreaks of rain followed by sunshine and showers in a blustery and cool NW wind before conditions relax down again from the West at the end of the run.

 

NAVGEM today shows quieter conditions with outbreaks of rain at times though not much in the South as weak troughs alternate with ridges across the UK through the period. Temperatures would be held close to average during the brighter spells with winds biased towards a NW point.

 

ECM shows an indifferent weekend with a more unsettled spell developing at the start of next week as Low pressure crosses East then SE to the North of the UK. Winds will become strong and cold from the NW then North as rain clears to sunshine and squally showers with distinct Autumnal conditions felt by all but more especially to the North and East.

 

In Summary the weather is looking like becoming more Autumnal after a rather benign week this week when just occasional light rain alternates with periods of mostly dry and bright weather with temperatures close to average. Winds then look like increasing later in the weekend with some rain and showers then expected for all with a cool and blustery NW or even North wind possible as we look towards next week. There isn't 100% certainty of this evolution yet though with some output suggesting a more gentle period of September weather similar to that expected this week. So as has been the case so often of late the mid to long term output remains elusive with no maintained and sustained trend apparent yet hence such a wide spread between members such as those shown by the GFS Ensembles.

 

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

 

[Tamara]

Plenty of very amplified solutions on the EPS members with that low from the weekend/early next week which appear to support the operational

.

However, how many times have we been here before at this distance with the amplification being totally overcooked? Plus as already stated, the whole modelling suites and anomaly charts are proving very erratic with the troughing and ridges and not to be relied on at all.

 

On that basis, at least for now, I would stick with the ideas of yesterday, and some rather changeable conditions this week, but with warmer temperatures from midweek. Then an attempt at unsettled conditions spreading from the north west...but how much inroads made southwards is very open to question and the suspicion is that the modelling will flip once more on this. The longwave pattern with time will pre-dispose us to these lows being more extensive, but I am not sure that the entrenched summer feedback pattern will be broken too prematurely.

 

So still every chance from then on of renewed high pressure and warmer more settled weather thereafter

Edited September 9, 2013 by Tamara Road

[Summer Sun]

After this possible deep low crosses north of Scotland around the 16th &17th the GFS ensemble shows pressure slowly rising again its not until deepest FI it falls again

 

 

t336 onwards is when it breaks up

 

 

The ECM ensemble also shows high pressure edging back in right at the end of its run

 

 

[Newberryone]

According to the GFS 12Z ensembles there is a chance for 2 days next week where daytime temps may touch 20c, before falling away sharply again and continuing cool. Nothing much exciting happening weather wise lately. Luckily this time of year though with summer like weather gradually disappearing again for another 5 months at least the chances of some exciting weather are greatly increasing. The autumn / winter storm season is just around the corner.

 

graphe_ens4-1.php.

Hopefully the dreaded Azores high will become less of a player in the coming months and allow the jet stream to move south again in order for this exciting weather you speak of to actually happen.

[Captain Shortwave]

Hopefully the dreaded Azores high will become less of a player in the coming months and allow the jet stream to move south again in order for this exciting weather you speak of to actually happen.

The Azores high needs to use up it's timeshare in the UK, or it will throw a wobbly and park itself over France for the entire winter, dooming us to persistent south westerly winds 

Here's a chart

 

Looks like westerly gales followed by a toppling northerly

Edited September 9, 2013 by Captain shortwave

[Summer Sun]

This possible low continues to show very strong maybe even gale force north to north westerly winds according to GFS for a time next week

 

 

Those in Iceland better batten down the hatches if this comes off 940mb low!!

 

Edited September 9, 2013 by Summer Sun

[Yarmy]

The Azores high needs to use up it's timeshare in the UK, or it will throw a wobbly and park itself over France for the entire winter, dooming us to persistent south westerly winds 

Here's a chart

 

Looks like westerly gales followed by a toppling northerly

 

Gavin would be chuffed

 

It really needs to go and visit Greenland for an extended period starting at the end of November, occasionally stretching over to Scandinavia.

[AWD]

Continuing on from SS's post above, the GFS Op, EC Op and GEM Op all show a notable depression across of near to the UK on or around the 16th September now;

The GEM has it over us, the EC & GFS just to the north of Scotland. Looking at the NAEFS pressure suite for London;

And for Scotland;

also show support for this depression, more so however towards the EC and GFS version of events with the core staying to the north of Scotland bringing strong winds hear and less so further south.

One to watch nonetheless has the track and intensity of this depression could have consequential affects further down the line, in the 2nd half of September.

[Summer Sun]

Longer term patterns show no let up currently with high pressure sitting in the Atlantic keeping it blocked

 

Next weeks possible low is coming down from the north due to a weak area of northern blocking over Greenland

 

note the 1040mb pressure

 

 

 

Over the next few days it slowly eases and by the 19th low pressure is back over there

 

 

By the 22nd an almighty deep low is heading straight for Iceland

 

 

And a fairly settled end from GFS with the exception of northern Scotland

 

 

Shorter term we need to focus on this low with it gaining ensemble support now it could still do what one a few weeks back did and track north of the UK and miss us with just over a week to go a lot can and probably will change between now and next monday

 

ECM ensemble

 

 

GFS ensemble

 

Edited September 9, 2013 by Summer Sun

[William of Walworth]

Yes, I'd be cautious about predicting too confidently that that monster of an LP shown on several charts will verify as fiercely, or necessarily as close to us, as currently seems on the cards early next week. I'd go so far as to stick my neck out and suggest it might have become a  significantly weakened feature by this time next week. Perhaps positioned somewhat further away N too -- with more of a N/S divide, in the end?

 

I admit this is guesswork as any prediction is at this stage, and partly hopecasting too. I'd personally be very keen on a more benign week next week (particularly the latter half). But I'm buying into Tamara's reasoning as well.

[Summer Sun]

The met office don't seems to be going into the full gales route yet so this low could well end up waking significantly over future runs. I think a cooler and windier start to next week looks fairly certain how windy isn't yet

 

The first half of next week has an autumnal look, conditions changeable, often windy and colder than this week as cloudier periods with rain are interspersed with spells of brighter weather with showers. Later next week and onwards for the rest of the forecast period looks likely to become a little less cold with temperatures returning to values nearer average for mid-September

[Tamara]

Yes, I'd be cautious about predicting too confidently that that monster of an LP shown on several charts will verify as fiercely, or necessarily as close to us, as currently seems on the cards early next week. I'd go so far as to stick my neck out and suggest it might have become a  significantly weakened feature by this time next week. Perhaps positioned somewhat further away N too -- with more of a N/S divide, in the end?

 

I admit this is guesswork as any prediction is at this stage, and partly hopecasting too. I'd personally be very keen on a more benign week next week (particularly the latter half). But I'm buying into Tamara's reasoning as well.

I think that there is little doubt that the improvement, suggested up to today, for after the weekend has been made more uncertain in terms of its timings, but the longer term outlook still suggests a return to better weather during the second half of September - albeit it might be more of a UK split scenario once again. However, the disclaimer applies back over the previous page in terms of the erratic nature of the modelling. Time as ever will tell

 

Updated NAEFS anomalies chart still sticks with the theme of improvement following the deep low as it moves away into Scandinavia next week.

 

 

 

However, its a case of how the jet stream aligns itself in terms of amplification with the low itself, and how it then flattens back again after the low. Too much uncertainty right now attached to all this

Edited September 9, 2013 by Tamara Road