Model Output Discussion October 2012

[Frosty.]

The latest 00z ensemble mean from both the gfs and ecm is painting a very unsettled picture for the next 10-14 days with low pressure either over the uk or just to the west, only towards the end of the gfs run is when there are signs of pressure rises to the southeast with a less unsettled pattern but for the north and west it looks a persistently unsettled pattern with rain and showers with temps mainly around average, no sign of any cold weather and a lack of overnight frost as there is very little in the way of anticyclonic weather until near the end of the gfs and that is only for the east and southeast of the uk. As for later this week, the weekend is looking very cyclonic with an area of low pressure slap bang on top of the uk on both the gfs and ecm 00z operational runs which indicates heavy slow moving showers and a little sunshine for most of the uk.

[Summer Sun]

When I do my reports I often emphasise it's what the weather feels like on the street to Joe public, most of whom don't care a toss about the synoptics. It's a case of hot wet, dry, cold or warm not what High pressure is doing 1000's of miles away that's important to most. I'm sure there are many who read these forums who become lost and confused about what the models show so I tend to fight their corner and make the model reading a bit more ABC like. I do of course take your pojnt that the synoptics are indeed not standard autumn fayre at the moment with some interesting outcomes possible in a month or so should the pattern maintain. However, there are some on here with greater scientific understanding who make great contributions to this and other forums at times and make debates about this and other weather factors even I don't fully understand very engaging and long may it continue.

Well said Gibby your summaries are very helpful and appreciated by most on here including my self, keep up the good work

[Radiating Dendrite]

Just looked at the 6z run.

Just picking my jaw off the floor, complete Northern blocking at the end of the run.

If this were to occur we would start November with pretty much no PV from what I can see!

Surely this would be unusual?

[AWD]

Some rather deep depressions showing on the 06z output, and not in deep FI either but at semi FI timescales such as T168.

One things for sure, it's looking increasingly likely that there will be copious amounts of rainfall over the next couple of weeks almost anywhere.

I may be wrong but it looks like the deep depressions are being fuelled by a tight thermal gradient over the Mid Atlantic, so not implausible IMO.

[bluearmy]

i need to find the time to look back at archive NH charts for late october and find corresponding years where the developing p/v has been so absent with so much northern blocking. beyond that, would be what happened in nov/dec and what was the state of the strat in late oct/nov. i assume we are looking at very rare late october patterns but until i go through the archives, i cant be too sure.

[Gael_Force]

i need to find the time to look back at archive NH charts for late october and find corresponding years where the developing p/v has been so absent with so much northern blocking. beyond that, would be what happened in nov/dec and what was the state of the strat in late oct/nov. i assume we are looking at very rare late october patterns but until i go through the archives, i cant be too sure.

This compares years back to 1948, nothing remotely akin to the GFS NH output for late October.

http://www.meteociel.fr/modeles/archives/archives.php?day=25&month=10&hour=0&map=4&mode=1

[Met4Cast]

I think the GFS is probably over cooking the low pressure systems for next week, ECM version offers a much more watered down version, but still wet nonetheless. It's now highly likely that some areas next week will see some high rainfall totals leading to probable flooding, where and how much is the question, I expect the GFS to back away from the very deep systems its showing in the next few runs

[Liam J]

I think the GFS is probably over cooking the low pressure systems for next week, ECM version offers a much more watered down version, but still wet nonetheless. It's now highly likely that some areas next week will see some high rainfall totals leading to probable flooding, where and how much is the question, I expect the GFS to back away from the very deep systems its showing in the next few runs

Given the rather unusual and extensive high lattitude blocking signals and disrupted jet I expect some pretty wild scenarios to be shown over the model outputs in the coming days. Still a little out of the reliable time frame atm but certainly not your typical NH autumn charts, thats for sure.

Edited October 10, 2012 by Liam J

[Summer Sun]

Looking at the big 3 for next Tuesday we see GFS is showing the deepest LP system, then UKMO is 2nd followed by ECM going for a less deep LP system

[Liam J]

Looking at the big 3 for next Tuesday we see GFS is showing the deepest LP system, then UKMO is 2nd followed by ECM going for a less deep LP system

I know your referring to the low close to the UK but the ECM actually shows a 980mb depression over the Atlantic, which is the deepest of the three models for that time frame.

Expect changes to the outputs as time marches on and the models get to grips with the pattern change. Exciting stuff

Edited October 10, 2012 by Liam J

[Summer Sun]

I know your referring to the low close to the UK but the ECM actually shows a 980mb depression over the Atlantic, which is the deepest of the three models for that time frame.

Yes that's true but like you said I was referring to the close to the UK

[BLAST FROM THE PAST]

Job done

Edited October 10, 2012 by BLAST FROM THE PAST

[BLAST FROM THE PAST]

Well said Gibby your summaries are very helpful and appreciated by most on here including my self, keep up the good work

Who said anything about not being appreciated? Gibby's explanantion of why he does that is more than fine, I only mentioned it because the models synoptically are currently away from the ordinary and what I read didn't identify that. Job Done......BFTP

[BLAST FROM THE PAST]

When I do my reports I often emphasise it's what the weather feels like on the street to Joe public, most of whom don't care a toss about the synoptics. It's a case of hot wet, dry, cold or warm not what High pressure is doing 1000's of miles away that's important to most. I'm sure there are many who read these forums who become lost and confused about what the models show so I tend to fight their corner and make the model reading a bit more ABC like. I do of course take your pojnt that the synoptics are indeed not standard autumn fayre at the moment with some interesting outcomes possible in a month or so should the pattern maintain. However, there are some on here with greater scientific understanding who make great contributions to this and other forums at times and make debates about this and other weather factors even I don't fully understand very engaging and long may it continue.

Thank you Gibby, explained nicely and it was a 'real' question and a fair question and not a dig..... something that a few wouldn't see as they are too short sighted

BFTP

Edited October 10, 2012 by BLAST FROM THE PAST

[SMU]

Looking at the hemispheric view of the UKMO its a lot less cluttered that of the last few days- with western greenland shredding any deep lows to bits-

That pattern is cool & wet / Windy for the South - dry & cold + Frosty in the middle & chilly in the North-

The reload into Northern europe at day 10 is still evident & expected with the UK under threat at day 12 ish-

Steve

[Severe Siberian icy blast]

Having looked at the gfs12 I notice there is big differences between that and the 6z , firstly you can see more cold amongst the blocking on the 12z as well as the blocking been further south , it also ridges into North Atlantic in fi giving us a northerly shot on two occasions , well in fi and not saying it will happen , but it is something that you would expect from northerly blocking in place. Iv tried posting relevant charts but the iPads playing up and not letting me copy pics.

All very interesting trends though and think there may be further alterations as the next 7 days come in.

[Frosty.]

The Gfs 12z operational run is looking very unsettled for the next 7-10 days with low pressure either over or very close to the uk with spells of wet and windy weather seperated by brighter and showery intervals but no high pressure during that time, pressure does rise eventually later in FI but it's only temporary before low pressure sweeps down from the northwest with a brief Northerly blast before high pressure moves in from the northwest and shunts the cold air away quickly, it does however hint at reloads as the jet is tilted nw/se. As for this week, a lot of rain spreading east tomorrow, especially for the west and on friday as the front becomes stagnant in the far northeast there could be some flooding with in excess of 75mm for ne scotland throughout friday and into saturday, elsewhere it becomes brighter but with showers around, also a cool NE'ly wind on sunday and then more low pressure throughout next week with strong winds at times but temps look close to average.

[SMU]

Look at day 6 over western greenland- if you have been following my posts you will seen my comments on how the jet is forcing lows into the tip & smashing them to peices-

After a few days of the models trying desperate to reset the pattern to the default reset we see the ECM smashing the low to splits & splitting the energy in 2 along that coast line...

Ring any bells???...

http://modeles.meteociel.fr/modeles/reana/2010/archivesnh-2010-11-21-0-0.png

Add 5 days on-

http://modeles.meteociel.fr/modeles/reana/2010/archivesnh-2010-11-26-0-0.png

Do I think the pattern will be identical- NO

however day 10 & 11 etc look strong for the vortex intowards western russia & Scandi with some form of greenland blocking...

Western greenland tip is our friend !

S

[peterf]

Steve,any chance of putting that into lay-mans terms?

[SMU]

HI Peter- Currently at wk- look at my posts yesterday in the winter thread-

Basically insted of going UNDER greenland & staying as deep low pressure systems as usual, the jet is steering them further North west-

so they crash into the western part of greenland- after that- rather like a hurricane they fall apart-

So the net of all that is there eastward penetration is very weak!

S

Edited October 10, 2012 by Steve Murr

[peterf]

cheers for that.

[Gibby]

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

All models show an increasing Southerly flow in association with a developing and complex Low pressure systen drifting in from the West. Rain will spread staedily NE overnight and tomorrow, reaching all areas by this time tomorrow. Some very heavy rain is possible, especially over the West Country and SW Scotland and the Lake District. By Friday the UK lies in a Westerly flow with a cold trough moving East over the SW with thundery showers. Other areas away from NE Scotland (which will stay wet) may stay dry with some brighter periods. The weekend shows Westerly winds continuing with showers in places but some bright spells too. A trough moving East in the flow on Sunday could mean more prolonged showers for a while.

GFS then shows a weak ridge on Monday drying things up for a while before further Low pressure deepens over NW Britain with heavy rain and showers for all for much of the working week as the Low remains slow moving over the North. FI continues in the same vein for a while before a slow improvement in conditions and temperatures occur towards the SE as pressure rises over Europe. Later on in FI High pressure takes control from the West with a cold Northerly flow with some wintry showers on Northern hills for a while before a weaker re-run occurs. With winds in the North rather cold weather would be likely with overnight frost and fog patches.

The GFS Ensembles continue the average pattern when taken as a whole. The operational was both a warm and cold outlier in it's respective phases in the South. Rainfall is quite quantitive in amount over the period for all locations. Temperatures at the surface will continue to be close to normal but feeling chilly in the wind and rain.

The Jet Stream shows the Northern arm ridging North up to the Arctic with the Southern arm extending slowly South and weakening. It's not long though before a new surge exiting the States steams across the Atlantic and ends up in a position over and then South of Southern Britain in a weeks time.

UKMO for noon on Tuesday shows a deep Low pressure over NW Britain with troughs sweeping East in a fresh to strong WSW flow delivering rain and showers to all areas at times.

ECM shows Low pressure unrelenting on its grip over the UK with centre after centre over or close to the UK throughout. periods of rain and showers would occur in all areas coupled with strong and squally winds too at times. With winds from a Westerly point for much of Britain temperatures will never stray far from normal but the far North could see rather colder incursions at times.

In Summary the weather looks very disturbed tonight and could be quite troublesome to some parts of the UK as flooding is a distinct possibility for many areas especially in view that the water table is virtually zero over many parts of SW Britain. All models support a 100% domination of Low pressure with just GFS in the far reaches of FI offering any real hope of drier conditions in the shape of a Northerly and rather cold conditions.

[lorenzo]

96 hrs through to 120 on the GFS 12z shows this very well, sometimes the jump in time frame on ECM leaves a lot of blanks to fill in. GIF of these hours.

The block in the GIN corridor developing strongly in the next 48hrs is also another good watch on this run.

Quite an outlook too..

Edited October 10, 2012 by lorenzo

[Zenarcher]

This evenings model comparison using the ECM, UKMO, GFS, NOGAPS, JMA and GEM.

96 hours 14th October: The ECM, JMA and GEM show the blocking to be stronger than the other models. None of the models can really make up their minds about the low pressure system to the South West of Greenland we have different solutions tonight. Some making it very deep and others not.

120 hours 15th October: This is where the models seem to be struggling a lot with recently, we have so much going on with the low from the South West of Greenland now moving and then of course the other low pressure systems in the Atlantic going everywhere. Anyway the ECM, GEM and GFS look similar here with the low pressure to the South West of Greenland gradually weakening and a weak low sits over the UK. Meanwhile we also have JMA and UKMO agreeing with each other they show the blocking to our North being slightly weaker but pretty much agree on what's going on in the Atlantic. NOGAPS like last year is baffled by all this but if it's close to anything it would agree with the ECM, GEM and GFS.

144 hours 16th October: All the models go their own way except from the UKMO and JMA which still agree, they show weak low pressure out in the Atlantic and across the UK. All models continue to show the blocking still in place.

168 hours 17th October: The remaining four show still show weak low pressure systems in the Atlantic and over the UK.

Overall - The models are still unsure on what to make of things between 96 to 120 hours but they do a similar trend right up to 168 hours with the blocking still in place and weak low pressure systems moving around. A interesting note even though it's in FI is the 240 hours charts on the ECM and GFS despite their differences they both manage to get the Atlantic blocked off.

Edited October 10, 2012 by weathermaster

[Gavin Hannah]

The GFS model is definitely picking up on a blocking pattern in FI. A trend to keep an eye on as we move into next week. Could we be in for a cold north easterly floe as we finish Ocotober?