Model Discussion And Chat 19th Feb.2012

[Frosty.]

I like the Ecm 00z as it brings a good blast of polar maritime air for most of FI with wintry showers and snow risk with -5 850's covering the uk and a southerly tracking jet which always runs the risk of depressions tracking into the cold air and inducing some heavy snowfalls. The Gfs 00z takes the low at the end of the week up the western side of the uk and pressure quickly rises from the west once the low is gone, next week would be more settled with high pressure centred to the west and eventually feeding milder air up and around the top of the atlantic high, the gfs run seems determined not to bring a cold blast to the uk despite all the bottled up arctic air just waiting for a trigger low to unleash it. So I would like the ecm to verify.

[Nick F]

The disparity between the GFS and ECM continues once we get beyond the end of this week. The GFS is keen to maintain a strong mid Atlantic high, which would keep the majority of Britain mainly dry but with a good deal of cloud, whereas the ECM has a much more active, colder and unsettled outlook with the Azores high pushed a long way south.

The GFS does seem more in line with yesterday's long term outlook from the Met' Office, although they indicated that high pressure would be more persistent to the south rather than the west, but I'm desperately hoping the ECM is correct.

Yes, certainly divergence after t+144 wrt how unsettled the outlook will be from the operationals this morning. The problem appears to be how much the Atlantic troughing can push through between the ridge building across Scandinavia and the Azores ridge.

ECM looks very bullish with pushing through more energy/troughing from the NW between the two ridges with the trough remaining intact across the UK. GFS, on the other hand, disrupts the trough over NW Europe, with the Azores high quickly linking up with the Scandi ridge - with pressure rising again across the UK.

Both scenarios do see some cold air dragged in across the UK from the NW, though it's not particulary deep cold, but perhaps cold enough for some snow towards the northwest.

The GFS ens do seem to swing more in favour of the ridge building back in across the UK like the operational. That Azores ridge just does not want to give!

[Timmytour]

Interesting to see the GFS build up a pool of cold air to the east during the start of next month only for the Atlantic to quickly go through it. Reminiscent of this time last month when models were showing the cold pool to be a lot more vulnerable to incurstion from the west than it turned out to be.

[I remember Atlantic 252]

much prefer GFS 00Z, coldish for a time, then settled, ECMWF 00Z stinks, who would want that at low levels in the south, ECMWF amazing for north 300m

[summersnow]

Interesting to see the GFS build up a pool of cold air to the east during the start of next month only for the Atlantic to quickly go through it. Reminiscent of this time last month when models were showing the cold pool to be a lot more vulnerable to incurstion from the west than it turned out to be.

For most of the country, the cold pool did actually prove vulnerable and so the models were technically correct. Much talk went on as to how the undercut might be achieved, but it never happened - again, as depicted in advance by the models! The cold that was experienced by parts of the country was only really the cold spilling over from the continent - as was modelled. The reason the cold wasn't more extensive and didn't become more sustained is because there was no undercut, no troughing and the Azores HP won the battle - as predicted by the models.

In this coming scenario, it is very reminiscent, as you say, with GFS showing a brief colder incursion followed yet again by the Azores HP regaining control. ECM continues however, to show a more sustained period of cold. There is now a fair bit of divergence between these two models and it will be really interesting to see which wins this time around. I would have said this time one month ago an easy win for the Azores HP and therefore the current GFS 00z, but given the time of year, I do think a pattern change is much likely in the next couple of weeks or so.

Obviously any cold that does arrive will be hugely moderated by the time of year but as I've said in previous posts, both the north an upland areas might be in line for some significant snowfall. On the other hand, we are just as likely to end up with balmy continental air from a more southerly/s'easterly quarter.

[summersnow]

GFS 06z continues deep in FI to suggest a a more PM flow, with eventual ridging into Greenland ....and finally an erosion of the Azores HP and fragmenting of the PV. A long way off but it has been quite consistent with a similar theme to this for a while now and the set up looks quite plausible for mid March - as is virtually any set up!

[Tim Bland]

Models all over the place. No strong signal beyond the weekend

[summersnow]

Modals all over the place. No strong signal beyond the weekend

Agreed - although a reasonably consistent theme from GFS on a PM flow after about 10 days. Also a sign of the season, sea ice melting, sun dipping its head into the Northern Hem, warming continent etc - all likely to throw the models into conflicting solutions.

Oh, and I also forgot to mention gradually coming out of La Nina phase, heading towards neutral will also be a factor for the models to deal with!

Edited February 28, 2012 by summersnow

[Frosty.]

The Gfs 06z follows the gfs 00z in sending that small but vicious looking low up the western side of the uk, (a completely different track to the ecm) and then the low moves away north but there is the added complication of some troughing over the near continent which swings the winds around to a NEly in the southeast which would make it feel quite roar for a short time before pressure rises strongly from the west, then next week pans out like the gfs 00z with atlantic high pressure and a strong ridge over the uk, chilly initially but then gradually milder winds blowing around the top of the high out west, there is another attempt to unlock an arctic blast later in FI but yet again the gfs fails to find the key to unlock it. So the gfs is showing a brief burst of polar maritime air after the current very mild spell, then wet and very windy where that small low hits and then colder and more settled before gradually turning milder and cloudier but mainly dry, still hoping for the ecm outcome with a persistant blast of cold zoneality in FI and the azores high put back in it's box.

Edited February 28, 2012 by Frosty039

[summersnow]

The Gfs 06z follows the gfs 00z in sending that small but vicious looking low up the western side of the uk, (a completely different track to the ecm) and then the low moves away north but there is the added complication of some troughing over the near continent which swings the winds around to a NEly in the southeast which would make it feel quite roar for a short time before pressure rises strongly from the west, then next week pans out like the gfs 00z with atlantic high pressure and a strong ridge over the uk, chilly initially but then gradually milder winds blowing around the top of the high out west, there is another attempt to unlock an arctic blast later in FI but yet again the gfs fails to find the key to unlock it. So the gfs is showing a brief burst of polar maritime air after the current very mild spell, then wet and very windy where that small low hits and then colder and more settled before gradually turning milder and cloudier but mainly dry, still hoping for the ecm outcome with a persistant blast of cold zoneality in FI and the azores high put back in it's box.

I think the arctic blast later in FI might end up being very different to the way GFS is currently modelling it. What GFS shows is the agressive meeting of warm air from the Azores and cold air from the Pole, causing a strong north Atlantic Low to form. This could form virtually anywhwere between Iceland and the Azores, with very different outcomes. All very volatile... watch thi space!

[Frosty.]

I think the arctic blast later in FI might end up being very different to the way GFS is currently modelling it. What GFS shows is the agressive meeting of warm air from the Azores and cold air from the Pole, causing a strong north Atlantic Low to form. This could form virtually anywhwere between Iceland and the Azores, with very different outcomes. All very volatile... watch thi space!

I would still like to think the gfs has the track of that first low competely wrong and that the ecm 00z, with it's sustained cold zonal wintry feeling outlook is closer to the actual outcome, I think we have seen enough benign high pressure weather and the southeast really needs the rain now.

The latest meto update appears to be supporting the ECM 00z rather than the gfs.

Edited February 28, 2012 by Frosty039

[summersnow]

I would still like to think the gfs has the track of that first low competely wrong and that the ecm 00z, with it's sustained cold zonal wintry feeling outlook is closer to the actual outcome, I think we have seen enough benign high pressure weather and the southeast really needs the rain now.

The latest meto update appears to be supporting the ECM 00z rather than the gfs.

Agreed! ECM only really deals with the reliable time frame or at least doesn't go as far into FI as GFS. I'm sure the Met O have access to more data, but it must always be a forecasting nightmare at this time of year to try 1 month ahead predictions.

I reckon they're on a pretty safe bet suggesting drier south/more unsettled north in the longer term though as this is pretty much the default pattern. I still think there is a reasonable chance of something a bit different happening 10 days hence, as GFS has for a while suggested.

[Terminal Moraine]

The latest meto update appears to be supporting the ECM 00z rather than the gfs.

Yes I noticed that, and it's a change from the futher outlook they issued a couple of days ago. On the strength of it, over the next few days, I'm expecting the GFS to lean more towards what the ECM 00z is showing with the mid- Atlantic ridge collapsing and the Azores high forced south.

[Frosty.]

Yes I noticed that, and it's a change from the futher outlook they issued a couple of days ago. On the strength of it, over the next few days, I'm expecting the GFS to lean more towards what the ECM 00z is showing with the mid- Atlantic ridge collapsing and the Azores high forced south.

We may see the Gfs 12z begin to alter the track of the low which will then bring it more in line with the cold zonal ecm which suppresses the azore high, the azores high has played a big part in destroying much of the cold potential this winter but hopefully it will soon go away but then come back just in time for the summer.

Edited February 28, 2012 by Frosty039

[phil nw.]

An attempt at a Scand hgh is trggered by the Atlantic troughing digging south east towards the uk at the end of the week.

Pretty good agreement at T96hrs on this but later output on the ECM and GFs show this as a temporary feature as the westerly flow returns next week.

The ECM looks a colder run further on with some Polar maritime air in the mix whereas the GFS brngs back our old friend/foe the Azores high towards the Uk.

http://www.wetterzen...cs/Recm1681.gif

http://www.wetterzen...s/Rtavn1621.png

Stll a somewhat cooler few days looks likely with more unsettled conditions,especially further north.

Looking at the overnight NOAA forecast mean hts still a lot of high pressure around md-latitudes projected.

http://www.cpc.ncep....y/814day.03.gif

The main core of high presuure stll in the Atlantic with some link up with the heights to our north east,however this is not shown on the ECM output which brings lower heights further south across the UK.

So uncertainty on developments beyond the weekend at present.

Edited February 28, 2012 by phil n.warks.

[KTtom]

http://www.wetterzen...s/Rtavn1501.png

A much more wintry outlook from the GFS 12z. Temps 4-5c over most of the country with plenty of PPN. The track of the low will no doubt change many times before T0. Looks like 12z will progress to an eastely next week.

Edit: Right on cue, that would feel bitter.

http://www.wetterzen...s/Rtavn1681.png

Heavy snow in the north east as -10's cross the north sea....well, as SM isn't here

http://www.wetterzentrale.de/pics/Rtavn1801.png

Heavy snow country wide by +192 as -10's reach Ireland!

Edited February 28, 2012 by KTtom

[johnholmes]

as is so often the case, run to run GFS does like its swings and round a bouts-no doubt the cold fans will come out of their igloos to explain why they feel its a more likely scenario around T+180-192 than the 06z was.

06z showed a slackish WNW flow with 850 temps about zero C over most parts of the Uk away from Eire; the 12z shows a strong NE flow and the -10C moving west close to eastern areas!

I have no idea which will turn out to be correct neither I suggest has anyone else but it will be fun disecting the output I'm sure.

Edited February 28, 2012 by johnholmes

[nick sussex]

Good GFS 12hrs run with a better chance for some snow especially over higher ground. The UKMO unfortunately doesn't want to know although its hard to say what would happen after 144hrs as it still has pressure rises to the ne.

Both though disagree with the ECM trend, hard to say whats going to happen with this much disagreement.

[summersnow]

Subtle but massive difference in GFS 12z compared to 06z by T+180hrs. Instead of the Scandi ridge being swamped by the Azores HP, the Scandi HP establishes itself further north and a classic stand off emerging between northern Scandi block and the Azores HP. Exciting stuff with GFS moving towards the ECM solution and a classic battle being depicted. This is what model watching is all about!

[Timmytour]

Blimey! One hell of an upgrade from GFS though still in line with turning it colder next week...Things might start getting a little busier in here

[Zakos]

I speculate that everything rests on the path of this low

Looking at 180 hours the 12z is miles better from a cold perspective.

But looking back at 144 hours, the 12z is similar to the 06z. The biggest discrepancy is the low. It is much further south on the 12z and hence produces much colder conditions later on the run

I would ignore anything post 140 hours that happens on any run until the path of this low has been decided.

Edited February 28, 2012 by Zakos

[SMU]

http://www2.wetter3.de/Animation_12_UTC/192_35.gif

Bye Bye Scotland see you in april

S

[Summer Sun]

http://www2.wetter3...._UTC/192_35.gif

Bye Bye Scotland see you in april

S

Would someone care to say what that show's I haven't got a clue.

[phil nw.]

I speculate that everything rests on the path of this low

Looking at 180 hours the 12z is miles better from a cold perspective.

But looking back at 144 hours, the 12z is similar to the 06z. The biggest discrepancy is the low. It is much further south on the 12z and hence produces much colder conditions later on the run

I would ignore anything post 140 hours that happens on any run until the path of this low has been decided.

Yes as the trough digs south over the UK it splits and allows the High pressure to build over the top.UKMO keeps those low heights around the north and brings the Azores high into play so no certainty`s on a cold easterly yet.

[Alex95]

The 12z shows the ideal snow setup for NE England really, -10 uppers for a short time early next week, and probably several inches of snow in NE England and E Scotland from snow showers (these don't usually show up on the models properly until +48). Post +192 would be cold and grey with a thaw of lying snow at sea level. I suspect its very unlikely to come off, but it shows that there is probably a 10% chance of a lucky NE'ly.

The 12z also shows cold 850s getting in via a W'ly later on Sunday, and this is much more likely to occur. It also shows the low moving over N'ern England with a blizzard in the Pennines. Interesting as I'm supposed to be travelling home from Cumbria on Monday.

Would someone care to say what that show's I haven't got a clue.

A lot of snow in Scotland.

FWIW, the 6z ensembles showed 40-50% of members opting for the snowy NE'ly next week, so I wouldn't totally write off the 12z.

Edited February 28, 2012 by Alza 2