Model Discussion And Chat 19th Feb.2012

[bluearmy]

is FI really T48 ?? uncertainty regarding the track of the shortwave but beyond that and any shortlived lee easterly, pretty good agreement for the middle part of next week.

[snowmadchrisuk]

is FI really T48 ?? uncertainty regarding the track of the shortwave but beyond that and any shortlived lee easterly, pretty good agreement for the middle part of next week.

Trend wise , the only thing that keeps flagging up to me is that the PV wants to weaken and Move East breaking up as it does.. but until this gets into a more reliable time then it will remain just a trend.

[karyo]

Well, we now have a further backtrack from the gfs! The 6z cancels the cold northwesterly flow and picks up the low to the south of the country which is similar to the UKMO and ECM. Not a good development as the northwesterly would have at least brought plenty of wintry showers (snow for some).

After that, it still shows the Atlantic taking over...

The CFS has been quite bullish about an above average March and it seems it will be right once again!

Karyo

[Frosty.]

The latest meto update in my opinion is suggesting a link up of the azores and scandi high (Ecm 00z) towards the middle of next week with clear frosty nights and mainly sunny days but the fine weather then disappearing after midweek with unsettled, windier and milder weather already into nw britain, pushing southeastwards followed by cold zonal spells with wintry ppn on hills in northern areas.

[damianslaw]

GFS and ECM showing different scenarios for Sunday - ECM keen on a southerly tracking low, GFS less keen on the low hitting southern shores - will be interesting to see who is right. Wintry precipitation reserved for higher ground only, but Sunday is looking a raw cold dank day and a bit of a shock to the system compared to many recent days with temps back down to 6-7 degrees.

Early next week - all models support the influence of heights to our NE bringing a shortlived chilly dry clear spell of weather with frosts at night and temps struggling by day thanks to the cold uppers.

By mid week - GFS and ECM support the atlantic returning on a westerly trajectory forcing those heights to our NE to retreat southwestwards, so a milder but unsettled spell looks likely and much windier than of late but not the balmy conditions of late.

Longer term - GFS and ECM to a lesser extent suggesting movement on the polar vortex further eastwards - introducing trough disruption over the country and a possible colder outlook with north west/northerly winds - but the azores high could easily scupper such developments - its been the main player of our weather for so long now.. its persistance is very notable.

Overall it looks like quite an interesting changeable outlook for the first half of March, never particularly mild for any great length of time, nor particularly cold, but by mid month we may enter a more colder set up thanks to a more favourable PV and strat profile. The PV traditionally weakens considerably during March and we are much more likely to see northerly and easterly set ups take hold.

[Zenarcher]

For the low on Sunday we still don't see 100% agreement between the 3 main models even at just 72 hours the positioning of the low seems very similar but each of them show a different deepness. After this each of them take a different route the ECM sends it over Northwest of France with the GFS showing something very similar except it has the low slightly more South and not as deep leaving the UKMO on its own which shows the low turning into a shortwave over France and Germany.

The ECM has done well with it most models were flattening it out in the Atlantic but the ECM was very confident that a low would come close to the channel on Sunday but didn't what to do with it but now we are seeing agreement before it approaches the UK I think we won't know for sure until tomorrow morning on where it will go and what effect it will have.

[Weather Wizard]

Very good UKMO at 120h for cold prospects GFS not as good but not bad

[Cheshire Freeze]

The GFS 12z shows that the PV just won't give us a break, again rooted to the place it's been stuck in for most of the winter. What will it take to budge it?

Interestingly, the 12z UKMO is quite similar at 144 to the earlier GEM with energy having the option to go under the block rather than simply sinking it.

Edited March 1, 2012 by CreweCold

[nick sussex]

The UKMO at 144hrs breaks with the recent operational trend and shows some trough disruption to the west.

http://www.meteociel...=144&carte=1021

Could the unthinkable happen?

It's a shame we're seeing these outputs now and not a few weeks back.

It's hardly been the most consistent model recently and that 144hrs although interesting is a long shot unless that is the ECM goes with this.

The GEM which had a similar trend to the UKMO on its morning output, continues with a similar theme this evening, the NOGAPS also goes for some trough disruption at 144hrs.

Hard to see the Atlantic being held back for an extended period of time but just a chance that this might take two attempts, whether any trough disruption leads to some snow hard to say at this timeframe.

Edited March 1, 2012 by nick sussex

[IDO]

The GFS 12z today is about the worse run since a cooler outlook has been modelled. Hopefully the ensembles will shed some light, and this does not become a trend:

http://nwstatic.co.u...e1cfc31ccd7074;

The above is at the end of FI but is representive of the whole run after Tuesday/Wednesday of next week.

Edited March 1, 2012 by i'm dreaming of...

[NorthernRab]

The above is at the end f FI but is representive of the whole run

Then why not just show the charts that are in the reliable time frame, if they're so similar?

[Suburban Streamer]

The UKMO at 144hrs breaks with the recent operational trend and shows some trough disruption to the west.

http://www.meteociel...=144&carte=1021

that ukmo 144 chart seems to match the gwo phase two pretty well....i think? Gp suggested phase two recently

[Shunter]

Well looking at the GFS 12z ensembles for London , FI begins at T96 !! The following perbutations resemble a dropped tin of spaghetti ( absolutely no consistency in temperature or rainfall ). I dont ever recall seeing this much divergence in GFS but typifies this winter's output.

Is technology really progressing the realms of forecasting? I dont think so

http://www.netweather.tv/index.cgi?action=charts;type=ens;sess=

[nick sussex]

Interesting new trend from the models apart from the GFS.

The ECM now goes for some trough disruption at 144hrs, it's gone with one of the few morning ensemble members that suggested that:

http://www.ecmwf.int/samples/d/inspect/catalog/samplers/banner/mean_sea_level_pressure_and_temperature_at_850hpa!156!pop!od!enfo!enplot!2012030100!!/

At 168hrs the Azores high moves in but will that verify?

I'd certainly look out for the ensembles tonight, will any of those send a shortwave into Europe allowing the ridge to the ne to back west again.

[KTtom]

Interesting new trend from the models apart from the GFS.

The ECM now goes for some trough disruption at 144hrs,

Can someone explain what is meant by 'trough disruption'? I hear the same comment regarding the UKMO, yet looking at the chart it seems to be intact to me??

[phil nw.]

After some Springlike conditions today and tomorrow the weekend beckons a change as low pressure moves down from the north west bringing cooler and unsettled conditions by Sunday.

That little low could bring quite a wet day for some parts.

By Monday we pick up a brief easterly as the low moves into the continent and pressure rises across the UK keeping things somewhat colder into midweek with night frosts.

As we look towards T144hrs the 12z outputs point to the usual +NAO pattern with High pressure to the south across the Azores and low pressure to our north.

There are some signs of possible further trough disruption as low pressure approaches the UK from the west but essentially any blocking to the north east looks unlikely to hold back the Atlantic for long with both ECM and GFS showing a continuing dominance of the Azores high and deepening of low heights to our north west towards T168-192hrs.onwards.

Edited March 1, 2012 by phil n.warks.

[Geordiesnow]

All the models do look more or less similar tonight with a very strong PV and height rises to the North East and all models have a massive low to the South of Greenland so you do have to question how any cold from the East will back westwards under the medium term.

That said, make the most of the very mild conditions tomorrow because it will turn cooler and a little bit more unsettled even though temperatures will be more nearer the seasonal average it will feel cool because of the lower dewpoints.

[johnholmes]

Can someone explain what is meant by 'trough disruption'? I hear the same comment regarding the UKMO, yet looking at the chart it seems to be intact to me??

I would use this web site for most weather definitions its probably the best site for unbiased weather information around

http://weatherfaqs.org.uk/node/61

[phil nw.]

Can someone explain what is meant by 'trough disruption'? I hear the same comment regarding the UKMO, yet looking at the chart it seems to be intact to me??

There`s a chance we could see a cut off low forming as the main trough advances against the block.Some of the ECM thumbs show this around T144hrs and the GEM on the 00z had this at T168hrs.

Something like this coming weekend where the trough digs south insread of advancing west to east the flow buckles and we get the new surface low.

It shows up well on the fax on my earlier post.

[I remember Atlantic 252]

I really hope GFS has sunday right, seems to give a cold settled day, where as meto give a horrid wet day, most likely meto right I think

[KTtom]

Thanks both above...

Got to add the +240 chart from ECM (as its quiet), ....imagine the northerly come +300

[Frosty.]

Well what a big downgrade in the cold potential since the 12z's yesterday, seems a lot longer than 24 hours in terms of how the models have changed but not surprising given how ghastly the last 4 months have been apart from that moderate siberian blocking in early feb which affected the southern half of the uk only. It does look like turning cooler into the weekend which I suppose is some sort of victory given how mild things have been recently.

[bluearmy]

the ridge thrown up to our ne is progged by most models to make a lot of progress across the hemisphere with a fair amount of WAA headed into the arctic. i think this is going to cause the modelling some headaches over the next few days. all the models have an impressive rise in heights well to our ne stretching across towards n siberia by day 6. expect the unexpected as far as the output is concerned is that verfies.

[Frosty.]

I mentioned it turning cooler into the weekend but temps will still be up to 13c in the southeast on saturday, it's really sunday when things kick off with a colder and potentially very wet and windy spell but the models still haven't nailed which area is going to get the biggest soaking yet.

[bluearmy]

interesting variation between naefs and ecm ens at day 10

ecm, as per its recent ops has a trough digging to our east. naefs shows a propensity to ridging. latest cpc charts appear to favour the troughing though a little less progressive than the ecm solution.