Model Output Discussion

[Thundery wintry showers]

I think by "potent spell of cold weather" it could be meaning "potent for the time of year"- some of the runs have shown E/NE'lys with maxima of 2-4C and sharp night frosts which is potent for mid to late March. But these cold scenarios are still very hypothetical, only just coming into the back end of T+180, and there is plenty of scope for them to be replaced, for example, with a much milder scenario with LP stalling to the W throwing up a mild cyclonic/southerly regime.

A very cold spell is certainly possible and would represent a strong contrast with the warm weather this week, but we still have a long way to go before it can be classified as likely to happen.

[cooling climate]

I think by "potent spell of cold weather" it could be meaning "potent for the time of year"- some of the runs have shown E/NE'lys with maxima of 2-4C and sharp night frosts which is potent for mid to late March. But these cold scenarios are still very hypothetical, only just coming into the back end of T+180, and there is plenty of scope for them to be replaced, for example, with a much milder scenario with LP stalling to the W throwing up a mild cyclonic/southerly regime.

A very cold spell is certainly possible and would represent a strong contrast with the warm weather this week, but we still have a long way to go before it can be classified as likely to happen.

Yep I would agree with all of that. Myself and NSSC had mentioned a growing signal in the models

in the last few days and then all three main models show strong blocking to the north and a possible

cold evolution that follows for us, but as you rightly say any cold incursion could go the way of the pear

although speaking for myself and I think NSSC the colder option for next week is gaining in momentum.

[Coast]

Just for general information (and for those missing the Regional Discussion threads) we have now opened a general weather banter thread here for all the conversation that doesn't fit into specific threads: netweather.tv/weather-banter

Cheers!

[johnholmes]

You could do with brushing up on your manners for a start.

All I was suggesting was that if the GFS 06z has the low in the Atlantic modeled wrong and

the ridge from the north is stronger then you might see a similar synoptics to what the ECM

shows.

ah

I had not realised that asking for how a view was arrived at and saying please was bad manners!

I have been keeping a rough check on how the GFS output is varying from run to run-not like me in the FI area, post T+168. To me its progged cold and mild scenarios with about the same frequency.

As to blocking-yes that is there, not constantly, nor is it, in my view, supported by all the necessary teleconnections.

As always the weather will do as it wishes as we all try to work out which model is nearer the probable outcome.

[snowfish]

I think by "potent spell of cold weather" it could be meaning "potent for the time of year"- some of the runs have shown E/NE'lys with maxima of 2-4C and sharp night frosts which is potent for mid to late March. But these cold scenarios are still very hypothetical, only just coming into the back end of T+180, and there is plenty of scope for them to be replaced, for example, with a much milder scenario with LP stalling to the W throwing up a mild cyclonic/southerly regime.

A very cold spell is certainly possible and would represent a strong contrast with the warm weather this week, but we still have a long way to go before it can be classified as likely to happen.

Spot on....! I am very much a novice in terms of model watching but I am learning fast thanks to everyone here on NW - Eugene has made some interesting observations along with a great many others - it makes it all the more fun and I am grateful to all that post here....

Edited March 16, 2010 by snowfish

[The PIT]

The 12 oz removed any hint of cooler weather in the reliable time frame and pushes any real code deeper into deep Fi. One thing it does do though just outside the reliable time frame is to reduce the mild air a bit so temperatures probably around average. Is the GFS12 oz been too progressive again??? All eyes on the ECM and see if that goes swap around.

[Guest North Sea Snow Convection]

Yep I would agree with all of that. Myself and NSSC had mentioned a growing signal in the models

in the last few days and then all three main models show strong blocking to the north and a possible

cold evolution that follows for us, but as you rightly say any cold incursion could go the way of the pear

although speaking for myself and I think NSSC the colder option for next week is gaining in momentum.

As is given some support by the telecommunications, in terms of blocking to the north, the ECM continues from this morning with a very promising output this evening in terms of setting up nicely for a super easterly for the UKand one that if this was a month or two back would be getting a lot more interest than now. Out to t192 so far, but evolves favourably from as relatively early as t120

ECM is being less progresive than the other models with low pressure. Might they move in line with it?

Long way out but this would be nice to start the last week of March

Edited March 16, 2010 by North Sea Snow Convection

[yamkin]

ECM 12Z is still going for a colder period next week. The FI E/NE flow looks very interesting at 240h

[phil nw.]

ECM 12Z is still going for a colder period next week. The FI E/NE flow looks very interesting at 240h

Mmm,not sure i would welcome that so late in the season Yamkin.

Could be quite unpleasant,raw and sleety maybe, but worse than a cloudy mild,S.Westerly imo.

As Tamara said a good setup 2months ago,but not now,at least not if you are wanting sustainable snowcover.

GFS not far away from the same setup at T240hrs either,

http://www.wetterzentrale.de/pics/Rtavn2401.png

but milder.

Meanwhile the Westerly driven flow continues this week,getting more unsettled after tomorrow and going into the weekend.

http://www.wetterzentrale.de/pics/Rtavn961.png

http://www.wetterzentrale.de/pics/Rukm961.gif

http://www.wetterzentrale.de/pics/Recm961.gif

Temps. remaining average or above.

[Cheese Rice]

Mmm,not sure i would welcome that so late in the season Yamkin.

Could be quite unpleasant,raw and sleety maybe, but worse than a cloudy mild,S.Westerly imo.

As Tamara said a good setup 2months ago,but not now,at least not if you are wanting sustainable snowcover.

If we got what the models are showing we would easily see snow cover, -5 850's can deliver pretty much across the whole of the UK if the precipitation is heavy enough. In March/April 2008 widespread snowfall was achieved across many areas with some areas (Leeds) receiving up to 6 inches of snow on two occasions at the end of March under -5 850's. Even in the centre of London in April there was lying snow.

I personally would welcome any wintry weather, and would take what the GFS is showing, there would be plenty of troughs associated with the northerly feed and temperatures wouldn't be that low (5-7.c) unless we can get a really potent feed (-10 or below).

[Thundery wintry showers]

As we head through March and April easterlies do have an increasing tendency to be overcast and raw, but that's because the upper air tends to be warmer relative to the SSTs, giving relatively stable conditions and stratocumulus layers instead of convectional cloud.

But the easterly on the ECMWF T+240 has very low thicknesses- below 520dam suggests itself for a large part of the UK- and these usually go hand in hand with very cold uppers. Hence I can't see how the result would be "raw and sleety"- I think some "I don't want any more cold weather now that it's Spring"-related confirmation bias could well be influencing that particular assessment.

The most likely scenario would be sunshine and snow/hail showers, with accumulations at times in the east, mainly overnight and during the morning, then a general thaw in the sunny intervals in between showers from late morning onwards. The 18th March 2001 gave a good example of this weather type in Tyne and Wear from a similar setup though it was dull and wet in the south from Atlantic systems on that occasion.

However I would be extremely surprised if anything like that came off. We probably have more likelihood of ending up with what GFS shows- just average temps and rather wet- the ECM is the extreme "cold-case scenario". But it all shows that the evolution beyond this week's mild spell is up in the air.

[phil nw.]

As we head through March and April easterlies do have an increasing tendency to be overcast and raw, but that's because the upper air tends to be warmer relative to the SSTs, giving relatively stable conditions and stratocumulus layers instead of convectional cloud.

But the easterly on the ECMWF T+240 has very low thicknesses- below 520dam suggests itself for a large part of the UK- and these usually go hand in hand with very cold uppers. Hence I can't see how the result would be "raw and sleety"- I think some "I don't want any more cold weather now that it's Spring"-related confirmation bias could well be influencing that particular assessment.

The most likely scenario would be sunshine and snow/hail showers, with accumulations at times in the east, mainly overnight and during the morning, then a general thaw in the sunny intervals in between showers from late morning onwards. The 18th March 2001 gave a good example of this weather type in Tyne and Wear from a similar setup though it was dull and wet in the south from Atlantic systems on that occasion.

However I would be extremely surprised if anything like that came off. We probably have more likelihood of ending up with what GFS shows- just average temps and rather wet- the ECM is the extreme "cold-case scenario". But it all shows that the evolution beyond this week's mild spell is up in the air.

Yes the ECM could give snow showers TWS but as you said yourself any accumulations would be shortlived being confined to night and early mornings.

I guess i was flippant in suggesting sleet but the point of that really was aimed at the futility of such a"promising"setup.

Yes i admit i want warmth now ,it`s been a good Winter, and i no longer understand the welcoming of Easterly`s that late in March.

Edited March 16, 2010 by phil n.warks.

[Thundery wintry showers]

There are plenty of reasons why people might welcome such an easterly in late March, although a northerly is usually more reliable for it at this time of year. Sunshine and wintry showers, solar heating assisting convection, towering cumulonimbus cells giving rise to picturesque cloudscapes with hail and snow shafts, sharp fluctuations in temperature, accumulations of hail/snow in showers followed by melting in the sunshine. For some- including myself- that type of weather has a lot of appeal. And of course there are those who just like it to be cold with wintry potential regardless of the circumstances, and while I'm not enthusiastic about genuinely raw sleety weather, each to their own. Just as long as they also respect the fact that those who want warm weather are equally entitled to their own preferences.

On very rare occasions an easterly has been known to bring sunshine and wintry showers even into May- around 16-18 May 1996 for instance- though it has to be sourced from high latitudes, for an easterly bringing continental air will usually be dull and drizzly especially near the east coast.

It is significant though that there is no hint of an easterly on the UKMO, which should never be ruled out as it is currently holding a healthy 2nd place behind ECM in the verification stats. GFS 18Z though is hinting at a colder outlook towards FI, to a lesser extent than the ECM.

[johnholmes]

The 00z GFS this morning suggests milder rather than colder for my area. Yesterday it was the opposite with a cold predict through most of the period for almost the whole run out to T+384.

High latitude blocking is there on some days but the major upper trough stays, for the most part, west of the Uk, preventing any major cold outbreak from any northerly point.

At T+240 the upper pattern on both GFS and ECMWF is quite similar although their surface centres are not as close.

Edited March 17, 2010 by johnholmes

[mushymanrob]

The 00z GFS this morning suggests milder rather than colder for my area. Yesterday it was the opposite with a cold predict through most of the period for almost the whole run out to T+384.

High latitude blocking is there on some days but the major upper trough stays, for the most part, west of the Uk, preventing any major cold outbreak from any northerly point.

At T+240 the upper pattern on both GFS and ECMWF is quite similar although their surface centres are not as close.

... indeed , yesterdays 00z was full of promis for some cold weather whilst todays suggests a normal atlantic driven regime. with high uncertainty even out to 72 hours looking into fi for any (prefered) trend is pretty pointless.

[cooling climate]

UKMO latches onto a colder pattern this morning while at the same time the

ECM and the GFS models drop the idea but I would not be at all surprised to

see a colder pattern emerge again from these models in future runs.

[conor123]

The 00z had identical charts almost for now and 384hrs interestingly.

Friday may well be a lovely day ahead of a long spell of very wet cooler/average weather.

[Guest North Sea Snow Convection]

Yes the ECM could give snow showers TWS but as you said yourself any accumulations would be shortlived being confined to night and early mornings.

I guess i was flippant in suggesting sleet but the point of that really was aimed at the futility of such a"promising"setup.

Yes i admit i want warmth now ,it`s been a good Winter, and i no longer understand the welcoming of Easterly`s that late in March.

I much prefer easterly patterns at any time of year Phil, not just the winter.

Certainly no guarantees that there will be one late this March because even though the renewed northern blocking is looking increasingly likely, the models are chopping and changing where this sets up and the GEM for instance keeps suggesting yet another west based pattern which is as a bad for the UK as any usual mild zonality. The UKMO looks better this morning, and although the ECM doesn't suggest the classic north easterly pattern of last night, it is not too far removed from it - again depending how the atlantic lows orientate and position themselves with the block based Greenland/Iceland rather than Greenland/Canada

Hopefully any west based suggestion is overdoing the reversal of zonal wind anomalies this time around, which don't look as strong as back in February, and just led to a poor cylonic/westerly pattern and a lot of cold rain for southern parts of the UK

Edited March 17, 2010 by North Sea Snow Convection

[The PIT]

No chance of any snow out of the ECM run I'm afraid. I think the best thing you can say about the outlook is changeable with temps from average to above average.

[Polar Continental]

I much prefer easterly patterns at any time of year Phil, not just the winter.

Certainly no guarantees that there will be one late this March because even though the renewed northern blocking is looking increasingly likely, the models are chopping and changing where this sets up and the GEM for instance keeps suggesting yet another west based pattern which is as a bad for the UK as any usual mild zonality. The UKMO looks better this morning, and although the ECM doesn't suggest the classic north easterly pattern of last night, it is not too far removed from it - again depending how the atlantic lows orientate and position themselves with the block based Greenland/Iceland rather than Greenland/Canada

Hopefully any west based suggestion is overdoing the reversal of zonal wind anomalies this time around, which don't look as strong as back in February, and just led to a poor cylonic/westerly pattern and a lot of cold rain for southern parts of the UK

Hi Tamara,

Yes bring on the east or north easterly and the colder the better, a few on here have no staying power lol. Only joking Phil.

Only just reached double figure temperatures here in the last few days, I was hoping that we could get at least to the end of March; the end of June would suit me better still.

As you say, the problem with this evolving pattern of height rises to the north west, it is again to far west, it does seem to be a repeating pattern. So the odds on another cold outbreak have shortened.

The 0z GEM also projects northern blocking, but because of its westward and north position we end up with a deep southerly.

0z GEM

[cooling climate]

No chance of any snow out of the ECM run I'm afraid. I think the best thing you can say about the outlook is changeable with temps from average to above average.

I take it then that you have not looked at the GFS 06z run or are simply dismissing it.

I know it is the 06z run which verifies the least well out of the four runs but this pattern

keeps showing up and it has just come into the range of the UKMO model which shows

it to.

My money is on much colder weather for the middle of next week onwards.

[Eugene]

Being abit kind aren't you PIT more like way above average, models moving away from cold weather IMO, GFS 06Z OP one of the coldest runs in FI.

[Guest North Sea Snow Convection]

Hi Tamara,

Yes bring on the east or north easterly and the colder the better, a few on here have no staying power lol. Only joking Phil.

Only just reached double figure temperatures here in the last few days, I was hoping that we could get at least to the end of March; the end of June would suit me better still.

As you say, the problem with this evolving pattern of height rises to the north west, it is again to far west, it does seem to be a repeating pattern. So the odds on another cold outbreak have shortened.

The 0z GEM also projects northern blocking, but because of its westward and north position we end up with a deep southerly.

0z GEM

Hi Paul,

I think there is a chance that the pattern may still be modelled too far west this time around. GEM is quite a good long range model but although it is good at picking up pattern changes, it can tend to overblow them at this sort of range

[Nick F]

Those wanting the easterlies or northeasterlies shown by 06z GFS to materialise, they may well bring cold, grey and damp weather off the North Sea. Not my idea of fun after these last few days of spring sunshine here. But each one to their own. Im still haunted when we get to this time of year, after getting into the swing of spring sunshine, of a spell in April 2000 when we a had a few days of cold nagging easterlies bringing slate grey skies with sleet. My favoured wind direction this time of year would be a polar northerly, bringing sunshine and heavy showers inland as the sun gains strength, not really much sign of that happening atm.

[The PIT]

I take it then that you have not looked at the GFS 06z run or are simply dismissing it.

I know it is the 06z run which verifies the least well out of the four runs but this pattern

keeps showing up and it has just come into the range of the UKMO model which shows

it to.

My money is on much colder weather for the middle of next week onwards.

Errr when was I talking about GFS.

Anyway you won't get any out of the GFS in the reliable time frame either or just outside it.

Edited March 17, 2010 by The PIT