Model Output Discussion

[SP1986]

I'm surprised people are saying that some of the upcoming temperatures (not all of them given a potetial northerly etc) are not mild, Ive always considered temperatures of 8-9C in January to be perceived as mild.

S4lancia, Im not sure of the answer to your question but I can say you'll be hard pressed to find anyone in here that will link any signal to potential mild, so you might get the answer you hope for there (ie every signal will have a cold bias, to be fair that's what people want because that's what everyone looking for)

[Weather-history]

Manchester 2m temps for 18z ensembles and not one single ensemble reaches the 10C mark

http://www.wzkarten3.de/pics/MT2_Manchester_ens.png

[nick sussex]

The latest GEFS ensembles look okay, perhaps alot better than expected.For London the mean 850's from the 1st February till the end is between -4 and -5.This is around the time we're expected to see a euro high close by, perhaps this can stay far enough north to keep it dry with some sunshine and frosts.

[SP1986]

I do actually think Ian's prediction has more chance of occurring as the models are moving away from this idea uninterrupted cold, which was in force not that long ago. The models are showing pattern that we would get in the winters before last year, and it looks awfully familiar in that context, ie topplers etc.

I do think people will now expect this type of winter to be the norm and people dont realise this winter has been extraordinary for cold. This occurred conversely in 2003 where some people, suggested a clone of that summer in 2004, of course many were disappointed.

Edited January 23, 2010 by JACKONE
To delete initial quote - now deleted.

[Lewis]

Manchester 2m temps for 18z ensembles and not one single ensemble reaches the 10C mark

http://www.wzkarten3.de/pics/MT2_Manchester_ens.png

They are close at 8-9c, this is what the models show.. They are models.

The GFS showed 6c for me the other day, i hit 8c

I never take notice of the ensembles at the surface.

[SP1986]

Manchester 2m temps for 18z ensembles and not one single ensemble reaches the 10C mark

http://www.wzkarten3.de/pics/MT2_Manchester_ens.png

I suspect by the coast that would look alot different, it's a shame we havent got ensembles for say Liverpool to demonstrate this.

[phil nw.]

I'm surprised people are saying that some of the upcoming temperatures (not all of them given a potetial northerly etc) are not mild, Ive always considered temperatures of 8-9C in January to be perceived as mild.

S4lancia, Im not sure of the answer to your question but I can say you'll be hard pressed to find anyone in here that will link any signal to potential mild, so you might get the answer you hope for there (ie every signal will have a cold bias, to be fair that's what people want because that's what everyone looking for)

Give us some links Stephen.

If you are referring to my last post, i was basing my points around 18z and linked some days where the max temps. were between 1-3C for many away from the favoured South West.

Edited January 23, 2010 by phil n.warks.

[J10]

The METO continue to lose credibility; look at the coming week and how many of their forecasts, both national and regional have talked about zero maxima for the coming week. The GFS has never really bought into that and has out performed the METO at every level, and it will be right again.

The set-up is all wrong I'm afraid; besides which these northerlies in recent years have seen some anomalously warm temps in the Southern half of the UK when they have occurred.

In the decade just gone, Northerlies brought regular heavy snow for here. Including the Saturday towards the end of the cold spell in Feb last year and Dec 31 last year.

Even Topplers have been quite productive for here.

[LomondSnowstorm]

Certainly the next week will not be mild and some days will be distinctly below average.

http://www.wetterzen.../Rtavn11417.png

http://www.wetterzen.../Rtavn13817.png

http://www.wetterzen.../Rtavn16217.png

However i think most of us can see that the Northerly is modelled to be a brief one as it`s pushed South East by the flow.

Having said that 18z does show an alternative to Ian B,s blowtorch solution, after the Northerly.

http://www.wetterzen...s/Rtavn1801.png

http://www.wetterzen.../Rtavn18015.png

Although the block sinks the jet is on a better NW-SE axis keeping the air colder and more of a PM variety.

Plenty of options going forward.

Agreed. Nice summary there Phil, very balanced and ground in the model output . The ensemble mean for eastern Scotland tonight stays around -5 for the entire period from the toppler onwards, with a lot of uncertainty but a lot of runs going for fairly cold solutions at times http://charts.netweather.tv/ensimages/ens.20100123/18/t850Fife.png

Actually it looks colder in the southeast as well http://charts.netweather.tv/ensimages/ens.20100123/18/t850London.png

http://charts.netweather.tv/ensimages/ens.20100123/18/t850Western~Isles.png The mildest uppers for the start of FI appear to be the Western Isles, meaning that the cold uppers shown on the mean are generally more from the east than the north. Having said that, the ensembles can change completely overnight, but it is an indicator that perhaps blowtorch is not necessarily the outcome for the start of February.

Anyway, I think, Stephen, that what people were meaning was that the temperatures are not, overall, that mild for a sustained period, as was suggested by some. However, people have to acknowledge that others are entitled to their own takeon the models, but also to healthy scepticism of others' views on them. This thread is meant to be enjoyable and informative for all members

LS

[Weather-history]

They are close at 8-9c, this is what the models show.. They are models.

The GFS showed 6c for me the other day, i hit 8c

I never take notice of the ensembles at the surface.

I think you are completely missing the irony here, Ian Brown was championing GFS and he was talking about plenty of double digit maxima and yet not one GFS 18z ensemble agrees with him and also the London ones are the same.

And it is pretty unusual as they are not that cold ensembles, the odds would favour at least one doing it.

Edited January 23, 2010 by Mr_Data

[SP1986]

Give us some links Stephen.

If you are referring to my last post, i was basing my points around 18z and linked some days where the max temps. were between 1-3C for many away from the favoured South West.

Sure thing Phil:

(27/01)

Admittedly its not everyday, and the highest temperature are generally reserved for the coasts, but the coasts count too, and whilst temperature might be around 5C inland on other days it's not generally too cold (just below around average, but still fairly mild compared to what we were seeing)

[Cloud 10]

A solid northerly from the 18z nogaps.

[J10]

Sure thing Phil:

(27/01)

Admittedly its not everyday, and the highest temperature are generally reserved for the coasts, but the coasts count too, and whilst temperature might be around 5C inland on other days it's not generally too cold (just below around average, but still fairly mild compared to what we were seeing)

The following day though is much colder, as the colder uppers spread from the north.

http://212.100.247.145/viewimage.pl?type=gfs;date=20100123;time=18;ext=117;sess=97306ca37275f91125d0c227ceffda3f;file=ukmaxtemp

[phil nw.]

Sure thing Phil:

(27/01)

Admittedly its not everyday, and the highest temperature are generally reserved for the coasts, but the coasts count too, and whilst temperature might be around 5C inland on other days it's not generally too cold (just below around average, but still fairly mild compared to what we were seeing)

Thanks Stephen.

Yes i did miss that but i had looked at the midday max.s.

Got to say though i did say average and on some days distinctly below,which if you look at all next week,is fair comment.

Anyway 18z is certainly not a mild run in the HR period i think you will agree.

[damianslaw]

I have to say that I agree with the toppler scenario here. Unless pressure builds south out of the arctic, as happened in December, these midatlantic high northerlies rarely last that long. HOWEVER, the fact that the high is being shunted westwards can only be good at upgrading duration and potency of the northerly next week. Also if the jet remains amplified, around the midatlantic high, then even with a positive AO we can see repeated polar maritime reloads as was the case in late autumn and early winter last year.

Interested to see how the subsequent runs develope the westward progression of the high though..

Indeed a toppling of the northerly won't necessarily mean we are destined for a south westerly flow, a very plausible evolution afterwards is a polar maritime airstream with the jet tracking NW-SE due to amplification. This would aid heights developing over Greenland as we head further into Feb, something I think is very likely to happen. People seem very assured that we will enter a mild zone after any northerly, any mild weather will be very short lived I feel.

[phil nw.]

Agreed. Nice summary there Phil, very balanced and ground in the model output . The ensemble mean for eastern Scotland tonight stays around -5 for the entire period from the toppler onwards, with a lot of uncertainty but a lot of runs going for fairly cold solutions at times http://charts.netwea...18/t850Fife.png

Actually it looks colder in the southeast as well http://charts.netwea.../t850London.png

http://charts.netwea...stern~Isles.png The mildest uppers for the start of FI appear to be the Western Isles, meaning that the cold uppers shown on the mean are generally more from the east than the north. Having said that, the ensembles can change completely overnight, but it is an indicator that perhaps blowtorch is not necessarily the outcome for the start of February.

Anyway, I think, Stephen, that what people were meaning was that the temperatures are not, overall, that mild for a sustained period, as was suggested by some. However, people have to acknowledge that others are entitled to their own takeon the models, but also to healthy scepticism of others' views on them. This thread is meant to be enjoyable and informative for all members

LS

Thanks L.S.

I try to always post objectively and support my points with links where usefull,as you have done here.

Looking at all the output since 12z it`s still quite seasonal i reckon.

I think we have to have a spell of Atlantic influence now but it doesn`t look mild next week.

We have some chilly Anticylonic days to come before a 2 day Northerly.

After that it is uncertain but if the block sinks as the 18z shows it could still remain chilly with the jet on a more NW-SE tilt bringing a lot of polar air into the mix.

Edited January 24, 2010 by phil n.warks.

[LomondSnowstorm]

Sure thing Phil:

(27/01)

Admittedly its not everyday, and the highest temperature are generally reserved for the coasts, but the coasts count too, and whilst temperature might be around 5C inland on other days it's not generally too cold (just below around average, but still fairly mild compared to what we were seeing)

Yuck, 9C here on those charts. Haven't seen those temperatures for months - t-shirt weather!!

[acbrixton]

Hi,

Also I have a question for you on here. It seems that a lot of posters on here do not seem to be optimistic about a cold and/or snowy February, at least for the first half with a mainly downbeat mood prevailing. Why is this so considering we have had the one of the coldest winters for the last 30 years and the fact that for this part of the world February is often the coldest month and for where I live at least it is the snowiest month. Is their any credible scientific basis at the moment to say that February will mild or will at least not be cold considering the winter we have had so far and especially looking at how cold parts of mainland Europe have been which has not been the case in the mild winters of the last two decades?

Luke

Luke taking your points in turn:

1. I do not know where you live but it is a fact that for almost the entire British Isles January and February have the same long term averages (the exceptions being areas with a pronounced maritime influence such as Shetland, the Isles of Scilly and the far west of Ireland which are slightly colder in February probably because sea temperatures are close to being at their coldest in February).

2. There is no long term statistical correlation supporting the idea that cold Januarys lead to cold Februarys. Taking the years 1960 to 2009 inclusive and applying the 1971-2000 averages the CET record shows:

12 years with cold Januarys and cold Februarys [by 'cold' I mean any value below 4.2c thus a number of the months described here as 'cold' would not in reality be regarded as cold as they would be marginally below average];

13 years with cold Januarys and mild Februarys;

8 years with mild Januarys and cold Februarys; and

17 years with both mild Januarys and Februarys.

In other words a cold January is about as likley to be followed by a mild as opposed to a cold February.

3. As regards snowfall the UKMO mapped averages for 1971-2000 indicate that there may be a slightly greater incidence of snowfall for February at low altitude but slightly less at higher altitude (possible because of of lower precipitation in February) but the differences are not significant.

4. I am not aware of any scientific basis for the assertion that a cold January is more likely than not to be followed by a cold February (certainly there is no statistical basis). Whilst it may be true that colder than average seas and a snow covered continent at the end of January would modify winds from an easterly direction it is worth bearing in mind that such modification would not apply to westerlies and that in any event SST anomalies and continental snow cover can and often are reversed in less than a month.

regards

ACB

Edited January 24, 2010 by acbrixton

[Frosty.]

Let me be the first to say the 00z Northerly is looking very good for late this coming week, a 2-3 day Arctic blast seems likely with potential for reloads as the jet axis is more NW/SE. I missed the gfs 18z but the 00z is a massive improvement on the 00z/06z/12z yesterday with much better amplification. The ukmo 00z is a stunner with a bitter N'ly tending more NE'ly and the ecm 00z is very impressive for a potent wintry blast, add the nogaps to that list and probably more to follow. Snow could be back with a vengeance fairly soon.

[snowhere2bseen]

Seems like the GFS has gone for a Big upgrade this morning, with the London ensemble, showing a long spell of cold into FI with just a minor "Blip" of Warm

However I'll believe it when a see the flakes.

[Iceberg]

TBH I won't trust any temp forecast more than 3 days in advance but hey ho...

The models have really improved in the last 12/24 hrs.

Even for Dorset the 850 temps average below -5 from the start of the norherly to the end of the run, so nothing in the way but cool to cold is really very likely.

A noticable difference between the 144Z charts of UKMET and GFS, GFS prevent the GH link up with as usual a Short wave development, The METO however doesn't going on past form the METO really has been the model that the other models have moved to over the last 24 hrs.

ECM is equally not warm or really average in any way, keeping PM or rPM air over the UK most of the time.

Anything beyond 120 is still FI and the northerly might last 48 hrs or 5 days.

I would say thought that the models, certaintly GFS and sometimes ECM have been far far too progressive in the movement of the split PV.

Also Snow looks likely for various places Thursday/Friday onwards, but far too early to look at specifics, except the favoured locations of the NE, East coast and SE, however surprises often happen.

Edited January 24, 2010 by Iceberg

[KTtom]

London Ensembles look to be the most interesting chart this morning. The mean remains below -5 for almost the entire run with virtually every run colder than average.

[winterof79]

TBH I won't trust any temp forecast more than 3 days in advance but hey ho...

The models have really improved in the last 12/24 hrs.

Even for Dorset the 850 temps average below -5 from the start of the norherly to the end of the run, so nothing in the way but cool to cold is really very likely.

A noticable difference between the 144Z charts of UKMET and GFS, GFS prevent the GH link up with as usual a Short wave development, The METO however doesn't going on past form the METO really has been the model that the other models have moved to over the last 24 hrs.

ECM is equally not warm or really average in any way, keeping PM or rPM air over the UK most of the time.

Anything beyond 120 is still FI and the northerly might last 48 hrs or 5 days.

I would say thought that the models, certaintly GFS and sometimes ECM have been far far too progressive in the movement of the split PV.

Also Snow looks likely for various places Thursday/Friday onwards, but far too early to look at specifics, except the favoured locations of the NE, East coast and SE, however surprises often happen.

Nice to see good agreement across the big three this morning.The met updated their 3-5 day outlook at 0300 this morning saying rainy I will bet there are a few boys and girls in Exeter crying in to their coffee this morning ,along with a choice few from this thread last night.Iceberg/CC i find your posts most informative and was interested in accu-weathers thoughts.JBs been on the money overall too.Heres to an extraordinary winter ......so far

Edited January 24, 2010 by winterof79

[Methuselah]

New thread, folks: