Model Discussion 12Z 25/02/13

[MR EXTREMES]

Spot on in my opinion GP. Whilst I haven't posted much recently the overall trend towards a cold March appears increasingly likely and a east based NAO has often been hinted at on the models.

Im actually slightly disappointed though. After giving British Gas plenty of my money due to the overall cold winter, it appears they will get even more from me due to the likelyhood of March being a cold month.

yeah and to top it off british gas or eon in my case done really well but the snow depths didnt really top the league board....

be intresting to see what kind of effect an east based nao would give in the month of march perhaps just a little perhaps something exciting although id of thought a rare event.

[The Enforcer]

I suspect that the current short term outlook for predominantly dry weather will suit as many Net-Weather members as those wishing for snowy weather. With the jet profile remaining so far south on repeated runs, I can't really see any move away from this anticyclonic dominated weather, in spite of some of the outcomes being portrayed for outside the 5-day period. Of course, it doesn't follow that this means that it is a foregone conclusion that it will turn colder once more, as several complex factors have to align to allow polar maritime air access to the UK, but it seems equally unlikely to me under the current scenario that tropical maritime air would be able to make any significant inroads towards us either.

Jet profile largely unchanged from yesterday, nothing to change my previous opinion as above.

The lack of posters on here speaks volumes for what most think will happen, a milder and unsettled trend next week looks like the form horse but when I say milder, I mean temps creeping back to average rather than anything particularly mild and still that small risk of colder air pushing south into the northern isles of scotland next wednesday/thursday.

That's not such a bad thing, nice to be able to get a word in edgeways for once.

[mushymanrob]

We better make the most of next weeks mild mixed weather then since winter could bite back towards mid march

of course it could, i for one doesnt believe that we will see no more cold after this gentle warming up takes place (and IF it takes place). but what can be realistically expected? imho its likely to be nuisance cold thatll act as a spring spoiler but not cold enough for anything too wintry. no winners.

but atm theres no sign of anything other then normal being predicted by the models. im happy with that!

[Cloud 10]

I see there are 2 straw-clutches (I mean massive outliers from early on), go perturbations 10 and 11, I believe in you

Yes,a couple of real rebels on the 06z ensembles,and at only 144 hrs!.

[nick sussex]

Yes,a couple of real rebels on the 06z ensembles,and at only 144 hrs!.

You just know that if the situation was reversed and we had a majority colder cluster with two mild outliers that given the UK's luck with cold synoptics the operationals would switch to the milder minority! Anyway interesting thoughts from GP and thankfully my earlier post has some support from him so I didn't make a fool of myself!!!

[Tim Bland]

Metoffice long term update signals a cold second half to Mrach. Most interesting is that they point to eastern areas being coldest but also wettest along with the south, could this mean southerly tracking lows / undercuting bringing an easterly drift? Control run from 06z shows this scenario

"Most areas are likely to stay colder than average, perhaps more especially across the eastern side of the UK, with some more frosty nights to come. Generally, there are no strong signals regarding precipitation, but taking the period as a whole, some northwestern areas of the UK will probably end up a little drier than usual, whereas southern and eastern districts will perhaps be wetter than normal."

[Summer Sun]

Metoffice long term update signals a cold second half to Mrach. Most interesting is that they point to eastern areas being coldest but also wettest along with the south, could this mean southerly tracking lows / undercuting bringing an easterly drift? Control run from 06z shows this scenario

"Most areas are likely to stay colder than average, perhaps more especially across the eastern side of the UK, with some more frosty nights to come. Generally, there are no strong signals regarding precipitation, but taking the period as a whole, some northwestern areas of the UK will probably end up a little drier than usual, whereas southern and eastern districts will perhaps be wetter than normal."

Its been along those lines for a week or more now so I wouldn't read much into it yet TBH

This time last week it said

Some areas still a little colder than average, perhaps more especially across the eastern side of the UK, with some frosty nights. Generally, there are no strong signals regarding precipitation, but taking the period as a whole, some areas of the UK will probably end up a little drier than usual for the time of year.

Updated: 1143 on Wed 20 Feb 2013

The only real change I can see is the one regarding precipitation, other than that its just minor wording changes

[Frosty.]

That's not such a bad thing, nice to be able to get a word in edgeways for once.

yes that's true, as for the weather, the anticyclone looks like becoming cloudy again for friday and the weekend with a rather cloudy north atlantic flow, albeit slack, and changes in the overall pattern look slow but pressure should be falling by early next week as it turns milder and more unsettled eventually.

[Jason M]

You just know that if the situation was reversed and we had a majority colder cluster with two mild outliers that given the UK's luck with cold synoptics the operationals would switch to the milder minority! Anyway interesting thoughts from GP and thankfully my earlier post has some support from him so I didn't make a fool of myself!!!

Interesting how the rogues are so close together though. Only worthy of slight interest at this stage, but will be interesting to see full 12Z suite tonight.

I still think its moving against us with a full on west based -NAO. Changes can occur though so worth just maintaining an interest.

If we do miss out a nice warm southerly feed would be very welcome after the last week.

Jason

[No Balls Like Snow Balls]

A marked rise in daytime temps next week for a few days according to the latest ECM ensembles, before falling away again later next week. Nothing extreme at either end of the cold/mild scale.

Edited February 27, 2013 by No balls like Snow Balls

[nick sussex]

Interesting how the rogues are so close together though. Only worthy of slight interest at this stage, but will be interesting to see full 12Z suite tonight.

I still think its moving against us with a full on west based -NAO. Changes can occur though so worth just maintaining an interest.

If we do miss out a nice warm southerly feed would be very welcome after the last week.

Jason

I think realistically the better chance for any colder weather is probably later into the second week of March although by that time expectations will have to be lowered in terms of whats possible with the fast increasing solar energy.

In terms of source of air my interest for the UK will be raised however if its from the ne because its looking like there will be some unseasonably cold air in that region to tap into but you do need everything to go right to lower the slush factor!

I don't expect to see much if any more snow down here, very happy with the recent snowfalls here the best of which came on Monday and thankfully it was the dry variety and not that slush which caused carnage a few weeks back.

Its quite interesting seeing just how slow the snow melt is in the shade given the last two days temps have been well above freezing, really shows how crucial lowish dew points are once any snow has fallen.

We'll see over the coming days whether that trend to diminish that western negative NAO continues and whether we can get something more east based.

[Snowman.]

Not from easterlies. Please read the post.

I have in April...

If there is a cold air pool then it will deliver.

You have to remember snow in March is more likely than December.

[Guest]

For Iceland this has to be one of the biggest spreads I have ever seen ....

How about this one...such a large spread I have it saved on my laptop:

The 06z GFS was quite a surprise to see after some of the previous runs, although with these kind of local (i.e. around the UK) differences between the GFS and ECM means is that a surprise?

Edited February 27, 2013 by CatchMyDrift

[Captain Shortwave]

I have in April...

If there is a cold air pool then it will deliver.

You have to remember snow in March is more likely than December.

Something tells me that a punt at a white easter might be a good call this year maybe. Whilst west based -nao might be setting in, this winter has been one where any high latitude blocking has never been too long lasting and wouldn't be surprised if the canadian high gets quickly dislodged as Glacier Point seems to be thinking.

GFS 12z is not following perturbations 10 and 11 from this morning, shame. Expected but a shame haha

[nick sussex]

Something tells me that a punt at a white easter might be a good call this year maybe. Whilst west based -nao might be setting in, this winter has been one where any high latitude blocking has never been too long lasting and wouldn't be surprised if the canadian high gets quickly dislodged as Glacier Point seems to be thinking.

GFS 12z is not following perturbations 10 and 11 from this morning, shame. Expected but a shame haha

The GFS is already breaking down the western negative NAO and the UKMO follows the trend of this mornings ECM operational run at 144hrs.

I think its look ne in line with that cluster of ECM solutions on De Bilt. Could be an interesting ECM later on.

You can see upstream in the east Pacific the main positive anomaly is there which was suggested by NOAA last night, this correlates with pressure rises to the ne so its bye bye frustrating western negative NAO!

Edited February 27, 2013 by nick sussex

[snowking]

A marked rise in daytime temps next week for a few days according to the latest ECM ensembles, before falling away again later next week. Nothing extreme at either end of the cold/mild scale.

Those are still tmax values you've got there my friend

Average T2m shown below:

Nothing I would describe as particularly 'mild' there.

But even then the average values a are a little misleading on that box plot....notice the large median values showing (suggesting much variation) and then take a look at the individual line plots:

A clear split in solutions into the day 7 period, though notice how even many of these milder solutions eventually fall away towards some cooler once again, that certainly fits in with GP/Nick's thoughts from earlier

SK

[mushymanrob]

I have in April...

If there is a cold air pool then it will deliver.

You have to remember snow in March is more likely than December.

weve just had a cold pool of air, it didnt deliver. it takes more then just low temps for snow.

[No Balls Like Snow Balls]

Those are still tmax values you've got there my friend

Average T2m shown below:

Nothing I would describe as particularly 'mild' there.

But even then the average values a are a little misleading on that box plot....notice the large median values showing (suggesting much variation) and then take a look at the individual line plots:

A clear split in solutions into the day 7 period, though notice how even many of these milder solutions eventually fall away towards some cooler once again, that certainly fits in with GP/Nick's thoughts from earlier

SK

I am pretty sure you will find the ave temps on these ensembles are the mean of the daytime and night time temps.

For example take the 1st of March temps. TMAX = 6c TMIN = 2c, 6 + 2 = 8 divide by 2 = 4, now look at temp ave for 1st march = 4c.

If your still unsure look at the daytime temp for Birmingham tomorrow on BBC weather, it's going to be 7c.

It's going to turn milder for a few days next week, with temps possibly reaching double figures in some places. Then it looks like after a few days of milder weather it will cool down slightly again.

Edited February 27, 2013 by No balls like Snow Balls

[cooling climate]

The UKMO is a carbon copy of what the ECM was showing this morning at the t144 timeframe.

Heights to build to the north of the UK in the extended period rather than Greenland which was

never a option really imho.

GFS starting to smell the coffee in FI range and the building blocks to what could be a noteworthy

cold spell from the east/ northeast into the second week of March slowly being laid.

[Snowman.]

Ahh looking back I remember the start of march 2006 being very cold.

Edited February 27, 2013 by SN0WM4N

[bluearmy]

The 06z GFS was quite a surprise to see after some of the previous runs, although with these kind of local (i.e. around the UK) differences between the GFS and ECM means is that a surprise?

thats cos those are the mean representations of the operationals days 6/10. since when did the ecm and gfs ever agree at that range ???? the fact that they are not completely different each run shows that a 4 day mean picture can hide a lot of detail. to iterate - those charts have nothing to do with ensembles.

[cheeky_monkey]

You can see upstream in the east Pacific the main positive anomaly is there which was suggested by NOAA last night, this correlates with pressure rises to the ne so its bye bye frustrating western negative NAO!

is it?...because there has been a huge postive anomaly in the eastern Pacific throughout January and February.

[nick sussex]

is it?...because there has been a huge postive anomaly in the eastern Pacific throughout January and February.

Yes that's why we haven't seen a Greenland high, there was much discussion at the time over at NOAA because the models wanted to do one thing but past history was against that, historically there isn't a strong correlation between Greenland highs and a ridge in the east Pacific, for that reason the main cold that's effected the UK has been those height rises to the ne in January, and recently the easterly all came about with that east Pacific ridge.

Its for this reason that in this instance for those wanting cold we want rid of the western negative NAO and that's likely to happen once the east Pacific ridge takes charge.

That ridge is then expected to transfer more to Alaska which is strongly correlated with pressure rising sw out of Svalbard.

Edited February 27, 2013 by nick sussex

[cheeky_monkey]

Yes that's why we haven't seen a Greenland high, there was much discussion at the time over at NOAA because the models wanted to do one thing but past history was against that, historically there isn't a strong correlation between Greenland highs and a ridge in the east Pacific, for that reason the main cold that's effected the UK has been those height rises to the ne in January, and recently the easterly all came about with that east Pacific ridge.

Its for this reason that in this instance for those wanting cold we want rid of the western negative NAO and that's likely to happen once the east Pacific ridge takes charge.

Exactly i have mentioned a few times in this thread this winter that people should look as to what is happening in the eastern Pacific and Western North American continent with that ridge and as to why there would be no severe outbreak of cold in the UK and there would be no Greenland high or Alaskan ridge whilst it was in place

[Thundery wintry showers]

For an easterly to bring widespread snowfalls at this time of year, it needs to be sourced from a fair way north, essentially an easterly with a "northerly" source, and this becomes increasingly true as the season progresses. I remember a couple of easterlies that brought sunshine and heavy snow showers to north-eastern Britain in March 2001, but most "easterly" Marches are dull, dry and cold- a particularly stark example happened in 1996. This is because the continent warms up a lot faster than the North Sea and so continental easterlies become increasingly stable, but it remains very cold at upwards of 70 degrees north and those air masses still provide a fair amount of instability during March and April.

In the meantime an easterly is looking increasingly unlikely in the near future as the GFS has been showing an evolution to a relatively mild and changeable southerly type with a slow-moving eastern Atlantic trough for several runs, and tonight's ECMWF is going the same way. It's not set in stone yet but I think it represents the most likely outcome. Beofre that, most places look set to be dry and predominantly sunny through to the 4th, with temperatures near or slightly above average by day, and below at night.

Edited February 27, 2013 by Thundery wintry showers