Model Discussion 12Z 25/02/13

[Gibby]

Good evening. Here is the evening review of the 12z output from GFS, UKMO and ECM for tonight Monday February 25th 2013.

All models show a High pressure centre slowly drifting towards Scotland from the NE. A NE flow remains in place over Southern Britain for the time being before the flow gets cut off later in the week as the High pressure sits right over the UK by then. The cloudy and cold conditions in Southern England with some light rain and drizzle in places and some mist over the hills continues over the next 48 hours before there are signs that the brighter and clearer weather over Scotland and Northern Ireland extends slowly South to other areas by the weekend. With brighter skies by day the return of frost and night looks highly likely as skies clear more.

GFS then keeps the High over the UK at the weekend before pulling it away East early next week with a SE flow developing over the UK by Monday. pressure then is shown to continue to fall with the SE flow veering slowly towards the SW with milder conditions likely with rain at times, this extending to all areas by the end of the week. Things then remain unsettled then until the final few days of the run when a build of pressure over Northern Europe sets up a blocking pattern once more with the UK seeing a chilly South or SE flow developing in largely dry conditions.

The GFS Ensembles show a change to milder uppers well under way now with the milder levels continuing then with a lot of support right out to the end of the run. There is more variability in the North in the latter part of the run with unsettled conditions both North and South shown in the second half of the run.

The Jet Stream shows the main thrust of the flow continuing in a location well South of it's normal position. However, with high pressure migrating towards Scotland an arm runs over the top of the High which aids to pull it away SE later in the weekend and next week.

UKMO for the weekend shows High pressure maintained over the Uk with fine and dry weather for all. With more sunshine possible the ambiance of the weather will improve despite temperatures still a little below normal with frosts at night highly likely.

ECM too shows High pressure over the UK at the weekend with fine and bright weather by day and frosty nights before the High pulls away east early next week leading to a freshening SE wind and rain moving into the SW first and probably to other areas later and with the setup as shown with cold air close to the North there could be some snowfall for a time over the higher ground in the North.

In Summary the pattern seems to slowly becoming more agreed upon between the models. After a dry and rather chilly week with rather a lot of cloud in the South rather brighter weather will be enjoyed by all as we reach the weekend before next week sees a slow decline into more unsettled weather as pressure falls from the SW and rain features again in places before term of the run. The breakdown is a little unconventional with some very cold air over the NW Atlantic and areas North of the UK which when engagement with the troughs to the SW occurs could spring a wintry surprise here and there.

[bluearmy]

So why should we place any faith in more 'jam tomorrow' ecm op charts? I suggest it depends on the polar profile. If that doesn't offer the right support, I doubt the 'snow' will verify. Quite a way to go from here.

[Ian Brown]

It's possibly interesting, but SErlies won't really cut it ahead of frontal PPN as we roll into March. It depends how far the Greenland High could ridge South and East to pull the PFJ down and increase the gradient but it's all a fair way off and the margins cannot be determined by the NWP at this sort of range.

[Stuie]

I think we have all learnt something this winter. I always thought get high pressure over Greenland and we were quids in-

Didn`t realise that if high pressure sat over the UK then that is negated somewhat.

The other point, strat warming. Unless I have completely missed something, not too much to look into future warmings.

We are all learning no matter what level of understanding you are at.

[Panayiotis]

I think we have all learnt something this winter. I always thought get high pressure over Greenland and we were quids in-

Didn`t realise that if high pressure sat over the UK then that is negated somewhat.

The other point, strat warming. Unless I have completely missed something, not too much to look into future warmings.

We are all learning no matter what level of understanding you are at.

Sorry but I have to disagree, the warming happened and a few weeks later the affects of it were felt by the troposphere. Was it not the PV weakening caused by the warming that allowed the Scandi high to develop, delivering cold and snow in January?

[bluearmy]

interesting to see the op and control ecm head in opposite directions again in the latter stages. Ecm mean looking less inclined to undercut so far south but the spread 850's still brings the cold air across the uk by day 10. no point in trying to second guess this. Still require either the ecm op to agree with its ens or for it to throw out 4 or 5 consistent fi solutions. I think the 12z op takes the count to 2.

And yes stuie, you have missed something.

Edited February 25, 2013 by bluearmy

[Stuie]

Sorry but I have to disagree, the warming happened and a few weeks later the affects of it were felt by the troposphere. Was it not the PV weakening caused by the warming that allowed the Scandi high to develop, delivering cold and snow in January?

If your argument is snow in January then sorry, no.

[Panayiotis]

If your argument is snow in January then sorry, no.

Thats up to debate really yes I shouldve taken your location in to account but for Wales/Central England/SW there was snow. I saw 4-6". Check stats vv Edited February 25, 2013 by Panayiotis

[mcweather]

Bitter experience has taught me not to give charts at 240 ( ECM or not) any validity. If the same pattern appeared at t48 and corrected about 200 miles south, I might be forced to raise an eyebrow.

[JP1972]

Some of the "lessons learned" posts are great.

But I'd bet my bottom dollar that come November, all lessons will have been forgotten

It's the same every year, because the fact is cold lovers will always chase the holy grail. Nothing wrong in that of course but Nick's Prozac stocks don't half take a hit!!

[Djdazzle]

This winter's model watching can be summed up in one word - potential. It's been a great winter in terms of the potential shown over and over again on the models. But considering the potential, this winter hasn't really delverered anything spectacular. There have certainly been far worse and far more boring winters in respect of cold in the past, but I don't recall a winter in my 10 years of model watching where there has been as much promise as this one. We have been so close on a few occasions to getting some really amazing Synoptics, but something has always popped up to either stop it or water it down. It's certainly been a very tiring winter for us model watchers, but unlike some I'm not throwing in the towel just yet. However, the thought of those longer days with the warm sun on my face is beginning to take over now!

ECM 12z again showing some potential. Sorry, I've used that word again!

[bluearmy]

Definite cooling trend mid march on the dutch ens. Week 2 naefs showing a return of avortex segment to n canada but a split to our north with associated pressure rise. The 'interesting' charts will continue.

[Tamara]

A very pronounced tease evident on some of the modelling this evening to suggest a glimpse of something pleasing to end the winter season and take us into Spring. But might we end up with a definite maybe instead of being twixt and tween the low pressure over Scandinavia pulling the cold air south, and the blocking set too far west to help advect the colder air across the fishing fleets of the North Sea

[Summer Sun]

Before we get to the weekend and sunshine we have some coming on Wednesday for those in an area from the midlands north

After a cold frost Saturday night Sunday warms up nicely in the spring sunshine

[cyclonic happiness]

Before we get to the weekend and sunshine we have some coming on Wednesday for those in an area from the midlands north

After a cold frost Saturday night Sunday warms up nicely in the spring sunshine

Dammit for a minute i thought that was heavy snow :-D

[phil nw.]

The ECM Op again has some promise for some colder conditions with possible snow in the north of the UK but importantly this is in it`s later frames.

http://cdn.nwstatic....ecmt850.240.png

If we compare it`s earlier output with the GFS around T144-168 there`s less difference than on the 00z runs as both models are now showing a reluctance for extending the Atlantic trough further east towards the Med.

http://cdn.nwstatic....168/h500slp.png

http://cdn.nwstatic..../ecm500.168.png

Looking at the mean charts at T192hrs we can see the setup is just too far north for the UK to get that cold air, except maybe the far north for a short while.

http://www.wetterzen...cs/Reem1922.gif

http://www.wetterzen...ics/Rz500m8.gif

The blocking over the Arctic now looks to be setting up too far west in week 2 and because of our own High slipping away to the SE next week the developing Atlantic trough becomes slow moving.

Lot`s of cold air still available not far away but with any meaningful blocking locating too far to our NW over Canada.

A look at the 12z height anomalies for the ECM and NAEF`s illustrate the forecasted setup quite well-this as at day 10

A good example of a forecasted west based -NAO.

It may be with time we will be looking south for milder conditions if the UK finds itself on the warmer side of that Atlantic trough.

Edited February 25, 2013 by phil nw.

[johnholmes]

I suspect it is the beginning of the end of the block for the UK area, I'll post some charts and views tomorrow

[johnholmes]

I think we have all learnt something this winter. I always thought get high pressure over Greenland and we were quids in-

Didn`t realise that if high pressure sat over the UK then that is negated somewhat.

The other point, strat warming. Unless I have completely missed something, not too much to look into future warmings.

We are all learning no matter what level of understanding you are at.

I think that because of the reputation chio especially built up with his well reasoned posts in the relevant thread a lot of folk started to make 2+2=anything but 4 regardless of what he and other quite knowleadgable folk posted. That is where most if not all the hype came from. A 'new' tool to predict the weather regardless, and of course it is nothing of the sort. What it is, is ANOTHER part of the puzzle in trying to predict at longer time scales what MAY happen.

PLEASE next winter can we all come back having spent at least part of the summer reading and taking note of all the available data, what can and cannot be predicted; and its all in the FIRST post or most of it that chio posted way back last autumn-PLEASE read it and remember what the links say.

Edited February 25, 2013 by johnholmes

[Panayiotis]

Nothing inspiring in the 18z apart from the deeply -NAO in the later stages of Fi,which shouldnt even be looked at..

Edited February 25, 2013 by Panayiotis

[bluearmy]

Following on from the naefs week 2 split vortex idea, we see the 18z gfs op follow suit. Another frigid run for the eastern states.

[nicknacknoo]

I think that because of the reputation chio especially built up with his well reasoned posts in the relevant thread a lot of folk started to make 2+2=anything but 4 regardless of what he and other quite knowleadgable folk posted. That is where most if not all the hype came from. A 'new' tool to predict the weather regardless, and of course it is nothing of the sort. What it is, is ANOTHER part of the puzzle in trying to predict at longer time scales what MAY happen.

PLEASE next winter can we all come back having spent at least part of the summer reading and taking note of all the available data, what can and cannot be predicted; and its all in the FIRST post or most of it that chio posted way back last autumn-PLEASE read it and remember what the links say.

Any chance of a quick link to this John so us learners can more easily do our homework over the summer?

[Harve]

Nothing inspiring in the 18z apart from the deeply -NAO in the later stages of Fi,which shouldnt even be looked at..

Just nudging into the period when most people no longer want it...

[Panayiotis]

Just nudging into the period when most people no longer want it...

Typical isnt it! Watch it verify!

[summer blizzard]

Well another week or so of settled weather at least before the models differ.

[Frosty.]

The models look pretty anticyclonic for a while yet and another cold dull day today for england and wales but tomorrow looks better with sunny spells developing and similar for the rest of this week, temps below average and with overnight frosts. Both the ecm and gfs 00z show a huge mass of arctic air slowly spreading south towards the uk during next week and they show the cold air reaching northern scotland with perhaps some sleet or snow showers by the middle of next week but further south it looks like slowly becoming milder and more unsettled from the southwest, the gfs 00z eventually shows cold air across the eastern side of the uk but that's deep FI range. The synoptics are interesting next week currently, especially if you live in the far northeast of the uk.