Model Output Discussion - 23rd Jan - 12z onwards

[knocker]

Sorry if I raised a non-sequitur there and you're right it was a casual remark. I meant that if the moisture at the surface is trapped under the high with warmer 850hPa's above then temperature inversion is likely, that's all. You do not, correct me if I'm wrong, so often see inversion under bone-chilling 850hPa's and dry ground? To cut to the chase, with projected uppers from this toppler high rising above 0C, as opposed to, say, -10C, given the ground conditions inversion is more likely. No?

 

If you have very cold 850s you are probably looking at an unstable airmass, not anticyclonic, and wouldn't get inversions under the 850s (this very much a generalisation).

 

Not too sure what you mean by the last sentence. Forget the toppler bit but an inversion of this nature associated with an anticyclone is a subsidence inversion as I mentioned in my earlier post. The inversion itself is not directly affected by surface conditions although snow cover would affect the minimum temperatures, particularly in calm conditions as there will be less turbulent mixing. In case you are going to ask why Sc forms and dissipates You will need to consult a higher authority as it's above my pay grade. Not that easy to forecast and of course it does affect the max and min temps.

[Gowon]

another surge of colder uppers incoming from the east?

 

[Captain Shortwave]

Trust the 06z GFS to throw up something completely different. The evolution is very quick with the initial north easterly never establishing with an Atlantic front pushing south as soon as Thursday. The pattern reloads itself and then builds the high through the north of the UK into Scandinavia. The week 2 charts could be very interesting as the high backs eastwards a little and cold air pushes westwards.

Has the GFS thrown a rogue run here? Who knows......

[Ice Day]

Trust the 06z GFS to throw up something completely different. The evolution is very quick with the initial north easterly never establishing with an Atlantic front pushing south as soon as Thursday. The pattern reloads itself and then builds the high through the north of the UK into Scandinavia. The week 2 charts could be very interesting as the high backs eastwards a little and cold air pushes westwards.

Has the GFS thrown a rogue run here? Who knows......

 

Just typing exactly the same thing.  Is this a massive wobble (which the 6z is prone to) or perhaps an emerging new trend.  I will be awaiting the 12z's with interest.

[chris55]

06z just highlights the scatter from the ensembles post the 6th Feb. A very nice run, with some -10 850s being dragged in on a chilly east wind.

[Long haul to mild]

I see the 6z is going off on one and bringing the Easterly back for later in the week!

Whilst this would be a welcome development, we need to see this backed up in the 12z model runs later. Until then, this is just a bit of eye candy as it goes against all the other indications at present.

[Polar Maritime]

Well looks like Blue's musings for the 6z have spoken.. Another shift 50m North of the High would be even better. It's not much to ask for is it !

 

Edited February 1, 2015 by Polar Maritime

[shaky]

This is a really cold run for England! ! it's just come out the blue and the changes take effect at just 90 hours so very early on!! Anyway over to the 12z to upgrade the easterly even futher! !

[TEITS]

Have to laugh. I moan because none of the GFS operationals have followed any of the colder GEFS members and up pops the 06Z.

 

This is an interesting run because the Op's have been leading the way in my opinion.

[chris55]

Not far off a feb 91 :0

[Severe Siberian icy blast]

Certainly a different scenario with extremely cold uppers heading our way . Wouldn't take much for a low to drop into the atlanitc and push up against the block along with that low pressure over far north siberia to drop South . Very different !

Edited February 1, 2015 by Severe Siberian icy blast

[Jason M]

Nothing marginal there!

For the channel islands that's got to about as close to perfection as one can get.

Whatever anyone thinks about the 06 GFS from a reliability point of view when something like that pops up at 90 hours out its got to be taken seriously. GEFS will be interesting.

[Ice Day]

 

 

-8's back into EA/SE.  100 mile sift north and we'd have most of the country under the cold again!  Amazing development, but almost certainly a massive model wobble (using the reverse psychology approach!)

 

Edited February 1, 2015 by Ice Day

[sunnijim]

I don't post on here very often these days, because my technical knowledge is not sufficient to enter into conversations with those who use complex reasoning to justify why they believe certain outcomes are more likely.  I prefer to look at charts in a more simplistic way which often seems to be the best way to see what the most likely outcome is.  Whilst many have used the charts to justify talk of unstable northerlies, complex features and polar lows, bringing the risk of heavy snow and not just the 'wishbone' effect, with very low temperatures, the more simplistic view suggested that for many this wintery spell would not bring anything significant.  For many over a large swathe of Southern England, we're still waiting for the bitterly cold weather to kick in.  Firstly we were told it was going to happen on Thursday - temperatures were around 5 or 6 in many areas - then we were told it's going to be Sunday - here are today's forecast maxima from GFS:

 

ukmaxtemp-Sun15;00.png

 

Once the cold is 'set in', the forecast maxima are as follows:

 

ukmaxtemp-Tues15;00.png

 

And then we have this for the end of the week:

 

ukmaxtemp-Fri15;00.png

 

So, this chilly period of weather, initially accentuated by the wind, remains pretty much as it is now for many areas, and there doesn't seem much chance of any significant snowfall either.  I'm sure further north it has been colder and there has been lying snow, although how much to widespread low-lying areas, I don't know,  and indeed there has been the occasional light covering down here, but if overnight snow, doesn't even make it to lunchtime, with daytime temperatures of 4 or 5c, it's hardly a major cold event and the outlook for this coming week just looks like more of the same to me

A super post and covering my thoughts and i am sure many others South of Derby.

I am afraid 'playing the glad game" because we have a 'faux' Northerly for a week is not my style! It has delivered nothing of interest here just a bigger heating bill.

My concern all along for the South of Britain has been the lack of a 'true' arctic pull to the winds,at best they are sourced in Northern Norway.Without a proper cold pool to tap into the South was always struggling with marginal events at best.

The latest gfs 6z shows more interest from Tuesday with colder uppers and the threat of a few snow showers,however it seems in a minority at present with wintry showers' ( i hate that description in winter) as its a mix of hail,sleet,and rain and nothing substanstial snow wise,on a slack NE flow.

[Dunlop Dave]

Nothing marginal there!

For the channel islands that's got to about as close to perfection as one can get.

Whatever anyone thinks about the 06 GFS from a reliability point of view when something like that pops up at 90 hours out its got to be taken seriously. GEFS will be interesting.

Safe to say I'm a little excited on this one. Somebody mentioned close to '91. We had 14" of snow at sea level and the highest point of Guernsey (100m) had nearly 2 foot from that event !!

[West is Best]

 

 

However, for those who would like to see the current setup continue or perhaps improve the GEFS ensembles continue to hold out some hope. The operationals are on the mild side, with many colder members:

 

Screen Shot 2015-02-01 at 08.06.47.png

 

However, the fact that the three operationals from GFS, ECM and UKMO go for the midweek toppler high makes the colder members probably around a 10% chance, maybe less

 

6z op proves the point. The issue is probably now to see how the op lines up with the other members. Looks like the ops are flitting from mild to cold, and back again, which isn't making the GFS look very clever, unless you watch the ensembles. Take the bunch of spaghetti as a whole and watch the trends.

 

(p.s. blizzard here. Been snowing for an hour, but it's all slushy muck on the ground.)

Edited February 1, 2015 by West is Best

[Long haul to mild]

Nothing marginal there!

For the channel islands that's got to about as close to perfection as one can get.

Whatever anyone thinks about the 06 GFS from a reliability point of view when something like that pops up at 90 hours out its got to be taken seriously. GEFS will be interesting.

Looking into my crystal ball, I see the words "massive cold outlier" being used in this thread in the next hour or so!

[Polar Maritime]

" because we have a 'faux' Northerly for a week is not my style! 

 

It is a Northerly honest! 

 

Edited February 1, 2015 by Polar Maritime

[Jason M]

Safe to say I'm a little excited on this one. Somebody mentioned close to '91. We had 14" of snow at sea level and the highest point of Guernsey (100m) had nearly 2 foot from that event !!

At that range it must surely have ensemble support. Will know soon enough.

It is interesting that the high is reluctant to sink as with the northern arm of the jet active it would normally be a slam dunk that it's going down. Must be some subtle background driver at play here.

[snowbob]

Just when we think we are getting a handle on this cold spell

The 6z comes along and scores in the 90th min.

Now we face extra time to the 12z to see if we can turn this dull game around

[EML Network]

Well the 06 z has pulled a Houdini, I'm really struggling to see what it is that is driving the changes in the various outputs. 

 

If you were to look at the GFS Op at + 96....

how many of us would have thought an Easterly would show up for the Southern half of England just 24 hours later ? it looks vey dubious to me, but it's nice to see none the less, I wonder if it will have any support from the control run ?

 

What strikes me as really weird is that if you were to look at the UKMO for the same time frame...

 

 

On the face of it, and if you were asked to put money on which of the two charts lead to an easterly 24 hours later, I would have laid money on it being the UKMO, but where as the UKMO has the High tracking back West, the GFS has it heading East and ends up as a Scandi High. 

 

 

The ECM takes the middle ground and just keeps it over the UK.

 

 

So we now have a 3 ways split for the end of this coming week onward.

 

1* UKMO wants the high to retrogress into the mid North Atlantic. 

2* The GFS wants the high to take a journey ENE and into Scandinavia

3* The ECM wants the high to stay in situ over the UK.

 

Not sure where I'd put my money, but the middle ground tends to be right and sadly that's the one option I'd rather not see in this situation. 

[seaside 60]

If we continue to get these rouge runs, then I think the people that say its a sure bet that we will just get a dirty high with cloudy murk and slowly rising temps are off the mark.

Having said that the models temp profile for this last few days and next couple has been well of the mark.

[Penrith Snow]

Don't dismiss the 06 GFS, I have known many Easterlies appear out of nowhere, particularly when high pressure is dominant and this is picked up by a sudden flip in the models.

It also makes the chance of a clean cold high more likely if we don't get the easterly, what I really don't want is two weeks anti cyclonic gloom which some if the models are promising this morning.

The 06 wouldn't bring snow here but it would bring some great frosts and winter sun and with Cumbria covered in snow would make a lovely winter spell while I watched Londoners digging themselves out the snow.

Andy

[Tim Bland]

Looking into my crystal ball, I see the words "massive cold outlier" being used in this thread in the next hour or so!

I wouldn't be so sure! For a a few days the OP was a mild outlier and the majority of the ensembles were going for the easterly. We lost the signal for 24hrs but now it may have come back with avengance! I expect the OP to be somewhere in the middle of the ensembles. 50/50 for easterly or UK high in a weeks time IMO

[Jason M]

Looking into my crystal ball, I see the words "massive cold outlier" being used in this thread in the next hour or so!

You may be right, but if we reversed the situation with a huge mild surprise at that range I think there would be something akin to the purge going on in this thread. It's just so early in the run!

The GEFS are still based on the old model and are much lower res. If a good few go with this solution then .....