Model Discussion 12Z 25/02/13

[Summer Sun]

Not much to report so far high pressure looks like dominating to the weekend before the Atlantic could push the high back east

Deep FI produces a northerly for a couple of days but thats about it really

After this the high builds again

Those who live in the midlands north will enjoy some sunshine tomorrow those south of the midlands look like sticking with the cloud

Its in the north where we see the highest temperatures tomorrow under the sunshine

Saturday and Sunday should see the cloud clear for the south bringing the first taste of the spring sunshine

Highs around 10c widely

Edited February 26, 2013 by Gavin.

[SomeLikeItHot]

Anyone ready for another let down?

Anything at + 300hrs is not something to build your hopes on, but at least its a nice change for the GFS low res to show something other than a series of lows coming in from the SW.

[No Balls Like Snow Balls]

Anyone ready for another let down?

At that sort of time frame you can expect to be let down 999 times out of 1000. After the HP disappears away to our East it still looks like turning unsettled, with temps neither particularly mild or cold.

[Yarmy]

this is just a thought, so please dont run me down,. but last year i feel that autumn arrived late, then winter arrived late, maybe winter may hang on in to march????? like i say just a thought as last year our weather seemed all over the place in terms of timing

Neither Autumn nor Winter arrived late, did they?

[smoggyjester]

i dont know, like i said it just felt as if they did with regards the weather

[phil nw.]

It looks like we are leaving Winter on a benign and mainly dry note with temps gradually recovering after the cold easterly.

The models continue to show a south/south easterly continental flow picking up as we go into next week as our high drifts away to the east.

http://www.wetterzentrale.de/pics/Rtavn1442.png

http://www.wetterzentrale.de/pics/Rukm1441.gif

Warmer air moving into the south with some sunshine quite likely would feel very pleasant after the cold and dull conditions of the last few days.

[snowmadchrisuk]

I don't know , I think we are so close to an undercut at +72 hours , You would almost expect it , if the Model only went out to +72. The Atlantic seems to be pushing them strong height's away to quickly for my liking . I have a feeling it might not quite work out like that. The lows are still being forced far South . It is one of them times where the Models could suddenly flip within T-96 IMO.

[Tim Bland]

Some of the ensembles suggest Chris's idea of an undercut. Bit of a long shot though IMO

[nick sussex]

The GFS drops the tease it had on the 00hrs and reverts to the pattern too far west,the UKMO at 144hrs has that shortwave to the nw and thats going to make a return to colder conditions difficult.

What seems evident from the GEFS is that we're seeing cold solutions appear and disappear frequently and this is evident because the cold is relatively close to the north but the different modelling of shortwave activity between runs changes how far south that gets.

I think the current output clearly shows why a negative western based NAO is a big hurdle to overcome to get cold into the UK, its a frustrating pattern because you often see the cold heading quite far south to the west.

It will be interesting to see whether the latest ECM persists with its chance of something wintry for northern areas or jumps ship and joins the GFS.

Edited February 26, 2013 by nick sussex

[snowmadchrisuk]

Some of the ensembles suggest Chris's idea of an undercut. Bit of a long shot though IMO

quite a lot of the Ensembles are maintaining a line of Height's to our North , with No p/v over Greenland. I currently think +144 - +180 is modeled incorrectly , but will be interesting to see if I am right ...

[Purga]

Oh dear, where have all the cold runs gone?

shoved further and further into FI I guess. Did Bluearmy suggest we were going into th freezer? Can't see it.

[weather_it_will]

Oh dear, where have all the cold runs gone?

shoved further and further into FI I guess. Did Bluearmy suggest we were going into th freezer? Can't see it.

Looks as much chance as a very cold spell, as a milder one, but no sign of anything mild.

Edited February 26, 2013 by snow is falling

[AWD]

Oh dear, where have all the cold runs gone?

shoved further and further into FI I guess. Did Bluearmy suggest we were going into th freezer? Can't see it.

No, I don't think he did. I think he said either NW Europe OR the Eastern States were heading into the freezer and it looks like the latter;

What the GEFS do suggest is a continuation of the conditions we currently have albeit with fluctuations of cloudcover and temperature. Looking at the PPN ensembles for Hampshire and Yorkshire;

They do suggest an erosion of heights over the UK as we progress through week 2, with an increasingly influential Atlantic in some form of another. As shown here;

The Operational perhaps a tad too bullish about this however.

So no late winter blast and no early springlike conditions really, aside from a pleasent day here and there. Just average UK weather.

Edited February 26, 2013 by AWD

[nick sussex]

The ECM seems determined to find a way to keep the interest going. Here pressure rises over the Arctic, the shortwaves separate like Moses and the Red Sea and we eventually see the removal of the PV with this relocating to Siberia.

[Cloud 10]

Yes,the last two frames of the ECM should be fun!

[chris55]

Yes Nick you simply can't ignore the ECM det at 192,

Although I have to say GFS was very good at picking up our UK high out in FI, seen here,

When ECM was looking a lot more wintry.

[chris55]

So much worthwhile cold so close, even in March. But as ever a miss is as good as a mile. So as we stand nothing extreme in the models actually affecting the UK, although it wouldn't take much to tap into it.

[Panayiotis]

Aint bad by the ECM! Something similar was shown by the CFS, however it brings it in much earlier at 174hrs. Hopefully it will have support in the ensembles later....

Edited February 26, 2013 by Panayiotis

[chris55]

ECM is such a tease!!!

[phil nw.]

No undercut early on Chris not with ridging from the south

http://www.wetterzen...ics/Recm961.gif

a lot of energy going over the top of the high and it goes the same way-ie.east at T144hrs as shown on the other models.

http://www.wetterzen...cs/Recm1441.gif

That cold air still lurking just to our north in the later frames and it wouldn`t need much to bring some of that south later on.

This is what makes early Spring interesting model wise where dramatic switches in the weather type from cold to milder and back can occur quite quickly.

Edited February 26, 2013 by phil nw.

[Cloud 10]

Plenty of interest at 240 hrs,as ever!

[nick sussex]

Tease, tease, tease! The ECM somehow manages to get the energy heading further se and at 240hrs that cold pool is advancing from the ne.

I still think the pattern is too far west and what shortwaves will appear come the time near Iceland as these could well scupper the cold but for fear of seeming to be a misery I'll say no more about the hurdles.

On a positive note at this time of year you need to be chasing the coldest source of air and its there waiting to break through the UK's defences!

[chris55]

No undercut early on Chris not with ridging from the south

http://www.wetterzen...ics/Recm961.gif

a lot of energy going over the top of the high and it goes the same way-ie.east at T144hrs as shown on the other models.

http://www.wetterzen...cs/Recm1441.gif

Yes, that was my point Phill. When ECM and some GFS ensemble members were showing some potential snowfalls on March 3rd out in FI, the GFS OP was first to spot the UK high developing and cutting off any cold flow. So with ECM once again teasing us out in FI, maybe GFS has called this more accurately once again.

[Ian Brown]

Ah the ECM T240 tease, perfectly plausible given what leads up to it and a question of whether the Greenland High can exert enough influence to stop the jet from the South winning the battle.

[Gibby]

Good evening. Here is the report on the 12z output from GFS, UKMO and ECM for today Tuesday February 26th 2013.

All models show a fine and settled spell of weather over the coming 5-7 days with subtle differences in the position of the High pressure day to day bringing different conditions from place to place. The centre will continue to jostle around over Northern Britain over the coming days eventually moving away SE early next week. There will be a lot of cloud over the UK in general with different areas seeing sunshine one day and not the next. It will be largely dry with a little drizzle possible from the thickest cloud patches and conversely some frost and fog patches overnight in lengthy clear spells.

GFS then shows Low pressure moving in from the SW through next week with an increasing SE wind bringing rain with time as fronts move up from the SW approaches. As winds turn Southerly and then SW milder air will move over the UK before a vigorous depression brings a stormy spell across the UKwith winds turning NW behind it with squally heavy showers before High pressure returns down to the SW late in the run quietening things down again.

The GFS Ensembles show the quiet settled spell continuing for up to another week before good agreement is shown on a breakdown to rain and strong winds at time from the middle of next week in temperatures well up to the seasonal normal. The cold and vigorous depression in the latter stages of the run is seen as a cold outlier within the pack. There is though more variability in 850's from the middle of the run in more Northern locations.

The Jet Stream flow for the next week shows a continuation of the Southerly tracking Jet as High pressure lies close to the UK. Although outside of the forecast range the synoptics would suggest the Southern arm of the jet moving Northward somewhat beyond the middle of next week.

UKMO for the start of next week shows High pressure having moved away East with pressure falling from the SW, though at this juncture it would stay generally dry over the UK.

ECM too suggests High pressure slipping away East with pressure falling from the South and SW. This means East or SE winds with some rain moving up from the SW slowly next week. Though no wintry element to this looks likely the chance is there if colder air becomes engaged in the flow, especially over high ground and on the Northern edge of the leading precipitation bands.

In Summary a breakdown is on the way but we are going to have to wait quite a while for it. There is still plenty of benign and often cloudy weather with rather cold conditions prevailing but some clearer spells may become a little more commonplace as time passes, though this will inevitably mean frost by night. then as we move through next week all models show High pressure slipping away East with a fall of pressure from the SW with rain likely first in the SW midweek and to other Southern and Western areas at least later in the week. The breakdown looks more progressive from GFS but ECM is at pains to keep the UK in rather cold air especially on the Northern side of the precipitation.