Spring Model Discussion 17/3/13 6PM onwards....

[winterof79]

Much better ecm this morning for coldies!!undercuts back peeps!!

Not on my output there isn`t

http://www.meteociel.fr/modeles/ecmwf/runs/2013031800/ECM1-168.GIF?18-12

UKMO still delivers though

http://www.meteociel.fr/ukmo/runs/2013031800/UW144-21.GIF?18-06

[winterof79]

GFS and ECM identical at 192z onward

http://modeles.meteociel.fr/modeles/gfs/runs/2013031800/gfs-0-192.png?0

http://www.meteociel.fr/modeles/ecmwf/runs/2013031800/ECM1-192.GIF?18-12

Is ukmo correct??

[IDO]

The GFS op has only a little support in the last five days of FI. It has the mildest 850s:

And highest 2m temps:

In the reliable we have a cold week with the north likely to get any snow and we have at D4 the Atlantic entering the SW. On the GFS op it looks like a snow to rain Birmingham north, and rain south of that line. The GFS then has the low pushed back west with HP east (giving the south some mild temps), and then the AH edging NE to co-join the high to our east, with the UK caught in the middle (Easter weekend): .

ECM is similar to GFS for the next few days with that attack from the SW. And at T192:

GFS: ECM:

Good agreement from the main two. So the op runs trending back to more average conditions and possibly mild for some (after D7). UKMO on its own with the undercut.

ECM hinting in the last frame that the PV is getting its act together and the zonal Atlantic train may be resuming service shortly:

[bluearmy]

ECM again between ukmo anf gfs. The east hanging onto the se feed best south uk. Ian's assessment from Exeter still looks valid.

Thereafter, difficult to say but perhaps a continuation of the broad pattern but with the whole thing pushed further north as one might expect given the time of year. That means damp in the south uk, uncertain central uk and probably remaining wintry for the scots.

[mushymanrob]

How have you derived uppers from the fax's?!

i dont think many will be happy with this mornings outputs, that ukmo run last night has changed and this mornings supports the gfs and ecm which both sing from the same songsheet this morning, in short, this cold spell is set to slowly die this week before milder/average weather takes over late in the week/ next weekend. both models strongly suggest a relaxing of the northern block.

i stick firmly with my 'little or no' frontal snow for most (higher ground clearly has more chance).

when i joined here i was told that the fax is the best chart in the near timeframe, it holds more info.... i was told that for certain snow you need the 528 dam, values above that become considerably more marginal.

so viewing this fax i cannot see any snow... the 528 is far too far away from the precipitation, that low IS advecting warmer air in front of it, you can see a nose of 546dam that looks like it would get drawn up and over us IF last nights ukmo slider was to happen...

[SLEETY]

more runs are needed that's my take of things.Seems the MET agree with me as well

At least for my region

Weather forecast: London & South East England

Outlook for Wednesday to Friday:

Wednesday largely cloudy, with limited sunny intervals, also scattered showers. Thursday generally dry and bright, although still rather cold. Friday frosty start then cloud and rain OR snow later.

Updated: 0333 on Mon 18 Mar 2013

Edited March 18, 2013 by SLEETY

[phil nw.]

Still quite cold with some snow around in parts of Scotland and NE England over the next 24-36hrs or so with cold easterly flow north of the area of low pressure but there are signs that the colder period is on the wane thereafter.

We can see on the T96hrs outputs that cold pool to the north east gradually retreating as the winds turn more into the south.

http://www.wetterzentrale.de/pics/Recm962.gif

The GFS ens.graph, although indicating the Op was on the mild side later,shows the 850`s at least trending towards average by the end of the week.

No great warm up yet but the Wintery conditions that seemed to have been around for ever look to be on the wane now.

[Man With Beard]

http://www.wetterzentrale.de/pics/Recm962.gif

Far from a done deal this one. I would suggest all possibilities on the table for Friday 22nd; if the angle of approach of the incoming front is more west - east, it could be just rain in the south and snow to rain virtually everywhere else; the more southerly the approach is, the further south the snow comes and the longer it sticks around. I think this will be a T48 forecast and I wouldn't bet against UKMO after it nailed a similar scenario in January.

What is noteworthy is that Ian F has already flagged up some very high rainfall/snowfall totals to come. Whether it's flooding or blizzards, we're all going to know about this one.

[Purga]

ECM hinting in the last frame that the PV is getting its act together and the zonal Atlantic train may be resuming service shortly:

Looks more like a west based -ve NAO shift rather than true 'zonal tain' etc..

[TEITS]

After looking at the ensembles for my location im going to sit on the fence with regards to the end of the week into the following week.

http://cdn.nwstatic.co.uk/ensimages/ens.20130318/00/t850Cambridgeshire.png

I haven't been impressed with the consistency of the model output for the end of the week but that is normal for these situations and will probably change many times over the next few days.

If I had to come off the fence then I would say snowfall seems restricted to E Scotland/NE England over the next couple days where heavy falls could occur. During the week it will become drier across these regions. Towards the end of the week the chance of rain moving into SW turning to snow as it moves NE but im not convinced of this just yet. As for the weekend/following week and it could become very cold but more likely cold at first with SE,lys winds before veering S,ly and eventually SW,ly.

Let me put it this way im not expecting any snow at the end of the week but I wouldn't be surprised if this did turn up on the models over the next few days. I equally wouldn't be surprised to see the front make no progress towards my location whatsoever as the undercutting LP remains to the S of me.

[Gibby]

Hi folks. Here is the report of the 00z output from GFS, UKMO, GEM and ECM for today Monday March 18th 2013.

All models show Low pressure centred over Southern Britain with an increasingly cold and strong East or NE flow over the North with spells of rain, sleet and snow. In the South the pattern will be more of sunshine and showers in light winds and frost at night. This pattern over the UK remains in situ until Thursday when a deepening Low down to the SW freshens up the SE wind over all areas making it feel cold and raw. An area of rain will move NE into the SW later on Thursday from a front which makes further slow progress NE on Friday with rain turning to snow over the hills further North and East.

GFS then shows a North/South split developing at the weekend with the North continuing cold and wintry with further snowfall possible with the South seeing milder and more showery conditions encroach from the South at times. Next week the model extend the milder conditions from the South to other areas too, though still very unsettled with rain at times and strong winds. Easter is shown with SW winds and Low pressure to the NW with rain at times for all though less cold than of late. The trend after Easter will be then for rain to be most prevalent to the North and West as pressure rises to the SE and then at the end of the run to the NE with drier weather to all before rain encroaches NE from the SW into the SW at the end of the run.

The GFS Ensembles show an unsettled spell continuing over the UK for the foreseeable with the trend for less cold conditions generally growing with time. The operational was a milder outlier though so things may not warm up as much as suggested above but things will most certainly be equally wet at times.

The Jet Stream continues to blow generally to the South of the UK for the foreseeable. It does weaken at times though and move a little further North at times towards latitude 50 deg N.

UKMO for the end of next weekend still looks a cold one with Low pressure filling down to the SW with a cold and strong ESE wind blowing over most of the UK. There will be some rain or snow in the North steadily dying out over Sunday while Southern areas see the risk of rain continuing for a while longer.

GEM fills the Low to the SW rather more slowly with the end result being that Southern Britain remains the focus of Low pressure with slack winds and outbreaks of rain out to the end of it's run with the North remaining under the influence of a cold and raw Easterly drift.

ECM shows any rain at the weekend die out early next week as pressure builds to bring a chilly drier spell with frost at night but little precipitation. It doesn't last long though as pressure falls, this time to the NW and SW winds bring wet and milder conditions NE across all areas as we approach Easter.

In Summary this morning despite disappointing charts for those looking for dry and warm early Spring weather the trend is shown this morning for things to be slowly become less cold with time as Low pressure locates at more Northerly latitudes over the Atlantic with time. Those living in Northern and particularly NE Britain may have to wait some considerable time for this change though.

[Summer Sun]

The good news this morning is ECM looses the coldest uppers for all but NE Scotland this morning by Friday so thats the positive the negative is some troublesome rainfall is looking likely in the southwest which could cause some localized flooding

Short term ECM remains cold

But by t96 we see some milder uppers to just starting to win the battle to the SW

T120 only Northern Scotland is left with the coldest uppers

This theme of slightly milder uppers continues right through ECM

[cooling climate]

I think the lack of posts tells the story this morning.

Nothing in this mornings output of any real interest for winter

weather lovers apart from those in the north.

Lol and then the 06z run brings very cold and wintry weather to

central southern England, Midlands and east Anglia Wednesday.

Edited March 18, 2013 by cooling climate

[TEITS]

Something of interest for those further S.

http://www.wetterzentrale.de/pics/Rmgfs543.gif

[Purga]

Something of interest for those further S.

http://www.wetterzen...cs/Rmgfs543.gif

Cold rain doesn't float my boat

[Nick F]

Well, an exciting few days ahead for northern Britain, a bitterly cold easterly wind and slow moving occluded front lying E-W will combine to bring alot of snow to Scotland and NE England in particular and we're talking 20-30cm over higher ground towards eastern Scotland and perhaps 10-15cm at lower levels by the end of Tuesday.

This occluded front then moves south on Wednesday, tending to weaken as it does so, but not before it brings rain, sleet and perhaps some back edge snow across more central and eastern parts of England and Wales during Wednesday looking at GFS.

Thereafter, it does look increasingly likely that milder air bringing wet and windy conditions will spread up from the south on Thursday/Friday, preceded by snow across N England northwards and perhaps staying as snow over Scotland into the weekend as the cold air hangs on - perhaps bringing a major snow event.

Quite a few EPS members this morning going for the cold to move back south and southwest again early next week, as the Atlantic trough disrupts southeastwards across France with energy undercutting the block to the N and NE, so worth bearing in mind the uncertainty and the milder incursion may only be temporary across E & W.

Edited March 18, 2013 by Nick F

[Joe Levy]

The angle of the low is a lot better for the westward advection of cold uppers and appears to have spawned a shortwave in front of it.

Edited March 18, 2013 by Joe Levy

[Man With Beard]

GFS 6Z stays cold and snowy throughout next weekend up north. Second chance Sunday for southerners? undercutting shortwave, low uppers dragged south - yet again! The weather is definitely not reading the calendar this month.

Edited March 18, 2013 by rjbw

[snowmadchrisuk]

http://modeles.meteo...s-1-150.png?6?6

GFS 0Z stays cold and snowy throughout next weekend up north. Second chance Sunday for southerners? undercutting shortwave, low uppers dragged south - yet again! The weather is definitely not reading the calendar this month.

I think if the first attack fails to deliver any Snow (Fri) then I don't think we are going to stand much chance of the second attack delivering ... Far NE continues to look ok for some significant Snow but for most of England Heavy Rain and temps starting to get into double figures .. The only Model that stands a chance of delivering further South is the UKMO , and given most of the other models and ensembles are against the UKMO then I would expect it to start heading towards the GFS solution later this afternoon.

[stodge]

Morning all

Well, you can file me under "none the wiser" this morning. The UKMO continues to tantalise with a cold offering while ECM continues its switcharound from last evening with a milder evolution. GFS 06Z throws a new option on the table;

http://modeles.meteociel.fr/modeles/gfs/runs/2013031806/gfs-0-174.png?6?6

Gavin will be pleased to see a hint of a more anticyclonic scenario and as the LP withdraws west into the Atlantic it's a possibility we could see pressure rise close to the British Isles.

http://www.meteociel.fr/ukmo/runs/2013031800/UW144-21.GIF?18-06

Just thought I'd post this again to please the mildies. The point is that as the LP in mid-Atlantic inclines north, it forces the Greenland HP to ridge SE.

http://www.meteociel.fr/modeles/ecmwf/runs/2013031800/ECM1-192.GIF?18-12

Again, I would argue this isn't a million miles away from the GFS 06Z option. I think an evolution to an anticyclonic outlook is far from unlikely with the HP to the E or NE of the UK. I doubt we'd see a cold NE blast but a modified SE (which wouldn't be too cold) is a trend I can see.

As ever, more data is required.

[Thundery wintry showers]

I'm continuing to be reminded of late-March 2001. The 17th-20th had some grey rainy sleety type weather in the south while the north was brighter with snow showers, with some heavy snow showers in the north-east on the 18th. Fronts came up from the SW on the 21st, bringing a spell of snow followed by less cold air. Then the cold easterly regime returned between the 24th and 26th, but not quite as cold as previously, with generally cloudy conditions as opposed to sunshine and snow showers. The next frontal attack finally brought in much milder air.

I can foresee a similar progression happening here. There will be an easterly blast on Tuesday/Wednesday with numerous snow showers for eastern Scotland and NE England, and then while the fronts coming up from the south may just give the Midlands southwards a brief snow-to-rain event, I can foresee rather more significant snowfalls for parts of Scotland and the northern half of England as the fronts become slow-moving, away from North Sea coastal areas where the onshore winds will tend to make conditions at the frontal boundary too marginal.

I then see a fair amount of support for a temporary southward push of cold air over the weekend, which may help push the frontal boundary south and introduce the colder air back into Scotland, though possibly relatively cloudy and dry rather than bright with snow showers (as was also the case around 25th-27th March 2001). The UKMO in particular continues to support this scenario:

http://www.wetterzen...cs/Rukm1441.gif

With the cold pool and northern blocking likely to recede a little, it may well be that the main pattern change to warmer weather will hold off for central and northern areas until early next week, but southern England may well see less cold conditions establish already by Thursday/Friday.

Edited March 18, 2013 by Thundery wintry showers

[TEITS]

Cold rain doesn't float my boat

Snow for some on that chart though!

[nick sussex]

I think theres still a lot of uncertainty for the end of the week with the orientation of the troughing making a huge difference to snow chances in the more marginal areas.

In these situations the more circular the low the more mixing out of the cold you have, the UKMO still looks best for snow chances as it elongates any troughing and cuts off the milder air.

Generally here from past experience you get more trough disruption than suggested by the outputs at longer range, corrections south are also more likely. The core of the block is shown to edge south and then sw for this reason I wouldn't discount the UKMO solution especially as the ECM still goes on to disrupt the low a little later.

The point of uncertainty is more in relation to areas away from the north and ne which are still likely to see some snow before any frontal attack from the sw but its as you head further south that it becomes more marginal.

Edited March 18, 2013 by nick sussex

[Captain Shortwave]

Afternoon, still a mixed bag from the models today

NASA model showing something decent for coldies though

Any frontal incursion would bring snow to all except the far southwest.

Pretty close if not a little better than the UKMO output this morning.

[SMU]

Morning-

Many dismissing the chances for the end of the week because they are using the GFS & the wrong parameters in this type of situation-

UKMO is VERY similar to the NAVGEM this morning which sees the 0c isotherm never making it past the M4-

The end of the week is looking Very snowy on those 2 models with the GFS out of filter-

but because still after months of being wrong most of the time ( barring a couple of decent hits) most people follow the GFS is already game set & match-

remember the GFS london Ensembles are gridpoint fo the IOW- so use the meteociel ones for london in future runs to see what the mean is for friday & sat in terms of 850s- remember -1c will do @ 850 if we get the right sort of undercut..

S