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

[Matty M]

A snowy snowy end to the ECM and some extreme cold nights.Ex

What a run.

[SP1986]

I would go as far to say had these synoptics occurred in early January, they would probably surpass the intensity (although not the longevity) of some of the 'great' winters of all time. Obviously it wouldnt surpass the great winters of the 20th centur, like 1947 and 1963 in a broad sense because they lasted so long but perhaps in severity (you get the idea)

Edited March 20, 2013 by SP1986

[Barking_Mad]

Courtesy of Matt Hugo, " Note the brighter colours highlighting a lot of vorticity associated with Fri's fronts = heavy precip. Vorticity - An important variable in forecasting, aids in the development of clouds/precipitation/low pressure"

[TEITS]

Must admit after looking at the ECM even a hardcore coldie such as myself is thinking "When will this cold weather eventually end"!

Back to the potential snow event at the end of the week and again I really wouldn't get your hopes up if you live in N England (except NW) especially NE England. Due to the alignment of the front W areas are more likely to see the heaviest precip whereas the NE the least. I continue to feel that Wales, W Midlands, NW England are the main areas at risk of snow but like I say this risk could extend further S. We also have the added complication that this front will pivot and push S and weaken but at the same time introduce colder air.

Time to post my snow maps I feel which I shall post in the relevant regionals later.

[Mucka]

Might as well throw in a cold and snowy (for some) JMA 12z

And did someone order a channel low as the grand finale?

Only thing is it might not be the end, cue the next Southerly tracking low hitting entrenched cold air?

Edited March 20, 2013 by Mucka

[phil nw.]

Surely the ECM is exaggerating the extent of the cold.. I can't really get my head around that.. it would deliver snow and cold of historical significance to some. As much as I hate that in Spring, even I have to stand back in awe and look at the ECM with my jaw collapsed on the floor. In relative terms it's more severe than December 2010 because of the time of year. So either; the models have it wrong completely.. which is unlikely, the models are showing historical winter spell in March, and who knows the probability of that.. or this will downgrade into a more conservative spell...

I don't really know, but the ECM does show the most extreme output Ive seen in a long time, relative to the time of year.

Yes my thoughts too Stephen.

I keep expecting one of these runs to show signs of the jet moving north with ridging from the Azores high in later frames but as yet nothing.

Remarkable continuity of outputs showing the cold draining into mid-latitudes across the hemisphere with a flat jet well south.

[WINTRY WALES]

Must admit after looking at the ECM even a hardcore coldie such as myself is thinking "When will this cold weather eventually end"!

Back to the potential snow event at the end of the week and again I really wouldn't get your hopes up if you live in N England (except NW) especially NE England. Due to the alignment of the front W areas are more likely to see the heaviest precip whereas the NE the least. I continue to feel that Wales, W Midlands, NW England are the main areas at risk of snow but like I say this risk could extend further S. We also have the added complication that this front will pivot and push S and weaken but at the same time introduce colder air.

Time to post my snow maps I feel which I shall post in the relevant regionals later.

Hi Dave

You think Wales as a whole or more central / northern parts of the country ?

Cheers

[snowking]

12z ECM as you were really with the placement of the snowfall for Friday:

It should be noted that the reason there is no snowfall east of this area is due to lack of precipitation rather than lack of cold air - this is the furthest north the 30F dew point isotherm travels:

As a result, the snow line for Friday Night/Saturday as the second front moves in is further South than previously:

SK

Edited March 20, 2013 by snowking

[Cheshire Freeze]

12z ECM as you were really with the placement of the snowfall for Friday:

It should be noted that the reason there is no snowfall east of this area is due to lack of precipitation rather than lack of cold air - this is the furthest north the 30F dew point isotherm travels:

As a result, the snow line for Friday Night/Saturday as the second front moves in is further South than previously:

SK

That first image fits the Metoffice warning almost to a tee.

[Barking_Mad]

[manutdmatt1986]

12z ECM as you were really with the placement of the snowfall for Friday:

It should be noted that the reason there is no snowfall east of this area is due to lack of precipitation rather than lack of cold air - this is the furthest north the 30F dew point isotherm travels:

As a result, the snow line for Friday Night/Saturday as the second front moves in is further South than previously:

SK

That 2nd chart has snow accumulation for my area. Bank! In reality though, I can't see it stretching that far south.

[lorenzo]

ECM had me at chart 1 - the 00z ! What a thing of beauty, a really commanding Arctic High. What then follows is equally bewildering, Following the NH view of the 850s that plunge of Asian cold really winds itself west over the next 48 hours and then you see it spilling all over Europe.

To add - AO Index chart just tweeted by Ryan Maue - extreme

Will be April before I defrost from that lot.. ECM really delivering Winter eye candy.

Edit - added ECM 1-5 day mean, fortunate timing on Twitter to help illustrate the above..!

Edited March 20, 2013 by lorenzo

[bluearmy]

Yeah, I'm sure there are inevitable case histories of similar guise. The UKMO folk tell me they can't wait for NAE to go. Sooner the better. The broadly poor view of GFS (more especially past t+144) in Exeter Ops Centre is an old story.

When the nae goes, will its replacement be freely available! If the answer is as i expect it to be then quite honestly, we will end up worse off for its demise!

[Gibby]

Hi everyone. Here's tonight's look at the 12z output from GFS, UKMO and ECM for tonight Wednesday March 20th 2013.

All models show Low pressure developing to the SW of the UK increasing the pressure gradient over the UK and consequently creating an increasing and strong SE breeze over the whole UK. A series of fronts also move North and slowly East over the UK in the coming days. Rain will reach the SW tomorrow and spread north and East to all areas except the far NE by the end of Friday. Areas North of the Midlands will see snow rather than rain with blizzard conditions over the higher ground through Thursday night and Friday. A brief less cold spell might reach southernmost England late Friday and Saturday before it's swept away by strong and cold Easterly winds extending back down from the North along with dying outbreaks of rain, sleet and snow over Sunday with the start of next week seeing cold and raw east winds with wintry showers possible in the East.

GFS then shows cold weather through the middle of next week before winds turn towards the Se again later in the week with rain spreading from the SW preceded by snow in the North. the Easter weekend looks like being unsettled with showers or longer spells of rain in association with Low pressure just to the West of the UK in temperatures struggling to near to normal values. Through the latter end of FI tonight's run shows a continuation of unsettled and cloudy weather with rain at times with temperatures at best close to average.

The GFS Ensembles show a cold spell lasting another week punctuated by a warmer blip in the South early in the weekend. there will be copious rainfall in the SW and snowfall for a time in the North. Later next week uppers rise strongly but under Low pressure systems conditions at the surface will be held back by wind and rain in abundance on occasion.

The Jet Stream shows the flow unabated blowing West to East to the South of the UK for the foreseeable future.

UKMO towards the middle of next week looks decidedly chilly with winds in the East in the South and light winds under a ridge of high pressure in the North. Most places will be dry and cold with sunny spells by day and sharp overnight frosts.

ECM shows cold East winds lasting right through to the first few days of Easter with wintry showers affecting many Eastern areas and driven well inland in the strong breeze. by Easter itself the cold weather continues with night frosts, lighter and more variable winds as a new push of Atlantic fronts move towards the SW on Easter Saturday.

In Summary the charts look broadly similar as this morning, at least schematically as cold weather proves very difficult to shift out of the UK. Most if not all of next week now looks cold with only GFS offering anything milder at the expense of wet weather which would take us through Easter. With the Jet flow still held well South for the foreseeable future Low pressure is encouraged to cross East at more Southerly latitudes than normal and with plenty of cold air still bottled to the North of the UK maintaining any leading edge precipitation from fronts be of a wintry flavour in the North in overall rather cold conditions.

[fergieweather]

When the nae goes, will its replacement be freely available! If the answer is as i expect it to be then quite honestly, we will end up worse off for its demise!

I posted a while back some detail on timescales and how the replacement will run within the GM framework at higher resolution. I recall the same post thread also examined met office upgrade to Doppler across all radar network (now almost complete). Worth checking back archives on this. I will ask Exeter tomorrow re how new model will be streamed to free public access sites.

Edited March 20, 2013 by fergieweather

[Stuie]

Oooh this backs up my post last night about Saturday.

Edited March 20, 2013 by StuieW

[winterof79]

12z ECM as you were really with the placement of the snowfall for Friday:

It should be noted that the reason there is no snowfall east of this area is due to lack of precipitation rather than lack of cold air - this is the furthest north the 30F dew point isotherm travels:

As a result, the snow line for Friday Night/Saturday as the second front moves in is further South than previously:

SK

Just to clear a point up.Some on here are mistaking the North midlands with Northern England(not you SK)The majority of West Yorkshire is in Northern england and as so is in the firing line for snow.

[fergieweather]

UKMO actively considering amber upgrades tomorrow am: firstly for snow (GM has 30+mm rain equivalent much of Central Midlands into NE: severe drifting & power line accretion a real hazard) and also for heavy rain in areas under the higher Theta-W air. Snowfall accumulations to t+84 look untroubling effectively south of Brum (a lIttle on UKV about as far south as Cotswolds etc) but potentially awful further north if this verifies.

EDIT GM dynamic snow accumulations have 16mm lincs across from wash to brum; 8mm Cotswolds across through E Anglia... may be overplayed as UKV less supportive that far south, but midnight output might better dictate either way.

Edited March 20, 2013 by fergieweather

[Cheshire Freeze]

UKMO actively considering amber upgrades tomorrow am: firstly for snow (GM has 30+mm rain equivalent much of Central Midlands into NE: severe drifting & power line accretion a real hazard) and also for heavy rain in areas under the higher Theta-W air. Snowfall accumulations to t+84 look untroubling effectively south of Brum (a lIttle on UKV about as far south as Cotswolds etc) but potentially awful further north if this verifies.

So roughly Birmingham northwards for the snowline on current thoughts Ian?

I'd have thought there will be a sharp boundary from this sort of situation.....i.e wet to white in a matter of miles.

Edited March 20, 2013 by CreweCold

[LomondSnowstorm]

UKMO actively considering amber upgrades tomorrow am: firstly for snow (GM has 30+mm rain equivalent much of Central Midlands into NE: severe drifting & power line accretion a real hazard) and also for heavy rain in areas under the higher Theta-W air. Snowfall accumulations to t+84 look untroubling effectively south of Brum (a lIttle on UKV about as far south as Cotswolds etc) but potentially awful further north if this verifies.

What's the northern and eastern extent likely to look like Ian? Seems likely that the front will affect Dumfries and Galloway at least but I do wonder if there's likely to be any impact across the central belt.

Cheers for all your input, it really does add another dimension to the discussion on here.

[JoeShmoe]

UKMO actively considering amber upgrades tomorrow am: firstly for snow (GM has 30+mm rain equivalent much of Central Midlands into NE: severe drifting & power line accretion a real hazard) and also for heavy rain in areas under the higher Theta-W air. Snowfall accumulations to t+84 look untroubling effectively south of Brum (a lIttle on UKV about as far south as Cotswolds etc) but potentially awful further north if this verifies.

How far north do you think the snow line will be Ian?

[Harsh Climate]

From looking at the zero degree isotherm charts I think there's no chance of any real snowfall south of the midlands

North east wales/north midlands/north west england and parts of northern england certainly look like being in the firing line at this moment.

Edited March 20, 2013 by Harsh Climate

[fergieweather]

What's the northern and eastern extent likely to look like Ian? Seems likely that the front will affect Dumfries and Galloway at least but I do wonder if there's likely to be any impact across the central belt.

Cheers for all your input, it really does add another dimension to the discussion on here.

Good consensus there from GM and UKPP: Approx 15-30cm of snow Dumfries & Galloway. Call it 20...!

[Matty M]

Well the ECM OP was an outlier to its mean particularly after 192hrs (outlier perhaps wrong word, to the cold end of the ensembles)

Edited March 20, 2013 by Matty M

[Yarmy]

A cross hemispheric easterly! Thousands and thousands of miles Now that IS reverse zonality

You have to laugh. Someone needs to tell the ECM that Earth rotates from West to East.