Spring Model Discussion 18Z 6/3/13 onwards....

[fergieweather]

Incidentally a note of caution (I'm sure already appreciated by many here) re these GFS snow accumulation charts posted on here: these are NOT to be misconstrued as representing LYING snow (this involves much more complex high-res modelling accounting for varied tricky factors such as depth temperature, surface class/vegetation etc, such as factored into UKV at 1.5km output).

[Severe Siberian icy blast]

Well a snow event been consistently forecast from the gfs now for Sunday morning .

May well give a quick covering .

But on a different note .

That's not a bad northern hemi profile to be looking at if its cold and snow your after. Mid march of not , still more than capable of producing snow with a strongly -NAO/-NO with low heights over Siberia . Just a pity this couldn't have been mid January

[TEITS]

So is another cold, dull and grey period looking to be the form horse then?, sigh....

Nope not for some.

Seems to be some misunderstanding of what may happen so I shall clear this up.

On Sunday a front will move S which could potentially turn to snow as colder air moves in from the NE.

http://www.wetterzentrale.de/pics/Rtavn724.png

Quickly replaced by snow showers during Sunday evening.

http://www.wetterzentrale.de/pics/Rtavn844.png

Amounts from snow showers is impossible to say at the moment.

[fergieweather]

Nope not for some.

Seems to be some misunderstanding of what may happen so I shall clear this up.

On Sunday a front will move S which could potentially turn to snow as colder air moves in from the NE.

http://www.wetterzentrale.de/pics/Rtavn724.png

Quickly replaced by snow showers during Sunday evening.

http://www.wetterzentrale.de/pics/Rtavn844.png

Amounts from snow showers is impossible to say at the moment.

Great post and timely clarification!

[Severe Siberian icy blast]

As far as any of us dare look at any given time , I'm sure ones would agree that it looks loaded with potential

[nick sussex]

Taken at face value a good GFS 06hrs run in the higher resolution for cold and snow, with some decent convection, then a shortwave develops and runs se.

There is likely to be a less cold sector associated with this but every chance any rain will turn back to snow as that clears.

Night time temps I think the Scottish Highlands could see some sub -10c readings, somewhere like Altnaharra or Loch Glacharnoch I think could hit lower if that northerly becomes slack.

[johnholmes]

If you go to the free link for chart comparisons, see below, you can see how the two main models out to 240h are fairly similar and out to 168h have not changed much in the overall upper pattern. This tends, note I say tends, to give more confidence in the models having the correct handle on developments. Both show that the initial deep cold is going to be modified through next week as the flow tends to become more from the west than the north. But little sign of any SW component to the flow, which is also the pattern shown on the 500mb anomaly charts. So it would seem spring is going to be on hold for a while yet. Much as I would prefer to have some warmth and sunshine on my back. I have never been so long without playing golf, okay I am more choosy than 10 years ago, ground, weather etc have to be just right.

http://www.netweather.tv/index.cgi?action=modelcomp;sess=

Edited March 7, 2013 by johnholmes

[johnholmes]

indeed reality check it is called-still a very cold 36-48 window for this time in March

[fergieweather]

So is another cold, dull and grey period looking to be the form horse then?, sigh....

The snow shower distribution will remain the trickiest element to forecast at this juncture. For example, the 00z EC DET runs convergence showers up through the Dover Straits on Tuesday, placing Kent at threat of snow, but this sort of detail cannot be wholly trusted at this range. Nonetheless it exhibits potential. Different set-up to the last easterly outbreak under very subsided conditions.

[No Balls Like Snow Balls]

The 00Z ECM ensembles (Birmingham) and GFS 00Z Ensembles (London) along with the GFS 06z op run all show a very short "very" cold spell, with daytime temps only falling below 5c for 2 days possibly 3 @ at push. A slight warm up would then take place with temps approaching 5c on the ECM and even warmer on the GFS with temps approaching 8c down South.

[Purga]

Depends what you define by a noticetable frost, uppers are around -10 - -12 and if there is no noticetable frost this weekend and into Next week, I'll be shocked! So no idea what charts you are looking at Purga!

One thing to look for potentially next week is the large temperature differences between day and night time temperatures and look out for potential inland daytime convection to develop if the winds turn NNW'ly next week, if that happens, whilst the temperature may be around 5C in the sun, the temperature will drop close to freezing during any showers therefore likely to fall as snow!

Hi Geordie - I did write notable rather than noticeable - not meaning to be pedantic mate. I' sure there will be some frost about but based on the T2M ens the nightime temps won't be especially low, examples below

Mancheter not bad and could get to -5C

So not notable

EDIT : to put things into perspective the record for March was: March* -21.1 °C 4 March 1947 Houghall (County Durham)

Edited March 7, 2013 by Purga

[Thundery wintry showers]

Ian Ferguson is probably going to be right about relatively small accumulations of snow because although this is forecast to be a very cold blast, it is only forecast to sustain for 36-48 hours and there is no significant trough activity being modelled. so scattered short-lived snow showers are likely. There will then be a general thaw on Tuesday as less cold air moves down from the north (though still cold enough to support wintry showers).

However sometimes the models pick out troughs at very short notice so I won't be surprised if limited areas of the British Isles end up with nearer 10cm on Monday morning depending on where any troughs set up. Alter all, even the grey and mostly dry easterly spell in late-February managed to produce 5-10cm of lying snow in some inland parts of NE England.

Edited March 7, 2013 by Thundery wintry showers

[peterf]

Hi Geordie - I did write notable rather than noticeable - not meaning to be pedantic mate. I' sure there will be some frost about but based on the T2M ens the nightime temps won't be especially low, examples below

Mancheter not bad and could get to -5C

So not notable

EDIT : to put things into perspective the record for March was: March* -21.1 °C 4 March 1947 Houghall (County Durham)

My first college on leaving school, wasn't 1947 though lol.

a well known local frost hollow.

[Purga]

My first college on leaving school, wasn't 1947 though lol.

a well known local frost hollow.

1937?

[Man With Beard]

GFS has a little feature running through N France and the English Channel on Monday morning - southern counties not far away. One to watch.

[Captain Shortwave]

The Nasa model this morning still wants to bring some very cold air over us, it's longevity similar to the 06z GFS

-16/18 uppers just across the north sea

[shedhead]

As Nick S alluded to earlier it's probably wise to manage expectations here by considering we're closing in on mid March, not mid winter. Without question the majority of available modelling now suggests a significant cold blast for all early next week, but those frustrated by the fact (myself included) this didn't occur in Winter will just have to deal with it, there's no option. Unfortunately where we go after mid week will also be dictated to by the fact it's mid March, with the snow/rain set ups again likely to be far more marginal than in Winter, but given this an option to a raging Atlantic I know what I would take.

[Purga]

Not overly exciting for the SE from METO today

Outlook for Saturday to Monday:

Cloudy again Saturday with some further rain at times. Becoming drier Sunday but also becoming colder and windier, and with sleet or snow showers in places by Monday.

Updated: 1029 on Thu 7 Mar 2013

[Summer Sun]

Based on the 06z run we once again see this cold spell easing after 48 hours Sunday and Monday will be the two coldest days where highs will struggle to get much above 1 or 2c for many

As we go into Tuesday and the rest of the week temperatures begin to moderate with highs pushing 10c in the south later on they'll be below normal still for many but too high for snow at lower levels with this becoming increasingly confined to higher ground in northern England and Scotland

So once again we are looking at a 48 hour spell of very cold temperatures before they moderate from Tuesday with snow accumulations looking temporary

[nick sussex]

Looking further ahead I think a problem for the models is to resolve the impact of the Alaskan ridge building.

Also a lobe of the PV is likely to drop south to the east of the UK so you could get another shot of very cold uppers as that happens.

There certainly looks to be a big change coming for Europe as a whole. Here today its a beautiful day with temps in the low twenties, some parts of France could see as much as a 20 degree drop in temperature between today and early next week.

[mushymanrob]

No thats wrong mushy, the deep cold uppers are incoming for late sunday and throughout mon and tues, it looks like moderating after that but staying cold all next week with frosty nights and daytime temps well below average, Brrrr and some parts of the uk will have snow during next week.

you are right, i didnt view every chart (wetter 850's plus time constraints), but they are less intense and not as long over the uk... but the rest of the week is 'normal' cold spell for march, frosty nights, cold but showery days with some sunshine (locations obviously vary in who gets what). in the sun in slack winds itll feel ok.

[SMU]

Ah, but to clarify: I did say UK4 totals 2cm plus. For example, some spot-totals on high ground progged as 5-10cm. Moreover, no model can yet adequately resolve/synthesise possible localised focus through shower banding at this range. But not widespread amounts exceeding circa 2cm in either UK4 or EC snow distribution mapping.

your correct- but I must admit I missed the PLUS!

As usual it looks like going down to T48 to resolve, although at this stage, norfolk,suffolk & the usual suspects in central kent look favourite.

S

[johnholmes]

the idea that the models beyond T+48 will give reliable totals of whatever falls from the sky is simply hype, it does not matter what season it is, the number of times the amount/timing even and area that they, all of 'em get wrong on occasion, is quite high. Two years ago I did keep records of NAE and NMM and neither, at the T+48 hours, and in summer not winter when it is even more complicated, covered themselves in glory shall we say.

Relatively simple at T+240 to get the upper air correct, similarly at T+120 with the overall surface pattern, falling from the sky?!-T+48 is about the best it gets and sometimes even at T+12 it is not as good as it might be.

Edited March 7, 2013 by johnholmes

[No Balls Like Snow Balls]

Looking at the 00Z ECM rainfall ensemble it looks relatively dry and sunny for most next week.

Birmingham below.

Also had a look at surface conditions applied from the ECM 00Z operational run for London, Manchester, Southampton and Aberdeen and this also show's fairly dry and sunny next week.

The ECM rainfall ensemble does however show the possibility of it turning wetter at the end of next week.

[snowking]

Looking at the 00Z ECM rainfall ensemble it looks relatively dry and sunny for most next week.

Birmingham below.

Also had a look at surface conditions applied from the ECM 00Z operational run for London, Manchester, Southampton and Aberdeen and this also show's fairly dry and sunny next week.

The ECM rainfall ensemble does however show the possibility of it turning wetter at the end of next week.

It should be noted those are for Birmingham though - not a location I would consider particularly prone to the easterly flow

Nevertheless, ECM produces nothing spectacular in terms of totals at present - could change closer to the time given convective potential

SK