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Model output discussion - after the beast, what next?


Paul
Message added by Paul

Please only post model discussion in here! 
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For more focused short-range model discussion:
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Posted
  • Location: Oakdale, Poole in Dorset
  • Location: Oakdale, Poole in Dorset
6 minutes ago, khodds said:

No - you need to look at the facts before posting. When I read your post the first thing I thought was you were trolling!! Seemingly I wasn’t alone 

I was only posting what the ECM is showing for Sunday. -4 or -5 in the last third or march isn't exceptional and therefore its unlikely to be snow for all under those uppers. Irrespective of whether the -10 air crosses the country, the ECM progs it to flash through pretty quickly. Not long enough in my opinion for the cold to be entrenched at ground level unlike the last cold spell a few weeks ago. Therefore, during Sunday, if the ecm was correct (*if*) as it doesnt have much support at the moment then I would imagine temps in the south would be more likely between 3-6 degrees and dew points between 0-2 degrees which would be pretty marginal for low level snow and/if there were any snow it would unlikely settle particularly well. 

However, thankfully for most, this isnt likely to happen based on the blend of 12zs this evening. Likely to be all snow if the low crosses east to west in a favourable manner.

However, I wouldn't discount the ecm at 72 hours showing the increase in marginality if the thrust of cold air is too far north. The latest BBC forecast at 6.28 showed temps indeed of 4c for London and Birmingham and 6 degrees in Plymouth whereas before they were only showing 2-3 c nationwide. Also the metoffice video published online does show rain mixed with snow with a 30% chance of this happening. The other 70% was for the Easterly to maintain snow showers across the east in particular.

I'm not trolling. I would like more snow like the rest of us but only posting to discuss the charts as they emerge. 

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Posted
  • Location: Siston, Bristol 70m ASL
  • Location: Siston, Bristol 70m ASL
29 minutes ago, SizzlingHeat said:

72 hours on ECM showing -3 to -6 uppers across the south on Sunday. Sleet rather than snow across the south if this was to happen! 

Screenshot_20180315-182246.png

Well considering the uppers were above 0C during the blizzard across the south and west that will not matter as DP's will be well below 0C! looks great for the SE

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Posted
  • Location: Cwmbach, Aberdare, Mid Glamorgan
  • Weather Preferences: Snow, wind and summer storms
  • Location: Cwmbach, Aberdare, Mid Glamorgan
9 minutes ago, SizzlingHeat said:

I was only posting what the ECM is showing for Sunday. -4 or -5 in the last third or march isn't exceptional and therefore its unlikely to be snow for all under those uppers. Irrespective of whether the -10 air crosses the country, the ECM progs it to flash through pretty quickly. Not long enough in my opinion for the cold to be entrenched at ground level unlike the last cold spell a few weeks ago. Therefore, during Sunday, if the ecm was correct (*if*) as it doesnt have much support at the moment then I would imagine temps in the south would be more likely between 3-6 degrees and dew points between 0-2 degrees which would be pretty marginal for low level snow and/if there were any snow it would unlikely settle particularly well. 

However, thankfully for most, this isnt likely to happen based on the blend of 12zs this evening. Likely to be all snow if the low crosses east to west in a favourable manner.

However, I wouldn't discount the ecm at 72 hours showing the increase in marginality if the thrust of cold air is too far north. The latest BBC forecast at 6.28 showed temps indeed of 4c for London and Birmingham and 6 degrees in Plymouth whereas before they were only showing 2-3 c nationwide. Also the metoffice video published online does show rain mixed with snow with a 30% chance of this happening. The other 70% was for the Easterly to maintain snow showers across the east in particular.

I'm not trolling. I would like more snow like the rest of us but only posting to discuss the charts as they emerge. 

I am chuckling at this. "You would imagine...." you're probably better off not imagining and going on what the models are showing. 3-6 degrees is not being shown neither are 0-2 degree DP (normal exceptions of course) so going by the models (which is what the thread is about) 99% will see snow. If your boat is moored in Cornwall you may not see settling snow on the deck ?

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Posted
  • Location: Eastbourne and Larnaca,Cyprus .
  • Location: Eastbourne and Larnaca,Cyprus .

Entrenched cold is not necessary for frontal snow, what’s needed is an undercut of drier air with low dew points.

It’s for that reason some of the rain associated with the fronts moving west in the fax chart will turn to snow .

There is no entrenched cold over the UK as this happens.

Anyway the ECM looks like an outlier solution at T72 hrs and best for the timebeing to wait and see what future runs say.

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Posted
  • Location: G.Manchester
  • Location: G.Manchester
7 minutes ago, SizzlingHeat said:

I was only posting what the ECM is showing for Sunday. -4 or -5 in the last third or march isn't exceptional and therefore its unlikely to be snow for all under those uppers. Irrespective of whether the -10 air crosses the country, the ECM progs it to flash through pretty quickly. Not long enough in my opinion for the cold to be entrenched at ground level unlike the last cold spell a few weeks ago. Therefore, during Sunday, if the ecm was correct (*if*) as it doesnt have much support at the moment then I would imagine temps in the south would be more likely between 3-6 degrees and dew points between 0-2 degrees which would be pretty marginal for low level snow and/if there were any snow it would unlikely settle particularly well. 

However, thankfully for most, this isnt likely to happen based on the blend of 12zs this evening. Likely to be all snow if the low crosses east to west in a favourable manner.

However, I wouldn't discount the ecm at 72 hours showing the increase in marginality if the thrust of cold air is too far north. The latest BBC forecast at 6.28 showed temps indeed of 4c for London and Birmingham and 6 degrees in Plymouth whereas before they were only showing 2-3 c nationwide. Also the metoffice video published online does show rain mixed with snow with a 30% chance of this happening. The other 70% was for the Easterly to maintain snow showers across the east in particular.

I'm not trolling. I would like more snow like the rest of us but only posting to discuss the charts as they emerge. 

In all fairness you might be right but it's the reductionist view that can sometimes come across as frustrating. A proportion of people seem to just stare at the 850's and produce a forecast based solely on those, when in actuality, there are a number of other variables (some of which are more important) when it comes to forecasting and marginalising precipitation type. Like all analytical science, forecasting requires an holistic approach.

Looking at the wider picture, I don't think we need to worry about temperatures for snowfall. As a shower passes over it will fall as snow, pretty much nationwide. It's the dry periods and sunshine between the snow showers that may reduce/prevent the snow building up. At night snow will probably fall everywhere and settle. 

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Posted
  • Location: NR Worthing SE Coast
  • Location: NR Worthing SE Coast
13 minutes ago, SizzlingHeat said:

I was only posting what the ECM is showing for Sunday. -4 or -5 in the last third or march isn't exceptional and therefore its unlikely to be snow for all under those uppers. Irrespective of whether the -10 air crosses the country, the ECM progs it to flash through pretty quickly. Not long enough in my opinion for the cold to be entrenched at ground level unlike the last cold spell a few weeks ago. Therefore, during Sunday, if the ecm was correct (*if*) as it doesnt have much support at the moment then I would imagine temps in the south would be more likely between 3-6 degrees and dew points between 0-2 degrees which would be pretty marginal for low level snow and/if there were any snow it would unlikely settle particularly well. 

However, thankfully for most, this isnt likely to happen based on the blend of 12zs this evening. Likely to be all snow if the low crosses east to west in a favourable manner.

However, I wouldn't discount the ecm at 72 hours showing the increase in marginality if the thrust of cold air is too far north. The latest BBC forecast at 6.28 showed temps indeed of 4c for London and Birmingham and 6 degrees in Plymouth whereas before they were only showing 2-3 c nationwide. Also the metoffice video published online does show rain mixed with snow with a 30% chance of this happening. The other 70% was for the Easterly to maintain snow showers across the east in particular.

I'm not trolling. I would like more snow like the rest of us but only posting to discuss the charts as they emerge. 

  • No the met office video does not show that whatsoever.it says 70%  chance . Sunday of 1-3 cm snow and 5 cm in places and 30% chance of 2-5cm of snow widely in the South Sunday,and No mention of rain,all of it snow .But keep with your agenda if you want .:gathering:
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Posted
  • Location: Oakdale, Poole in Dorset
  • Location: Oakdale, Poole in Dorset
4 minutes ago, SLEETY said:
  • No the met office video does not show that whatsoever.it says 70%  chance . Sunday of 1-3 cm snow and 5 cm in places and 30% chance of 2-5cm of snow widely in the South Sunday,and No mention of rain,all of it snow .But keep with your agenda if you want .:gathering:

The graphics were not all snow though, that's my point.

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Posted
  • Location: Stroud, Gloucestershire
  • Weather Preferences: Extreme!
  • Location: Stroud, Gloucestershire

ECM hinting at a continuation of the cold flow on the 12z. It has looked probable the high will sink and the milder Atlantic air will ride in from the west.....however tonight's ECM just 'suggests' that path might not be a foregone conclusion.....

One to watch!

at 96 the potential for some renewed WAA west of Iceland could well support the high.

IMG_3463.thumb.PNG.8ddde0f2472585511689dbdd81957bfb.PNG 

The 12z still sinks the high but never really gets the Atlantic system through

144

IMG_3465.thumb.PNG.96d1a1dda7a19e0beecde3a5f0b74d8a.PNG

Then we get further trough disruption and southerly tracking lows.

IMG_3466.thumb.PNG.10c6083e7d4a465fd8d2cac09dc35298.PNG

 

Edited by chris55
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Posted
  • Location: Beccles, Suffolk.
  • Weather Preferences: Thunder, snow, heat, sunshine...
  • Location: Beccles, Suffolk.
1 minute ago, SizzlingHeat said:

The graphics were not all snow though, that's my point.

Though I suspect (hope) that you'll be horribly wrong SH, I'll no' be calling you a 'troll'; we all get things wrong from time-to-time.:good:

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Posted
  • Location: Cobham Surrey
  • Weather Preferences: clear skies , hard frost , snow !
  • Location: Cobham Surrey
2 hours ago, bluearmy said:

It runs through on Saturday, not sunday

It is showing a bit further north in some models but I suspect that allows the frontal snowfall to reach you - I know which I would prefer.......

Fair enough I thought the upper cold pool was Saturday night into Sunday morning ...

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Posted
  • Location: NR Worthing SE Coast
  • Location: NR Worthing SE Coast
6 minutes ago, SizzlingHeat said:

The graphics were not all snow though, that's my point.

The map showed nothing but snow,no sign of rain.Think your Just overacting to the graphic not showing snow on it .

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Posted
  • Location: Kirkburton, Huddersfield - 162.5mtrs asl.
  • Weather Preferences: Winter synoptics.Hot summers.
  • Location: Kirkburton, Huddersfield - 162.5mtrs asl.
8 minutes ago, SizzlingHeat said:

The graphics were not all snow though, that's my point.

The new BBC graphics are total pants....the snow looks like passing clouds.Stick to EURO4 and live radar on netweather

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Posted
  • Location: Drayton, Portsmouth
  • Location: Drayton, Portsmouth
42 minutes ago, SizzlingHeat said:

I was only posting what the ECM is showing for Sunday. -4 or -5 in the last third or march isn't exceptional and therefore its unlikely to be snow for all under those uppers. Irrespective of whether the -10 air crosses the country, the ECM progs it to flash through pretty quickly. Not long enough in my opinion for the cold to be entrenched at ground level unlike the last cold spell a few weeks ago. Therefore, during Sunday, if the ecm was correct (*if*) as it doesnt have much support at the moment then I would imagine temps in the south would be more likely between 3-6 degrees and dew points between 0-2 degrees which would be pretty marginal for low level snow and/if there were any snow it would unlikely settle particularly well. 

However, thankfully for most, this isnt likely to happen based on the blend of 12zs this evening. Likely to be all snow if the low crosses east to west in a favourable manner.

However, I wouldn't discount the ecm at 72 hours showing the increase in marginality if the thrust of cold air is too far north. The latest BBC forecast at 6.28 showed temps indeed of 4c for London and Birmingham and 6 degrees in Plymouth whereas before they were only showing 2-3 c nationwide. Also the metoffice video published online does show rain mixed with snow with a 30% chance of this happening. The other 70% was for the Easterly to maintain snow showers across the east in particular.

I'm not trolling. I would like more snow like the rest of us but only posting to discuss the charts as they emerge. 

Actually I have some sympathy with your post, and I'm a bit disappointed at the tone of some of the responses.

I recall the horror of February 2005. For days, a major snowfall on an easterly was progd by everyone including the METO. Only on the day did the "fail" become apparent. The post-mortem revealed the air had not been cold enough. All the pros and the experts on here were caught out that day.

So why not ask questions??

Now I think the reasons why the mild uppers can be ignored on this occasion have been well covered. I'm much more confident than i was on 1 March that it will be all snow.

But it was a good question to ask.

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Posted
  • Location: Drayton, Portsmouth
  • Location: Drayton, Portsmouth
22 minutes ago, winterof79 said:

The new BBC graphics are total pants....the snow looks like passing clouds.Stick to EURO4 and live radar on netweather

I think the radar in particular!!

I know snow is hard to predict but I don't think I've seen a situation where the possibilities are so widespread. The fax chart has two convergence zones - lots of snow underneath them, maybe quite little even 50 miles away. A small shift in the wind changes everything! Saturday lunchtime - how well will the front moving south maintain intensity? And for those like me on the south coast, that warm front on the tip of the Isle of Wight reminds me of the tease of March 11 2013.

This is as much a lottery as I've ever seen.

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Posted
  • Location: Belper
  • Weather Preferences: Snow and lots of it
  • Location: Belper
9 minutes ago, Man With Beard said:

Actually I have some sympathy with your post, and I'm a bit disappointed at the tone of some of the responses.

I recall the horror of February 2005. For days, a major snowfall on an easterly was progd by everyone including the METO. Only on the day did the "fail" become apparent. The post-mortem revealed the air had not been cold enough. All the pros and the experts on here were caught out that day.

So why not ask questions??

Now I think the reasons why the mild uppers can be ignored on this occasion have been well covered. I'm much more confident than i was on 1 March that it will be all snow.

But it was a good question to ask.

Agreed. Childish responses above. People don't half get silly on this world wide Web.  Be nice. Be polite. Be respectful. Adults sulkily squabbling about a others interpretation of weather charts :-). Not a good look. 

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Posted
  • Location: Wantage, Oxon
  • Weather Preferences: Hot, cold!
  • Location: Wantage, Oxon

After looking at the 12s, it seems clear that the major global models don't have much more to tell us about how this weekend will pan out.  The spreads on the ensembles give a good indication of the uncertainty that remains, here the GEFS spread at just T66, it's all around the south of the UK and I guess it is all to do with the instability or otherwise, which of course will affect snowfall bigly:

gens-22-1-66.png?12

Prior to the Beast #1 we've not seen convective snow for a long time, certainly the last time was before I starting model watching.  So we have several new higher resolution, short timescale models available to view that we haven't had in previous events, so this a really good time to evaluate them.  I think it's accepted that HIRLAM did well a couple of weeks ago, what do these models say now?

Here's some cumulative snow charts, recognising that this is total precipitation as snow based on an assumption of a 10:1 ratio of snow to water, not snow depth.  ARPEGE first, out to Monday 6am:

arpegeuk-45-114-0.png?15-18

HIRLAM next, out to Saturday lunchtime:

hirlamuk-45-48-0.png?15-17

ICON-EU (not to be confused with the ICON global model) to Monday 6am:

iconeu_uk1-45-90-0.png?15-16

Finally the Finnish HIRLAM, this is just pure precipitation in mm, but given the T850s we can assume it's mostly snow at a 10:1 ratio, here up until 6pm Saturday:

fmiuk-25-54-0.png?15-19

Pick the bones out of that lot!  

Lot's of uncertainty, everyone in with a chance.

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Posted
  • Location: Cwmbach, Aberdare, Mid Glamorgan
  • Weather Preferences: Snow, wind and summer storms
  • Location: Cwmbach, Aberdare, Mid Glamorgan
5 minutes ago, Mike Poole said:

After looking at the 12s, it seems clear that the major global models don't have much more to tell us about how this weekend will pan out.  The spreads on the ensembles give a good indication of the uncertainty that remains, here the GEFS spread at just T66, it's all around the south of the UK and I guess it is all to do with the instability or otherwise, which of course will affect snowfall bigly:

gens-22-1-66.png?12

Prior to the Beast #1 we've not seen convective snow for a long time, certainly the last time was before I starting model watching.  So we have several new higher resolution, short timescale models available to view that we haven't had in previous events, so this a really good time to evaluate them.  I think it's accepted that HIRLAM did well a couple of weeks ago, what do these models say now?

Here's some cumulative snow charts, recognising that this is total precipitation as snow based on an assumption of a 10:1 ratio of snow to water, not snow depth.  ARPEGE first, out to Monday 6am:

arpegeuk-45-114-0.png?15-18

HIRLAM next, out to Saturday lunchtime:

hirlamuk-45-48-0.png?15-17

ICON-EU (not to be confused with the ICON global model) to Monday 6am:

iconeu_uk1-45-90-0.png?15-16

Finally the Finnish HIRLAM, this is just pure precipitation in mm, but given the T850s we can assume it's mostly snow at a 10:1 ratio, here up until 6pm Saturday:

fmiuk-25-54-0.png?15-19

Pick the bones out of that lot!  

Lot's of uncertainty, everyone in with a chance.

Hi,

When do these charts start from? Would they include any precip prior to the snow? Or is it purely snowfall? 

To be clearer, they start from when all the parameters for snow are met? 

Thank you 

Edited by JamesL
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Posted
  • Location: Hull
  • Weather Preferences: Cold Snowy Winters, Hot Thundery Summers
  • Location: Hull
21 minutes ago, Man With Beard said:

Actually I have some sympathy with your post, and I'm a bit disappointed at the tone of some of the responses.

I recall the horror of February 2005. For days, a major snowfall on an easterly was progd by everyone including the METO. Only on the day did the "fail" become apparent. The post-mortem revealed the air had not been cold enough. All the pros and the experts on here were caught out that day.

So why not ask questions??

Now I think the reasons why the mild uppers can be ignored on this occasion have been well covered. I'm much more confident than i was on 1 March that it will be all snow.

But it was a good question to ask.

I think back then dew points were marginal. This was the 24th February event you referred to, the problem with that one was that dew points were much higher. Look at Leeds/Bradford airport for example.

https://www.wunderground.com/history/airport/EGMC/2005/2/24/DailyHistory.html?req_city=Leeds&req_statename=United Kingdom

https://www.wunderground.com/history/airport/EGKA/2005/2/24/DailyHistory.html?req_city=Southampton&req_state=&req_statename=United+Kingdom&reqdb.zip=&reqdb.magic=&reqdb.wmo= - In hampshire dew points were above freezing all day.

Expressing concern is fine but its got to be backed up with good stats. Initially saying -3/4C uppers will fall as rain will just serve to confuse new members. 

Edited by Quicksilver1989
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Posted
  • Location: st albans
  • Location: st albans

Hang on @Man With Beard - @SizzlingHeat was referencing an ecm chart and stating that would produce sleet and cold rain rather than snow. Bringing the met office or beeb forecast and what might happen is surely not relevant to that ?? 

If he had said that the ecm is trending to less cold uppers in the south and this could be the start of a drift to sleet rather than snow come Sunday then that wouldn’t  be a problem.  The actual ec op run shows conditions conducive to snow - nothing else with those dp’s. Whether the run is correct is open to debate - that’s what we’re here for. 

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Posted
  • Location: Wantage, Oxon
  • Weather Preferences: Hot, cold!
  • Location: Wantage, Oxon
9 minutes ago, JamesL said:

Hi,

When do these charts start from? Would they include any precip prior to the snow? Or is it purely snowfall? 

Thank you 

Hi JamesL, the first three are just from when the precipitation is just snow, the Finnish one is all precipitation from the start of the run (12pm today), doesn't differentiate snow.

By the way, I am not suggesting any of these models are accurate, as others have said forecasting snow even this far out is difficult, I am posting them so that we can evaluate the models' performance once we see what actually happens.

Edited by Mike Poole
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Posted
  • Location: st albans
  • Location: st albans

By the way - anyone notice the trend on the ec suite to build a ridge of sorts to our east day 10/11 with the trough stalling ???  Could we do it all again ??? Unlikely ..........

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Posted
  • Location: Cwmbach, Aberdare, Mid Glamorgan
  • Weather Preferences: Snow, wind and summer storms
  • Location: Cwmbach, Aberdare, Mid Glamorgan
2 minutes ago, Mike Poole said:

Hi JamesL, the first three are just from when the precipitation is just snow, the Finnish one is all precipitation from the start of the run (12pm today), doesn't differentiate snow.

Many thanks Mike ??looks like SE Wales could do pretty well again. 

30cms in December 2017

40cms+ Feb/march 2018

?? March 

not a bad winter here snow wise it must be said 

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Posted
  • Location: Ramsey, Minnesota (USA)
  • Weather Preferences: Thunderstorms/Snow/Hail & Strong Winds
  • Location: Ramsey, Minnesota (USA)
1 minute ago, bluearmy said:

By the way - anyone notice the trend on the ec suite to build a ridge of sorts to our east day 10/11 with the trough stalling ???  Could we do it all again ??? Unlikely ..........

Whatever the outcome, Spring is well and truly struggling to stay afloat for the foreseeable future.  

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