Interesting stuff there Q, plenty of interest this week which makes looking beyond the next few days pretty futile.

But I will do it anyway: 0Z London GEFS had a cluster that stayed cold from 30 Jan right to the end, avoiding any warm-up. That has largely gone from the 6Z but there is still a decent cold cluster from around Feb 4th, and both the op and the control join it. Control looks especially good for a February freeze.

 

Interesting, as the METO have gone with a milder outlook than previously, still with the usual caveats that there may be colder outbreaks.

 

For the 29th of Jan to 7th of Feb - 'Unsettled conditions look likely to dominate for this period, with low pressure across the UK. Therefore, this should bring changeable weather to most of the country, with periods of rain, showers, and strong winds at times. While mild westerly and south westerly winds are expected to be dominant for most of the period, occasional colder northerly winds are possible.'

 

I think, that as you say looking beyond  4 or 5 days seems futile.

A dive down around the 2nd , can it be maintained ???

I find the way to get the most from these ensemble charts is by following the following protocol:-

The first week the mean is usually accurate and meaningful with only slightly variations. From then on look for a visual trend or clusters.

So here, after the first 1st is a clear downward trend but the actual mean value is unreliable.

From the 5th there is just random noise but often there are two sets of random trends. One milder one colder. Here there is a hint that the colder cluster is stronger.(It has both the op and the control)  If one trend becomes stronger than it is reasonable to assume that the mean during that period will trend towards that group as the rest fall into line.

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I'm amazed the BBC are not doing the usual thing during high uncertainty and 'forgetting' to do the forecast that covers it.

For me it could rain or snow tommorow, neither would suprise me.

Given that a majority of the models (more reliable ones at that) suggest the cold air lingering in N england and Scotland it seems ridiculous to be so certain about what will happen tommorow onwards.

As I say a good number of the ARPEGE ensembles have a disrputive snow event (amber warning level) for southern parts of England tommorow and its a majority when you get Yorkshire northwards.

 

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The AROME 9z ensemble mean which are coming online now show this:

Note that what's going on is less a 'marginally cold enough' scenario across the midlands but 50% being cold enough and 50% not being cold enough.

In other words AROME (very reliable short term model) is going for 50:50 snow tommorow in parts of the Midlands on low levels.

 

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Probability of more than 1cm of snow falling up until Thursday night.

80%+ for higher ground N England, Highland scotland and central belt.

50%+ For Yorkshire northwards and central wales.

Still 30%+ for most of the southern Midlands northwards.

Don't forget -5% for the S.E corner. 

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ARPEGE P19 shows one possibility that cannot be ruled out. Keep this in mind, the sort of synoptic correction this would require from the mean is similar to the error yesterday and much less than the Harrogate/Ripon snow event a few weeks ago.

 

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For me I prefer Pertubation 6:

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AROME9z ensemble freezing level uncertainty for wednesday. Very high for all central parts.

 

It will definitely turn mild for Cornwall.

That's about all we can say at this stage.

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ICON9Z freezing level vs 6Z:

Slightly more progressive on the 9Z but airmass also colder. Its enough for it to be snow rather than rain for my area.

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Interesting, as the METO have gone with a milder outlook than previously, still with the usual caveats that there may be colder outbreaks.

 

For the 29th of Jan to 7th of Feb - 'Unsettled conditions look likely to dominate for this period, with low pressure across the UK. Therefore, this should bring changeable weather to most of the country, with periods of rain, showers, and strong winds at times. While mild westerly and south westerly winds are expected to be dominant for most of the period, occasional colder northerly winds are possible.'

 

I think, that as you say looking beyond  4 or 5 days seems futile.

Have to say I'm surprised at the words in bold used by METO in describing the UK outlook to 7 February. The MO is certainly not showing a dominance mild W/SW winds for Northern England/Scotland during the period.

Unless of course it's based on data which is not publicly available?

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I confess my enthusiasm is waning - purely based on the fact that the decent charts remain at 10 days. I’m not begrudging the significant snow many have seen but on the snow free south coastal margins (and a lot of the SE) there’s only a few specific set-ups that deliver and these remain in the far reaches of virtual space. The timeframe for any influence from the recent SSW event(s) has come and soon to be gone.

Well, I have been eyeing the period around Feb 4th as a good chance at another cold blast for a few days now (since it was at T360) so they are getting a bit closer. If Feb 4th does still look promising when we get to the end of the week then we might be on course for something.

 

and re the above post by Arbroath, I was also surprised to see the mention of mild W/SW winds in the Met Office forecast. I think that line has been there for 2 or 3 days now.

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Great analysis Q, reminds me all a bit of some of the 1980's winters where surprise snow events could occur. Should be interesting to see whether the snow is any further south than Yorkshire and the north midlands.

 

ICON9Z freezing level vs 6Z:

Slightly more progressive on the 9Z but airmass also colder. Its enough for it to be snow rather than rain for my area.

ICON9Z freezing level vs 6Z:

Slightly more progressive on the 9Z but airmass also colder. Its enough for it to be snow rather than rain for my area.

Whats your thinking for central Scotland, Q? 
i’ve drew my on conclusions right enough lol

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Whats your thinking for central Scotland, Q? 
i’ve drew my on conclusions right enough lol

For the central belt it looks like 80% probability of snow vs Rain.

 

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COSMO12z is the first out

Right on the edge of marginal for parts of Yorkshire.

 

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Thanks for the superb analysis Q, it's what sets this forum apart from its rivals imo.

Meto have heavy rain here later tomorrow at 3C with temps getting no higher than 7C for the rest of the week.

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I confess my enthusiasm is waning - purely based on the fact that the decent charts remain at 10 days. I’m not begrudging the significant snow many have seen but on the snow free south coastal margins (and a lot of the SE) there’s only a few specific set-ups that deliver and these remain in the far reaches of virtual space. The timeframe for any influence from the recent SSW event(s) has come and soon to be gone.

 

https://worldclimateservice.com/2021/01/22/mjo-forecast-and-stratospheric-warming/

 

I think this link was posted over the weekend, but here it is again anyway. A very interesting read regarding the influence of  SSWs over subsequent months especially when linked to high MJO activity in the Western Pacific (currently modelled over the coming weeks).

 

Thanks for the superb analysis Q, it's what sets this forum apart from its rivals imo.

Meto have heavy rain here later tomorrow at 3C with temps getting no higher than 7C for the rest of the week.

No probs, its actually facinating to see the uncertainty so large at such a short range. Its because, I guess, a very slight difference in how the shortwave develops will have massive consequences for the temp of the airmass.

This is a perfect example of why deterministic forecasts are not good for this sort of range.

For my area tommorow there is a 33% chance of disruptive snow, 33% chance of sleety mush and 33% chance of rain and turning very mild.

If we end up with the former (but even the later) scenario there will be egg on faces for those organisations just going for the middle ground to try and cut any losses.

 

 

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The other thing I have at the back of my mind is that these sliders tend to not make as much progress NE as expected. Like on the radar tommorow morning if the rain is 50 miles further SW than expected it would have huge implications for the forecast for the rest of the day. Models will be totally useless. Just like how they were yesterday when the radar had the band further NE than expected.

 

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Interesting Quantum, many thanks, Admire your passion and optimism, would be nothing more romantic than an unexpected snowfest where the mild air is beaten away. 33% chance of something decent , is certainly worth keeping an eye on.
Surely the precpitation intensity will be key too. Alongside the uncertainty in the models above, Met Office automated based on UKV has 2c then 1c with sleet here tomorrow and sleet and rain on Thursday. It is very borderline.

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