Model output discussion - is the beast awakening?

[kold weather]

1 minute ago, Mr Brown said:

Umm 30mm is 3cm...

 

The snow ratio is much higher, so 30mm of rain could be anywhere from 20-40cms based on the usual snow ratio.

Very rough estimate is 1mm=1cm, but usually in the UK thats a little a lower due to our air source, unless its from Europe.

[Mr Brown]

Just now, kold weather said:

The snow ratio is much higher, so 30mm of rain could be anywhere from 20-40cms based on the usual snow ratio.

Very rough estimate is 1mm=1cm, but usually in the UK thats a little a lower due to our air source, unless its from Europe.

Ahh thank you, this makes sense.

[East_England_Stormchaser91]

17 minutes ago, General Cluster said:

But that (I think) was an entirely different situation:

The air that reached us, via Scandinavia, in early January, started-out with T850s of around 20C and was progressively cooled, resulting in relatively high dewpoints; so Uppers of -7C were simply not cold enough for non-marginal snowfall;

The air we MIGHT get, next week, starts out cold and dry, and only really picks up warmth & moisture as it crosses the North Sea, resulting in very low dewpoints; and combining that with Uppers of colder than -10C, marginality shouldn't be any problem whatsoever;

And... the North Sea SSTs are lower than they were, at the very beginning of January!

Well, at least that's the way I see it!

Even with sea temps at 2-3c at most, you can still get some big sea effect snow. The German Baltic coast proved this back in 2018. Pretty sure I saw pictures of places like Lübeck and Rostock with snow up to 30-40cm deep!!

[Phil Blake]

8 minutes ago, Radiating Dendrite said:

Bit pedantic lol  

It is actually still above average for this time of year. Anyhow, -10c 850s and some instability will certainly do the trick. Some parts of the SE got 30mm of rain from the NY easterly.....it was not torrential, but just didn't stop.

30mm rain = 1ft of snow - think about that for a minute.

[john mac1]

Waiting for the ECM to come out. 
anticipating the mother of easterlies with an abundance of booms !!!

[pyrotech]

4 minutes ago, Mr Brown said:

Umm 30mm is 3cm...

 

What he was saying to you is water content of precipitation that would result in 30mm (3cm) rain falls as around 10 times as much. So 3cm rain equals around 30cm snow. its a ball park figure but most snow conversion is 8-10 x rainfall amount.

Thats falling snow not necessarily settled snow

[tight isobar]

1 minute ago, Phil Blake said:

Until the easterly is in the 48 hr window..convection and infer are pointless....pop up north sea features are a classic...in such situations....

[Frank Trough]

14 minutes ago, winterof79 said:

Delayed..... No... The days longer the sun stronger.. The paths warmer.... Can't think of owt else

Delays are never good. They are often the canary in the coal mine with modelling cold spells. 

IMBY (I’m done with being happy for everyone else this winter) a visitation from the -5 850 hasn’t really got any nearer in time since Friday. While not the only factor it’s a quick down and dirty one to use as a reference. 
 

sometimes the bigger picture and trends are missed in the clamour for detail.
 

 

[Phil Blake]

1 minute ago, tight isobar said:

Until the easterly is in the 48 hr window..convection and infer are pointless....pop up north sea features are a classic...in such situations....

I agree. 

[East_England_Stormchaser91]

Just now, pyrotech said:

What he was saying to you is water content of precipitation that would result in 30mm (3cm) rain falls as around 10 times as much. So 3cm rain equals around 30cm snow. its a ball park figure but most snow conversion is 8-10 x rainfall amount.

Thats falling snow not necessarily settled snow

Varies a fair bit on the relative water content within the snow. Drier snow equates to higher accumulations per mm/cm of rain measured. 

[MJB]

33 minutes ago, Valleyboy said:

Its not that they don't understand, its that they have been here before with models backtracking, and that often starts with the delay of any cold.  

No , that's not correct , you can't say it's a horror show because what has happened in the past - GEM isn't a horror show 

[danthetan]

1 hour ago, winterof79 said:

I really do not think that is bad at all

 

Me neither we need that low piling in from the west to shunt the meandering low over the uk east to pull the cold air westwards and prop up the block.

[Methuselah]

8 minutes ago, winterof79 said:

I get the feeling we are going to go from winter straight to warm weather akin to 2018.The warmings are going to have a longlasting effect and I think the PV will remain on a sabaticle. 

I hope it does do that, So79. As much as I love snow, during winter, I cannae stand the stuff once Spring arrives! But, in the meantime, we must enjoy whatever we get? 

Ten-foot drifts PLEASE!

[Badgers01]

10 minutes ago, Mr Brown said:

Umm 30mm is 3cm...

 

30mm of rain would give around 39cm of snow squally 

[kold weather]

4 minutes ago, MJB said:

No , that's not correct , you can't say it's a horror show because what has happened in the past - GEM isn't a horror show 

I'd say for the SE its a horror show? Literally 0 snowfall (yet alone settling!) for us down here but alot of cold rain and possible flooding. Its at best down here a 3/4 out of 10 type job sadly. Especially poor for those who have still not seen any settling snow down in some unlucky parts of the SE. Most of the south north of the M4 and west of the IoW does see some brief snowfall so its got something to look at, but its rubbish compared to what some of the models have been showing.

Again that sort of run is going to draw out alot of IMBY type posts, especially when the situation still allows decent snows further north as per the 12z GEM. I'd say for the north its more of a 8, maybe 9 out of 10 solution?

 

 

Edited January 31, 2021 by kold weather

[Methuselah]

8 minutes ago, East_England_Stormchaser91 said:

Even with sea temps at 2-3c at most, you can still get some big sea effect snow. The German Baltic coast proved this back in 2018. Pretty sure I saw pictures of places like Lübeck and Rostock with snow up to 30-40cm deep!!

Aye, of course EES... I wasn't suggesting we'd nae get sea-effect snow, just that marginality oughtn't be a problem. After all, T850s of around -10 to -12C should create an ample (>13C) SST-T850 temperature contrast?

[supernova]

8 minutes ago, tight isobar said:

Until the easterly is in the 48 hr window..convection and infer are pointless....pop up north sea features are a classic...in such situations....

 

6 minutes ago, Phil Blake said:

I agree. 

Such as a mesoscale low perhaps and that which made Jan 2010 so memorable. Good article about it here https://rmets.onlinelibrary.wiley.com/doi/abs/10.1002/wea.740

[ANYWEATHER]

Now this chart makes me shiver!!!

[Froze were the Days]

2 minutes ago, General Cluster said:

Aye, of course EES... I wasn't suggesting we'd nae get sea-effect snow, just that marginality oughtn't be a problem. After all, T850s of around -10 to -12C should create an ample (>13C) SST-T850 temperature contrast?

You're not a Scotsman living in Suffolk by any chance?...

[Man With Beard]

As we wait for what could be the defining run of the winter, a reminder: Almost none of its ensemble runs looked like the ECM op this morning by D7. In fact, more missed the easterly by getting rid of the low too quickly.

Not that this matters of course

[kold weather]

2 minutes ago, Frosty Winter said:

The Met Office are still expecting the cold solution to prevail so there’s no need to panic just yet.

To be fair even the GEM is still probably classed as a 'cold solution' for the south, its just not cold enough for snow, cold rain!

Most models look distinctly below average, very little signs other than maybe the extended 00z ECM op of anything that could be described as mild other than maybe Wednesday-Thursday for the south.

[Methuselah]

1 minute ago, Froze were the Days said:

You're not a Scotsman living in Suffolk by any chance?...

Noooo... I'm a born and bred Sassenach who spent more that 20-years living in the Highlands. Hootsmon!

[Gary L]

No idea why people are negative. I'd bank the latest runs!

[AFCBSNOW]

3 minutes ago, kold weather said:

To be fair even the GEM is still probably classed as a 'cold solution' for the south, its just not cold enough for snow, cold rain!

Most models look distinctly below average, very little signs other than maybe the extended 00z ECM op of anything that could be described as mild other than maybe Wednesday-Thursday for the south.

Ironically, ground level temp in Bournemouth is 2c lower today than forecast.  I don't think the models have a handle on the anything real wold at all.

[Cold Winter Night]

Ahead of the EC 12z, my take of the models so far:

GFS+GEFS pretty good.
GFS // alright.
GEM is like yesterday's EC12z and goes to the naughty corner.
UKMO, not a downgrade, as some see it. Perhaps even an upgrade.

Yes, that low is further North, but its alignment brings in an Easterly flow. But don't just look at that one low in our vicinity, look further upstream. Especially in the West Atlantic sector it moved away from EC 0z.

EC 0z and UKMO 12z at 144h. 12 hrs apart, but still, they are not that much alike IMO.

So on the EC 12z, look at that area too. New WAA may start there, perhaps related to that delayed easterly some are talking about?