Model output discussion - Winter has arrived

[SLEETY]

Poor performances by the ukmo if we look back to yesterday, now it's trying to get the low to go under the high and not through it like yesterday. Looks like the BBC forecast was wrong to just use the met computer model when they gave their long range forecast yesterday. Another long range forecast of meteogroup goes down the pan, lol

Edited December 5, 2020 by SLEETY

[Kentish Snowman in Yorks]

2 minutes ago, northwestsnow said:

For comparison...

Yesterday's ukmo 12z 144

This morning at 120...

Massive difference there!

To be fair that UKMO 144 chart from yesterday didn't look right to me.  That's not to say it won't revert back later but I do think today's UKMO 120 chart is closer to how things will pan out with the high to our East if anything strengthening and pushing West and sliders being the order of the day (week).

[northwestsnow]

7 minutes ago, Kentish Snowman said:

Massive difference there!

To be fair that UKMO 144 chart from yesterday didn't look right to me.  That's not to say it won't revert back later but I do think today's UKMO 120 chart is closer to how things will pan out with the high to our East if anything strengthening and pushing West and sliders being the order of the day (week).

Precisely why I didn't like yesterday's UKMO run...

144 this morning looks knife edge and certainly a chart for more knowledgeable than myself...

[West is Best]

18 minutes ago, SLEETY said:

Poor performances by the ukmo if we look back to yesterday, now it's trying to get the low to go under the high and not through it like yesterday. Looks like the BBC forecast was wrong to just use the met computer model when they gave their long range forecast yesterday. Another long range forecast of meteogroup goes down the pan, lol

Well it will be interesting to see if the ECMWF also backtracks. If it does then I'd be more inclined to agree but I'm also awaiting the GFS 0z ensembles. For the last 4 runs the operational has been below the mean, even an outlier at times, with far more ensemble members taking the Atlantic pile through route. That's also what the T120 Fax chart shows and it's a brave person to bet against that at this range.

 

Generally speaking if things appear to be on a West vs East knife edge then 19 times out of 20 you need to bet on the Atlantic to win out. It's the prevailing condition and it requires several upstream and downstream cards to fall right for a proper block to occur. I don't really see it happening at the moment.

Edited December 5, 2020 by West is Best

[West is Best]

7 hours ago, damianslaw said:

Last night and today proof once again if needed you don't need very cold uppers to produce snow, indeed most of our snow comes in very marginal situations, fine margins. 

You do need cold uppers for snow. What was 'produced' yesterday was mostly rain and sleet, especially at low levels. Many of us on here remember the days when snow would fall consistently out of the sky and pile up sufficient snow to wade through and sledge in, even in early December. That's snowfall and you roughly require -5C 850hpA for it to occur in the UK at low altitudes. 

[Daniel*]

5 minutes ago, West is Best said:

Generally speaking if things appear to be on a West vs East knife edge then 19 times out of 20 you need to bet on the Atlantic to win out. It's the prevailing condition and it requires several upstream and downstream cards to fall right for a proper block to occur. I don't really see it happening at the moment.

But you never do no matter what, you are west is best after all. 19 times out of 20 things don’t look like this. It all rests on the positioning of block can it back enough west ect. We have low heights in Europe, no crazy vortex in way, and a not very active Atlantic the chances are raised.  

[Radiating Dendrite]

Just now, Daniel* said:

But you never do no matter what, you are west is best after all. 19 times out of 20 things don’t look like this. It all rests on the positioning of block can it back enough west ect. We have low heights in Europe, no crazy vortex in way, and a not very active Atlantic the chances are raised.  

Yes, would be nice for some to change the record a little. 

In terms of blocking, I've seen the models underestimate just as much as they can overestimate. 

[KTtom]

Still stuck in a bit of a stalemate at the moment, neither particularly cold or particularly mild, personally cant see the pattern changing for the foreseeable... if the pattern were a net weather member it would be called Crewe is Best!

Ukmo 144 and maybe a glimmer of hope that the forming scandi high can seperate from the Russian version allowing colder uppers to dig south on its eastern flank?

 

Edited December 5, 2020 by KTtom

[snowlessayr]

1 hour ago, West is Best said:

You do need cold uppers for snow. What was 'produced' yesterday was mostly rain and sleet, especially at low levels. Many of us on here remember the days when snow would fall consistently out of the sky and pile up sufficient snow to wade through and sledge in, even in early December. That's snowfall and you roughly require -5C 850hpA for it to occur in the UK at low altitudes. 

you do not need -5 at 850hPa, here just off the west coast of Scotland we got couple of inches yesterday. I haven't had lying snow here since 2018, this was from -2 or -3 upper air temperatures. The vast majority of big snowfalls come from slider scenarios which most don't have -5 upper air temperatures, you just need the flow off the right wind direction. if we always need -5 at 850hPa, then we would get nowhere near as much snow as we receive during winter which granted usually isn't much anyway

Edited December 5, 2020 by snowlessayr

[West is Best]

8 minutes ago, snowlessayr said:

you do not need -5 at 850hPa, here just off the west coast of Scotland we got couple of inches yesterday. 

I was referring to England. Scotland is sufficiently far north for the same rules to be a little less rigid.

Edited December 5, 2020 by West is Best

[West is Best]

42 minutes ago, Daniel* said:

But you never do no matter what, you are west is best after all. 19 times out of 20 things don’t look like this

This is completely untrue. I can ramp like the best if I think there's something worth ramping. The synoptics are far less dramatic and exciting than many I've seen in FI over the past decade. I can recall FI eye candy with -10C 850 hPa uppers all across the UK and true deep cold pooling over Europe. We have neither. Some transitory blocking occasionally showing. Meh.

I've been watching the ensembles carefully and the GFS operational have been on the cold side, sometimes by a long way, over the past 4 runs. However the 0z has bucked the trend. The most interesting thing about this, however, is the amazing scatter at Day 5. You see this often in FI but for just T120 it's amazing to have a 25C scatter. Quite incredible. It's a long time since I've seen such divergence at such short range:

 

This helps explain why the UKMO may have appeared to have altered its tune, why their 0z model output diverges so significantly from their Fax chart at the same T120 point and why the ECM is having none of it:

 

As I say, 19 times out of 20 in these situations always bet on the Atlantic winning. Once in a while it won't but generally it does.

[Captain Shortwave]

A rather messy set of charts this morning with a split flow most favoured close to the U.K. towards the end of next week. Better than the realignment of the jet proposed a day or so ago where south westerlies would push through the U.K. and into Scandinavia.

ECM day 7 looks like a possible frontal snow event as 850s on the northern flank are around the -4 to -6c range with a surface flow off the continent.

 

 

only for observational purposes at this point. 

 

 

Edited December 5, 2020 by Captain Shortwave

[West is Best]

46 minutes ago, Radiating Dendrite said:

Yes, would be nice for some to change the record a little. 

 

The record isn't mine, it's the prevailing westerly flow under which the UK sits. So 19 / 20 it's the record player which plays the same disc.

Have a good day all.

 

[swfc]

Morning not been around for a week for health reasons but anyway. Was hoping to see Steve Murrs easterly on the models. Saw some snowflakes yesterday which is more than last winter in total. Looking at nhp not a. Lot of great interest for low ground. Looks cold and dank this weekend then unsettled and wet next week. Not sure if there's anything been added in regard to back ground signals - nao or the like. 

[That ECM]

Nice looking output from ECM this morning.

Edited December 5, 2020 by That ECM

[SMU]

Morning.

A full on 24 hour 100% transformation from the ECM ( & to be fair UKMO )

168 today very cold surface Easterly 

 

 

Edited December 5, 2020 by Steve Murr

[SMU]

3 minutes ago, swfc said:

Morning not been around for a week for health reasons but anyway. Was hoping to see Steve Murrs easterly on the models. Saw some snowflakes yesterday which is more than last winter in total. Looking at nhp not a. Lot of great interest for low ground. Looks cold and dank this weekend then unsettled and wet next week. Not sure if there's anything been added in regard to back ground signals - nao or the like. 

Its still there > all be it not massively cold uppers- More swing to cold today though especially ECM & UKMO

[swfc]

4 minutes ago, West is Best said:

The record isn't mine, it's the prevailing westerly flow under which the UK sits. So 19 / 20 it's the record player which plays the same disc.

Have a good day all.

 

I'd agree with you wib. The build up of cold to the east does seem to be a major problem plus getting it to back west. It used to be said "et the cold in first" and the snow will follow. This is true but a bit elusive for decent snowfall on low ground in my location

[swfc]

4 minutes ago, Steve Murr said:

Its still there > all be it not massively cold uppers- More swing to cold today though especially ECM & UKMO

Indeed Steve just lookedanythoughts on it building going forward. Tia

[swfc]

Nothing major but better Heighths on ec towards Iceland be it day ten. 

[Kentish Snowman in Yorks]

1 hour ago, West is Best said:

You do need cold uppers for snow. What was 'produced' yesterday was mostly rain and sleet, especially at low levels. Many of us on here remember the days when snow would fall consistently out of the sky and pile up sufficient snow to wade through and sledge in, even in early December. That's snowfall and you roughly require -5C 850hpA for it to occur in the UK at low altitudes. 

-5 air can be used as a general rule for snow but we in the UK especially England can get huge dumpings of snow from air only just below freezing at 850 level provided we have a cold continental feed.

Likewise -5 air doesn't sometimes cut it for low ground if the air is more Atlantic sourced?  You would probably need more like -8 or -9 for snow to stick significantly at low levels under that scenario?

I do agree though at the moment we are just trying to eek out the best possible position snow wise from what is synoptically quite conducive to snowfall in the UK but in reality is not so good due to the general lack of cold pooling in Europe.

That said the UKMO and ECM at least keep us in the game in the medium term this morning.  The weak PV and quietish Atlantic are certainly allowing that Russian High to influence our weather for the foreseeable.  Fingers crossed for more upgrades later

[carinthian]

Morning all, cold lovers have reasons to be joyful this morning. All main models have put the break through of the Atlantic back towards the end of the medium term forecast period( 6-10 day) . Thats all ways a good sign. The picture below from ECM shows a build up of upper height values towards the Greenland Sea area with the Russia block still in place. As time goes on the surface cold and lower layers will only get colder in NE Europe and should even help to strengthen heights. How will this to affect the weather for the British Isles during the coming week I ask ? The view from a foreign field is still 60/40 in favour of extension of the colder conditions lasting in your part of the world. Its towards next weekend that a more active front comes up against the colder block that could become interesting but out of reach of most snow prediction models but certainly the risk of snowfall remains in the developing stand off (ie ) Atlantic v Russian  and you guys in the potential battle ground.

C

 

 

Edited December 5, 2020 by carinthian

[syed2878]

1 hour ago, snowlessayr said:

you do not need -5 at 850hPa, here just off the west coast of Scotland we got couple of inches yesterday. I haven't had lying snow here since 2018, this was from -2 or -3 upper air temperatures. The vast majority of big snowfalls come from slider scenarios which most don't have -5 upper air temperatures, you just need the flow off the right wind direction. if we always need -5 at 850hPa, then we would get nowhere near as much snow as we receive during winter which granted usually isn't much anyway

 scotland get more snow in winter most years even in the most crappy winters day have snowfall at least once so it’s nothing unusual you had lying snow yesterday

[mountain shadow]

The question I have is  where is the really cold air?

By mid month the Russian high will have been in place for about a month and a Southerly jet stream with low pressure into Southern Europe. The British Isles will have been on the cold side of the jet for a considerable period. 

Yet, the air in Europe is still only cool as opposed to cold and the really cold air still 1000 of miles away. 

 

[tesaro]

2 hours ago, West is Best said:

You do need cold uppers for snow. What was 'produced' yesterday was mostly rain and sleet, especially at low levels. Many of us on here remember the days when snow would fall consistently out of the sky and pile up sufficient snow to wade through and sledge in, even in early December. That's snowfall and you roughly require -5C 850hpA for it to occur in the UK at low altitudes. 

Here in lowland West Suffolk 4cms of lying Snow from uppers barely scraping -4. We were forecast Rain with the possibility of a few flakes mixed in. If Lows continue to slide under the huge Russian Block, scenes like this will become more widespread.