Model output discussion - deep cold inbound?

[Kasim Awan]

P17 is a winner

[Scott Ingham]

1 minute ago, Paul T said:

Reading many posts, I think many have read Scotts post like those totals are by Sunday...as he references the stalling front on Sat night/Sunday (bold in quote). However, they are to Close of Play Tuesday and i guess that front is specifically reference as a significant contributor to those numbers

Thank you my post is taken out of context and i dont claim im going to be right but im being brave and making a call

[danm]

1 minute ago, Kasim Awan said:

In 2010 the models were going for 10-15cm

Quite a large area outdid those totals

Streamers can cover hundreds of square miles

Anyway I agree, best to leave the snow forecast discussion for now

I get both sides of the argument. If we were issuing a formal forecast we wouldn’t say a foot of snow. If people are discussing possibilities in a weather forum based on the expected parameters and past events, then a foot in a few localised places can’t be entirely ruled out, but more likely is a wide expanse of the east seeing in the range of 5-15cm up to Tuesday, localised areas seeing more, with battleground snow taking over from the west Wednesday onwards. 

[radiohead]

19 minutes ago, Kasim Awan said:

GFS snowfall accumulations initialized on 26th February for 28th Feb midday. Boy were they underestimations @Scott Ingham

Looking back at 2018, this was the GFS snow prediction just before Storm Emma, which  actually produced an offical snow depth on the level of up to 69cm in the east of Ireland and drifts of up to 7 meters in places there due to strong winds.

Edited February 4, 2021 by radiohead

[Eastbourneguy]

With regards to instability, I would say in basic terms we have the SLP being much lower than 2018 in the southeast, for when the flow was a more favourable ENE direction. Pressure was 1030/1025 hPa when there was decent sea track (though a slack flow).

2018

Once the flow became much stronger as the pressure dropped, the ESE nature of the flow killed much of the convection from the shortsea track in the SE.

Incredibly cold 850s, but too dry a flow now. 

Comparing now to 2010 for the southeast is probably a closer match.

 

This brought a foot of snow to Eastbourne and much of Sussex I believe, with some very so so, 850s, showing why they are not the be all and end all! SSTs being very high in December probably aided the convection in this case.

Back to current prospects...

Talking more about the north now, while the depth of cold is not as strong as 2018, the SLP is around 10/15 hPa lower, which will aid convection here.  (There is of course much more to look at when thinking about convection).

I think talking about amounts beyond using the word significant is probably wrong at this time. However, how many times in the past have we seen dry easterlies forecast and people have to be reminded that the models aren't going to resolve convective showers very well at that time frame. Currently, the GFS, UKV and EC are modelling reasonable totals in the east for many, from purely parameterized convective processes.  We shall see what the high res models think soon, and even they won't get it completely right!

Good night everyone!

 

Edited February 4, 2021 by Eastbourneguy

[Maidstone marginal]

14 minutes ago, Scott Ingham said:

Where did i quote sunday??

I said somewhere in that huge area by tuesday pm??? 

You telling me not one street will hit 30cm in the south east by tuesday pm?

Because i am certain one area will

One area in yorkshire will hit 20cm

One are in the midlands will hit 20cm

I respect your opinion but to ridicule mine is a tad premature in this set up

Forum do me a favour and if you hit any of these amounts by tuesday pm private message me

For the south east. I'm taking a punt that Lenham in mid Kent with a bit of altitude stands a chance of 10 cm

[Jarrow Posh]

17 minutes ago, Mike Poole said:

Me as well, TEITS ( and have liked your posts ever since i started following this thread in 2011). Given the output now, you would have to say no to the GFS, it is just not consistent with itself or with any other signal.  I think you mentioned a couple of days ago that the easterly would be in earlier if it was to happen, well it will happen, and it is in earlier.  Saturday is the start...

I remember it well TEITS.heaviest snow I've ever seen.Will be interesting to see how well the HRes models do in picking up on the convective showers an possible streamers this time round.All eyes will be on the radar from Saturday PM for me.

Edited February 4, 2021 by Jarrow Posh

[john mac1]

15 minutes ago, Paul said:

Come on folks enough of the willy waving, it's not a competition...

My daughter always uses that phase as she works with a load of Middle Aged blokes!

[Penrith Snow]

Wow, GFS 18z goes from Blizzard to Bartlett in FI.

I am ignoring it, anything beyond 144 in this set up is chicken fodder.

Andy

[Snowman.]

7 minutes ago, radiohead said:

Looking back at 2018, this was the GFS snow prediction just before Storm Emma, which  actually produced an offical snow depth on the level of up to 69cm in the east of Ireland and drifts of up to 7 meters in places there due to strong winds.

At the mouth of the thames. I had 20CM plus.

One shower gave me 5cm, convection will play a big part.

BUT, the MSLP was signifcantly lower in 2018 at the same. Judging snow calls this far out is only going to lead to anger and tears. Best thing to do is just observe.

[marksp]

10 minutes ago, Kasim Awan said:

In 2010 the models were going for 10-15cm

Quite a large area outdid those totals

Streamers can cover hundreds of square miles

Anyway I agree, best to leave the snow forecast discussion for now

Some of the comments about streamers etc,ect are spot on. posted in here a few years back and JH can confirm, midnight 2cms, 6.30am we had 35cm everywhere, 42cm on back yard

and in the garden topped out at 56cm, whilst in Chesterfield 10 miles NE there was 10 to15cm , JH said Donny area had 5 to 10, whilst in Derby City 5cm. 

It seems a Humber streamer set up and once in land a NNE wind directed it over this area. The band of ppn was only30 miles wide but kept on giving. When streamers get going they are magnificent, the current models show plenty of scope for these,.

it was December 1st sons birthday, I told him it was a rare thing that schools would be shut on 1st Dec because of snow (cannot remember year but will look at archive charts)

[samadamsuk]

GFS 18z looks pretty good to me - yes the HP fetch turns milder after a while but that troublesome low in a weeks time gets wiped out by the block and we get dumped on in the process... 

[jacke]

33 minutes ago, TEITS said:

Sometimes you need to use instinct and experience rather than simulated models. I have a very good idea of snowfall distribution across my area under the conditions suggested by the models for next week. Never forget how in the 80s an E,ly brought 1ft of snow in Peterborough in under 2hrs from a band of snow showers.

At times we can become too dependant on computer models. For example I just knew the GFS was way off with its handling of the low for this weekend. At one stage it even had the low move NW to Iceland against the huge block to our N. Instantly I knew this was wrong.

Yes TEITS and is just 20 miles South had about 3 inches. Incredible difference in 20 miles. Streamers and showers impossible to predict, just now watching. How do you average it out over a region I ask?

[Livet Laddie]

14 minutes ago, That ECM said:

Someone will definitely post 40cm depth cause most can’t measure snow depth and bend the measure

Well, we need another 7 cm then....We have had snow on the ground since 23rd December. ! Models from now on showing streamers and instability for many on the eastern side of the UK. Looking at how it will pan out....up here we will experience higher pressure from Monday/ Tuesday so that will kill or suppress shower activity and allow winds to calm. Expect severe frosts/ Ice Days where this happens over snowfields

[Mapantz]

Model discussion please..

If you want to continue with the general chat, head over to here:

 

[londonblizzard]

GFS op not without GEFS support and doing what a cluster of perturbations has been doing for a number of runs now.

Just incredible the amount of scatter still there for southern england, a 9.5°C range at T60. Probably represents both the fine margins involved in regards to the position of the low as well as the GFS's inability to handle it.

[Guest]

1 hour ago, Eastbourneguy said:

Meanwhile, over the pond...

 

Back to the UK... 3/4 days of a potent easterly followed by war with the Atlantic. I don't think anyone can ask for too much more!

ps: For cold and snow lovers anyway!

Lol - -36c 850s at the same latitude at Rome pretty much..

[Fourty Point Three Degrees]

Can someone explain what are "streamers" and "sliders"? As i see them mentioned a lot in here. Thankyou. 
I'm more of a summer person than a winter person so i don't know these words when following winter charts. 

[Frosty the Snowman]

7 minutes ago, 38.7°C said:

Can someone explain what are "streamers" and "sliders"? As i see them mentioned a lot in here. Thankyou. 
I'm more of a summer person than a winter person so i don't know these words when following winter charts. 

A streamer is a replenishing line of showers coming from the same initial disturbance out at sea (the North Sea in this case) often creating near constant barrages of precipitation for areas in their line of sight (in this case an East to West line across the country). They can be extremely localised though compared to a low pressure system which generally has a wider area. 

[Maidstone marginal]

Remember that the surface winds don't follow the isobars they are always directed a few degrees of the compass left. So there for the wind will be rather more north east  and north/North East than some may think

[Battleground Snow]

14 minutes ago, 38.7°C said:

Can someone explain what are "streamers" and "sliders"? As i see them mentioned a lot in here. Thankyou. 
I'm more of a summer person than a winter person so i don't know these words when following winter charts. 

A snow streamer  is  heavy, localised snowfall that occurs when cold winds move over relatively warmer water

A slider is when a low pressure hits a high pressure block and slides down the block or goes under completely

Edited February 5, 2021 by Battleground Snow

[Man With Beard]

43 minutes ago, Penrith Snow said:

Wow, GFS 18z goes from Blizzard to Bartlett in FI.

I am ignoring it, anything beyond 144 in this set up is chicken fodder.

Andy

This type of thing is in the ensemble spread though, believe it or not. East Anglia would go from 17 F to 17 C in 4 days! (Perhaps not many will agree with me but I'd quite like that )

[East_England_Stormchaser91]

22 minutes ago, 38.7°C said:

Can someone explain what are "streamers" and "sliders"? As i see them mentioned a lot in here. Thankyou. 
I'm more of a summer person than a winter person so i don't know these words when following winter charts. 

A few have beat me to it, but yes, a streamer is almost like a train of showers in a concentrated area, which can then alter relative to wind direction.

A Thames streamer affects central London, Heathrow, Slough, Reading on a direct easterly. N Kent, South London, Surrey and Hants, even down to the Solent/IOW out into the Channel on an ENE flow, and then North London, S Herts, Bucks on an ESE direction (rarer than the former). 

A slider is an area of low pressure that elongates against a block of cold or high pressure and sinks away usually SE from initially heading east. A front of snow that is stagnant is usually the result 

Edited February 5, 2021 by East_England_Stormchaser91

[Snowman.]

8 minutes ago, 38.7°C said:

Can someone explain what are "streamers" and "sliders"? As i see them mentioned a lot in here. Thankyou. 
I'm more of a summer person than a winter person so i don't know these words when following winter charts. 

Sliders - A low pressure system that travels under a block, usually N or NE. Cold air is usually in place and as the mild air makes inroads usually leads to heavy snowfall upon the front edge.

Streamers - A continous area of shower activity that goes penetrates deep into the country that due to winds changing very little will lead to long amount of time under precip. In Easterlies they have been responsible for large totals due to heavy showers over many hours.

[Mike Poole]

2 minutes ago, 38.7°C said:

Can someone explain what are "streamers" and "sliders"? As i see them mentioned a lot in here. Thankyou. 
I'm more of a summer person than a winter person so i don't know these words when following winter charts. 

Yes, hi @38.7°C, i will try!  Streamers are lines of convective snow activity like storms in summer, exactly the same rules apply - a temperature differential , caused by convection, but in winter is convection because of a warm sea under very very cold air ( as will be the case by the weekend).  They form lines similar to squall lines in the summer. 

A slider is an Atlantic low that instead of going across the UK, or Scotland, instead slides under a high pressure cell and goes south of the UK. 

All these things are in play at the moment.....