Model output discussion - deep cold inbound?

[Maidstone marginal]

11 minutes ago, Maidstone marginal said:

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

That's good for east kent. So folkestone and the hills behind may yet take the sweet spot 

[kold weather]

Wednesday could be an exceptionally cold day looking a the latest models. Winds may start to bend a little more ESE by that point ahead of any diving low, and under any snow cover and 850hpa profile around -10/11c.

Depending on cloud cover levels we could well end up seeing -4c and -5c, and even without snow cover -2/3c looks reasonable.

Just for reference, thats similar levels to the BFTE 2018, but without the -16/17c isotherm at 850hpa!

[geordiekev]

33 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. 

An example, below from last year, in a Northerly flow, which although there was no moisture laden low pressure system the long draw of cold wind down across warmer waters generated a stream of showers (which often hit land at the same localised point) for extended periods of time.

Precisely why watching the radar with wind vectors turned on is so fixating 

Edited February 5, 2021 by geordiekev
2019, not last year

[Fourty Point Three Degrees]

26 minutes ago, Frosty the Snowman said:

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. 

 

23 minutes ago, Battleground Snow said:

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

Well thankyou very much for the explanations. 
Sounds like a decent snowfall can come in from either way. 

17 minutes ago, East_England_Stormchaser91 said:

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 

 

15 minutes ago, Snowman. said:

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.

 

14 minutes ago, Mike Poole said:

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..... 

Well thankyou very much for the explanations. 
Sounds like a decent snowfall can come from either way. 

Edited February 5, 2021 by 38.7°C

[Snowman.]

Just now, 38.7°C said:

 

Well thankyou very much for the explanations. 
Sounds like a decent snowfall can come in from either way. 

 

 

Well thankyou very much for the explanations. 
Sounds like a decent snowfall can come from either way. 

They can.

But are very hard to model and predict. If one does set-up the MO warnings are likely to come in quickly.

 

[SnowLover87]

23 minutes ago, Man Without Beard said:

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 )

I agree.  This is nota Beast from The East.  Watch this space.  Going to disappoint many including me. BBC pickling up on it. 

[Snowman.]

I will say this as a passing comment.

The GFS currently has more snowfall for the weekend/early next week here than the 2018 BFTE.

2018 GFS never predicted more than 10cm here ended with 20cm or more, people like @Southender could back this. Just bare that in mind.

Either way it's going to be an interesting weekend.

[Nick L]

A fair few off topic posts hidden. Streamers are a very relevant and interesting topic for the upcoming spell, but might be best to create a thread elsewhere and keep this reserved for model discussion please!

[SLEETY]

Some of the charts look like 1947 redux,amazing to think we have got to something similar this winter . Going to be fun watching low pressure and how it interacts with the cold block over the UK,, think we will see some fierce blizzards as the low attempts to break down the block,won't break down like gfs is showing,that is a certain, wouldn't surprise  me, if the cold stays in place for at least next week. 

[Daniel*]

2 hours ago, Eastbourneguy said:

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.

 

That wasn’t quite the reality the 28th February 2018 was by far my snowiest day in my part of London 2 miles east from Tower Bridge, Wednesday morning had a serious dumping some of heaviest snow I’ve seen dropped 5-8cm in less than a hour. Oddly showers through Estuary aligned much more like there was an easterly than an eastsoutheasterly which I’ve always known to be dry. I think the upper flow was different to surface flow it’s not as easy to interpret as you think. 

 

Edited February 5, 2021 by Daniel*

[Maidstone marginal]

I'll get shot down. But only when north France joins in to the game Will I have any confidence  regarding areas south of Luton 

[Matty-H]

2 hours 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.

Great post, even if only to highlight how unreliable snow accumulation charts are. I remember when we were first introduced to Euro 4, or it’s previous name, and it appeared to be on the money time after time. Was more of a phase really. The cold is locked in early doors. Once we get to Saturday night let’s play fax charts and radar. Buckle up. 

[Eastbourneguy]

16 minutes ago, Daniel* said:

That wasn’t quite the reality the 28th February 2018 was by far my snowiest day in my part of London 2 miles east from Tower Bridge, Wednesday morning had a serious dumping some of heaviest snow I’ve seen dropped 5-8cm in less than a hour. Oddly showers through Estuary aligned much more like there was an easterly than an eastsoutheasterly which I’ve always known to be dry. I think the upper flow was different to surface flow it’s not as easy to interpret as you think. 

 

I should probably have referred to kent and sussex instead of the southeast as a whole haha! Those showers start bang on north of  Kent when the sea track becomes larger. 

Edit: It is definitely odd how the furthest south streamer is pretty much easterly orientated as you said, while the ones further north are definitely ESE!  Good old weather.

Edited February 5, 2021 by Eastbourneguy

[Snowman.]

Very low MSLP on the Icon.

Decent convection off that defo.

[Daniel]

Low a lot more south on the latest icon allowing the easterly to continue upgrade! Good start 

[Snowman.]

Direct convective Easterly

[Snowman.]

Wedge low is beginning to elongate.

[Daniel]

Wednesday would be freezing across the whole country! Slack easterly winds with widespread -10 uppers brrr!! 

[Snowman.]

Scanid wedge, shortwave south. Some trough disruption, cold air still across a decent chunk of the UK.

Hmm

[Kasim Awan]

GFS & ICON have both stepped up the depth of the SE low on Sunday.

[Snowman.]

0z gone further north with the mild sector.

 

[Snowman.]

UKMO is a peach.

 

[Daniel]

More of a direct easterly on 0z gfs rather than a NE tilt so uppers aren't so cold down south but cold enough for snow 

[Snowman.]

1 minute ago, Daniel said:

More of a direct easterly on 0z gfs rather than a NE tilt so uppers aren't so cold down south but cold enough for snow 

8th 13.00

Very cold.

[Daniel]

The low is a little bit futher north aswell so has a little more influence across the far south.