[Model Output Discussion - A cold start to Spring?]

Latest MO thinking is of the Atlantic low sliding ESE.  Skirts with Devon and Cornwall before edging away into the Channel. 
 

Areas just north and east of a line from Bristol to Bournemouth could see a prolonged dumping with the snow possibly flirting with M4 before it moves away south.  
 

Parts of Hampshire and Sussex could see very high snowfall totals and strong winds too. 

[Model Output Discussion - A cold start to Spring?]

15 minutes ago, ICE COLD said:

Got a bad feeling the 18z is following the ECM here

if that verifies the cold will have barely reached Orkney’s by Monday.

[Model Output Discussion - A cold start to Spring?]

The cold air is coming. We just need to clear away the low pressure coming south on Sunday/Monday. 
By Monday showers IK the blue area should be snow and hail. And these will move steadily south on Tuesday.  
 

Alex Deaking had it all as rain on Sunday but I think the precip in Scotland could well be wintry by then. Especially over the hills ! 

[Model Output Discussion - A cold start to Spring?]

1 hour ago, Met4Cast said:

Cold & wintry!

Higher resolution modelling beginning to come into rang of next week now.

The December snow event resulted from a low that developed off Dorset from a line of deep convection in the Channel and spun into a shallow low that tracked east then north then north west bringing snow to the south and south east.  It’s conceivable this could happen again with cold air in situ and warmer channel waters below. 

[Model Output Discussion - A cold start to Spring?]

13 minutes ago, Singularity said:

Bit of a trend afoot to hold the main Atlantic low further west toward D10 which allows part of the major blocking high to drift back toward Iceland.

Perhaps via interplay between a new round of lagged MJO phase 7 forcing (encourages high pressure over N Europe) and downwelling anomalies from the stratosphere that keep the AO negative and allow high pressure to locate further northwest than would usually be the case.

Given I’ve long been expecting main SSW impacts by the start of 3rd week March, this is concerning for those who’d prefer springlike weather - there could be a very long spell of well below normal temps (overall day & night combined). A chance of light winds and sunshine providing respite on some afternoons, though.

Agreed. With the caveat of lows passing down the North Sea or channel lows skirting the southern most counties, high winds maybe an issue at times, accentuating the cold  

[Model Output Discussion - A cold start to Spring?]

Anywhere to the right of the red line could see outbreaks of sleet or snow on Monday from the LP moving SSE.  Central southern England could see quite a fall over the downs and chilterns 

[Model Output Discussion - A cold start to Spring?]

40 minutes ago, RainAllNight said:

I'm more worried about the dodgy EPS than the UKMO.

Someone was anticipating the fax chart for Monday earlier, here it is:

Warm sector moving down the spine of the country to the west. Thankfully it’s a reasonably small wedge. 

[South West and Central Southern England Regional Weather Discussion]

51 minutes ago, mountsbaysnow said:

Can anybody please help me understand what it is we need for it to snow in West Cornwall? 

Snow streamers coming off Pembrokeshire with a strong cold wind between North and North easterly should do the trick. 

[Model Output Discussion - A cold start to Spring?]

The 528 dam line advancing into the far north east on Sunday. Regions to the east of this line should see hail or snow in any showery precipitation.  Monday fax not out yet. So will be interesting to note how far south it moves in 24 hours. 

[Model Output Discussion - A cold start to Spring?]

There’s a lot of chatter about the sun strength and snow being unable to settle. Does anyone recall the dates in March ‘18 when the mr beast delivered a covering of snow that lasted for many days.  Solar heating did not cause snow cover to turn to slush in a matter of hours. Ultimately it comes down to the 850’s and clear very cold nights to sustain the snow cover. 

[Model Output Discussion - A cold start to Spring?]

10 minutes ago, Mike Poole said:

……..once cold is entrenched, it can be harder to shift than the models predict - will we see this?  We have some confidence we’re going cold, the question is about the longevity.

 

 

 

Until recently, I would’ve tend to have agreed with this

However, last December, the Atlantic smash the cold out of the way a little more than 18 hours. Temperatures rose, almost 20°C in some places in a matter of 12 hours or so.  
 

I cannot recall such a rapid transition on such a large scale previously, but that event left me very surprised at now. I wonder about cold longevity go forward.  

[Model Output Discussion - A cold start to Spring?]

The latest runs (wind direction likelihood chart ) show the northerly wind establishing it self on Sunday and lasting well into Tuesday. Whilst from there the winds turn southerly. It would only take a small adjustment for those winds to me more south easterly pulling in what will be a colder flow from the continent. 
green = meridional winds , blue = northerly and red = southerlies. The most recent runs at the top of the chart. 

[Model Output Discussion - A cold start to Spring?]

1 hour ago, RainAllNight said:

How's that shortwave looking?

It’s starting to enlarge on Monday. Depending on the track it could bring a lot of snow. Alternatively if the warm sector gets any larger it could be mostly cold rain.  The track if the low moving south east will be vital. 

[Model Output Discussion - A cold start to Spring?]

4 minutes ago, January Snowstorm said:

Just looking through the other models and we have significant agreement tonight on a collapse of the Greenland high by day 8/9. GFS, ECM, GEM and JMA all singing from the same hymn sheet. This is quite a large change from where we were last night!!

Quite astonishing really when you consider the background signals. As Nick Sussex would say we seem to end up with mutton rather than Lamb.

Having said all that is it the right signal or just a bump on the frosty road. As ever more runs needed

The one caveat I would raise is the models may not be handling the outcome of the SSW downwelling. And currently only showing the retrogressing HP that we’ve had close by for what seems like weeks.  As they get a better handle on it we may see another high appear on the charts which will be on the making over the coming 4-5 days.  The High you mention doesn’t disappear. It actually continues travelling NW eventually passing the west coast of Greenland. The downwelling may well reinforce the separate surface High showing later next week, over Greenland. 

[Model Output Discussion - A cold start to Spring?]

We need to keep an eye on this cheeky short wave. It’s dragging some milder air around the high, potentially squeezing through a gap between the two highs.  We don’t want it developing too much or creating a significant warm sector. 

[Model discussion highlights]

1 minute ago, RainAllNight said:

What did happen next in March 1997?

It was April 1997

Original post: https://community.netweather.tv/topic/98450-model-output-discussion-a-cold-start-to-spring/?do=findComment&comment=4813913

[Model Output Discussion - A cold start to Spring?]

1 minute ago, RainAllNight said:

What did happen next in March 1997?

It was April 1997

[Model Output Discussion - A cold start to Spring?]

Looking at the 2m surface temps for southern England the nadir of the cold next week is around Tuesday with temps climbing from Wednesday. Any battleground sleet and snow events in the south / south west and the midlands would seem to be incoming during Wednesday day time period.  And a transition to rain would depend on whether the low makes in roads over the UK or moves up the channel into Belgium and Germany.   The cold lingers a lot longer in scotland into the weekend, and I would imagine is favoured for the highest snowfall totals. 

[Model Output Discussion - moving into Winter]

It has to be said, that a long lasting easterly flow is on the cards now. And possible well into fantasy land, even beyond.  
 

It is early in the season to see such a domination of northern blocking. A pattern reinforced downstream by La Ninia. 
 

The longer this trend / pattern prevails the greater the chance of pooled air to the east becoming steadily colder. 
 

I think the week 10/ days before Christmas may well bring some unseasonably cold air.  We’ll see.

[Model discussion: Hunt for cold - into mid-January]

46 minutes ago, Anthony Burden said:

ECM going in a totaly different direction tonight collapsing the high pressure at 8 to 9days out yet 168 hrs

high pressure showing strongly to the northwest.Looks odd to me,we of course will see if correct or not 

but find it unusual to see high pressure collapsing so quickly.possible outlier.

If i am correct, were the charts not similar to this set up in the day or so before Christmas where the High Pressure slid away SE into Europe when  days earlier it had not been modelled to do so.

[Model output discussion - Christmas approaches]

2 hours ago, TSNWK said:

I actually preferred the previous run low to west looks more slider the 12z low is too round? What I’m I missing here?

Anticipating how the front may look here its most likely to take one of two paths. or elongate and split into two lows being a third possibility. If the low were to track into the southern baltic there could be some very fierce north easterlies pulling in some very cold air over most of the UK. So I wouldnt worry unduly about the low barring it moving due north into the Greenland High.

[South East, London and East Anglia regional discussion - 8th February onwards]

Radar speeded up somewhat. You can see the decaying remnants of Darcy ebbing away south. Then the first streamer to follow is incoming of the Norfolk coast. Alas it runs out of steam well before the M11. Not sure any streamer will make it even as far as London over the next day or so, unless the wind increases a lot or the winds shift to a perfect ENE.  For now things are easing in Southern Central England.

[South East, London and East Anglia regional discussion - 8th February onwards]

Temp rising from -1.9 to -0.8C.... hmmmm

[South East, London and East Anglia regional discussion - 8th February onwards]

6 minutes ago, Neilsouth said:

What radar is that? looks good!

Rain/snowfall radar

[South East, London and East Anglia regional discussion - 8th February onwards]

2 minutes ago, alexisj9 said:

Great so it's gonna rain on my ice.

The radar was showing a little bit of rain to the east just over an hour ago, but im not sure if that has made it in land now. It could fall as snizzle or ice pellets possibly ?