Model output discussion - mid-winter

[carinthian]

My experience of previously living in the NW of England has seen snow falling and holding at lower levels for more than just a few hours in a similar weather type . Night time hours are still long and will keep snowfall. I have seen 10 inch falls produced by convective cells aligning the Cheshire Plain with even higher DPs than forecast for next week.

C

[andymusic]

3 minutes ago, karlos1983 said:

there's an echo in here today 

That runner that develops and crosses the UK at around +126 would be rain for most imo. But it is a long way out, could miss the UK altogether or disappear on the next run (less likely).

double click issues - sorry - and i'm a sound engineer too know all about delay/reverb lol - anyway back to models - whole week of wintriness so far on this run - gonna be very cold

[tight isobar]

Upcoming cold spell...

The gift that keeps on giving!!!

-8 minima extensive...

As the north/north easterly-easterly sets up.

Walikng into a winter wonderland is becoming high in the stakes..  

Gfs 6z...

Edited January 12, 2018 by tight isobar

[Mr Frost]

2 minutes ago, Nick F said:

Over 200m? Just elaborating more on what I included in my last post that those lower level areas where continuous snow showers fall in the WNW flow, i.e. western and northwestern coastal areas, or inland areas affected by streamers such as through central belt of Scotland may see snow accumulate to decent depths due to the temperature kept low by the continuous snowfall.

 

Spot on Nick.

I am based in West Central Scotland and Metoffice are going for 5cms for low ground on latest weather warning for Monday night through Tuesday. (See attached) 

 

 

[Singularity]

9 minutes ago, Nick F said:

Agree, although dew points looks low enough for snow to fall to lower elevations in any showers, the surface temperatures in such a long-track and strong maritime polar flow will be too high to support sustained snow cover away from higher ground or where snow showers are continuous. Would need a low/wave to bring a prolonged fall of snow to lower the ground temps then winds to fall light following the clearance of the low/wave, but that looks unlikely in such a mobile/strong WNW flow. But I think many will see snow falling, but any accumulations temporary and slushy away from high ground.

It sounds very much like many cold spells tend to be in March down this way; snow falls, it starts to settle and you begin to wonder, then it stops and the tufts of white among the grass are gone within the hour.

 

LP just south of Svalbard being put to use although it could do with tracking south through the UK with ridging building in behind ... picky I know 

[Rickoza]

5 minutes ago, Mr Frost said:

Where are you, I'm in Bellshill and thoroughly fed up with the past few years of heavy snow forecasts and it then just goes south and north of here.  It's a weird bit this, the Clyde Valley, even thunderstorms give us a wide berth.....-).  Hoping this time it at last goes right!

Spot on Nick.

I am based in West Central Scotland and Metoffice are going for 5cms for low ground on latest weather warning for Monday night through Tuesday. (See attached) 

 

 

 

[Nick F]

06z GFS continuing the protracted cold outlook, we still get the amplification from upstream from around day 7 which allows a ridge to build north toward Iceland next weekend and results in a N or NEly flow, -10C T850 into Scotland by day 10. GFS breaks down the cold from the west thereafter, but in low res, so wouldn't worry at that range, particular given ens support for ridging to maintain near Iceland area out to day 15. 

[Man With Beard]

EC clusters starting to get behind the op run solution - not as amplified as some have been, but still with a tinge of wintryness as a flow from Iceland sets in for a day or two:

Beyond D11-D15 we have dreaded one cluster scenario, which as usual, upon inspection of the members on weather.us, means next to nothing. My feeling from the individual members is a period of Wlys or SWlys D11-D13 seems most likely (which does tie in with the one cluster given), but D14 onwards sees pressure rises in various places and I suspect favouring a pressure rise through the N Atlantic once more, and some members also having ridges far to the north too - a few runs link the two up. 

 

[bluearmy]

35 minutes ago, frosty ground said:

At the risk of being a little silly where are the post showing low level on shore snow cover?

I don’t mean near the coast - I mean areas which have no upland between them and the coast 

if I posted the posts saying how snowy next week is going to be I would use the next 2 pages up!

streamers (as nick mentioned) can’t be discounted but they will be localised 

[Snowmadsam]

I wonder how many people will be tuning into the 12z’s now. Need that runner low flatter and further south IMBY ???

otherwise looking soooo interesting 

[andymusic]

10 minutes ago, Nick F said:

06z GFS continuing the protracted cold outlook, we still get the amplification from upstream from around day 7 which allows a ridge to build north toward Iceland next weekend and results in a N or NEly flow, -10C T850 into Scotland by day 10. GFS breaks down the cold from the west thereafter, but in low res, so wouldn't worry at that range, particular given ens support for ridging to maintain near Iceland area out to day 15. 

agreed - I think the cold is locked in for the forseeable

[Glacier Point]

3 minutes ago, Man With Beard said:

EC clusters starting to get behind the op run solution - not as amplified as some have been, but still with a tinge of wintryness as a flow from Iceland sets in for a day or two:

Beyond D11-D15 we have dreaded one cluster scenario, which as usual, upon inspection of the members on weather.us, means next to nothing. My feeling from the individual members is a period of Wlys or SWlys D11-D13 seems most likely (which does tie in with the one cluster given), but D14 onwards sees pressure rises in various places and I suspect favouring a pressure rise through the N Atlantic once more, and some members also having ridges far to the north too - a few runs link the two up. 

 

There is a suspicion here, advertised by the 06z GFS op, that the extended range modelling will be subject to the (false) tropical forcing signal, but which will not tend to get this beyond the day 8-10 range as the extratropical / tropical interactions become apparent to NWP.

Phase 5 of the MJO is where the modelling will want to go, but this idea of ridging to out south is false IMHO.

[Frosty.]

Interesting to see the upcoming changes  in the jet stream between what we have now and what we can expect next week on the Gfs 6z which is a dramatic change from the generally quiet murky dank weather to a much colder / stronger polar sourced air mass bringing cleaner, clearer air to sweep away the filthy murk! I'm really looking forward to next weeks cold blast and potential snow!

Quote

 

Edited January 12, 2018 by Frosty.

[MattStoke]

1 hour ago, stewfox said:

Are you basing that on the 850s ? Or historic NW'ly that have delivered much more ?

I think people can say what they want but there are some folks who just post for a reaction. So would be interested in why you feel ?

""Just can't see how it's going to be the most potent NW'ly in many years, that's all."

 

Less cold uppers and surface temperatures higher.

-5 uppers widely, -6 to -7 in some spots. Compared to -8 to -10 widely in December.

Surface temperatures widely above freezing (around 3-5 degrees for most). Compared to places struggling to get much above freezing in December.

Looking like snow to low levels will be marginal and dependent on timing and evaporative cooling. Snow fell widely to low levels in December, even in the lightest showers.

[Snowjokes92]

A winter wonderland if gfs is correct. Lots of possible snow events and a main snow event showing for nw england, yorkshire, midlands and wales on thursday. On top of snow accumalatilons from other days

[carinthian]

38 minutes ago, carinthian said:

My experience of previously living in the NW of England has seen snow falling and holding at lower levels for more than just a few hours in a similar weather type . Night time hours are still long and will keep snowfall. I have seen 10 inch falls produced by convective cells aligning the Cheshire Plain with even higher DPs than forecast for next week.

C

Hi , just to highlight the above post, even with 2m Dew Points at or just below 0c snowfall can settle at lower levels, particularly under convective cells or on the cold side of a wave ( as NF as inferred ) .this snow chart map below if verified would be from convective cells in the Northwest and possibly from the wave  passing further South and East. Still a long way off to predict this sort of chart but having just seen our out perimeter snowfall forecast charts not unreasonable prognosis.

 C

Edited January 12, 2018 by carinthian

[tight isobar]

11 minutes ago, Glacier Point said:

There is a suspicion here, advertised by the 06z GFS op, that the extended range modelling will be subject to the (false) tropical forcing signal, but which will not tend to get this beyond the day 8-10 range as the extratropical / tropical interactions become apparent to NWP.

Phase 5 of the MJO is where the modelling will want to go, but this idea of ridging to out south is false IMHO.

Always someboby to put the spoiler in?

No i get your gist, and mjo signal may-well be being over/underlooked...

And the risk of a return to mobility/westerly regime is a major possibility....

But its knife edge imo...

And we need to see how any forcing plays out next 3/5 days!!!

Certainly interesting times.

Edited January 12, 2018 by tight isobar

[Glacier Point]

2 minutes ago, ShortWaveHell said:

I read that as GP saying signals for W signal are false 

Correct

[Sky Full]

These images show what's being being modelled for just four days away:

Now that's looking very interesting - especially western Scotland, most of Wales and - well, nowhere in Ireland is safe!   I keep asking myself what could go wrong at this distance?  Nothing, of course! 

 

[tight isobar]

4 minutes ago, ShortWaveHell said:

I read that as GP saying signals for W signal are false 

Yep your correct i viewed/commented on the composite posted...not the views!!

Quick over-reaction on my part!!!

Edit;..

however  that scenario cant be ignored..however unlikey.

Edited January 12, 2018 by tight isobar

[ItNeverSnowsInWindsor]

Surely the uppers don’t need to be as cold as they were in December as the SSTs should be a bit colder in January to cause less modification ?

Edited January 12, 2018 by prolongedSnowLover

[radiohead]

[TEITS]

GEFS control has the low much further N.

Have to say I understand the discussion about how much snow may fall but personally I think such detail is more suited to the regional threads. Beside you have a greater chance of picking the right Lotto numbers than who will see snowfall next week. Obviously favoured higher elevations are exempt from this.

[Bazray]

Just now, Daniel* said:

Not that it’s bound to happen but.. the less deep the better less cold air doesn’t get mixed in as much. And a south correction would be fab for IMBY this is warranted I’ve not had a covering of snow in five years!  

Yes lets have a south correction, Northerners get enough snow - need to share ot out a bit. Last decent snow event I remember here was Jan 2010, got pasted, cant remember what caused it? Easterly, nw? Would be interested to know if anyone rembembers that far back?

[shaky]

15 minutes ago, Glacier Point said:

Correct

What is w signal?