Model Output Discussions 18z 31/01/2016

[shaky]

Euro4 looks pretty good with dew points for central and eastern england at 48 hours!!gota agree with steve and nick here and think the models arw underplaying snow on the leading edge and if they are then some places could see snow from start to finish!!

[feb1991blizzard]

8 minutes ago, nick sussex said:

T60hrs fax chart, I'm still very surprised the UKMO aren't mentioning snow ahead of the front, you can see the comparison between that and the earlier one to T72hrs.

 

Louise Lear Mentions leading edge on here.

http://www.bbc.co.uk/weather/2635167

[nick sussex]

4 minutes ago, I remember Atlantic 252 said:

This looks to be where cold air ahead of front mixed out, to me this looks SW'ly Atlantic air, surely with that it cannot start as snow, but just what it looks, I'm no expert but surely need the air on more negative SSE angle

Yes unlikely to start as snow because of that especially towards the west but as the shallow low forms and digs se this brings back some colder 850's, the main mixing out is towards the west the far se will still have enough of a surface feed off  France. Because of the slack flow you'll likely get some evaporative cooling, much depends on the intensity of the precip.

I think the UKMO currently are just going for back edge snow as the precip is undercut by that PM air.

Edited February 15, 2016 by nick sussex

[feb1991blizzard]

1 minute ago, shaky said:

Euro4 looks pretty good with dew points for central and eastern england at 48 hours!!gota agree with steve and nick here and think the models arw underplaying snow on the leading edge and if they are then some places could see snow from start to finish!!

Euro4 looks poor to me.

[chris55]

Definitely one to watch, Louise Lears 6.30 forecast summed things up nicely!

Can things actually fall into place at least one time this winter?

Lets hope so.

[Aaki Khan]

Ecm 144. Am i just chasing again.

[nick sussex]

Putting aside the shorter term the ECM is all over the place between runs. We may well see some more interest next week as the models seem to be picking up more amplitude, perhaps the MJO is helping things along.

[phil nw.]

GFS shows dew points above zero ahead of the front on Weds along with -2c uppers

which would favour back edge snow more as the colder air from the west cuts in later and dews come down..

 

On those snow charts just to stress they are indeed only % risk as it says on the tin and they include the freezing levels (mtrs above sea level).Based on these just for fun as they say we can see how patchy any snow fall may be and would favour elevated areas.

Of course the individual models will have different detail  but it does show the forecasting difficulty with such a marginal setup.

 

[nick sussex]

The ECM tries to develop a ridge to the nw but the PV returns. However it seems the models are shortening the milder interlude.

The ECM is quite cold from T144hrs right through to T240hrs, if we could find a bit more amplitude upstream then it could develop more favourably. I think however any proper cold is more likely to be coming from a ridge to the  ne rather than nw at this time.

 

[Frosty.]

Nothing mild about the Ecm 12z run this evening apart from fleetingly on Sunday (T+144 hours) further south but generally it looks at least a little colder than average with the jet axis tilted more towards nw / se bringing colder polar maritime shots and further chances of wintry ppn including snow, especially to hills and night frosts, even a settled spell later with crisp sunny days and widespread frosty nights.

[Eskimo]

Also lets not forget about those all important thicknesses. Higher thicknesses getting mixed out rapidly on the euro4. For newbies, thicknesses need to be blue. This is just one of many factors to consider. 

 

[Eskimo]

Also lets not forget about those all important thicknesses. Higher thicknesses getting mixed out rapidly on the euro4. For newbies, thicknesses need to be blue. This is just one of many factors to consider. 

 

[feb1991blizzard]

17 minutes ago, PerfectStorm said:

Also lets not forget about those all important thicknesses. Higher thicknesses getting mixed out rapidly on the euro4. For newbies, thicknesses need to be blue. This is just one of many factors to consider. 

 

The blue/green line only represents a 40% chance of anything falling being snow, obviously that depends on other factors.

[shaky]

24 minutes ago, PerfectStorm said:

Also lets not forget about those all important thicknesses. Higher thicknesses getting mixed out rapidly on the euro4. For newbies, thicknesses need to be blue. This is just one of many factors to consider. 

 

Must say those thicknesses look pretty damn good on the euro4!!hopefully it continues on the 18z!!

[ANYWEATHER]

Evening All......As regards Wednesday weather, Cold rain for most , and the precip does not look to heavy either for most.  You know ,Im desperate to see snow falling and settling even for a few hours, as at the moment I see a depressing damp ,raw miserable day. Thursday for some holds more potential......

Edited February 15, 2016 by ANYWEATHER

[SMU]

1 hour ago, shaky said:

Euro4 looks pretty good with dew points for central and eastern england at 48 hours!!gota agree with steve and nick here and think the models arw underplaying snow on the leading edge and if they are then some places could see snow from start to finish!!

Thanks Shaky

The thicknesses across t48 ( the mildest point ) are very very good in the SE

if we look at the following 3 images of euro 4 partial thicknesses -

T 42/45 & 48:

 

at T 48 this is where the PPN is : 

 

so my suggestion would be rain spreading SE - & where it lies at T48 no front edge snow infact at T48 minimal about except at height, however the thicknesses & dewpoint suggest that some snow will already be falling - however what the EURO4 doesnt have is the height of the 0c isotherm.

Because of the lapse rates I would suggest more saturated than normal so perhaps 3/400 M & above all snow.

if we move onto t60 ( UKMO ) the milder wedge is mixed out -

This suggest that as darkness decents weds all parameters move past the borderline point -

* sub 2c dewpoint for transitioning sleet

* - 5c 850 air mixing out the warmer layer

* partial thicknesses of sub 1290 DAM spreading west from the East & east from the west!

whats missing is the height of the 0c isotherm - probably lowering to 100m

The forecast should then move on to say that overnight weds with The above falling into place the rain will steadily turn to snow for most - especially further North & with a smidge of elevation.

Ground level accumulations would depend on how the PPN rates fair in bringing that ZDL level down to ground level.

The models have suggested a secondary wave developing along the front siding SE towards the South coast across East wales & the midlands, this may well be the trigger for accumulations in this area.

you will also not the progs suggest the SE clings onto a developing pool of sub 1290 air with 1280 DAM thicknesses pushing west out of france - so as the front edges into the SE overnight weds then it may well turn to snow as well - PPN rates dependent...

 

 

best regards

s

 

 

 

Edited February 15, 2016 by Steve Murr

[shaky]

Hope ian fergie can come on later and elaborate more on the wednesday thursday snow situation!!!it reall is gona go down to the wire!!

[Tim Bland]

Whilst temperatures  may be faverouble for snow in the south east, I think lack of precipitation may be the issue. Most models show the front stalling in central areas and by the time it finally clears into south eastern areas it is just light and patchy drizzle

[Lukesluckybunch]

Just going to state out here ,that the latest BBC forecast I saw showed the front on Wednesday and it was more speckled white so I think the snow chances have increased 

[Lukesluckybunch]

Just now, Lukesluckybunch said:

Just going to state out here ,that the latest BBC forecast I saw showed the front on Wednesday and it was more speckled white so I think the snow chances have increased.just my own feeling here but I would hazard a guess of the sweetspot being ,east Midlands down towards central southern England angeling southwestward!somwhere like Oxfordshire  would see heavy falls just my opinion

 

[Eskimo]

2 minutes ago, Lukesluckybunch said:

Just going to state out here ,that the latest BBC forecast I saw showed the front on Wednesday and it was more speckled white so I think the snow chances have increased 

There's a common saying here in this forum, "if the bbc graphics show white, the rain doth bite" 

Pretty sure I made that up however...

[Lukesluckybunch]

Just now, PerfectStorm said:

There's a common saying here in this forum, "if the bbc graphics show white, the rain doth bite" 

Pretty sure I made that up however...

Lol

[Captain Shortwave]

And..... back to the model discussion please, there are other threads to comment on the metoffice/bbc outlooks.

The regional threads are also a good place to go for a more localised outlook.

Cheers

 

Edited February 15, 2016 by Captain Shortwave

[Lukesluckybunch]

Somthing more positive which is beginning to firm up is the threat of cold conditions back next Monday.this theme has been repeated on the last few runs now,both ecm and gfs showing this!could we be doing all this drama again come next week!

[karlos1983]

36 minutes ago, shaky said:

Hope ian fergie can come on later and elaborate more on the wednesday thursday snow situation!!!it reall is gona go down to the wire!!

To be honest after seeing his Twitter feed, I think the poor bloke has higher priorities than us snow chasing nutters.