South East and East Anglia Regional Discussion 21st February 2013 18:00hrs>

[VillagePlank]

Well the precipitation charts look like something akin to a Thames streamer,

But, I think, in scenarios like these, we should use the precipitation charts as a guide, not as a OMG I'm in the firing line.

There are three parameters to look for: convection, convergence, and orography. The North Sea is currently warmer than the air above it,

So this means that moisture will move off the sea surface and into the lower atmosphere. It's not by any stretch of the imagination vigorous convection that might produce thundersnow, say - it is more likely, and indeed it is, to produce uniform long stretches of stratus. The hope is that as the air cools further after night fall, the rate of moisture transport is increased by the difference between the temperature of the sea, and the temperature of the air.

The second parameter is convergence. This is not going to happen across the whole period, and the best (most likely) convergence to produce lift is this one,

Winds bumping into each other force air to rise, and moist air being forced to rise is more likely to produce clouds capable of precipitation.

The third parameter is orography. In this set up it's the Medway towns lying on the North Downs that is likely to see the best out of any precipitation produced out of air being forced to rise since it hits hills; in the lee of the hills is the best place to be. So, I wouldn't rule out Maidstone, say, sitting behind the North Downs at the foot of Bluebell Hill.

All in all, these parameters are not great. The chance of a slight covering, but that's about it, really. None of the required parameters happen at the same time, and even when they do happen, the computer forecast for the effect is weak, to none. Best chance is for North West Kent around midnight, tonight, due to convergence, and orographic lift.

Edited February 22, 2013 by Boar Wrinklestorm

[weathertoski]

Just noticed first flakes here

[dubmuffin]

The odd flake turned into a flurry as I got to Croydon this morning, the flurry turned into a brief light shower, but is now back to flurrying - was flurrying actually a word before today?

[Keraunic]

Morin each. Just had a few snow flurries ( I do like that word.....flurrrrriiieeeees) here in Ippy. Very grey and still very cold. Went to Tesco's last night and it was icy cold in the wind. Brrrrrrrrr!

Have a great Friday, everyone and ready for the weekend.

[Gary_R_Walker]

I think it's a bit rich people blaming the radar for getting this incredibly light snow/snizzle/sleet slightly wrong. The precipitation is so inconsequential that it's almost invisible.

[Pixel]

'Boar Wrinklestorm' post at 375..

is just the sort of post that could be enjoyed in the 'Mad' thread if anyone wanted to learn anything in there. Nice one Boar, thanks for posting in here.

[Gowon]

Nothing settling here and now turned back to light snow.

[Paul Sherman]

Well the precipitation charts look like something akin to a Thames streamer,

But, I think, in scenarios like these, we should use the precipitation charts as a guide, not as a OMG I'm in the firing line.

There are three parameters to look for: convection, convergence, and orography. The North Sea is currently warmer than the air above it,

So this means that moisture will move off the sea surface and into the lower atmosphere. It's not by any stretch of the imagination vigorous convection that might produce thundersnow, say - it is more likely, and indeed it is, to produce uniform long stretches of stratus. The hope is that as the air cools further after night fall, the rate of moisture transport is increased by the difference between the temperature of the sea, and the temperature of the air.

The second parameter is convergence. This is not going to happen across the whole period, and the best (most likely) convergence to produce lift is this one,

Winds bumping into each other force air to rise, and moist air being forced to rise is more likely to produce clouds capable of precipitation.

The third parameter is orography. In this set up it's the Medway towns lying on the North Downs that is likely to see the best out of any precipitation produced out of air being forced to rise since it hits hills; in the lee of the hills is the best place to be. So, I wouldn't rule out Maidstone, say, sitting behind the North Downs at the foot of Bluebell Hill.

All in all, these parameters are not great. The chance of a slight covering, but that's about it, really. None of the required parameters happen at the same time, and even when they do happen, the computer forecast for the effect is weak, to none. Best chance is for North West Kent around midnight, tonight, due to convergence, and orographic lift.

Great Post Boar

Converging winds look the main problem to me as well, back in Feb 2009 these were absolutely perfect with a North Easterly pushing against an easterly just east of London, you forgot the Cape charts as well but to be honest dont even look at those as you will be sorely dissapointed

CWT Obviously has a different set of charts than us which must be showing why his forecast is for a much deeper kind of snow than we are seeing, what charts are you using CWT Just out of interest ?

[SMU]

Sky getting grey here- especially out the back towards the estuary-

Snow up to level 4 as speak.

nope make that 5!!!!!

[Gowon]

Yep...it's picked up again.

[Ruthie]

Can confirm the flurries have arrived here. Blowing in the wind, not much. Also saw the sun just now, gone again though..

[blackprince]

a bit better thanks just having my first warmish cup of tea a little pain but bearable, yes will keep updating but i wouldnt hold your breath on comming home to a white bay

No its full of old grey wrinklies LOL

[SMU]

heavy Snow

[throwoff]

Started settling on the grass here in EG.

I think today will be a bit quiet, bring on tonight over Gillingham

[VillagePlank]

Great Post Boar

Converging winds look the main problem to me as well, back in Feb 2009 these were absolutely perfect with a North Easterly pushing against an easterly just east of London, you forgot the Cape charts as well but to be honest dont even look at those as you will be sorely dissapointed

CWT Obviously has a different set of charts than us which must be showing why his forecast is for a much deeper kind of snow than we are seeing, what charts are you using CWT Just out of interest ?

I looked at the skew-T and was violently confronted with a negative K-index! But, for a clutching at straws madness moment, I am slightly bouyed by the lack of CIN, which should mean any convergence, orographic lift potential is fully realised. The problem is, there isn't much!

However, the air from the surface to about 3km up is forecast to rise: since there's no convection to talk of, really, this must be down to convergence. The problem is that at about 3km it stops, so we have a maximum cloud depth, of, say, 2-2.5km, which is not going to produce 1980s style snowmaggedon,

Therefore, based on the computer models to hand, the only forecast possible, in my view, from this set up is that snow is going to happen, there's not going to be a lot of it (if any settling), and geographic location is the key. As always, there will be exceptions - hence my punt for North West Kent.

Edited February 22, 2013 by Boar Wrinklestorm

[Tom Jarvis]

Not got any heavy snow here yet hope the wind shifts it down my way

[Southender]

Another mod snow shower moving through Southend. Lasts about 2 mins then stops again. Been doing this all morning. No accumulations.

Temp 0.9c

Dew -4.5

Wind NE @ 14mph

[throwoff]

Getting more substantial here in East Grinstead now.

[Paul Sherman]

Yep cloud tops on that Skew-T look no higher than 5,000 to 6,000ft

Which would suggest deeper parts of stratocumulus might give a covering if a heavy enough patch can sustain, other than that just grains and light snow blowing around.

Things might change with later model runs so there is still hope I would imagine.

[london-snow]

Well nothing here in slough at work in fact clouds are breaking up with the sun trying to break through.

Just phoned home and they have snow there so look forward to seeing a possible dusting when i return.

[Weathizard]

Sunny with scattered clouds here on the south coast freezing mind

[dallas]

heavy Snow

Is that Greenhithe Steve?

[SMU]

the run of the estuary all the way from london out to the north sea is full now. with light blue echoes-

however last 3 frames are seeing more and more blue pixels & dark blue pixels-

snow level moderate still & going well-

S

in greenhithe...

Edited February 22, 2013 by Steve Murr

[TheGate]

Temperature has been fluctuating a little between -0.7c and -0.3c, currently -0.5c. Snow seems to be picking up in intensity again, and the wind has also picked up. Got a nice covering on roads and pavements and the grass has developed white patches. It's nothing like January, but I'll take it.

[Gary_R_Walker]

It is snowing here, but I'm a little concerned about using the word "snowing" as I could be prosecuted under the Trade Descriptions Act.