SE, London & EA - Weather Discussion

[Nick F]

A bit further north please, just outside the warning area by a few miles! I'm at 180 m asl, so would hopefully see snow if precipitation gets this far north.

 

Edited January 15, 2023 by Nick F

[alexisj9]

8 minutes ago, Dbarb said:

These are the type of events that interest me the most and give the most suprises. Depending on how far the front extends north to how heavy the precipitation is and local conditions maybe some surprises 

If it gets to far north, Frances 70mph wind gusts will be in SE England and stronger, as it would have deepened more, to bring it north. Not sure wanting things more north is a good idea. May be a little further, but not like last time.

[Nick F]

1 hour ago, alexisj9 said:

If it's deepend more it might come further north, we do not want that, if it already deepens fast enough to be named by the French. It also sounds to strong wind wise, to mix out any warm uppers it might pick up from the south, so I guess expect rain.

Still uncertainty how much it will deepen, still a frontal wave on the noon fax, GFS shows it starting to deepen and form a closed circulation in the developmental left exit of jet by 3pm 

By 3am it's deepened further over English Channel

Edited January 15, 2023 by Nick F

[Spikey M]

1 hour ago, SHM040519 said:

So the met have put a yellow warning on us. Do wonder why! Seems a pointless warning.

It's not pointless if you look at the matrix. Unlikely but would cause disruption if it happens. Which is correct. 

If it does snow and they didn't have a warning out we all know they would be dragged through the mud.

[Bradley in Kent]

This has got sleet written all over it with perhaps a bit of slush on top of cars on the highest ground of the Downs. 

Uppers are looking okay but DPs, wind and ground temps are looking less favourable. 

It feels like the Met Office are approaching this with caution after all the flack they took in December!

[Atmogenic]

looks like some pretty big cells between folkstone and the english channel, could see them from here but nowhere near folkstone to get a good picture of them

[Vortex3929]

30 minutes ago, Spikey M said:

It's not pointless if you look at the matrix. Unlikely but would cause disruption if it happens. Which is correct. 

If it does snow and they didn't have a warning out we all know they would be dragged through the mud.

Damned if they do, and damned if they don't. I'm not completely convinced it'll happen other than sleet for most apart from higher elevation. Plus now meto are warning, its been jinxed

[MAF]

 down to 38% snow chance from 78 this morning. still it is winter  

[Eagle Eye]

Do I hear the words lamppost and watching ?

[Nick F]

35 minutes ago, Eagle Eye said:

Do I hear the words lamppost and watching ?

May not start until 1-2am, fine if you don't have work/school in the morning.

 

[BLS]

Latest GFS pushes the snow risk a little more north by the looks of it might not be a bad thing for lower grounds but still think will only wake up to snow on the high grounds 

[Eagle Eye]

2 minutes ago, Nick F said:

May not start until 1-2am, fine if you don't have work/school in the morning.

 

I have school but no one will know if I stay up. I'm safe 

Edited January 15, 2023 by Eagle Eye

[Mark wheeler]

10 minutes ago, BLS said:

Latest GFS pushes the snow risk a little more north by the looks of it might not be a bad thing for lower grounds but still think will only wake up to snow on the high grounds 

As does the arome 12z . However it shows as rain on this run.

[VillagePlank]

The critical thicknesses for 500, and 850 are:

• 500hPa : 540dm
• 800hPa : 130dm

The critical thickness is where precipitation is equally likely to fall as rain or snow. 

The lower the values go the higher the chance of snow - the snow line tends to  be 122dm at 850hPa and 524dm at 500hPa, but change dependent on location. Clearly, the higher you are above sea level the less height there is too, so some adjustment needs to be for height.  Of course, these are rules of thumb, not cast-iron guarantees!

If stuff falls out of the sky, and the heights are low enough -  both which look to occur over the SE tonight and into the morning - then snow is likely.

(I gave up looking at the 850hPa temperature as I've seen rain fall at -8degC and snow fall at 0degC, when the hypothetical temp line is meant to be -5degC)

 

[Snowangel-MK]

Whatever the PPN is when it lands the system is now arriving from the west and seems much further north atm than the models predicted

[sunnijim]

25 minutes ago, Snowangel-MK said:

Whatever the PPN is when it lands the system is now arriving from the west and seems much further north atm than the models predicted

Was looking at that, the system seems much further North.

Not sure what this all means but given the channel isles and Normandy are on a Wind watch with the Low progged further South, we could be looking at Bin bothering in the early hours on the South Coast.

Did someone say a rush hour blizzard?

No, of course not.

[throwoff]

Think Medway is out of the running for this one, rain inbound

[Whether Idle]

Evening All.  A classic channel low situation, except its even more marginal than in days of yore thanks to higher SSTs and other background factors.  Much variance in the modelling of the feature, though in the last 24 hours the trend has been to take the feature further north than had been forecasted yesterday.  Clearly areas that benefitted from the pre Christmas fall may again get some wet snow accumulating.  Areas with an altitude of greater than 100m will be better off to catch some snow, plus there will be some input from our old friend evaporative cooling in the heavier bursts of precipitation.  Im expecting rain on this corner but I guess places on the north Downs and High Weald may well be favoured.  Going to be interesting to see if anything transpires across the region. 

Edited January 15, 2023 by Whether Idle

[Hammer]

Here is what METO PPN predictor says for 10pm tonight in terms of position. 

[alexisj9]

42 minutes ago, Snowangel-MK said:

Whatever the PPN is when it lands the system is now arriving from the west and seems much further north atm than the models predicted

That's not a good thing, it might delay the cold getting over us till after it's gone. Snow only on when it exits. Still I guess we'll see. 

[Hammer]

And METO PPN predictor for 3am.

[Gowon]

58 minutes ago, VillagePlank said:

The critical thicknesses for 500, and 850 are:

• 500hPa : 540dm
• 800hPa : 130dm

The critical thickness is where precipitation is equally likely to fall as rain or snow. 

The lower the values go the higher the chance of snow - the snow line tends to  be 122dm at 850hPa and 524dm at 500hPa, but change dependent on location. Clearly, the higher you are above sea level the less height there is too, so some adjustment needs to be for height.  Of course, these are rules of thumb, not cast-iron guarantees!

If stuff falls out of the sky, and the heights are low enough -  both which look to occur over the SE tonight and into the morning - then snow is likely.

(I gave up looking at the 850hPa temperature as I've seen rain fall at -8degC and snow fall at 0degC, when the hypothetical temp line is meant to be -5degC)

 

Good to see you posting again VP

[alexisj9]

17 minutes ago, sunnijim said:

Was looking at that, the system seems much further North.

Not sure what this all means but given the channel isles and Normandy are on a Wind watch with the Low progged further South, we could be looking at Bin bothering in the early hours on the South Coast.

Did someone say a rush hour blizzard?

No, of course not.

Hope it's not that far further north, don't need the SW winds on the south coast 

[Hammer]

5 minutes ago, Hammer said:

Here is what METO PPN predictor says for 10pm tonight in terms of position. 

So at 10pm radar shot tonight, should be interesting to see how it compares. I will look to post that later.

[Whether Idle]

4 hours ago, Atmogenic said:

looks like some pretty big cells between folkstone and the english channel, could see them from here but nowhere near folkstone to get a good picture of them

Yes indeed, those cells looked full of menace, glowering and laden with trouble.  The atmosphere had a very disturbed look as I cast my eye southward from Dover Castle this afternoon.  The appearance of the atmosphere suggested to me that there is scope for some rapid deepening and heavy precipitation.  Some place on the north west side of any closed circulation could get quite a pasting in a short space of time - around rush hour.  All quite impossible to be certain of in predictions at this distance of time, but the possibility is there for some mayhem - poss a 1/4 chance, though maybe up to 1/2 over areas with a good altitude to get rapid accumulation of snow.