London & The South East Regional Discussion - Part 6

[polarlow2]

Just to add, let's not go mad on the predicted snow totals. 20cm+ is highly unlikely, 5-8cms widely seems the order of the day to me, perhaps 10-12cms north of London. At this rate, by this afternoon we'll be predicting 3ft widely across the south-east!

[Eskimo]

I think this band of snow will be here quicker than forecast, and leave us quicker than forecast! I do hope it stalls somewhat, moving pretty quick on the radar

It will slow down and stall, dont worry

Just to add, let's not go mad on the predicted snow totals. 20cm+ is highly unlikely, 5-8cms widely seems the order of the day to me, perhaps 10-12cms north of London. At this rate, by this afternoon we'll be predicting 3ft widely across the south-east!

Remember this country has hills and not everyone lives at sea level

[Coast]

Should I cancel? Is the outlook for next week that we will be getting more? More concerned about getting home than getting there.

That will be down to what happens in the latter part of the next 24 hours. Keep any eye on this forum, the radar and the local news as transport may be affected to a greater or lesser degree and its a call you may want to make with more information to hand.

[polarlow2]

It will slow down and stall, dont worry

Remember this country has hills and not everyone lives at sea level

Very true, but I would be hugely surprised if anywhere reaches 20cms. I'd be delighted to be proved wrong though!

[VillagePlank]

Just to add, let's not go mad on the predicted snow totals. 20cm+ is highly unlikely, 5-8cms widely seems the order of the day to me, perhaps 10-12cms north of London. At this rate, by this afternoon we'll be predicting 3ft widely across the south-east!

NAE goes for 27mm, GFS goes for 21mm, and MetO goes for 10mm, of which the average is 19mm of precipitation - possibly, because of the low boundary temperatures (because of frozen ground) we could possible push for a liquid to snow ratio of 11:1; which equals 19*11 ~ 21cm. Much higher with orographic effects associated with the North and South Downs.

I am certainly expecting one foot of the stuff at the normal favoured locations.

Edited February 4, 2012 by Boar Wrinklestorm

[kold weather]

Sorry for the pessimism, I have memories of February 1996. Still brings me out in a cold sweat. I'm still punting for somewhere just north of London as the 'sweet spot' I said Watford yesterday and that's still my thinking.

Faoir enough, to be fair its a rather different set-up, in that case the shortwave developed way west and pushed the froint in from close to Ireland. Its always a hard ask in that type of set-up. This time the system develops over England, which should be good enough for us.

NAE does not go for 27mm???

It shows widely between 8-12mm in our region, which suggests about 8-12cms normally.

[Eskimo]

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[essex coast matt]

Feeling very raw and cold here, with very light snow grains, temp -0.6c, still think inland areas of essex around stansted will do very well tonight with maybe 10cm plus. still think only 5cm at best on coast.

[VillagePlank]

NAE does not go for 27mm???

My apologies, 23mm.

For Bluebell Hill (I know IMBY!) if you cycle through the link adding up each of the numbers you get to 23mm. I am doing this wrong?!

http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&MENU=0000000000&CONT=ukuk&MODELL=nae&MODELLTYP=1&BASE=-&VAR=prec&HH=6&ZOOM=1&ARCHIV=0&WMO=&PERIOD=

[yamkin]

YAMKIN'S RAMPING BRIGADE IS IN TOWN :w00t:

[Lt. Dan]

Morning all,

At less than T+72 hours heights and thicknesses become important for determining whether any precipitation will fall as snow, sleet or rain. We can get this information from public charts. Here's the analysis for tonight over the SE quadrant (Kent/Sussex/E Sussex),

As a rule of thumb (read: local factors such as how high up you are, if you are on the coast, how intense the precipitation etc etc modify this) for snow we need,

• 1000/850hPa < 129
  
• 850/700hPa < 154
  

Importantly, as the 850/700 approaches 154 then the chances of some sleet getting mixed in increases. From this, my forecast is perhaps a little wet snow over midnight, but, otherwise, all precipitation will fall as snow, especially with height. Local heating from large bodies of water (coasts) may push these values over the threshold, but the hopes are that the cold ground will modify such heating such that it falls at least as sleet there as well.

Incidentally, 1000/850hPa > 131, and 850/700hPa > 154 certainly indicate rain - and we're not even close to those values.

Happy snow hunting

Quick question...How does the Wet bulb pot temperature fit in with the low thickness/generally colder air? Is it less of an issue when those two are generally low enough for snow anyway?

[BLUNT]

Am i imagine it, most of it seems very light and pachy or will it perk up later?

[sarah7meme]

Nw forecast gives 14 mm ppn for me tomorrow am

Hubby working ambulance night shift

Not sure he will get through rural roads home at 7am ! He is taking walking boots !

[blackprince]

YAMKIN'S RAMPING BRIGADE IS IN TOWN :w00t:

Morning Rampkin how far into next week has your council got warnings for?

[SMU]

Temp check in guys

-1c here -5c DP- thats a guess BTW

high layer of cloud still keeping that sun away-

S

[kold weather]

Feeling very raw and cold here, with very light snow grains, temp -0.6c, still think inland areas of essex around stansted will do very well tonight with maybe 10cm plus. still think only 5cm at best on coast.

Stansted nearly always does well in these sorts of snow events, so yeah I agree, maybe even more IMO, could be 12-15cms....

[VillagePlank]

Quick question...How does the Wet bulb pot temperature fit in with the low thickness/generally colder air? Is it less of an issue when those two are generally low enough for snow anyway?

As I understand it the (pessimistic) theoretical 850hPa theta-w threshold for snow possibility is as high as 8degC! It is a better indicator of air-type mass, however, and therefore shows fronts wonderfully with today's showing up clearly and easily,

It can't show the occluding nature of the front which keeps air in the important last 300hPa to ground cool with the warm air mixing, and therefore rising and creating clouds with the right stuff falling out of it. If we used the isopleths on this chart, we'd probably forecast a warm spring rain!

Edited February 4, 2012 by Boar Wrinklestorm

[sarah7meme]

Is everyone's focus on tomorrow

Met office has amber warning for Kent from noon today too

[Discombobulation Man]

Morning all,

At less than T+72 hours heights and thicknesses become important for determining whether any precipitation will fall as snow, sleet or rain. We can get this information from public charts. Here's the analysis for tonight over the SE quadrant (Kent/Sussex/E Sussex),

Great, when are you doing the London analysis for the other 10 million in the SE? :winky:

[BLUNT]

On the Snow Forecast maps, it is showing Sleet for tomorrow and Monday or will that change??

[Coast]

Well I guess it's just a case of the radar and how much now.

I hope I can get into the garage tomorrow, all the booze is stored in there!!!!!

[jackie]

Hmm

Temp -1

Dew -2

If the dew goes above 0 it won't snow will it ?

[donna-m]

Went bed early last night so i can have a radar, lamp post night tonight but after my excitement this morning I'm reading again- sleet next to the Sea and coasts lines

WHY ???

I know its harder to snow here but it doesnt mean it can't today does it

[Lt. Dan]

As I understand it the (pessimistic) theoretical 850hPa theta-w threshold for snow possibility is as high as 8degC! It is a better indicator of air-type mass, however, and therefore shows fronts wonderfully with today's showing up clearly and easily,

It can't show the occluding nature of the front which keeps air in the important last 300hPa to ground cool with the warm mixing, and therefore rising and creating clouds with the right stuff falling out of it.

There was me looking at 4degC and thinking it looked high!

[snowking]

Stansted nearly always does well in these sorts of snow events, so yeah I agree, maybe even more IMO, could be 12-15cms....

Sounds silly to say for an area as flat as east anglia but the east anglian heights do tend to give us just a little bit of orographic lift - Late Jan/Feb 2003 and the fiasco on the M11 is a great example of that.

Being just 2 miles away from Stansted i'll be sure to report in later tonight!

SK