London And The South East Regional Discussion Thread - Part 3

[snow raven]

Here we go everyone - ramp away! (and let's hope there will be something to ramp about!!) :lol:

[username home]

quasi or mesoscale ramping?

[john pike]

i just watched the weather forecast on news 24

for sundays weather onwards

she showed 2 options

1-how warmer it would get if warmer air wins

2-how cold it would be if the colder air wins.

i can honestly say i have never seen the forecaster do that before.

if its a choice i will have option 2 please

[Tom Montalbano]

Sorry SR if I could pop this back in here.

Dont know if anybody has asked the question yet re.criteria that needs to be met for initiation of "lake effect snow".

In other words the possibility of snow showers being triggered by cold 850 temps as winds from the NE/ENE flow over the North Sea during the next few days. Doesnt seem to be much enthusiasm from the models for much snow shower activity, I'm guessing air pressure of 1036+ mbs being the inhibiting factor.

Have read a few articles on the subject, we look as if we're going to meet some of the criteria. For convection to initiate we need at least a temperature differential between sea surface and the air at 850mbs to be at least 13c and the flow to be passing over a body of water at least 60 miles wide.

North Sea temps at the moment are around 7c and from around 6 p.m Weds eve 850 temps over the North Sea are expected to be around -10c and falling to around -12c or so by Thurs eve. So we're looking at a differential there of at least 17c.

The distance from the S.Essex/N.Kent coast to the Dutch coast I estimate to be 130 miles, give or take a bit.

We seem to meet those 2 criteria comfortably but the sticking point seems to be air pressure of 1036+ mbs or so.

My question now, is there a formula that combines these temp differentials with air pressure to produce a point where convection would be initiated despite high air pressure or am I looking at this in a far too simplistic way and that there are other factors involved?

Would love to hear anyones thoughts on this.

Regards,

Tom.

[Paul Sherman]

I am not to up with how Lake Effect Snow works in the Great Lakes and Buffalo Tom, but do they not need some sort of disturbance then to trigger this off, or is it solely a favourable wind direction making the Convection kick off ?

Sorry not much help

[mesocyclone]

Great question Tom, my concern this whole period is the high pressure. It's extremly high! RJS lives in Canada I believe, he seems to think it will kick of big time tomorrow judging by his posts. I guess if nobody answers we will soon find out. It certainly looks good for streamers.

[Guest archiesmummy]

Hi there

Forgive me if this has been discussed in the previous thread but is the GFS 18z not looking good?

[john pike]

http://onlinelibrary.wiley.com/doi/10.1256/wea.73.03/abstract

hope this helps tom

[Tom Montalbano]

I am not to up with how Lake Effect Snow works in the Great Lakes and Buffalo Tom, but do they not need some sort of disturbance then to trigger this off, or is it solely a favourable wind direction making the Convection kick off ?

Sorry not much help

Hi Paul and MC,

I think one of the articles I read mentioned a triggering disturbance but also I think that sometimes streamers set-up offshore from Essex and Kent because of the very topography of those counties coastlines, in the way that they converge together at the mouth of the Thames and causing local disturbances in the flow.

Obviously I hope RJS is right but I cant for the life of me see that happening.

If I were to choose a location where a streamer may initiate it would be the Mid-Kent coast, perhaps just east of the Medway towns, the flow profile looks favourable there.

I work with a colleague who lives in Rainham (Kent) and the amount of times he has reported falling snow with a NE flow, with at least a dusting, when there has hardly been any ppn on the radar, amazes me.

Anyway, lets hope some of our region get lucky in the next few days.

Btw, hope Steve M. and TEITS are right re. the Meto and their Faxes backing everything west as we near the actual date.

This chart could be very interesting come Sunday.

http://nwstatic.co.uk/fax/PPVO89.png

Regards,

Tom

Edited February 1, 2012 by TomSE20

[john pike]

http://www.meteociel.fr/modeles/archives/archives.php?day=8&month=1&hour=0&year=2003&map=4&mode=2

put in jan 8th 2003

plenty of info there

[Tom Montalbano]

http://onlinelibrary....73.03/abstract

hope this helps tom

Thanks jp, I shall get stuck into that. Compliments again Paul to your tremendous write up on the Feb 09 streamer, polystyrene balls an' all! .

Regards,

Tom

Edited February 1, 2012 by TomSE20

[danm]

http://www.meteociel...03&map=4&mode=2

put in jan 8th 2003

plenty of info there

Remember this event well. Was an excellent streamer for Essex, London and north Kent.

[Tom Montalbano]

Thanks jp, I shall get stuck into that. Compliments again Paul to your tremendous write up on the Feb 09 streamer, polystyrene balls an' all! .

Regards,

Tom

[Tom Montalbano]

Remember this event well. Was an excellent streamer for Essex, London and north Kent.

Remember this well too jp, we had about 4 inches in Bromley, quite a bit more at Biggin Hill and 8 inches at Bluewater.

And from what looks to be a very slack flow.

Regards,

Tom

[john pike]

hello tom

the 09 streamer if i remember was on a east north east wind

there was not a lot of precipitaion around but as soon as a

small amount of precipitation went up the estuary it reacted with the

thames and made a snow making machine.

if i remember the time right i had really heavy snow here

and nothing was showing on the satellite

also there was no warnings for this i remember the met

office putting a warning up for this after it started.

i had a look at fridays 00 fax and would not be surprised to see

#something brew up from that.

[danm]

Remember this well too jp, we had about 4 inches in Bromley, quite a bit more at Biggin Hill and 8 inches at Bluewater.

And from what looks to be a very slack flow.

Regards,

Tom

Back then in January 2003 I was in 6th form (1st year A-Levels) at school in Chigwell, which is on the border of SW Essex and NE London. Got to school around 830am and by 9am it had started to snow heavily and continued right through until about 2pm. We clocked up about 5 or 6 inches of snow. It was very heavy and intense at times. Great event.

Its also worth noting that this event was not picked up until the evening beforehand. A disturbance had developed in the southern North Sea, which was mentioned on the BBC weather the night before. There was no forecast for this before that. Shows how snow events can crop up at short notice.

Edited February 1, 2012 by danm

[ZONE 51]

Created a snow forecast map, looking at the model data there is the risk of snow showers setting up from the North sea from Thursday early hours(if they fire up earlier than expected we would be looking at them moving in from wednesday night late-tonight, but the risk rises really into thursday morning and afternoon, although the models indicate more potential into EA i would expect some swing across the SE, the increase in convective activity on friday looks like more widespread snow showers, the chances are only lighter precipitation would materialise through the first risk period(thursday)but things can change! its hard to pin point this stuff but the increasing chance of snow is there through thursday/friday, at the moment a drier air slot is around and this lasting though wednesday(today) with sunny skies! then cloud increasing as we go into the night time.

Edited February 1, 2012 by ElectricSnowStorm

[dallas]

Nice map Electric, hoping to see something by the weekend, then more after the reload mid month. Meto end of the month update are hinting at something. UKMO keeps the cold temps for next few days with the east corner clinging on longer than most. Will the ECM do the same, lets hope so

Edited February 1, 2012 by dallas

[crazy_diamond]

First post for some while, just a few observations noted when taking hubby to Ockendon station at 6 am this morning. As was predicted on here last night, no frost, but interestingly, the moisture on the car roof had frozen solid. Car thermometer read 1.5c for part of the two mile journey, dropped to 0.5 then rose and remained at 1.0 for the journey home again. Quite a breeze blowing. I don't have a compass, but it was coming from the direction I'd look for sunrise, which I know is somewhat north of east this time of year. Rather cloudy too and despite what the thermometer said, it felt bitterly cold to me!

Looking forward to at least a sniff of real winter!

CD

[Tom Montalbano]

Interesting updated faxes for our region.

http://nwstatic.co.uk/fax/PPVG89.png

http://nwstatic.co.uk/fax/PPVI89.png

-10 uppers start to appear later this evening, would expect a few snow showers in the east of our region after midnight.

Regards,

Tom

[Jayces]

Hi there

Forgive me if this has been discussed in the previous thread but is the GFS 18z not looking good?

Nobody really knows and we won't know until the weekend what this weekend will bring for us but if it's any help the forecast for 2 weeks away is amazing.........shame that was the same for the forecast for this weekend 2 weeks ago and then look what happened.

[Paul Sherman]

Hi Tom

Great UKMO Faxes there. Shows a trough in the Southern North Sea for about 36 hours (Snow Making Machine Hopefully) Those faxes show 12pm (Thursday) and Midnight Thursday with the trough not having moved if at all.

Would suggest tomorrow afternoon all the way through to Friday morning will be prime for the Streamer to set-up and also the flow is much better from tomorrow mid afternoon (Stronger ENE)

Looking good!

[Coast]

quasi or mesoscale ramping?

MEGA!!!!!!

Morning South Easterners!

[Paul Sherman]

Right - Not saying there is defo going to be an "Event" before whatever happens at the weekend but after viewing the faxes and a few of the GFS Charts relating to humidity etc this is looking quite favourable for us.

1. The Uppers should be between -10c and -12c

2. There is a Trough sitting in the Southern North Sea (The Trigger)

3. The Flow is favourable from the ENE

4. Relative Humidity Increases tomorrow (Moister air)

5. Lapse Rates are decent enough for the possibility of marginal Thundersnow.

6. The flow is much better (Tighter Isobars helped by a lower pressure gradient over NW France) tomorrow from 12pm.

I reckon with all of that we have at least a 24-36 hour timeframe to maybe pull off something quite interesting from tomorrow afternoon right through to friday afternoon!

Regards

Paul S

[Coast]

GFS sill loves us from Friday:

But Sunday (which showed such promise yesterday) it shuts up shop:

Oh well, another run, another day!!!! Radar watching for me this afternoon!