London & South East Regional Discussion 16/01/13 18z------>

[SMU]

So to tonights update:

Most of use have been around a while, some of us lucky enought to remember 1987, some can remember 79 & some even 47 & 63-

They are the archive charts that we search & find every year when we want to enjoy our memories of cold & snow-

Note its nearly 50 years to the day for the famous winter of 63.....

We stand on the cusp of charts ( like Dec 10 as well) that could stand in the archives years to come..- especially if the ECM vairifies tonight which would see the cold spell stretch to day 13 & beyond ( assuming Monday was day 1)-

Without going into the background of whys & what nots the first thing we might consider is the rarity of this weekends pattern.

We have had a 'few' undercutting type scenarios in the last few years but they all held one common theme - no blocking high to the east- usually we have low pressure in the north sea that allows low pressure from the atlantic to pass through with little or no resistance- so anything coming from the SW is either snow to rain or freezing rain to rain.

last time we had a stalling frontal zone that delivered high quantities of snow was 5th feb 1996- thats 17 years ago. - so whilst theres a chance that it could miss the SE the pattern on the whole is RARE.

Here is the 1996 chart-

Crucially when we talk about 850 temps the -2c line is a good guide-

heres those temps at 12pm that day

http://modeles.meteociel.fr/modeles/reana/1996/archives-1996-2-6-0-2.png

I recall the Kettley forecast saying ' the front is really getting a speed on now & its even snowing in the channel islands-... where we can see the -2line.

So for this scenario if we look at mid term models in THIS scenario- any sliders or creepers along the channel- the -2 line is the guide.

The event for friday for the SE has no marginality in terms of temps- except for the EXTREME SW of the region coastal areas- southampton sort of way- however you only need travel a few miles inland away from any onshore breeze to be secure.

so there she is in all her beauty-

http://www.meteociel.fr/ukmo/runs/2013011612/UW48-21.GIF?16-18

The UKMO chart at T48 shows the low slightly positioned further south than 96 & the upper blocking high further North- this means V 1996 the atlantic should move further east into the country as the amplitude of the jet isnt quite as high. ( slightly lower wave )

The SW taking a beating there with snow friday for 12 odd hours really building up-

Then we enter the fray- around T54/T60 & out to 78/84- so 24 hours is a **POSSIBLE** bet.

http://www.meteociel.fr/ukmo/runs/2013011612/UW60-21.GIF?16-18

The T60 shows the low sliding SE- which is great as the PPN sheild ahead of it isnt actually getting any further east-

The low is also pumping up moisture & instability across the SE which will enhance the PPN rates-

so at T45/48 we are starting out-

http://www.meteociel.fr/ukmo/run/U48-594.GIF?16-18

but at 60 we have that push & onshore flow from the SE

http://www.meteociel.fr/ukmo/run/U60-594.GIF?16-18 &

The Raw output between 12pm Friday & 12pm Saturday are suggestive of 15mm widespread- especially to the south & SW of the region-

Because the air is so dry & he dewpoint very cold the accumulation ration will be higher than your usual wet rubbish we get.

I suspect being very light with high air content the ration could be 1mm : 1.5CM-

That points to 22CM being the mean & 30cm being the TOP END-

SO for forecast purposes & for the fact the low could fragment / weaken & stay west my forecast for the period is

London/essex/ kent / East sussex 5-10cm.

Surrey / West Sussex 7-15cm.

Areas like the downs- all around banstead etc- ~ 20cm.

this is based on the UKMO-

For the ECM knock 3/4cm of all totals-

**** remember the biggest caveat to this ISNT temperature for once- but how far east the PPN goes & holds together.

**** Where it stalls will get persistent snow for 30 hours before it fragments ****

So does it end there????????- NO, for this to be special & one for the archives you need a sustained period over 2 weeks- so lets open the ECM curtains for next week - after sub -10c minima sat night-

Snow approaching from the west-

http://en.vedur.is/photos/atlant_evr_urkomuspa/130116_1200_114.png

http://en.vedur.is/photos/atlant_evr_urkomuspa/130116_1200_120.png

http://en.vedur.is/photos/atlant_evr_urkomuspa/130116_1200_126.png

another 12 / 18 hour event that rolls into convective snowfall post that- & very cold out to day 10-

In Summary then:

A snow event friday- DONT ramp it up to much on the PPN front as the ECM is fast through with no real stall- so amounts are in the sub 10cm camp- where as the UKMO is VERY aggressive with PPN..

until then- total ice day tom & friday- freezing the ground & some ponds/lakes ready for the snow...

S

[Sussex Jules]

The NMM only goes up to 48 hours yet so it won't cover the main event

[Neilsouth]

This is exactly what I saying a little while back about the models, they have pushed the front further west and it's much weaker as it comes towards the east. There is also a RISK of it not arriving at all, this is going to be a nowcast situation on Friday it could go either way.

It's rather annoying with people getting so excited beyond Friday, when even Friday could go completely wrong for such a large part of the country(east). It could well end up amazing, but we need to be careful.

Wait till friday morning

[WillinGlossop]

Just a pic after the snow we had in Deal this morning!

Drove to deal for walk on the beach you guys hit the jackpot out of east kent..... 2/3 inches on the pebbles....

[Crystal Memories]

Snow moving in again

​A pick from earlier

[dubmuffin]

After all the disappointment from earlier this week I have been resisting the urge to get excited, but it is beginnning to look like we are in for a real chance. Nothing excites me more than the chance of Friday night snow so I can stay up late watching it fall, and enjoy the following day without the inconvenience of work getting in the way.

However, this weekend I have tickets for the outdoor/bike show at Excel in London so will have to be up early on Saturday battling my way through the snowdrifts to the station to wait for non existent trains Hope it sticks around for a Sunday sledging sesh

[Jezzer]

Fergie is a class forecaster, oh why can't he do SE forecasts! Peter Cockcroft Pfffft!

was about to say exactly the same, he shows how it should be done

[WillinGlossop]

dont worry everybody apperently kaddy is back on friday doing the weather forecast on south east today so hopefully we will get a bit more info then on what will happen on friday

Yey we usually get now when shes on! She loves the snow too.....

[ChartViewer]

So to tonights update:

until then- total ice day tom & friday- freezing the ground & some ponds/lakes ready for the snow...

S

Bloody amazing post thanks Steve..Buzzing ....T60 Sliding South east.....yum...Snow for London....Peter C update is well out of date!

Question - any thaw Sunday/Monday?

Edited January 16, 2013 by ChartViewer

[Suburban Streamer]

The NMM only goes up to 48 hours yet so it won't cover the main event

the nmm goes out to t60, the nae goes to t48

http://www.meteociel...rfnmm.php?map=0

Edited January 16, 2013 by Suburban Streamer

[Jayces]

BBC South East - http://www.bbc.co.uk/weather/me1

BBC London - http://www.bbc.co.uk/weather/2643743

Click on the videos to see the difference!

The funny thing about Peter's forecast is that if you click on the days on the page that video is on it only shows snow for the whole weekend and colder temperatures then he is predicting.

I suspect it's an old forecast maybe?

[Southender]

So to tonights update:

Most of use have been around a while, some of us lucky enought to remember 1987, some can remember 79 & some even 47 & 63-

They are the archive charts that we search & find every year when we want to enjoy our memories of cold & snow-

Note its nearly 50 years to the day for the famous winter of 63.....

We stand on the cusp of charts ( like Dec 10 as well) that could stand in the archives years to come..- especially if the ECM vairifies tonight which would see the cold spell stretch to day 13 & beyond ( assuming Monday was day 1)-

Without going into the background of whys & what nots the first thing we might consider is the rarity of this weekends pattern.

We have had a 'few' undercutting type scenarios in the last few years but they all held one common theme - no blocking high to the east- usually we have low pressure in the north sea that allows low pressure from the atlantic to pass through with little or no resistance- so anything coming from the SW is either snow to rain or freezing rain to rain.

last time we had a stalling frontal zone that delivered high quantities of snow was 5th feb 1996- thats 17 years ago. - so whilst theres a chance that it could miss the SE the pattern on the whole is RARE.

Here is the 1996 chart-

Crucially when we talk about 850 temps the -2c line is a good guide-

heres those temps at 12pm that day

http://modeles.meteociel.fr/modeles/reana/1996/archives-1996-2-6-0-2.png

I recall the Kettley forecast saying ' the front is really getting a speed on now & its even snowing in the channel islands-... where we can see the -2line.

So for this scenario if we look at mid term models in THIS scenario- any sliders or creepers along the channel- the -2 line is the guide.

The event for friday for the SE has no marginality in terms of temps- except for the EXTREME SW of the region coastal areas- southampton sort of way- however you only need travel a few miles inland away from any onshore breeze to be secure.

so there she is in all her beauty-

http://www.meteociel.fr/ukmo/runs/2013011612/UW48-21.GIF?16-18

The UKMO chart at T48 shows the low slightly positioned further south than 96 & the upper blocking high further North- this means V 1996 the atlantic should move further east into the country as the amplitude of the jet isnt quite as high. ( slightly lower wave )

The SW taking a beating there with snow friday for 12 odd hours really building up-

Then we enter the fray- around T54/T60 & out to 78/84- so 24 hours is a **POSSIBLE** bet.

http://www.meteociel.fr/ukmo/runs/2013011612/UW60-21.GIF?16-18

The T60 shows the low sliding SE- which is great as the PPN sheild ahead of it isnt actually getting any further east-

The low is also pumping up moisture & instability across the SE which will enhance the PPN rates-

so at T45/48 we are starting out-

http://www.meteociel.fr/ukmo/run/U48-594.GIF?16-18

but at 60 we have that push & onshore flow from the SE

http://www.meteociel.fr/ukmo/run/U60-594.GIF?16-18 &

The Raw output between 12pm Friday & 12pm Saturday are suggestive of 15mm widespread- especially to the south & SW of the region-

Because the air is so dry & he dewpoint very cold the accumulation ration will be higher than your usual wet rubbish we get.

I suspect being very light with high air content the ration could be 1mm : 1.5CM-

That points to 22CM being the mean & 30cm being the TOP END-

SO for forecast purposes & for the fact the low could fragment / weaken & stay west my forecast for the period is

London/essex/ kent / East sussex 5-10cm.

Surrey / West Sussex 7-15cm.

Areas like the downs- all around banstead etc- ~ 20cm.

this is based on the UKMO-

For the ECM knock 3/4cm of all totals-

**** remember the biggest caveat to this ISNT temperature for once- but how far east the PPN goes & holds together.

**** Where it stalls will get persistent snow for 30 hours before it fragments ****

So does it end there????????- NO, for this to be special & one for the archives you need a sustained period over 2 weeks- so lets open the ECM curtains for next week - after sub -10c minima sat night-

Snow approaching from the west-

http://en.vedur.is/photos/atlant_evr_urkomuspa/130116_1200_114.png

http://en.vedur.is/photos/atlant_evr_urkomuspa/130116_1200_120.png

http://en.vedur.is/photos/atlant_evr_urkomuspa/130116_1200_126.png

another 12 / 18 hour event that rolls into convective snowfall post that- & very cold out to day 10-

In Summary then:

A snow event friday- DONT ramp it up to much on the PPN front as the ECM is fast through with no real stall- so amounts are in the sub 10cm camp- where as the UKMO is VERY aggressive with PPN..

until then- total ice day tom & friday- freezing the ground & some ponds/lakes ready for the snow...

S

Super. Thanks Steve. Could you please explain where the 15mm ppn totals are pulled from?

And also if you wouldn't mind, could you explain what the T+72 fax is showing please?

Thanks mate. Great stuff.

[anything-but]

Just in from a damm cold day on the bike,havn`t had a chance to follow things here today so can anyone bring me up to speed as to where things stand this evening please?

[alexisj9]

BBC South East - http://www.bbc.co.uk/weather/me1

BBC London - http://www.bbc.co.uk/weather/2643743

Click on the videos to see the difference!

Great I hope croydon is close enough to kent to be covered by your forcast, defo says rain saturday on our one.

[Joker]

One thing I will say about Cockthaw is that he seems to focus on central London. Last Feb he talked about minimal amounts of snow in London, which came as a surprise to many in the capital who had 3-4 inches and a Sunday of sledging. Yet central London was clear. Not saying this is what is happening here but maybe he is factoring the intense heat trapping that occurs in the middle of town. Just a thought.

"Cockthaw" - love it!

[NO LONGER POSTING]

As ever Steve you make a cracking forcast! Really good read... Heres hoping guys!

BTW Petter Cockhandler can do one... He ain't got a bloody clue and just cares about what the weather will be like at the football and promoting BBCs radio stations

[Neilsouth]

Just in from a damm cold day on the bike,havn`t had a chance to follow things here today so can anyone bring me up to speed as to where things stand this evening please?

We are on the cusp of one of the best falls of snow for many years and possibly leading into more and more!

BUT things could go very wrong and there are signs of that happening ( weaker front / not pushing as far east ), even the mention of rain for the weekend. But different models different possibilities

[AmershamMike]

So to tonights update:

Most of use have been around a while, some of us lucky enought to remember 1987, some can remember 79 & some even 47 & 63-

They are the archive charts that we search & find every year when we want to enjoy our memories of cold & snow-

Note its nearly 50 years to the day for the famous winter of 63.....

We stand on the cusp of charts ( like Dec 10 as well) that could stand in the archives years to come..- especially if the ECM vairifies tonight which would see the cold spell stretch to day 13 & beyond ( assuming Monday was day 1)-

Without going into the background of whys & what nots the first thing we might consider is the rarity of this weekends pattern.

We have had a 'few' undercutting type scenarios in the last few years but they all held one common theme - no blocking high to the east- usually we have low pressure in the north sea that allows low pressure from the atlantic to pass through with little or no resistance- so anything coming from the SW is either snow to rain or freezing rain to rain.

last time we had a stalling frontal zone that delivered high quantities of snow was 5th feb 1996- thats 17 years ago. - so whilst theres a chance that it could miss the SE the pattern on the whole is RARE.

Here is the 1996 chart-

Crucially when we talk about 850 temps the -2c line is a good guide-

heres those temps at 12pm that day

http://modeles.meteo...996-2-6-0-2.png

I recall the Kettley forecast saying ' the front is really getting a speed on now & its even snowing in the channel islands-... where we can see the -2line.

So for this scenario if we look at mid term models in THIS scenario- any sliders or creepers along the channel- the -2 line is the guide.

The event for friday for the SE has no marginality in terms of temps- except for the EXTREME SW of the region coastal areas- southampton sort of way- however you only need travel a few miles inland away from any onshore breeze to be secure.

so there she is in all her beauty-

http://www.meteociel...48-21.GIF?16-18

The UKMO chart at T48 shows the low slightly positioned further south than 96 & the upper blocking high further North- this means V 1996 the atlantic should move further east into the country as the amplitude of the jet isnt quite as high. ( slightly lower wave )

The SW taking a beating there with snow friday for 12 odd hours really building up-

Then we enter the fray- around T54/T60 & out to 78/84- so 24 hours is a **POSSIBLE** bet.

http://www.meteociel...60-21.GIF?16-18

The T60 shows the low sliding SE- which is great as the PPN sheild ahead of it isnt actually getting any further east-

The low is also pumping up moisture & instability across the SE which will enhance the PPN rates-

so at T45/48 we are starting out-

http://www.meteociel...8-594.GIF?16-18

but at 60 we have that push & onshore flow from the SE

http://www.meteociel...0-594.GIF?16-18 &

The Raw output between 12pm Friday & 12pm Saturday are suggestive of 15mm widespread- especially to the south & SW of the region-

Because the air is so dry & he dewpoint very cold the accumulation ration will be higher than your usual wet rubbish we get.

I suspect being very light with high air content the ration could be 1mm : 1.5CM-

That points to 22CM being the mean & 30cm being the TOP END-

SO for forecast purposes & for the fact the low could fragment / weaken & stay west my forecast for the period is

London/essex/ kent / East sussex 5-10cm.

Surrey / West Sussex 7-15cm.

Areas like the downs- all around banstead etc- ~ 20cm.

this is based on the UKMO-

For the ECM knock 3/4cm of all totals-

**** remember the biggest caveat to this ISNT temperature for once- but how far east the PPN goes & holds together.

**** Where it stalls will get persistent snow for 30 hours before it fragments ****

So does it end there????????- NO, for this to be special & one for the archives you need a sustained period over 2 weeks- so lets open the ECM curtains for next week - after sub -10c minima sat night-

Snow approaching from the west-

http://en.vedur.is/p...16_1200_114.png

http://en.vedur.is/p...16_1200_120.png

http://en.vedur.is/p...16_1200_126.png

another 12 / 18 hour event that rolls into convective snowfall post that- & very cold out to day 10-

In Summary then:

A snow event friday- DONT ramp it up to much on the PPN front as the ECM is fast through with no real stall- so amounts are in the sub 10cm camp- where as the UKMO is VERY aggressive with PPN..

until then- total ice day tom & friday- freezing the ground & some ponds/lakes ready for the snow...

S

Hi Steve, Great thoughts and forecast from you tonight....as usual. Any thoughts on snowfall amounts for Amersham at the bottom of the Chilterns? Cheers Edited January 16, 2013 by AmershamMike

[WillinGlossop]

As ever Steve you make a cracking forcast! Really good read... Heres hoping guys!

BTW Petter Cockhandler can do one... He ain't got a bloody clue and just cares about what the weather will be like at the football and promoting BBCs radio stations

Im guessing if ecm/ukmo forecasts are correct quite a few matches would be called off.... My partners meant to be going to man city v fulham on train sat morning......ouch.....

Edited January 16, 2013 by willinkent44

[chionomaniac]

Following on from Steve's post I wonder where the SE sweet spot will be come Saturday morning if we see a stall and pivot. My guess would be Mid West Sussex somewhere.

[Joker]

IAN F's forecast seems to be following the along the lines of the ECM and that channel LP for Monday: Blizzard 2 - The Return.

[Neilsouth]

That's ALOT of snow out in the north sea, does anyone have the current steering wind map?

not xcweather

[svalji]

Cheers Steve - what a fantastic summary. Thanks for taking the time and trouble to help explain things for those of us who are not so well informed! Do keep your posts coming - really add to the value of this forum.

Edited January 16, 2013 by svalji

[SMU]

Super. Thanks Steve. Could you please explain where the 15mm ppn totals are pulled from?

And also if you wouldn't mind, could you explain what the T+72 fax is showing please?

Thanks mate. Great stuff.

The PPN totals are pulled from the 12hour interval 48-60 in MMs on UKMO raw which is 5-10mm & 60-72 on UKMO raw 2-5mm

Also what I didnt add is any residual snow post 72-

So the totals are 7-15mm total.

However the ECM was disapointing....

THe fax at 72 that your referring to in some of your posts has the decaying front over EA & another occlusion moving SW over bristol- that would be the dividing line of cold / mild air-

There will also be NO snowmelt sunday or monday.....

Sothern Chiltern- again depends where the core of the PPN holds together- the chilterns may well force some further lift & increase PPN rates- so possibly 10-15

** all of this info based on UKMO raw- next update would be tomorrow 9am for T36-60 period- which is also good as we get 6 hour increments-

S

Edited January 16, 2013 by Steve Murr

[Katiewombat]

Hi Steve, Great thoughts and forecast from you tonight....as usual. Any thoughts on snowfall amounts for Amersham at the bottom of the Chilterns? Cheers

Not far from you but much higher. Very interested in steves reply