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

[Tom Quintavalle]

Snow moving in again

​A pick from earlier

Hi frosty,

At last, those showers have been faffing about in the N.Sea for what seems like an eternity.

Looking at the last few radar grabs, the flow seems to be steering them towards the N.E.Kent coast.

Good luck, keep us updated!

Regards,

Tom.

[Davey80]

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

Great forecast Steve - What would you predicted snow depths be for North Hampshire . Alton/Basingstoke area?

[Redmc13]

Just had a dusting in Sandwich

[WillinGlossop]

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

not xcweather

http://expert.weatheronline.co.uk/uv90_frame.htm

http://expert.weatheronline.co.uk/uv90_frame.htm

http://www.metoffice.gov.uk/weather/marine/shipping_forecast.html#All~Thames

[Jasmine]

Good Evening Guys, Steve how many cm of snow do you predict London's going to get.

[kold weather]

Just looking at the models, I think the front weakens through Friday afternoon only to see another burst of energy re-strengthen the front from the south through the eveing. Somewhere maybe unlucky and not get that much snow due to getting the front in its weaker form and the heavier stuff that redevelops may stay a little further south.

I suspect somewhere will luck out here and get 15-20cms, but equally some places may end up struggling to get much beyond 3-4cms, expect fairly wide range of falls.

[NO LONGER POSTING]

Guys.. Dont ask about snow depths in your area.. Until it is on the radar and falling out of the sky can we make a judgement then

[Lampostwatcher]

Sorry Peter cockfrost is a angel delight

[DAVID SNOW]

Just had a dusting in Sandwich

Bit gritty?

[WillinGlossop]

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

not xcweather

http://www.meteoradar.co.uk/

Wowza somewhere in east kent could get a bit from that!

[abruzzi spur]

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.

Chino my experience leads me to conclude that I would put it about 10 miles north and 20 miles east of your suggestion. Somewhere like, oooh I'm not really sure, maybe... hazarding a guess, somewhere like, possibly, Reigate.

Edited January 16, 2013 by abruzzi spur

[Jayces]

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.

I'm supposed to be driving to Crawley Saturday lunchtime....

[NO LONGER POSTING]

North Surrey Sweet spot No only kidding I think a little North of my Region will be the sweet spot

[Crystal Memories]

Hi frosty,

At last, those showers have been faffing about in the N.Sea for what seems like an eternity.

Looking at the last few radar grabs, the flow seems to be steering them towards the N.E.Kent coast.

Good luck, keep us updated!

Regards,

Tom.

Hi Tom We have been getting light snow for about 15 mins now giving a little fresh layer so all looks pretty again & hopefully a sign that more is on the way

[10 Days Away]

Just had a dusting in Sandwich

Did you pick up the ornaments or work around them !!

[Jan_Bromley]

Just back online after major pc problems.

In time for the main event on Friday. Lovely.............

[10 Days Away]

I think we had a false radar reading for Ashford. I got all excited for a minute and rushed to look out of the window.

Alas, to no avail

[Neilsouth]

http://www.meteoradar.co.uk/

Wowza somewhere in east kent could get a bit from that!

IF!!!!!!!!!

that's a massive IF, the winds change more to the north east expect east kent to get upto 5cm or more! However Margate/Ramsgate/Dover is currently looking good for a few cm or more.

[alexisj9]

IF!!!!!!!!!

that's a massive IF, the winds change more to the north east expect east kent to get upto 5cm or more! However Margate/Ramsgate/Dover is currently looking good for a few cm or more.

The wind will change to ENE,.......

In my dreams.

[Southender]

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

Thanks Steve.

Super explanation.

So in short we want the UKMO output to verify. But the rest all show the same but a smaller dump of the white stuff.

That will do me.

[WillinGlossop]

IF!!!!!!!!!

that's a massive IF, the winds change more to the north east expect east kent to get upto 5cm or more! However Margate/Ramsgate/Dover is currently looking good for a few cm or more.

Im not saying fav will but yes deal/manston/dover/folkestone etc ould get a decent 5cm if and when the winds veer round to se direction ie http://www.metoffice.gov.uk/weather/marine/shipping_forecast.html#All~Thames

Ps the met warning is valid until 2355 so if it does happen they can claim they warned of it.....

Edited January 16, 2013 by willinkent44

[SMU]

Yes - there are NO mild runs- just variations on PPN totals-

** REMEMBER THE INCREASE OF PPN FROM THE SOUTH!**

S

[Southender]

Just looking at the models, I think the front weakens through Friday afternoon only to see another burst of energy re-strengthen the front from the south through the eveing. Somewhere maybe unlucky and not get that much snow due to getting the front in its weaker form and the heavier stuff that redevelops may stay a little further south.

I suspect somewhere will luck out here and get 15-20cms, but equally some places may end up struggling to get much beyond 3-4cms, expect fairly wide range of falls.

Yep. The 3-4cm spot looks like it has SE ESSEX name on it! Hey ho, I will take that though!

We aint the driest spot in the UK for no reason.

Edited January 16, 2013 by Shrimper

[sarah7meme]

A friend is travelling from Kent to Wales Friday !

[2810lollypop]

I'm supposed to be driving to Crawley Saturday lunchtime....

may be on ski's lol