London And The South East Regional Discussion Thread - II

[snowfall09]

http://www.bbc.co.uk/weather/features/16821819

[Buzzit]

http://www.bbc.co.uk...atures/16821819

BBC Weather's John Hammond said: "At this stage it's clear that the forecast is on a knife-edge and is definitely one to keep an eye on in the next few days. We could see the cold air holding on or the mild air will move right across the country which will make for a dull, damp, dreary and less cold end to the weekend."

Translation "Met office do not have a clue"

We are going to stay cold folks

[Roger J Smith]

On balance things continue to look promising for locally heavy snowfalls with east Kent obviously best placed, but other regions further west and north not entirely left out even before the main event which looks to be a mesoscale low Friday night into Saturday ahead of the slow-moving breakdown frontal system. While many will be describing this snow potential as "ahead of warm front" it is more related to an upper level low circulating around in the ENE flow of exceptionally cold air, and more of an independent player that will receive a boost in later stages from the warm front.

Would suggest that tomorrow is moderately good for streamer potential and could produce a few local amounts in the 10-20 cm range but wider amounts of 2-5 cms, these not limited to the southeast but also showing up in parts of the east Midlands and east Anglia.

Thursday then becomes a bit less favourable for wind speed but has some of the coldest air beginning to circulate around and any hint of troughing, however weak, could become a focus for locally intense snow bands that will tend to hover in one place (Canterbury?) for several hours due to weaker steering currents. Localized snowfalls of 10-30 cms are possible with this. It is going to be cold enough to keep daytime highs near or sub-freezing. By the way, a reverse way of thinking about this is as follows ... the upper dynamics support temperatures in the range of -10 to -5 C, but these seem intuitively too cold, so what prevents them? Snow streamers and cloud.

Friday then looks best for snow development on a wider scale, especially later in the day towards the Friday-Saturday overnight when I think the model consensus indicates good chance of mesoscale snowfall development widely over the Dover straits region. Extremely cold air aloft will be interacting with the North Sea to augment this development, and it is the lunar "northern max" which is always a boost for snowfall or severe weather intensification. As this mesoscale feature remains quasi-stationary into Saturday, the advancing warm frontal trough with Atlantic moisture will overrun and possibly set off even heavier snowfall amounts. There is potential for 20-40 cms of snow in all of this activity and a fairly widespread production of at least 10 cms. There are also risks of freezing rain and ice fog to be considered for road maintenance and other interests.

In general, I think the public forecasts are giving the impression of a rather cold period with a few snowflakes in the air and a slight frost, but I'm seeing this as a deep freeze situation with surprisingly cold temperatures and locally heavy snow. The 12z model runs are all slight upgrades on earlier trends model for model and the GEM actually brings the 510 dam ashore and into London which would be quite a shocker both ways.

[Cheese Rice]

Interesting..

[SMU]

12 Zeds's excellent tonight ( well the important ones )

People its going to be freezing until at LEAST Sunday- with snow

ECM at 96 has upgraded west again with -15c air into SE kent & -13/-14 over the region- Thickness around 510 DAM-

Thursdays TMAX looks to be around 0 in the city & -2c in the suberbs-

snow to come & that the hardest part of the forecast, but at least we know the mercury is unlikely to get above 1c in the next 5 days

S

[Jo S]

Things getting exciting again.just a little lull that lasted a couple of hours on here,then here we go again.

[Met4Cast]

On balance things continue to look promising for locally heavy snowfalls with east Kent obviously best placed, but other regions further west and north not entirely left out even before the main event which looks to be a mesoscale low Friday night into Saturday ahead of the slow-moving breakdown frontal system. While many will be describing this snow potential as "ahead of warm front" it is more related to an upper level low circulating around in the ENE flow of exceptionally cold air, and more of an independent player that will receive a boost in later stages from the warm front.

Would suggest that tomorrow is moderately good for streamer potential and could produce a few local amounts in the 10-20 cm range but wider amounts of 2-5 cms, these not limited to the southeast but also showing up in parts of the east Midlands and east Anglia.

Thursday then becomes a bit less favourable for wind speed but has some of the coldest air beginning to circulate around and any hint of troughing, however weak, could become a focus for locally intense snow bands that will tend to hover in one place (Canterbury?) for several hours due to weaker steering currents. Localized snowfalls of 10-30 cms are possible with this. It is going to be cold enough to keep daytime highs near or sub-freezing. By the way, a reverse way of thinking about this is as follows ... the upper dynamics support temperatures in the range of -10 to -5 C, but these seem intuitively too cold, so what prevents them? Snow streamers and cloud.

Friday then looks best for snow development on a wider scale, especially later in the day towards the Friday-Saturday overnight when I think the model consensus indicates good chance of mesoscale snowfall development widely over the Dover straits region. Extremely cold air aloft will be interacting with the North Sea to augment this development, and it is the lunar "northern max" which is always a boost for snowfall or severe weather intensification. As this mesoscale feature remains quasi-stationary into Saturday, the advancing warm frontal trough with Atlantic moisture will overrun and possibly set off even heavier snowfall amounts. There is potential for 20-40 cms of snow in all of this activity and a fairly widespread production of at least 10 cms. There are also risks of freezing rain and ice fog to be considered for road maintenance and other interests.

In general, I think the public forecasts are giving the impression of a rather cold period with a few snowflakes in the air and a slight frost, but I'm seeing this as a deep freeze situation with surprisingly cold temperatures and locally heavy snow. The 12z model runs are all slight upgrades on earlier trends model for model and the GEM actually brings the 510 dam ashore and into London which would be quite a shocker both ways.

I don't doubt your forecasts Roger, your long range forecasts are usually second to none, however.. 10-20cm in some areas tomorrow? What is this based on? All the models, even the short term high res models are showing it to be dry and mostly cloud free tomorrow?

[Marie]

Thanks RS and SM ,put the smile back on my face,great posts

[Pixel]

Would suggest that tomorrow is moderately good for streamer potential and could produce a few local amounts in the 10-20 cm range but wider amounts of 2-5 cms, these not limited to the southeast but also showing up in parts of the east Midlands and east Anglia.

.... Friday-Saturday overnight when I think the model consensus indicates good chance of mesoscale snowfall development widely over the Dover straits region. Extremely cold air aloft will be interacting with the North Sea to augment this development, and it is the lunar "northern max" which is always a boost for snowfall or severe weather intensification. As this mesoscale feature remains quasi-stationary into Saturday, the advancing warm frontal trough with Atlantic moisture will overrun and possibly set off even heavier snowfall amounts. There is potential for 20-40 cms of snow in all of this activity and a fairly widespread production of at least 10 cms...

I'd just be just happy if the decimal point in your forecasts moved to the left - I thought it was just in the USA where everything was bigger.

No offence I just love your enthusiasm - hope you're correct.

Edited January 31, 2012 by Pixel Precipitation

[Snow Queen one]

Thanks for the heads up Roger I hope you are right lol But we are never that lucky here in the SE for those amounts of snowfall.

[Tim Bland]

Come on RJS that some ramp! Adding up you totals there you are expecting 90cm of snow by the weekend in some spots! Meto say " a few snow flurries" and snow turning to rain at the weekend. I will take my hat off to you of you are right though!

[Paul Sherman]

Lol Really ?

Feb 2009 = 52cm of LEVEL Snow (Not Drifted Snow)

Dec 2009 = 34cm of LEVEL Snow (Not Drifted Snow)

Dec 2010 = 37cm of LEVEL Snow (Leigh on Sea) with 2 foot drifts measured at Belfairs Woods.

I think we are quite lucky where we are placed in the South East personally

[tinybill]

after watching the weather looks like we might have to put the snow spades ready out for the weekend could be some late nights model watching,radar watching!!

Edited January 31, 2012 by tinybill

[Jayces]

I think people need to realise that the kind of things Roger is talking about (correct me if I am wrong) are very localised affairs and he is not suggesting that the whole of the SE would get that sort of snow fall.

If streamers do occur they would only be forecast by the Met at extremely short notice, usually within hours of them starting so don't expect to see anything from the until tomorrow night for Wed / Thu.

[donna-m]

mmm..unbury kids sledge from under swimming pool in shed or leave it for now ???

oh decisions decisions

[Snow Obsession]

There are one of 3 possibilities for us at the weekend.

1) The Atlantic returns with a bang and we get a snow to rain event as milder air sweeps in.

2) The Atlantic and Cold fight it out above the SE and the front stalls in the cold air giving us copious amounts of snow.

3) The Cold air holds it own and we stay cold but with no snow.

Unfortunately we will not know until Saturday which scenario it's going to be.

As it's my birthday on Saturday, the best present would be scenario number 2... Can you sort that out for me please?

[leemondo]

the local weather on BBC was rubish! but the national one showed a battlefront??? if they all use the same data from the Met Office how can they be different?

90cms seems a tad on the large side, 9mm would be welcome at the moment lol

[Mr_Pessimistic]

Lol Really ?

Feb 2009 = 52cm of LEVEL Snow (Not Drifted Snow)

Dec 2009 = 34cm of LEVEL Snow (Not Drifted Snow)

Dec 2010 = 37cm of LEVEL Snow (Leigh on Sea) with 2 foot drifts measured at Belfairs Woods.

I think we are quite lucky where we are placed in the South East personally

yes, indeed you are very lucky.. no more than 2-3 inches here at any one time for over 20 years now (and im not kidding!)

Im not expecting any more than a light dusting, if that, here from the next couple of days, and none at the weekend due to the front never making it this far east.

[tinybill]

As it's my birthday on Saturday, the best present would be scenario number 2... Can you sort that out for me please?

will we dare open the curtains saterday morning !!

[k66yla]

apologies for being off topic but......... It would be great if certain weather forecasters would dress normally instead of some sort of cheap fashion show. A snow suit & goggles perhaps and maybe a balaclava for some <rant over> Been wanting to say that for ages....lol

[Snow Obsession]

will we dare open the curtains saterday morning !!

LOL! I love/hate that moment! So fabulous/disappointing...

[Met4Cast]

I think people need to realise that the kind of things Roger is talking about (correct me if I am wrong) are very localised affairs and he is not suggesting that the whole of the SE would get that sort of snow fall.

If streamers do occur they would only be forecast by the Met at extremely short notice, usually within hours of them starting so don't expect to see anything from the until tomorrow night for Wed / Thu.

True, but surely snowfall of the intensity to bring 10-20cm, even if it is very localised would at least be being hinted on the High Res models? Instead, there's absolutely nothing showing tomorrow on a single model.

[leemondo]

to be honest if the cold wins this weekend, then i think we may see some record breaking snowfall down here, and at the end of the forecast i just watched i think he dropped a hint at what he thinks will win..............

[sarah7meme]

What's the confidence / likelihood I get 10cm snow then this week? And when's best chance,?

[shivering]

the local weather on BBC was rubish! but the national one showed a battlefront??? if they all use the same data from the Met Office how can they be different?

90cms seems a tad on the large side, 9mm would be welcome at the moment lol

on our local one - east anglia - she also mentioned the battlefront - yippeee