South West & Central Southern England Regional Discussion 26th January 2013

[Bristawl Si]

The latest ECM Det, regardless of what you read in the MOD thread, is actually quite a cold run. Nothing substantial nor nothing too snowy due to the air often being west of north, so moderated somewhat, but with elevation and a bit of luck, I wouldn't rule out a bit of transient wintriness at times for some next week if indeed the ECM verified.

Me being me here!

When cold comes in 1st half of February it's normally a decent spell with some snow for us in the West - the forecast setup seems more akin to late Feb/early March.

I'm hoping for a gradual upgrade in the coming days.

[katemart]

Wind turbine blown down in Devon:

http://www.guardian....lown-down-devon

Sorry, just noticed that actually happened on Sunday night.

Edited January 30, 2013 by katemart

[dec10snow]

Wind turbine blown down in Devon:

http://www.guardian....lown-down-devon

Sorry, just noticed that actually happened on Sunday night.

How ironic

[cerneman]

Wind turbine blown down in Devon:

http://www.guardian....lown-down-devon

Sorry, just noticed that actually happened on Sunday night.

Maybe Wind not what caused Turbine to fall?????????

[fergieweather]

New (modified) NAE continues trend back to consensus, of sorts, with UKMO-GM and ARPEGE. Less deep, with more southerly centre of gravity as per other models - hence less developed with colder 'tuck' from N and hence much reduced threat of strong winds and snow. So, all positive from those perspectives - but rainfall signal for rush-hour Fri morning still looks pretty bothersome.

[dec10snow]

New (modified) NAE continues trend back to consensus, of sorts, with UKMO-GM and ARPEGE. Less deep, with more southerly centre of gravity as per other models - hence less developed with colder 'tuck' from N and hence much reduced threat of strong winds and snow. So, all positive from those perspectives - but rainfall signal for rush-hour Fri morning still looks pretty bothersome.

If it does track further south, this would mean higher rainfall overall yes?

[Andy Bown]

New (modified) NAE continues trend back to consensus, of sorts, with UKMO-GM and ARPEGE. Less deep, with more southerly centre of gravity as per other models - hence less developed with colder 'tuck' from N and hence much reduced threat of strong winds and snow. So, all positive from those perspectives - but rainfall signal for rush-hour Fri morning still looks pretty bothersome.

Thank you for the updates Ian.

Is there any chance of ...

1. The LOW racing through by rush hour time on Friday?

2. The LOW being delayed until later in the day?

3. It diving totally South taking the worst rain with it?

[gottolovethisweather]

On top of the wonderful analyses already provided, I wish to add my initial thoughts for the first third of February and perhaps beyond.

As usual, I am basing my evidence on consecutive GFS 12z runs and where need be, additional tweaking from other sources from elsewhere.

As ever, I urge newbies and/or unexperienced model output followers to please view things only from a global perspective. In general, miniscule yet undeveloped surface features often at the >t+96 timescale only serve to confuse your interpretation of the model output. This week, being a special case in point of this, as we have a very difficult forecasting situation at the <48 hour timeframe.

In fact, let us look at where the NH Jetstream was projected to be by todays date (Wednesday 30th January, 12pm), some two days ago. As a consequence, what were the expected associated T850s.

To be expected, it did develop into what we basically witnessed at the surface, a breezy type of day with the NH Jetstream roaring directly above our heads. However, when we move forward another 48 hours to Friday 1st February, 12pm), we were expected to see the following conditions, NH Jetstream and T850s profile wise.

Compared to what is now expected on the hugely anticipated date of Friday 1st February, 12pm.

Not much has changed from the GFS 12z expectations of two days ago, compared to what is now projected. If anything, today's 12z run has upped the anti with the depression. However, the split flow in the NH Jetstream is much more of a talking point because after Friday's event it offers the UK a complete reversal in terms of airflow from tropical maritime to polar maritime, albeit temporarily.

So now what of what on Monday was the t+144 timescale, Sunday 3rd February, 12pm. Previous expectations against todays, having moved forward to t+96 timescale. Firstly in terms of NH Jetstream.

Monday's 12z at t+144.

Todays's 12z at t+96.

How about Sunday's T850s profile wise. Then and now.

What is apparent now is quite a divergence in output, from just the last couple of days.

Two important points to note here IMHO are, that we MUST NOT DISMISS the relatively high chances of backedge snowfall (I guess at a 60% to 70% risk for my location) from the Friday event. This takes place between the previously shown chart above and the current one. What is not shown is the large range of t850s diving South from polar regions, in between the two charts, i.e come the very cold February 2nd as hinted at by AWD.

My second point is such charts, on the face of look rather disappointing springlike synoptics, after a brief tempory excursion from the North, in fact by t+144 (Tuesday 5th February, 12pm) end with us heading towards an ever cooler wintry type of synoptic yet again.

NH Jetstream diving South once again.

Associated T850s profile at Tuesday 5th February, 12pm timeframe.

And then some, come Thursday 7th February, 12pm, courtesy of NH Jetstream and T850s once again.

It would be futile to look in detail, any further than next Thursday, however I firmly believe there will be a significant upgrade in the coming days, when speaking of further cold potential and wintry type synoptics. Three dates seemingly stand out for me as ones to watch at this range, they are Friday 1st February, Tuesday 5th February and yet further potential for yet deeper cold from the 10th February onwards.

• For the more immediate timeframe, regarding the appoach of the potentially dangerous (hopefully trending less so) development, I advise folk to follow posts containing NAE output, NMM output and/or MetO Fax chart updates.
  

Stay safe and stay tuned to this regional for many more updates.

Edited January 30, 2013 by gottolovethisweather

[Beast of Plympton]

Thank you sir, very good as ever.

Edited January 30, 2013 by Beast of Dartmoor

[Beast of Plympton]

GTLTW, what do you reckon the chances of that line of snow hitting dartmoor on friday??

[Freddie123]

Does appear to be some lightning strikes associated with the front approaching overnight, its currently over western Ireland. Better get some sleep now, it could be an early wake up call.

http://www.metoffice.gov.uk/public/weather/observations/#?tab=map&map=Lightning&fcTime=1359543313&zoom=5&lon=-4.00&lat=54.63

[gottolovethisweather]

GTLTW, what do you reckon the chances of that line of snow hitting dartmoor on friday??

UKMO data online currently suggests otherwise I believe, but elevation is key and I don't really see why you shouldn't see some sleet as an example. My patch, more especially the downs I suspect could catch a pasting. This is a tricky beast (not the Dartmoor beast I might add) for the UKMO right now as it has the makings of a deluge and/or significant snowfall event, especially at elevation.

fergieweather stating similar thoughts from earlier I believe.

http://forum.netweather.tv/topic/75744-south-west-central-southern-england-regional-discussion-26th-january-2013/page__st__480#entry2579182

Edited January 30, 2013 by gottolovethisweather

[stevofunnelcl]

quite a cluster of sferics for south-west ireland, heading east, if they keep going

[Costa Del Fal]

Chance of an overnight thunderstorm for Cornwall tonight? Looks like some good activity has occurred in Ireland.

David back on Spotlight tonight.

[Dorsetbred]

A very nice feature out in Lyme Bay currently heading our way, fingers crossed it cruises over us.

[Blizzardof82]

Some really torrential rain this morning around 5am, all clear now and breezy.

[Beast of Plympton]

UKMO data online currently suggests otherwise I believe, but elevation is key and I don't really see why you shouldn't see some sleet as an example. My patch, more especially the downs I suspect could catch a pasting. This is a tricky beast (not the Dartmoor beast I might add) for the UKMO right now as it has the makings of a deluge and/or significant snowfall event, especially at elevation.

fergieweather stating similar thoughts from earlier I believe.

http://forum.netweat...80#entry2579182

Thanks GTLTW, very bored of the rain again now so hopefully size (of the hill) does matter!! Will nowcast on friday.

[AWD]

Thanks GTLTW, very bored of the rain again now so hopefully size (of the hill) does matter!! Will nowcast on friday.

You aren't going to like this for tomorrow then;

[Beast of Plympton]

You aren't going to like this for tomorrow then;

No, your right, absolutely don't like that!! Got the wood for my Arch ready.

Edited January 31, 2013 by Beast of Dartmoor

[Coast]

You aren't going to like this for tomorrow then;

At least the worst of the winds have gone now:

Edited January 31, 2013 by Coast

[SilverWolf]

You aren't going to like this for tomorrow then;

Is the ppn moving west to east tomorrow? Just wondering if that shows its most northerly extent. Thanks

[dec10snow]

Is the ppn moving west to east tomorrow? Just wondering if that shows its most northerly extent. Thanks

I believe it is going west to east, yes

[Coast]

They don't make 'em like they used to!!

Wind turbine blown down in strong winds in Devon

Residents express fears over safety after 24-metre turbine collapses

http://www.guardian.co.uk/environment/2013/jan/30/wind-turbine-blown-down-devon

[AWD]

Nice little "semi" squall line stretching down NE/SW from East Gloucesteshire, Bristol and into west Somerset.

Just passing over me now and there is some torrential downpours associated with it.

[TwisterGirl81]

Heavy rain and very very blustery/squally winds here in Exeter.....Calm before the storm maybe?