Model Output Discussion - Colder but how cold and for how long?

[Mark wheeler]

Gfs 6z

[Penicuikblizzard]

Looking potentially pretty good for the North on Tuesday with the possibility of a snow event, the models have shown this for a few days now. Warnings now out for this too

[doctormog]

7 minutes ago, Kasim Awan said:

Yeah looking like going to the South now. Around a 15/20% chance of a more northerly track. 

Even the risk of snow showers into the Cheshire gap has reduced somewhat.

The fact is over 90% of the UK population will remain snow free from this toppler.

The risk of troughs forming in the flow is very low because it gets shunted out by Atlantic air very quickly.

Enjoy everyone  

To describe this weather as a toppler is misleading and sounds like “everything that comes from the north that doesn’t give me snow” is a “toppler”. The synoptics show a bitterly cold Arctic/polar flow and not something casually dismissed as a toppler even if large parts of the country do not see snow.

[sunnijim]

4 minutes ago, Mark wheeler said:

Gfs 6z

Looking like a correction South from the 00z?

A South coast snow tickler .

[Kasim Awan]

4 minutes ago, doctormog said:

To describe this weather as a toppler is misleading and sounds like “everything that comes from the north that doesn’t give me snow” is a “toppler”. The synoptics show a bitterly cold Arctic/polar flow and not something casually dismissed as a toppler even if large parts of the country do not see snow.

Well as far as I can see the cold topples eastwards so by definition parts of the cold snap is a toppler even if initially it is a cold polar air mass.

[MJB]

11 minutes ago, tight isobar said:

Indeed snow chances evaporating every run now !!!@countrywide.

But wasn't this going to be snow a plenty set up  I have seen this many times and end up with nothing ( I'm talking MBY ) 

IMO it's a brief cold snap with no WOW factor.

[Penicuikblizzard]

4 minutes ago, doctormog said:

To describe this weather as a toppler is misleading and sounds like “everything that comes from the north that doesn’t give me snow” is a “toppler”. The synoptics show a bitterly cold Arctic/polar flow and not something casually dismissed as a toppler even if large parts of the country do not see snow.

A toppler is normally a 24/48hr event this is a 5/6 day cold spell so most definitely not a toppler.

[frosty ground]

1 minute ago, Kasim Awan said:

Well as far as I can see the cold topples eastwards so by definition parts of the cold snap is a toppler even if initially it is a cold polar air mass.

Well that’s not a toppler, it’s your version of one but for those of us who have been a round for a while’s that’s not a toppler.

 

[Midlands Ice Age]

33 minutes ago, Cambrian said:

The 0z UKMO, is a fascinating and, I feel, quite a concise run. The pressures and heights chart shows the machinations of the PV, the Siberian lobe dropping down into Northern Europe during the first 5 days, the main lobe of the PV actually brushing our shores, before spinning back around north and bridging through Svalbard and Greenland to the regathered Canadian lobe, ultimately coalescing over northern Greenland, leaving the UK and Ireland in a westerly flow by day 6. 

It’s the T850s that caught my eye though. Pulses of very cold air heading south through the UK and Ireland, cold through to day 6 before it turns milder. The first warm sector gets squeezed out to our west around day 5, before the second one manages to break through. 

 

It might be well worth keeping an eye on the shape of these warm sectors and how far north they are, this could well change over the next few days, with the scope for some chilly uppers to follow from the eastern seaboard, mixing with cold air being pushed south out of Greenland. With such a lot going on with the PV, the models might well struggle with the north-south placement of the Atlantic jet stream for a fair few days. 0z ECM / GEM / GFS ops at day 7, a wide range, particularly at our end.

  

So over the last couple of days, a more sudden curtailment of the deeper northerly flow than that being indicated previously in the models, let’s not pretend, but another good cold week in the middle of January, which we rightly saw coming for a fair few weeks.

Up here, we still have sections of solid ice where normally bubbling springs froze over a full week ago, so irrespective of if and where the snow falls over the coming days, this is quite different to many of the Januarys we have seen in the last couple of decades, an interesting spell in a winter that is far from a typical winter too.

IMO ...

These gif's show the impact of the development of the Bering high.

If one looks at the NH graphicals,  the development and inclination of this high is key to what happens to the total northern hemisphere.

Get it slightly different and everything will change by the 'pushing' process.

MIA

[weathercold]

One for those with historical knowledge- has there been a winter in the last 30 years which has had so much going for it in terms of background signals heading into winter which has developed as uneventful and non-descript as this? Granted we still have Feb but by mid month winter starts to reduce its impact as we can finally look forward to spring.

Feels like this winter has been a real lesson in that background signals can be as rosey and favourable as possible but it means diddly squat for our tiny island in reality. 

[high ground birmingham]

39 minutes ago, Kasim Awan said:

Well as far as I can see the cold topples eastwards so by definition parts of the cold snap is a toppler even if initially it is a cold polar air mass.

 It is not a toppler which is a transition of a 24-48 hour period of colder weather with the Atlantic then moving in

Edited January 14 by lorenzo
Removing the inflammatory part of the post.

[EML Network]

So regarding Wed/Thurs the ECM has shifted around 50 miles north and the GFS around 50 miles south in terms of how far north it is suggesting any PPN might fall as the LP system makes it's way across the north of France. 

Those hoping to see snow falling AND SETTLING in the extreme south probably aren't going to like this chart below

The entire coastline probably to a good 10 miles inland has dew points the wrong side of freezing, meaning anything that does fall is going  to struggle to settle on the ground, add saturated ground into the mix and it's not really supportive of laying snow, perhaps the tops of the South Downs might see something. 

Personally I think your best bet would be to get a boat and head off into the middle of the English channel

Also regarding the overnight Tuesday / Wed snow potential it's a similar story



High ground is going to make all the difference IMO

[Ali1977]

Strong mean for the south still 

[tight isobar]

We are now over the cusp and into arctic airflow.. and that being on the very verge of a new week- That all taken into account today’s 12z suites would/ should offer up much sterner exaction’s!.. on local overheads- as well as nationwide!.. 

[tight isobar]

1 minute ago, Ali1977 said:

Strong mean for the south still 

Now that a solid mean!! Over to the 12z on this 1

[StingJet]

9 minutes ago, AltonMatthew said:

Cant see justification in the models for the 3 day warning event they have put out? Especially for my patch. 

 

Are they perhaps seeing an increased risk of showery activity? 

More than likely yes ..down to this "potential"  feature Tuesday into Wednesday 

 
English Channel battleground Wednesday - interesting to see how this actually pans out 

[AO-]

44 minutes ago, high ground birmingham said:

This is nonsense. It is not a toppler which is a transition of a 24-48 hour period of colder weather with the Atlantic then moving in

Well, I'm glad I get an explanation. I thought a toppler was a wedge that gets overrun by shortwaves and does not become a ridge. 

Edited January 14 by AO-

[summer blizzard]

Small changes from the Euro that May have been missed.

So firstly the low on the 19th has a bit more negative tilt delaying the breakdown an extra day to the 21st. The low is also weaker.

Then the second low instead of zipping north east, moves south east.

The crux is that while we end up with a +AO, there’s enough amplification that high pressure keeps everything north of most of England/Wales.

So as I said yesterday, don’t be shocked if the outcome is much more high pressure influenced than zonal.

[TillyS]

20 minutes ago, MJB said:

But wasn't this going to be snow a plenty set up  I have seen this many times and end up with nothing ( I'm talking MBY ) 

IMO it's a brief cold snap with no WOW factor.

In the interest of balance, whilst I agree that this probably won’t produce much in the way of snow for southern Britain (at least that’s how it looks at the moment), it does look as if it is going to be very cold this week. The GFS shows some hard frosts ahead of the Atlantic returning:

 

I guess you’re right though. To think ‘WOW’ when the temp is -5C in the south is a bit of a sorry state of affairs. The CET will take a hit for sure this week but the way the models look it’s quite possible it'll finish back above average.

[MJB]

Beeb forecast have lowest temps around 2 c by day ( south ) but mentioned sharp overnight frosts.

Windchill from this tomorrow in the South -2

More widespread snow in Central Southern Scotland on Tuesday. No mention or chart shown for the LP in the Channel, tells me it's insignificant. Mild and wet next weekend.

Standard winter week I'd say.

 

 

[That ECM]

Not a bad fi.

[sunnijim]

27 minutes ago, EML Network said:

So regarding Wed/Thurs the ECM has shifted around 50 miles north and the GFS around 50 miles south in terms of how far north it is suggesting any PPN might fall as the LP system makes it's way across the north of France. 

Those hoping to see snow falling AND SETTLING in the extreme south probably aren't going to like this chart below

The entire coastline probably to a good 10 miles inland has dew points the wrong side of freezing, meaning anything that does fall is going  to struggle to settle on the ground, add saturated ground into the mix and it's not really supportive of laying snow, perhaps the tops of the South Downs might see something. 

Personally I think your best bet would be to get a boat and head off into the middle of the English channel

Also regarding the overnight Tuesday / Wed snow potential it's a similar story



High ground is going to make all the difference IMO

Hii EML, you were once Brighton?

Hence the need as illustrated so well above for the really fine margins on this system to work out if it is a snowfall on the South Coast.

Yesterday's GFs 06z was perfect in that respect, we held on to good dewpoints .The amounts of snow were reduced as the system held a little further South, Northward corrections are allowing milder air to mix in, all be it with heavier snow that doesn't stick in the far South.

Edited January 14 by sunnijim

[bluearmy]

Gfs fi has us chasing an arctic ridge again - lucky they can be relied upon! 

[That ECM]

Just now, bluearmy said:

Gfs fi has us chasing an arctic ridge again - lucky they can be relied upon! 

Got a chase something.

[Purga]

Something 'interesting' appears to be happening on the 06z run. Short lived mild spell anyone?

Rinse & repeat - only better next time

 

Edited January 14 by Purga