Model output discussion 14/04/18

[I remember Atlantic 252]

GFS too far east for Monday's washout, watch it correct west over the next few runs, EC  and UKMO look correct, these systems tend to be further west than forecast by GFS

I'm certainly ready with my canoe for Monday, GFS is rubbish

[Mike Poole]

2 hours ago, Mike Poole said:

 

Big upgrades over recent output. If this pans out, credit to ECM for picking this up first, look forward to tonight's ECM. I'll be looking for a decent high pressure signal by day 9.

Here's the ECM, first at T192:

Then at T216, and yes it supports the idea of high pressure but over the south of the country primarily:

Edit, I wasn't really expecting this at T240!

Edited April 26, 2018 by Mike Poole

[Frosty.]

The Ecm 12z certainly shows a big improvement for the south later next week as high pressure ridges in and becoming much warmer compared to the cold, wet and windy start to next week..another taste of summer...for the south!?

Edited April 26, 2018 by Frosty.

[Biggin]

52 minutes ago, Sky Full said:

Sleet or even snow for central and southern England on Monday according to the Arpege..! 

Is that for real ? 

[bluearmy]

24 minutes ago, Biggin said:

Is that for real ? 

Ec op in broad agreement! Dew points above zero but T2 mid to upper thirties most of the day and with heavy precip there looks to be a decent chance of snowfall on the hills in central southern England! 

Will change run to run (the 00z ec op had significant accums across Kent and Suffolk) but this run dumps accumulated snowlfall of a foot across the chilterns and Salisbury plain.  

Edited April 26, 2018 by bluearmy

[Singularity]

Some serious evaporative cooling on the ECM 12z run. It will take such exact positioning of the most intense rainfall relative to the coldest air being entrained to produce snow to low levels, but it's not out of the question.

Not that long after, continued hints of a heat build getting underway over NW Europe in the 9-12 day range. 

Seems like we've got one of the most extreme spring seasons in living memory on our hands!

[Man With Beard]

3 hours ago, Sky Full said:

Sleet or even snow for central and southern England on Monday according to the Arpege..! 

This is absolutely bonkers. Who's ever heard of snow following after a 29C heatwave?!? But from what I consider the top model on frontal snow. 

[Interitus]

4 hours ago, Mike Poole said:

Here's the ECM ......

Edit, I wasn't really expecting this at T240!

Interesting, the ECM switches towards earlier GFS runs, while the GFS tends towards the previous ECM -

[snowsummer]

5 hours ago, Man With Beard said:

This is absolutely bonkers. Who's ever heard of snow following after a 29C heatwave?!? But from what I consider the top model on frontal snow. 

Has the south of england ever had snow in may, let alone following the 29C we've  just had?  Cant say i remember such an event, but once the sun came out  last week i could barely remember the winter just gone! 

[Summer Sun]

Great ECM 00z for the BH weekend with increasing warmth

Hope it's right

[Summer Sun]

No wonder the met office have yellow warnings out for the SE on Monday certainly flooding potential

[Newberryone]

20 minutes ago, Summer Sun said:

Great ECM 00z for the BH weekend with increasing warmth

Hope it's right

Here's hoping is right Gavin, however looking at the day ten chart one can't help but get the overall feeling there may not be much longevity attached to this more settled/warm interlude as that ominous looking feature to the west seems like at best reintroducing a cooler west to northwesterly airflow yet again with something akin to what we have at the moment.  

[Frosty.]

The Gfs 00z shows high pressure building in later next week bringing increasingly fine and pleasantly warm conditions across most of the uk..it currently looks like a very decent BH weekend..especially with the Ecm 00z firmly on-board, indeed, looking even better than last night's 12z!?  

[Relativistic]

10 hours ago, Man With Beard said:

This is absolutely bonkers. Who's ever heard of snow following after a 29C heatwave?!? But from what I consider the top model on frontal snow. 

Something similar occurred in 1945. According to TORRO, a high of 26.1C was recorded on the 18th (the record for that date). The end of the month then saw sleet and snow showers, with temperatures widely down to -4C. Full details can be found in the Met Office weather report for the month:

https://www.metoffice.gov.uk/binaries/content/assets/mohippo/pdf/l/0/apr1945.pdf

In terms of the mean CET, four daily records were set in April 1945. The 15th, 16th, and 18th all hold daily record highs, while the 30th holds the daily record low, just 12 days later.

Edited April 27, 2018 by Relativistic

[Summer Sun]

00z GFS offering hope at D7

 

[Sky Full]

ECM and GFS currently agree on an arm of the Azores high pressure extending across the UK by 4th May only to be shunted out of the way somewhat by the 7th or 8th by low pressure arriving from Greenland....

                            ECM                                                      GFS

   

 

GEM, on the other hand, sees the Azores high being made of stronger stuff and holding the low pressure off to the west...

GEM.    

(Edit:  ECM gif not working, apparently....)

 

Edited April 27, 2018 by Sky Full
.

[Purga]

Very cool for Sun / Mon with huge precipitation potl rain / sleet /snow & the GFS Op run not well supported for any warm up.

Decidedly chilly outlook for Blighty here

Could we squeeze one more snow event in the south?

[Interitus]

1 hour ago, Relativistic said:

Something similar occurred in 1945. According to TORRO, a high of 26.1C was recorded on the 18th (the record for that date). The end of the month then saw sleet and snow showers, with temperatures widely down to -4C. Full details can be found in the Met Office weather report for the month:

https://www.metoffice.gov.uk/binaries/content/assets/mohippo/pdf/l/0/apr1945.pdf

In terms of the mean CET, four daily records were set in April 1945. The 15th, 16th, and 18th all hold daily record highs, while the 30th holds the daily record low, just 12 days later.

Quite remarkable, while not quite as extreme overall a quicker turn around occurred in 1866 when the mean CET for April 27th was a firmly summery 16.5°C and just two days later winter returned with a CET of 3.8°C

[stodge]

Morning all

It doe seem as though some may get a final taste of winter later this weekend and into Monday which looks a particularly cold and unpleasant day for many but it's May (nearly) so in the battle between the warmer and colder air masses which has characterised the past two or three months the warmer side is getting the upper hand but it's been a real spring of contrasts which can be blamed on the weaker influence of the Atlantic.

Moving on and looking at where we might be on Bank Holiday Monday, May 7th, and starting as always with the ECM 00Z at T+240:

It all ends perfectly well for fans of warm settled conditions but the start of the week won't be pleasant with a couple of unpleasant cool wet days. As the LP moves off and fills, the Azores ridge builds through the south midweek and then transfers to the east setting up as a new HP cell over the southern Baltic leaving the British Isles in a warm ESE'ly wind for the Bank Holiday Monday.

GEM 00Z at the same time:

A very similar evolution in broad terms to the ECM. The HP ends up over Scandinavia with the ridge aligned SW back across the British Isles and a light NE'ly but still very pleasant. The critical moment is on Tuesday when the LP looks to dive SE across the British Isles but the ridge from the Azores gets there first.

GFS 00Z OP at T+240:

Something slightly different from GFS. The overall evolution is initially similar but as the HP transfers across the British Isles it declines and the core of heights never develops as a new cell over Scandinavia but is a ridge to a core much further north. In addition, the LP over the Continent is more pronounced and much closer so it's an E'ly flow but with a risk of showers for southern and south eastern parts. Further into FI heights remain to the north with LP to the south so it's variations on a mainly E'ly flow but quite a messy evolution.

GFS 00Z Control at T+240:

Very similar to yesterday with the Atlantic very much in charge and a fresh W'ly wind over the British Isles. Further into FI and the flow becomes more amplified ending with a developing LP over Europe and an E'ly for southern parts.

So, two very contrasting GFS evolutions at T+240 so let's look at the GEFS:

http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=240

I'd say the emphasis is on an anticyclonic evolution but where the HP sits and how it is oriented is far from clear. I see more support for an OP type set up than the strongly Atlantic evolution favoured by the Control (though that has some support as well). The Mean suggests HP to the SW and that's well advertised. Further into FI we get our usual signal of heights to the NW but no strong trend as we move into the middle of the month apart from the obvious of no warm southerlies or cold northerlies.

In conclusion, the evolution for the next week or so looks fairly well defined, After an unpleasant 48 hours or so especially through Monday, the ridge builds back from the SW drying and warming the weather through midweek. From there GEM and ECM build the HP over Scandinavia ushering in a new period of warmth but GFS is less convinced and the threat of showers from Europe remains or the whole pack of cards collapses as the Atlantic returns.

The GFS OP this morning intrigues with further strong northern blocking as we move into May (not atypical) so we'll see where that goes after the weekend.

 

[Scorcher]

1 hour ago, Sky Full said:

ECM and GFS currently agree on an arm of the Azores high pressure extending across the UK by 4th May only to be shunted out of the way somewhat by the 7th or 8th by low pressure arriving from Greenland....

                            ECM                                                      GFS

   

 

GEM, on the other hand, sees the Azores high being made of stronger stuff and holding the low pressure off to the west...

GEM.    

(Edit:  ECM gif not working, apparently....)

 

I can't see the high being 'shunted out of the way' on the ECM run- are you seeing something I'm not? It seems to get better and warmer as the run progresses to me.

It's certainly showing a stronger pressure build than it was showing yesterday.

[Frosty.]

Incredibly cold last day of april on the Gfs 6z with temperatures struggling in the low single digits celsius and even colder on high ground with snow in places, a thoroughly cold, wet and windy day for many parts of england and wales and more chance of the rain turning to sleet or wet snow than the 00z showed!

Edited April 27, 2018 by Frosty.

[Man With Beard]

So we start next week potentially in the Arctic Circle. ARGEPE, ECM and METO raw data all have marginal snow events Monday morning for the southern half - ECM showing lunchtime temperatures of 1C or 2C in places!!!

But by the end of the week, we're back on the Costa Del Sol, with temperatures in the low 20s once again.

Every month of the year all in one week!

[Sky Full]

4 hours ago, Scorcher said:

I can't see the high being 'shunted out of the way' on the ECM run- are you seeing something I'm not? It seems to get better and warmer as the run progresses to me.

It's certainly showing a stronger pressure build than it was showing yesterday.

Forgive my use of a highly non-technical term - it just seemed appropriate at the time !   It's a pity that the ECM gif was not working properly because it showed the low pressure system moving strongly south-east and pushing the high pressure in front of it.  Admittedly by the 7th the ECM still has high pressure in charge but it's already moving away.   If the ECM went out further than +240 I am sure it would have shown the low pressure dominating by the 8th or 9th.  I have attempted to post the gif again here:

 

I think it works if you click on it.

The GFS never let the high build in strongly in the first place, so it was only the GEM from this mornings output which seemed to plant the high pressure firmly over us and build against the Atlantic lows.  Of course, we are talking about a period which is still 10 days away and things are already moving along - a different evolution will no doubt be the reality.

[Tim Bland]

?☃️

 

[Scorcher]

27 minutes ago, Sky Full said:

Forgive my use of a highly non-technical term - it just seemed appropriate at the time !   It's a pity that the ECM gif was not working properly because it showed the low pressure system moving strongly south-east and pushing the high pressure in front of it.  Admittedly by the 7th the ECM still has high pressure in charge but it's already moving away.   If the ECM went out further than +240 I am sure it would have shown the low pressure dominating by the 8th or 9th.  I have attempted to post the gif again here:

 

I think it works if you click on it.

The GFS never let the high build in strongly in the first place, so it was only the GEM from this mornings output which seemed to plant the high pressure firmly over us and build against the Atlantic lows.  Of course, we are talking about a period which is still 10 days away and things are already moving along - a different evolution will no doubt be the reality.

Thanks for the clarification, it does look like a breakdown would follow soon after this chart:

But just how quickly we don't know. Also as that low encroaches it would pump up more warm air towards us from the south. There is also a chance from that chart that the low could drop south towards Iberia which would be a perfect situation for drawing in more warmth. Will be interesting to see what the ECM comes up with later on.