Model output discussion 10/02/21

[Guest]

Thankfully the models seem to be backing off from a really extended cold spell. Monday to Wednesday will be a shock but GEM & GFS ensembles start edging back up towards the following weekend. GFS has temps back up to high teens and 20’s by the w/c 12/04.

[Mike Poole]

ECM T72 compared with UKMO and GFS:

ECM looks slightly east as per GFS, in fact maybe more so.  Would like UKMO to be right here.

[I remember Atlantic 252]

Aye, UKMO best out of them for western areas, precip charts though seem to have wishbone effect on GFS, like it was January, surely won't be bone dry with strong April sun

[Tim Bland]

7 minutes ago, I remember Atlantic 252 said:

Aye, UKMO best out of them for western areas, precip charts though seem to have wishbone effect on GFS, like it was January, surely won't be bone dry with strong April sun

ECM is cold and dry for most early next week..

[Cheshire Freeze]

7 minutes ago, Tim Bland said:

ECM is cold and dry for most early next week..

Yeah the instability it looked like we would get is now being shown in the N sea. 

No point in cold at this time of year if it isn't going to snow. 

[HellItsHot]

22 minutes ago, Alderc said:

Thankfully the models seem to be backing off from a really extended cold spell. Monday to Wednesday will be a shock but GEM & GFS ensembles start edging back up towards the following weekend. GFS has temps back up to high teens and 20’s by the w/c 12/04.

Proper cold next week but a proper warm up the following week? 
 

That gets a from me. 

[I remember Atlantic 252]

9 minutes ago, Tim Bland said:

ECM is cold and dry for most early next week..

EC is the furthest east, UKMO looks better, CC yes, cold and dry sucks in April

[Thundery wintry showers]

Tonight's ECMWF looks similar to the GFS, so with relatively high pressure a "wishbone effect" is more likely with relatively few showers developing inland, still a chance of some snow showers heading through Wales and into the West Country overnight 5th/6th as per the GFS.  The UKMO with lower heights and the northerly a little further west would result in showers developing more widely inland.

Not sure about the "cold wet yuck" for southern areas, most current model runs are going for predominantly cold bright weather for the south with scattered wintry showers mainly around north-facing coasts, and just one or two weak rain belts coming down from the north-west.  It's fine not wanting cold northerlies, but not to let it bias one's perceptions of what the models are showing.  The "cold and dry and thus not particularly snowy" assessment of a few recent posts looks likely to be accurate for many in the south though.

Edited April 2, 2021 by Thundery wintry showers

[Geordiesnow]

At least the GFS had kinks in the isobars despite the flow being further east so some organised PPN is possible. ECM looks quite boring really for most places.

Yet again though, heights are failing to develop over Greenland and the northerly flow gets shunted further east as a result, if this was the 70s, that probably won't happen. 

[Daniel*]

Has anyone ever seen lower dew points from a northerly? And it’s April! DPs of -11C down to south coast, ECM is drier but anything which falls out sky would certainly be snow temps would crash, east coast very likely to see snow showers. I’d go as far to call the air mass historic there are very small number of incidences this late, certainly colder than 2008.

[Thundery wintry showers]

To be fair, northerlies having their main "thrust" go out into the North Sea has happened quite a lot in the past including in the 1970s:

Also, heights over Greenland do get notably high as the northerly approaches the UK, and on the latest ECMWF and UKMO runs they're still pretty high at day 5-6.  I think it's more of an issue that the probability of any given northerly giving UK the "ideal" hit for widespread snow is fairly low, as it always has been - though with today's warmer climate it takes a more intense northerly to be cold enough than it used to.

[Geordiesnow]

I just think given how much WAA heads upto Greenland, not being able to get a decent proper ridge is something that occurs more these days thanks to increase shortwave activity. As another poster in this thread said, starts off with decent heights, then the ridge becomes more of an Atlantic ridge and then the high bulges further east in time so shifting the northerly flow further east. 

Thank goodness this is not January otherwise there would of been hell on. The only thing that is saving this on the ECM is the fact its April so the sun affect could come into play but keep shifting this northerly further east then even Eastern areas may not have enough instability to create showers. 

[Iceman2606]

Signs of a warming trend as we approach mid-month with the GFS 12z ensembles with some of these ensemble members going quite warm

 

Still a way off yet but hopefully signals grow

[Frosty.]

Will it or won’t it snow?...all I know is these are EPIC charts for coldies from the ECM 12z operational for early April, I don’t see there being much more eastward adjustment, indeed looking at some current output it could adjust westwards again?..but anyway.,it all kicks off The Day After Tomorrow!  

 

[Cambrian]

GEM 12z keeping with yesterday’s idea of 1-2 centimetres of snow for large parts of England and Wales by Wednesday morning from the little feature running down the west coast of Scotland and down the Irish Sea early Tuesday clipping North Wales and then SE across England, looks like some lines of showers set up as it comes through. Good part of Ireland in the mix too and many parts of Scotland already pasted by then!

[Mapantz]

53 minutes ago, Daniel* said:

Has anyone ever seen lower dew points from a northerly? And it’s April! DPs of -11C down to south coast, ECM is drier but anything which falls out sky would certainly be snow temps would crash, east coast very likely to see snow showers. I’d go as far to call the air mass historic there are very small number of incidences this late, certainly colder than 2008.

That would suggest relative humidity levels circa 20% or perhaps lower..

May scrape a station record if that materialises?! 

[Mike Poole]

ECM mean and spread T72:

We will see more maybe from the clusters later, but that light blue spot in central England on the spread tells you all you need to know - the UKMO solution has traction...

[Cheshire Freeze]

2 minutes ago, Mike Poole said:

ECM mean and spread T72:

We will see more maybe from the clusters later, but that light blue spot in central England on the spread tells you all you need to know - the UKMO solution has traction...

Mean looks bang on GFS to me...so *perhaps* the ECM op was too far E

[Mike Poole]

Just now, CreweCold said:

Mean looks bang on GFS to me...so *perhaps* the ECM op was too far E

Yes, I think so Crewe, it is fine margins now at T72 but at this time of year there’s little margin for error at all!

[Cheshire Freeze]

2 minutes ago, Mike Poole said:

Yes, I think so Crewe, it is fine margins now at T72 but at this time of year there’s little margin for error at all!

Would be nice to see the GFS hold firm or even go slightly west on the 18z run

[Mike Poole]

So, the 12z ECM clusters at the timeframe T72-T96:

Purple borders throughout.  Phew!  That’s the Atlantic ridge scenario sorted, as if we didn’t know!  

Cluster 3 with 14 members is the one we want for snow, it is the cluster the UKMO would be in.  

[ICE COLD]

I reckon the EC op was to Far East the mean is further west and very cold from T72 to T120 . 

[Mike Poole]

8 minutes ago, ICE COLD said:

I reckon the EC op was to Far East the mean is further west and very cold from T72 to T120 . 

Yes, I posted the GEFS extremes, and there is still some considerable uncertainty, and the ECM ens seem to back that up.  Will all be firmed up tomorrow I expect, cold, but how cold?

[Daniel*]

1 hour ago, Mapantz said:

That would suggest relative humidity levels circa 20% or perhaps lower..

May scrape a station record if that materialises?! 

Not quite that low but it’s low.

 

in any case the first half of April looks to be well below average 2-4C below average?

 

[Mike Poole]

ICON 18z looks slightly east of where we might want it at T66:

T66 - can’t believe I’m commenting on developments at such short times, but this situation seems to require it.