Model Output Discussion - Spring Has Sprung

[Ali1977]

 sheikhy How does the Arpege match up against UKV and the other models? UKV and Arpege are very different at such short time frame !! At the minute we have ECM and Arpege vs UKV and GFS!! 

[CoventryWeather]

 Pembroke Dangler Whilst you may be right, I'm not expecting much more of a shift south. Very complex situation but feel the ECM probably near the final solution. No ensembles have anything south where the ECM has it. 

[Battleground Snow]

 Ali1977 06z gem pulling some colder air further south compared to the 00z run

Nice to have some closer range charts to micro analyse again

[winterof79]

 Ali1977

 

UKV

Arpege

[BLAST FROM THE PAST]

For me we / I zoned in for 10-14 Feb for the next cold spell to strike (with Scotland/North maybe a touch earlier) before I went skiing last month.  I think the latter half of Feb that many places across the board are in with a chance of decent snowfall throughout the rest of the month.  I suspect some parts of our islands will get walloped but if anywhere is to miss is the far south/SE on the initial contact…..  We shall see how this develops…..an easterly down the line ‘with bite’ imo is not out of the equation.  All aboard the rollercoaster.

 

BFTP

Edited February 4 by BLAST FROM THE PAST

[Ali1977]

 Battleground Snow nice, a more elongated low. I think the 12z’s will give us a better idea - and further shift north then I think it’s more likely the south should focus on day 9/10 onwards - shift south then things could really ramp up as a prolonged snow event could happen. 

[Cloud 10]

 Battleground Snow

 

Things must be getting serious if we are analysing the 06z GEM.

[Battleground Snow]

 Cloud 10

Haha, somewhere is going to get a 20cm dump in the sweet spot ,but that could be anywhere from Scotland to Oxford at the moment.

The clash of the 2 air masses will really pep up the precipitation.

[BLAST FROM THE PAST]

It would seem around the 7th is the day to watch….that marks the southward extent of the cold from the north before the LP coming up from the SW engages with the cold air.

 

BFTP

[bradymk]

These systems do often correct south historically. However it depends on what forcing there is on the low.

When you have a wedge of higher heights to the north or some cold air in place, the models have often struggled and underestimated this and the system then corrects southwards and becomes more elongated closer to t+0. 

But for now, I don’t think this is one of those. Although we’ll see further changes with this low next week given its still 100+ hours, I don’t think it’s the classic keep correcting southwards as I don’t see enough forcing on the low from heights to the north (at the moment).

[MJB]

Control setting up nicely late on 

[sheikhy]

 Ali1977 arpege and ecm are very similar!!!ecm tad further north!!!not sure whose correct at the moment!!i feel we are just one ecm update away from the answer though!!if the ecm 06z stays the course then im expecting southward shifts from the others later on!!!im still going for the gfs solution as it stands!!!

[Met4Cast]

I think if you’re in the Midlands northwards you can be relatively excited for what’s on offer next week. 

A scandi trough/south shifted jet stream combination will allow for cold air to seep south across the UK with incoming lows bumping into it. Those further south, how does cold rain sound? 

Seems unlikely that this is a scenario where we’ll see lows trend increasingly further south until they miss the UK given the lack of any forcing from a block. 

Quite a standard affair really. 

[snowblind]

 CoventryWeather I think that was the case in January as well and yet it still ended up in France.

[Harsh Climate]

 blizzard81

Ye that's still a plausible option mate : ) Nothing is conclusive at this stage. 

[damianslaw]

 BLAST FROM THE PAST This is the key timeframe, the behaviour of the low pressure is dependent on the behaviour of the cold polar air advection south, how far it penetrates and the depth of cold, will determine where the polar front will lie, i.e. the position and shape of the low pressure and its 'base' trajectory. Its a complex set up and as said yesterday the models will continue to play around with the feature, but it won't be until Wednesday we have much more certainty on its affects. 

[CoventryWeather]

When does the ECM + ensembles get released on the 6z? 

Think if they start a bit of a move north then perhaps it can be settled that N England northwards get a decent snow event.

If they stick, which is what I'm expecting then expect others to start following. Think if the UKMO follows the ECM then I'd start saying it's a done deal. 

[blizzard81]

 CoventryWeather it's just coming out now but only goes to 90 hours. The control goes to 144 hours but another couple of hours until that comes out. 

[TURNED OUT NICE AGAIN]

 Pembroke Dangler and the Bay of Biscay by Wednesday!!!

[Rain All Night]

23 hours ago, RainAllNight said:

0z/6z ensemble means, Sat 3rd to Sun 18th (day 15)

It doesn't look like there's any chance of the "big low" sliding underneath anywhere other than perhaps the very far north of Scotland upon its initial arrival now, though there may be further opportunities for some as it passes over us (see the deterministic runs below). After it has moved on, we might see a chilly surface high moving in over us, followed by a more significant rise in pressure in our vicinity in subsequent days. The Atlantic doesn't look too far away from us initially, though ECM and GEM edge the mean heights westwards in their later frames, suggesting chillier scenarios, whereas GFS is reluctant to do this.

0z/6z deterministic runs, Sat 10th (day 7)

There still seems to be some prospect of areas further north getting a cold air flow for a while during the passage of the "big low".

0z/6z ensemble members, Tue 13th (day 10)

At this juncture, I really want to know what's going to happen after the "big low" has departed. Below are all of the ECM, GFS (0z/6z) and GEM ensemble members at day 10. The majority of them show raised heights at middling latitudes, many showing dry conditions for us with the Atlantic on pause, some of these offering chilly but not remarkable surface temperatures. A small number of runs show raised heights to our northeast, whereas I don't see any at all showing raised heights to our northwest.

0z/6z deterministic runs, Sun 4th to Sun 11th (day 7)

Contrary to my previous assessment, the models have continued to offer some hope of the "big low" delivering snow further south than Scotland (other members have posted short range 6z model outputs offering us updates on this situation), and as the selection of runs presented below illustrate, there may be further opportunities for various locations later on during the low's journey over the UK. By day 7, the next low coming in from the Atlantic has a very southerly track, and is being squashed and hindered by high pressure to its east and/or north.

0z/6z ensemble means, Sun 4th to Mon 19th (day 15)

There remains agreement on high pressure building over the UK once the "big low" has passed. There is also agreement that this will gradually migrate to the west, and possibly to the northwest. This gives us the impression that Atlantic lows will be blocked from reaching us again for quite some time. There is even a hint, on the GFS and GEM ensembles in particular, that some low heights may be able to approach us from the northeast late in the run, which would open up support for some very interesting winter weather scenarios.

The wind roses on this ECM ensemble meteogram for the south coast show us in simple terms the pattern change that is approaching.

Edited February 4 by RainAllNight

[CoventryWeather]

Minimal difference on the ECM06z. Perhaps a tad further north when looking at the precipitation charts. 

Wouldn't follow the GFS, but most likely similar evolution to it's 00z run. 

Edited February 4 by CoventryWeather

[sheikhy]

Very very good ecm 06z for midlands north at 90 hours!!!

[phil nw.]

The latest fax at T84 showing the progress of the cold front which looks like reaching the south coast later Wednesday and alongside the raw 850,s for that time.

 

A good visual of the long boundary separating the 2 airmasses from the Atlantic into Russia.

We can see the low complex and it's fronts lurking to the south west ready to head into the cold air in place over the UK. where some part of the country will see snowfall on the northern edge of this.

[nick sussex]

What drama ! Waiting for the ECM 06 hrs control run.

Its not just about this low but the effect the evolution has on the Scandi cold pool.

The elongated low set up will keep a colder bank of air there and so down the line if we get a ne e flow that would help .

 

[Rain All Night]

 Mike Poole The full gallery of ECM 0z ensemble members behind those T+360h cluster mean anomaly charts... you wouldn't kick this lot out of bed for eating biscuits...

Edited February 4 by RainAllNight