Model output discussion - after the beast, what next?

[Daniel*]

3 minutes ago, CreweCold said:

GFS is showing several marginal (but perhaps very heavy) snow events across central UK in the mid range. The ironic thing is that these have the potential to put down more disruptive, albeit brief, snow accumulations for some parts than the E'ly just gone.

GFS has been doing that this for a while now, even the Met Office written outlook say there’s a chance of snow in central and southern areas amongst the primary rain and wind. It’s quite probable we’ll see an event.

[Derecho]

18z ensemble swingometer updated. Not much change from previous runs but a few things to note:

- The runs which have the storm crossing the UK brings some really strong gales. A nasty storm with lots of rain
- There is a subtle nod towards stronger heights developing just to the south of Greenland. Could explain why the orange line has risen a little.
- Although pressure rises to the south of the storm its not really enough to put us in a zonal pattern
- Quite a lot of the runs have cold air returning to the UK in the wake of the storm.

Don't be surprised if the orange line continues ticking upwards at the expense of the blue...

[bobbydog]

snow for my location on the 16th?

could happen, but so could a sharknado.

even chance of either i think...

[Pixel]

I just want to say:

this really did happen (-:

amazing things happen & chaos theory proves it.

 

Edited March 5, 2018 by Pixel

[nick sussex]

Quite a change in this mornings UKMO, gone is the much  deeper low which goes against the other models and overall it looks very messy across the board .

The ECM drops its height rise to the nw and now is more interested in a rise to the ne.

The GFS is more interested in higher pressure to the nw.

For coldies at this time of year a northerly or ne is the better source of air unless the mini beast turns up!

Some of the GEFS do show a more wintry set up with low pressure tracking quite south .If a height rise to the nw is the correct solution still issues with getting the pattern sufficiently se .

Overall you can make a case for several things this morning , could be more white than wet later but equally the UK could be more on the wrong side of the jet with a milder flow from the south.

So I think confused sums it up.

 

Edited March 5, 2018 by nick sussex

[Summer Sun]

UKMO extended has a deep low to our east at t168

ECM at the same time

 

[coram]

36 minutes ago, Summer Sun said:

UKMO extended has a deep low to our east at t168

ECM at the same time

 

Surely if the jet remains far to our south, there will be less of a north-west trajectory to this low. It could therefore produce more white than the models currently predict. 

[stodge]

Morning all

As the recent cold spell fades into history or romanticised nostalgia, thoughts are turning among some on here to spring and a yearning for the first 20c day. Unfortunately, the weather isn't like a light switch and as I noted last week, the model output wasn't showing a quick path to spring-like temperatures as the battle between colder and warmer air-masses continues and with both the jet well to the south and cold air not that far away to the north and north-east, will there be more twists and turns to come this month ?

This morning's mid-range analysis takes us to Thursday March 15th and starts as always with the ECM 00z OP at that time:

An unsettled outlook. One LP has crossed the British Isles filling from SW to NE and is over Denmark but a new LP is in the southwest approaches with the main LP close to Iceland. A mild SSE'ly covers the British Isles in advance of frontal systems bringing rain slowly from the south west. Residual heights remain over Scandinavia.

GEM 00Z OP at the same time:

A shallow trough covers the British isles and extends from Scandinavia back into the Atlantic with the jet running to the south. LP centred in the North Sea is drawing in a slack but cold N'ly flow over the British Isles. A secondary shallow LP is approaching from the SW but might only affect southernmost counties and the Channel Islands. Pressure remains high over Greenland with a weak ridge SE.

GFS 00Z OP at T+240:

The first LP crossed the country from SW to NE over the weekend and is in the Norwegian Sea but a new area of LP is approaching and deepening from the SW and is to the south of Cornwall with strong winds on its western flank. Any drier periods in central areas will be erased by rain moving from the south and south west. The eye is drawn to a developing but weak mid-Atlantic ridge. However, further into FI it gets squeezed out and the jet seems to buckle back north as the Azores HP becomes more influential.

GFS 06Z OP at T+234:

The evolution is different with the Azores HP much more pronounced and ridging north as the LP moves away to the NNE. A light NW'ly airflow covers the British Isles at this time. Further into FI and a much more zonal evolution develops with the classic sine wave of ridges and troughs.

GFS 00Z Control at T+240:

A much colder evolution with a NE'ly flow over the British Isles and a more significant mid-Atlantic ridge than on the OP. Further into FI, the cold snap doesn't last but the jet remains well to the south allowing LP to cross the British Isles keeping the weather unsettled with temperatures often below average.

GFS 06Z Control at T+240:

The 06 GEFS at T+240:

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

Plenty of colder options in there to my eye. The exact position and orientation of the LP varies greatly but the possibility of a more N'ly airflow can't be excluded. I don't se much sign of settled HP at this time.

To conclude, little has changed since last week. The extreme cold has gone but the transition to what many would regard as spring-like conditions is going to be very slow. Indeed, the immediate future looks very unsettled with plenty of rain in the coming weekend as a vigorous system moves up from the SW and a repeat performance next week is on the cards from GFS next week. Other models keep the trough over the British Isles so with an unsettled and often cold theme especially in the north.

GFS further into FI tries to bring the jet back north allowing the warmer air-mass to encroach but there is also a signal for renewed Scandinavian blocking. At the moment this is all speculation - I can't see a ready route to spring warmth and indeed rain (and plenty of it) will be the theme for the next week to ten days.

 

 

[Derecho]

Today's swingometer so far. The GFS ens are becoming less bullish about deepening that Azores low as it heads to us. A few things of note:

- A few members seem to not really develop a low of note this weekend
- A stronger signal for a rise in SLP over Spain seems to be emerging again could introduce much milder air later.
- A stormy weekend still seems to be favoured though its becoming less clear how the weekend will shape up.

[nick sussex]

Looking ahead , I think it’s all down to whether the pattern is edged further east and se .

Theres some decent upstream amplification but the models are reluctant to get the UK on the cold side of the jet , or it takes an age to get there.

The PV is unlikely to re-organize and it’s looking very messy with small wedges of higher pressure and shortwave energy flying all over the place .

Its the sort of pattern that can flip to a colder outlook equally the UK might stay in generally more average conditions or milder if low pressure gets stuck to the west.

 

[Daniel*]

Some stormy weather could be fairly widespread in scope, is gaining traction this weekend for low presssure to rapidly deepen nearby Bay of Biscay. Good if you like that sort of thing I suppose..

[BlueSkies_do_I_see]

Enjoyed the late snow. Not so much the wind chill. But it was impressive to behold.

 

We now appear to be in a period of weather that does not interest me. Until we start hitting temps in the 18C plus range towards April, I prefer the snow and cold to wind and rain, like many on here. But when will we record an 18C? I would definitely be hoping to achieve this in March here in Coventry, but not sure this year.

[stodge]

IF the GFS 06Z OP verified, a very wet theme for south western parts:

6 inches of rain over the moors in the next ten days - 3-4 inches widely in Devon, Cornwall and South Wales on top of the huge recent volume of melted snow.

Flooding issues ?

[karlos1983]

UKMO has a very nasty low at D5 eyeing up the southern UK

[Man With Beard]

Yesterday's 00Z ECM clusters hinted at a Greenland High - today the clusters are more mobile with any blocking more likely to be too far NW or out east (which could actually promote warmer weather to the UK if an E Europe block rather than NE). So no clear patterns emerging except the probably of a mobile period of weather.

[karlos1983]

An  (un)happy mothers day potentially for some

GFS not quite as bad and the strongest winds stay over North West of France

Edited March 5, 2018 by karlos1983

[swebby]

19 minutes ago, Man With Beard said:

Yesterday's 00Z ECM clusters hinted at a Greenland High - today the clusters are more mobile with any blocking more likely to be too far NW or out east (which could actually promote warmer weather to the UK if an E Europe block rather than NE). So no clear patterns emerging except the probably of a mobile period of weather.

Hi MWB - not sure mobile is the appropriate term here?  For UK i'd define mobile as a strong west to east flow with a strong jet over/near the uk with lows exiting the Eastern seaboard and being driven into the Uk/Scandinavia at a good rate of knots.  Looking at the 0z ECMWF it looks to me that the jet is still a long way south of the UK and we have lows meandering aimlessly around the Atlantic/nw Europe.  The clusters i feel are showing some ideas of where the main core(s) of the low sets up home?  Admittedly - the outcome will be same - very wet, probably windy with an even chance of it being cold to average in temps.

Edited March 5, 2018 by swebby

[bradymk]

UKMO pretty grim for Sunday. GFS although grim too, does keep the strongest winds in France as Karlos says above.

Of more interest is the mighty GEM. That potentially a more white than wet and windy Mother’s Day. Just one of many options on table for weekend.

[Summer Sun]

ICON 12z gives a mild day on Saturday for the south quite wet for most but gradually becoming drier in the southwest further north temps are around mid-single figures with parts of Scotland still at or below zero

[nick sussex]

Still some uncertainty with the weekend low .

In terms of depth and whether any snow will fall on its northern flank.

Looking forward its a case of whether the pattern gets sufficiently se to get the UK on the cold side of the jet.

If the UKMO follows a similar evolution to the GFS then that’s likely to provide the colder solution as there’s a better clearance of upstream energy attached to the low over the UK and that’s likely to swing ne further east .

Certainly wouldn’t rule out a northerly nw flow next week if we do see pressure build to the nw.

[Daniel*]

19 minutes ago, Summer Sun said:

ICON 12z gives a mild day on Saturday for the south quite wet for most but gradually becoming drier in the southwest further north temps are around mid-single figures with parts of Scotland still at or below zero

Always the bearer of good news. 

Winter in Scotland and spring like temperatures in Southern England although doubt it’ll last. I really can’t see any chance of ‘warmth’ for the foreseeable. Atmosphere has been shaken like a snow globe...

[mb018538]

Looks pretty rubbish to be honest. Certainly no real spring warmth on the cards yet, jet a long way south and we are generally on the colder side. No signs of anything settled either, so if cool rain is your thing, you are in luck.

[Nick F]

Although there is a southerly tracking jet stream across the Atlantic, crossing the Azores, Iberia and on east into the Mediterranean, the flow is very zonal so there is little in the way of ridging in the mid to high latitudes to prevent slow-moving areas of low pressure wallowing around western and northern Britain, with little upper flow to move them until later in the week, which keeps a mild and showery flow across the UK.

However, looks like some momentum gathering in the upper flow by the end week and through the weekend southern UK, which could see a deepening low over the Atlantic head towards or just south of the UK. 12z UKMO showing quite a deep low heading in towards the south on Sunday, 12z GFS has a deep low to the SW but it fills to become a weaker low across the south on Sunday – 00z EC had a similar idea to GFS

Upstream there are signs from the models of anti-cyclonic wave breaking in the North Pacific, probably being driven by an east Asian mountain torque event, which results in amplifying the downstream trough south of Alaska which in turn develops a +PNA ridge. This more amplified flow feeding through to the N Atlantic next week, but because of the short wave-lengths,  may favour an amplifying / slow-moving trough to the west of the UK initially – which is not ideal to get cold back south – but into low res 12z GFS does get the trough east with a cold Nly. And with absence of a TPV over Greenland or NE Canada, we could see blocking develop easily over the NW Atlantic – with help of expected amplification upstream

[I remember Atlantic 252]

11 minutes ago, mb018538 said:

Looks pretty rubbish to be honest. Certainly no real spring warmth on the cards yet, jet a long way south and we are generally on the colder side. No signs of anything settled either, so if cool rain is your thing, you are in luck.

maybe taste of Spring warmth for the south

[mb018538]

Yes I should have added that one in - as that low spins up from the south we may get a fleeting glimpse of some mild air before it all goes mammaries verticus once more