Model Output Discussion - 23rd Jan - 12z onwards

[Neilsouth]

If we could just get a more north east feed rather than a n/nw shown in the models everyone would be in for the fun!

[The Northern Ramper]

Everyone apart from the West.

[Man With Beard]

UKMO not bad at all - reasonable amplification

Crumbs that's close to a 3 way split in the polar vortex! That would help us go into the freezer!

Also, the upper trough over Scandi is not properly connected to other parts of the vortex - I think this means it might be slower to clear off to the north...?

Edited January 27, 2015 by rjbw

[samalllpop]

Its completly dead in here... does that mean the charts have downgraded.... i can't really tell as i am a newbie and no one is commenting ahha

[nick sussex]

So far this evening the GFS is quicker to flatten the ridge, mainly due to shortwave issues. The UKMO is far better but theres a big difference in the NH profiles especially towards the polar regions between the two.

 

In terms of worries regarding the UKMO bringing the low centre further west at T96hrs, looking just at the 850 calculation, I've taken the mid range 980 value and with the 510 dam and that comes to roughly 850 value of -5.9.

 

At T120hrs between -6 and -8, at T144hrs the -10 850 does get into the UK, these are just rough calculations using the chart posted by Lorenzo a few days back.

Edited January 27, 2015 by nick sussex

[Mucka]

The UKMO has the trough further West and in the short term we want it to be further East to limit warm sectors.

 

The GFS is a little further East than this morning.

 

We want to keep the core of the trough and any secondary features to the East of the UK. The warm sectors will pass through Friday/Saturday with the prospect of any snow showers turning to rain or sleet in this period but the devil will be in the detail.

Colder air digs back in as the trough pulls away and showers will be more likely to turn back to sleet/snow

Edited January 27, 2015 by Nick L
Deleted quote removed

[Captain Shortwave]

Its completly dead in here... does that mean the charts have downgraded.... i can't really tell as i am a newbie and no one is commenting ahha

No downgrades to me, it's just got to a point in my view where a lot of discussion has moved into the regionals as the risk of snow is now just 24 hours away.

 

As for the models, the GFS is similar to this morning, cold tomorrow and Thursday, slightly less cold Friday and possibly Saturday before a cold northerly digs south from Sunday. The GFS again squeezes out the showery activity by the end of Wednesday in the east, earlier in the west. I would add that the GFS again produces an organised band of snow which moves south of Monday. The UKMO looks better than the GFS over the mid range and would in my view deliver a longer northerly.

For the record the benchmark has pretty much been the middle of next week of the cold spell to end in some way, most likely the development of a settled and frosty spell and the Atlantic high moves east over the UK.

 

For the life of me I cannot see the downgrades that ER can see 

Edited January 27, 2015 by Captain shortwave

[Daniel*]

Its completly dead in here... does that mean the charts have downgraded.... i can't really tell as i am a newbie and no one is commenting ahha

No steady as she goes, sometimes it just goes quiet the calm before the storm .

UKMO 12z is a beauty, the PV is in tatters following MO model it looks far from zonal SW'lies.

[phil nw.]

Pretty consistent modelling over the last few days wrt the onset and length of the cold spell commencing tomorrow.

Just for an idea Weds pm and overnight look like giving fairly widespread snow showers as the polar air comes south east in a strong north westerly flow.

 

then the period Sunday to Tuesday another window for more widespread snow coming south as the real cold Arctic air cuts in with -10c 850's approaching Scotland

if we look closely we can see the kink in the isobars up there indicating a more organised band of snow  moving down across the country.

These charts of course are just to give an idea as the distribution of snow may well be different come the time but these minor troughs often form in a very cold unstable Arctic airflow at short notice. 

Edited January 27, 2015 by phil nw.

[Frosty.]

It looks like we will have some ice days starting later in the weekend and during at least the first half of next week, really very cold. The ukmo 12z at T+144 is a peach, indicating even more ice days to follow. The best wintry spell for a few years is only hours away now.

[shaky]

No downgrades whatsoever! ! Gfs still toying with thr length of the cold spell and could lengthen it further!! Ukmo is brilliant expect the low to disrupt even more at 168 hours near greenland! ! Hopefully ecn shows the same!!

[Mucka]

GFS control has some nice trough disruption, hope this becomes a strengthening signal.

 

 

We will need further upstream to be slower and more amplified to benefit than currently modelled but the potential trough disruption ahead has only just crept into the output so it is not a forlorn hope. We certainly need the signal strengthen before we can get excited though.

 

GFS short ensembles still going for a breakdown 3rd/4th and a 7 day cold spell is still the form horse. At least the Op and control want to extend the cold a day or so.

 

Edited January 27, 2015 by Mucka

[Nick L]

Can someone point me towards the regional threads, e.g. the one for the south east?

 

All regional threads can be found here:

 

https://forum.netweather.tv/forum/142-regional-discussions/

[Hotspur62]

Looking at latest models I don't think an awful lot has changed today. UKMO at 144 is a solid chart(if I knew how to post it I would but pc skills are  limited lol!!) and the odd tweak here and there will make a massive difference down the line. As "rjbw" said earlier this chart does show the PV nearly split in 3 and with a High pressure approaching the North Pole and the High over the Atlantic, it wouldn't take a lot for those to link up. This is something Joe B I think alluded to last weekend and it will interesting if this pans out. If they do link up that could form a nice block. Just my thoughts and I look forward to another evening of model watching

[J10]

Just seen the charts for the first time today, {so didn't see this morning outputs} and things look pretty good.

 

The theme of turning colder quickly over the weekend looks a bit steadier now.

 

That is after the cold front being sleet and snow showers in about 24 hrs time.

Edited January 27, 2015 by J10

[weather eater]

In the short term we have no upgrades or downgrades just standard modelling as they get to grips with the small details, this will keep changing right up to zero hour, although no doubt some will see things that way from an IMBY prospective

 Overall and at long last this winter the UK is on the cusp of a decent cold spell but longer term there is much to resolve.

 

1. Will the high topple setting up a MLB over the UK This seems to be odds on at the moment.

 

2. Will it topple and let the Atlantic back in, not showing in the modelling at the moment except in the far reaches on the GFS and after a period of MLB. Certainly little sign of a topple and a straight return of the Atlantic, so I would put that as the least likely mid range plus evolution at this stage.

 

3. Can we keep the lobe of the PV far enough west to allow HLB to develop over Greenland, also, not showing as yet as the models seem keen to shift it east. but I would say slightly more likely than 2 at present although history would say otherwise.

Edited January 27, 2015 by weather eater

[Mark Neal.]

EURO 4 12z is out..

 

 

 

   

 

 

Edited January 27, 2015 by Mark N

[Geordiesnow]

The UKMO has the trough further West and in the short term we want it to be further East to limit warm sectors.

 

The GFS is a little further East than this morning.

 

We want to keep the core of the trough and any secondary features to the East of the UK. The warm sectors will pass through Friday/Saturday with the prospect of any snow showers turning to rain or sleet in this period but the devil will be in the detail.

Colder air digs back in as the trough pulls away and showers will be more likely to turn back to sleet/snow

 

Yep very typical isnt it really, as I say, there will be a milder sector occuring during Friday(although PPN wise, there probably be less so no real harm there) but we really don't want that trough to hang around our shores for much longer, the further East the better and its typical that the UKMO is backing down now in this respect. Stll time for some minor changes in what is important crucial detail I feel.

 

At least we are seeing some upgrades in terms of the strength of the Atlantic ridging especially from the UKMO.

[Frosty.]

Hope we see more GEFS perturbations like these which extend the wintry spell through much of next week, these show the arctic spell still going strong by the middle of next week with power to add. A noteworthy cold spell is almost here, initially we will have the most potent polar maritime outbreak for a few years and then followed by a powerful blast of Arctic winds with troughs pushing snow showers down across the UK along with several ice days.

[Severe Siberian icy blast]

GFS control has some nice trough disruption, hope this becomes a strengthening signal.

 

 

We will need further upstream to be slower and more amplified to benefit than currently modelled but the potential trough disruption ahead has only just crept into the output so it is not a forlorn hope. We certainly need the signal strengthen before we can get excited though.

 

GFS short ensembles still going for a breakdown 3rd/4th and a 7 day cold spell is still the form horse. At least the Op and control want to extend the cold a day or so.

 

Good post .

I noticed the first signs of trough destruption yesterday I think ? But yes there's certainly a possibility with such a deep euro trough it would encourage high rises to our North west, just depends on the strength of the high pressure , and of course the strength and angle of the low pressure exiting the vortex over Canada . If we can hold the low pressure back just 24 hours then it gives the high pressure chance to build north of the uk . If the low can disrupt against the high , then that massively increases our chance of extending the cold , if she goes under the high and cuts it off the it could be all sorts of fun and games!

[SMU]

Wow - UKMO 144-!!!!!!!

 

Where did the EPO- ridge appear from !!!!!! Surprised no one has noticed-

 

UKMO !

 

GFS

 

The UKMO would certainly slow the eastward progression down due to the 2 wave pattern being progged.- the UKMO is the best run thus far-

 

S

[bluearmy]

Wow - UKMO 144-!!!!!!!

 

Where did the EPO- ridge appear from !!!!!! Surprised no one has noticed-

 

UKMO !

UKMO144JAN.gif

 

GFS

Gfs144Jan.jpg

 

The UKMO would certainly slow the eastward progression down due to the 2 wave pattern being progged.- the UKMO is the best run thus far-

 

S

I noticed Steve but because I found no support I thought I'd pretend it wasn't there. Tbf, mucka posted it earlier.

[gottolovethisweather]

Beautiful ECM development from within reliable timeframes.

 

From this

 

 

To this within 24 hours. 

 

 

Then this at t+48hrs and +72hrs.

 

 

Plenty of forecasting headaches for the professionals yet alone for us amateurs to decipher whether it might snow and perhaps even settle and cause potential travel disruption in one's back yard or region. Strong winds added to the mix along with hail and thunder, there is plenty to anticipate, all before the FI shenanigans. One wintry and cold to very cold period is just about to begin, I say bring it on. 

Edited January 27, 2015 by gottolovethisweather

[SMU]

A band of snow moving down the east on day 4-5 on the ECM with the very cold uppers penetrating south behind it

 

http://www.meteociel.fr/modeles/ecmwf/runs/2015012712/ECU0-120.GIF?27-0

 

-9c in the north chasing the -6c line that's exiting the south.

Dewpoints subzero everywhere-

516 DAM thickness touching Shetland

520 DAM in the NE

524 DAM in the South.

 

all parameters condusive to snow.

 

S

Edited January 27, 2015 by Steve Murr

[Geordiesnow]

A band of snow moving down the east on day 4-5 on the ECM with the very cold uppers penetrating south behind it

 

http://www.meteociel.fr/modeles/ecmwf/runs/2015012712/ECU0-120.GIF?27-0

 

-9c in the north chasing the -6c line that's exiting the south.

Dewpoints subzero everywhere-

516 DAM thickness touching Shetland

520 DAM in the NE

524 DAM in the South.

 

all parameters condusive to snow.

 

S

 

I assume those factors would work in our favor aslong the winds stay off shore because any winds coming in off the sea will sure affect whether snow will fall or not no matter what those figures say?

 

I still rather sacrifice any longer outbreak of PPN for a nice clean Northerly flow which will bring the proper cold air and ensures any PPN does fall should be of snow.