Model Output Discussion - 23rd Jan - 12z onwards

[The Enforcer]

Got to disagree,mainly this being a more unstable airstream than a regular northerly.And also when the coldest winds set in,sunday onwards,kinks in the isobars show bands of showers spreading south.

What is it about this particular northerly airstream that makes it so unstable? Is it the proximity of the Low Pressure?

[joggs]

We'll see but I'm in the over 50s bracket and I can tell you now these are as rare as hens teeth and apart from coastal districts and down the Eastern side of the country this will be a dry but very cold spell of weather from Sunday onwards, I hope I'm wrong I really do.

I really hope your wrong too lol.Still a nice trend on tonights 12z in the longer term,hope this continues and gathers momentum.Good luck though coldies re snow.Sorry mods

[snowice]

What is it about this particular northerly airstream that makes it so unstable? Is it the proximity of the Low Pressure?

-9 T 850 on a strong north wind PPN will increase!

[Timmytour]

Weather porn at its very best... I could just see this place going bonkers if a chart like that appeared around t72.....

I doubt it....by that time attention would be more directed to the apparent breakdown seven days later

[snowice]

I doubt it....by that time attention would be more directed to the apparent breakdown seven days later

Haven't you heard David Cameron has blocked weather porn.lol.;

Edited January 27, 2015 by snowice

[joggs]

What is it about this particular northerly airstream that makes it so unstable? Is it the proximity of the Low Pressure?

We don't want the low modelled west anymore,further east the better.The airstream that kicks in sunday onwards has cold uppers and the long fetch stays in place for a few days(not your regular 24hr toppler).The fetch is from north of Svalbard with small noticeable kinks in the isobars which mean more organised bands of snow showers pushing south.Obviously the nw,n,ne then east and west coast will have the lions share but to me this is not a true wishbone effect northerly.Time will tell

[nick sussex]

The ECM mean not really backing the operational run however looking at the short De Bilt ensembles there is a colder cluster than the operational run on days 9 and 10.

 

http://www.knmi.nl/exp/pluim/Data/PLUIM_06260_NWT.png

 

I'm wondering whether the mean is quite diluted with two opposing solutions, the spreads do suggest a possible EPO ridge and the spread whilst at first look might suggest low pressure to the nw, a look at Scandi suggests some colder air heading south there. That would be on the eastern flank of a high, theres also a bit more spread over the south of the UK.

 

The actual mean 850's at day ten are still on the cold side so the lack of spread to the nw might be a red herring, the spread on the western side of Greenland suggests a different upstream trough set up.

Edited January 27, 2015 by nick sussex

[SMU]

Plus Nick the control looks cold again!

S

[SE Blizzards]

Plus Nick the control looks cold again!

S

 

Control stays cold all the way to the end.

 

Edited January 27, 2015 by SE Blizzards

[Duane S.]

What is it about this particular northerly airstream that makes it so unstable? Is it the proximity of the Low Pressure?

I think what you are asking is why in particular is a northerly airstream often regards as unstable. An Arctic Maritme air flow in the winter, and to a degree PC and PM air masses, are unstable because as it modifies (I.e. as it moves away from its frigid source towards a warmer UK) it will warm up from the bottom layers and, naturally, rise. What goes up must come down and often it does, quickly, as snow.

Worth remembering that the much overused polar low can only truly form in a true AM airmass and one of a decent duration. Will be worth keeping an eye nearer the time for the formation of these rare little beasts from next weekend when a northerly kicks in. No point trying to look outside 12 hours or so as they normally pop out out of nowhere and disappear as quickly as they arrived. Great fun to be underneath one at the time though!

[bryan629]

The ECM mean not really backing the operational run however looking at the short De Bilt ensembles there is a colder cluster than the operational run on days 9 and 10.

 

http://www.knmi.nl/exp/pluim/Data/PLUIM_06260_NWT.png

 

I'm wondering whether the mean is quite diluted with two opposing solutions, the spreads do suggest a possible EPO ridge and the spread whilst at first look might suggest low pressure to the nw, a look at Scandi suggests some colder air heading south there. That would be on the eastern flank of a high, theres also a bit more spread over the south of the UK.

 

The actual mean 850's at day ten are still on the cold side so the lack of spread to the nw might be a red herring, the spread on the western side of Greenland suggests a different upstream trough set up.

Like this Nick, a nor`easter. 

 

 

Did someone mention the words undercut too?

[BLAST FROM THE PAST]

Just a quickie for the moment I read this mornings posts re 00z, it was like yesterday and I couldn't understand the deflation [although some saw the positives for sure] and again I refrained from comment.  They were better than yesterday.  12z ecm superb, 12z ukmo superb ...as it has remained.  This is a 'spell' coming, not a snap....now to catch up on the rest of the day 

 

BFTP

Edited January 27, 2015 by BLAST FROM THE PAST

[Pembroke Dangler]

Like this Nick, a nor`easter. 

 

ECH101-240t.GIF

 

Did someone mention the words undercut too?

That's a strong high on the anomalies chart centred just east of Iceland could this be the trend that the other models may pick up? I hope so that's got reload potential written all over it and undercuts my fingers are crossed

[BLAST FROM THE PAST]

We can't be disappointed with the UKMO 144 chart, the ridge surviving shortwave dramas.

 

Absolutely correct, stormer of  a set up

 

BFTP

[Frosty.]

We are seeing the cold spell extending well into next week, at least until midweek and perhaps longer, only yesterday at 0z the models showed a very watered down event ending by Sunday, there seems to be a momentum behind this upcoming cold spell, it's evolving all the time and we may not see anything remotely mild next week, instead we could see a reload when it looks like the cold is weakening, anyway the Ecm 12z ensemble mean as with the Gefs mean, is lengthening the wintry spell little by little which is very good news.

[bluearmy]

The EC control is a sceuro block right to the end. Staying cold if that was to verify with a continental drift for the uk.

What catches my eye (and probably some of you) is the anomoly at day day hints at the Atlantic undercutting the small ridge. This continues in the post day 10 period. could be a bit close to the uk but the mean 0c isotherm is well to our sw and the mean jet looks ok too. seems to be a developing theme across the modelling today and interesting to see if it's there tomorrow aswell.

And nick, I'm steadily moving to the camp that the spread moving across to our north is indeed where the runs are clustered with higher heights.

Edited January 27, 2015 by bluearmy

[damianslaw]

ECM once again interesting suggesting shortwave activity to the NW early next week prolonging the NW airstream but perhaps scuppering a decent lengthy northerly, its a positive for those wanting an extension of the cold weather as it prevents the azores high from toppling in quickly and forces it to ridge further NW lifting its core heights away from the azores themselves. Thereafter we finally see it nosing in, but at a higher lattitide ridging into the country and NE - such a position would cause a split jet flow, and who knows we could be in undercutting territory if the energy in the jet is transferred into the southern arm.

 

In the meantime we have a week at least of below average temperatures particularly so in the northern half of the country.

[Severe Siberian icy blast]

Just a quickie for the moment I read this mornings posts re 00z, it was like yesterday and I couldn't understand the deflation [although some saw the positives for sure] and again I refrained from comment.  They were better than yesterday.  12z ecm superb, 12z ukmo superb ...as it has remained.  This is a 'spell' coming, not a snap....now to catch up on the rest of the day 

 

BFTP

To be fair I agree with that although I was one that posted moaning about the strength of the vortex , I sort of went against my own advise to be honest cause all the signals are there for us all to see and they do now seem to be driving our winter finally.

The 0z although the worst run of the day were better than yesterday's 0z and we are told to compare like for like . A good day of model watching though and great to see the trough disruption causing headaches .

[BLAST FROM THE PAST]

To be fair I agree with that although I was one that posted moaning about the strength of the vortex , I sort of went against my own advise to be honest cause all the signals are there for us all to see and they do now seem to be driving our winter finally.

The 0z although the worst run of the day were better than yesterday's 0z and we are told to compare like for like . A good day of model watching though and great to see the trough disruption causing headaches .

Indeed SSIB, spot on re like for like....JH does dish out some good advice and that is one I do like of his 

 

BFTP

[polar vortex]

UKMO t144 chart looks excellent with the prospect of more amplification going forward but you would not want to 

hang your hat on a UKMO chart at that range, plus it is the only run to show such a strong EPO ridge. 

The outlook beyond the middle of next week could go either way but there seems to be more uncertainty of a return 

to more zonal westerly type weather. I would not be seduced or put off by ECM extended ens as these can flip, flop 

as we have seen this winter but with a continuing strat signal on our side I would not be surprised if the models took 

a step towards a much colder mid and long term outlook. 

Plenty over the next week to keep us more than interested though, so personally I am more than happy with that 

for the next several days. 

[Longshanks]

Just a quick question - how is it that both Met office analysis and GFS models are forecasting max temps above 4degs C for North Wirral Coast - 2 degrees higher than last weeks cold spell - but yet the coming few days are being much vaunted as coldest spell of this winter hereabouts??

[shaky]

Well well gfs reverts back to what it was showing 36 hours ago!! Shortwave cuts off in the atlantic and heads south east west of ireland!!

[TSNWK]

Well well gfs reverts back to what it was showing 36 hours ago!! Shortwave cuts off in the atlantic and heads south east west of ireland!!

Forgive me for asking.. But is that good or bad?

[BLAST FROM THE PAST]

Forgive me for asking.. But is that good or bad?

Its good, look at the LP SW of Greenland being cut off by HP looking to link between Greenland and Atlantic...should lead to more sustained Atlantic block and cold northerlies

 

 

BFTP

Edited January 27, 2015 by BLAST FROM THE PAST

[TSNWK]

Its good, look at the LP being cut of from HP looking to link between Atlantc and Greenland...should lead to more sustained Atlantic block and cold northerlies

 

 

BFP

Many thanks BFTP and you're just down the road from me..