Model Output Discussion 29th December - Into mid-Winter.

[Paul]

16 minutes ago, Cloudy daze said:

Some alarmingly deep cold to ,government might need a cobra meeting !

The GFS has often had a thing about overdoing cold temps over snow, I suspect that chart is a good example of it!

[Paul]

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[Doctor96]

I recall the 1978 well , but then it was an easterly in mid february when the north sea was very cold and thus the sea could not temper the easterly. Any views on how the north sea temps may limit the cold from an easterly in early January.

[Paul_1978]

I've been looking at the GFS archive for past wintry periods, eg Feb 1981, Jan 1987, Feb 1991 - and one thing is for sure, as long as we can keep low heights in Europe then for me that's a big step in the right direction. 

The 06z keeps low heights there during the run, resulting in the easterly, albeit a long way off. 

So for me, I'll certainly be keeping a close eye on what's going on in Europe and the Med, as well as to the North West (Greenland/Iceland). 

[mhielte]

17 minutes ago, Paul said:

The GFS has often had a thing about overdoing cold temps over snow, I suspect that chart is a good example of it!

Two 6z runs in a row! Tells you it's not wise to drink early #newpubrun

[Seasonality]

And on a model related note it is interesting to see the 06z ensembles, the Op run is at the bottom end of the ensemble members but not a clear and unrealistic looking outlier like 24 hours ago. Looking better and better for cold imho.

 

Edited December 30, 2016 by Polar Maritime
To move discussion on.

[snowking]

In the interests of the upcoming potentially colder period I've just taken out a short trial of a tool I first used a few years ago when I was forecasting

We can see below the increasingly cold trend from the last three ECMWF EPS suites for London (Red is 0z today, Blue is 12z Yesterday and Green is 0z Yesterday):

So a decent ensemble trend, though of course there are likely numerous synoptic solutions behind this surface cold. We see impressive cold clustering in the 0z ensembles as a result:

I'll be honest, I've not seen a better set of ECMWF Ensembles since 2013. In fact some of the charts posted in here in the last 24 hours have been pure filth and have no business being posted on a public forum without an 18+ warning attached

Of course synoptically the main trend in the last few days, as surmised in my previous post, has been for the low heights to remain more towards the Canadian sector as opposed to the Siberian sector (a common theme in recent winters) as shown below:

(Not an entirely fair comparison as they are 24 hours apart, but you get the picture)

This has left us looking NE as opposed to NW...for now at least (given forecast falling AAM the Jet should pack less of a punch as time goes on through January and give rise to retrogression potential) - an outcome which, living in the East of England does not particularly displease, but there is always more frailty to advecting the coldest air to the UK under an Easterly scenario, so plenty more trials and tribulations to come I suspect.

SK

 

 

[SteveB]

I've been checking back through the CET since 1679 and can't find any that have had a bitterly cold Jan after a mild December, We will have to set a new trend if we want to see a cold Jan!

[Coopsy]

7 minutes ago, Doctor96 said:

I recall the 1978 well , but then it was an easterly in mid february when the north sea was very cold and thus the sea could not temper the easterly. Any views on how the north sea temps may limit the cold from an easterly in early January.

Negligible when looking at monthly averages at say Lowestoft. Jan 7.2oC/Feb 7oC/March 6.8oC 

[Coopsy]

Just now, SteveB said:

I've been checking back through the CET since 1679 and can't find any that have had a bitterly cold Jan after a mild December, We will have to set a new trend if we want to see a cold Jan!

No but warm spells followed by extremely cold spells happen. Dec 86- Jan 87 is one that jumps out. I'm happy to have just a week not a whole month 

[Polar Maritime]

A few posts hidden, Any issues please contact a member of the team and not air it in here, Thanks.

[NorthYorksWeather]

7 minutes ago, sorepaw1 said:

 

Very jealous of your location as we head into the New Year,  it does look like NE could see some hefty snow showers Sunday overnight into Monday.

Whilst my area is prime for some snow showers, no doubt the best place to be is the North York Moors which sticks out into the sea and eats snow showers for breakfast, dinner and tea!

Edited December 30, 2016 by Polar Maritime
To move discussion on.

[SteveB]

3 minutes ago, Daryl Dixon said:

No but warm spells followed by extremely cold spells happen. Dec 86- Jan 87 is one that jumps out. I'm happy to have just a week not a whole month 

True, just seeing snow will do me, but if we want that Easterly in  a couple of weeks times I bet the CET will be very low by then, and little chance of recovering once it sets in.

 

[Snowy L]

14 minutes ago, Doctor96 said:

I recall the 1978 well , but then it was an easterly in mid february when the north sea was very cold and thus the sea could not temper the easterly. Any views on how the north sea temps may limit the cold from an easterly in early January.

A mild North Sea can be good and bad. As long as the air is cold enough to cancel out the mild effect it's fine. Also a higher gradient between air and sea will bring more precipitation.

[blizzard81]

A crucial set of 12z runs coming up, arguably the most important of the season so far. Would be nice to have the ukmo on board.

[Methuselah]

6 minutes ago, Snowy L said:

A mild North Sea can be good and bad. As long as the air is cold enough to cancel out the mild effect it's fine. Also a higher gradient between air and sea will bring more precipitation.

I usually find that, as a rule-of-thumb, northerly-sourced air with uppers of about -9C or less is sufficient, for snow to fall to sea-level, on the coast...An easterly is an entirely different kettle of fish, however.

[I remember Atlantic 252]

1 minute ago, Ed Stone said:

I usually find that, as a rule-of-thumb, northerly-sourced air with uppers of about -9C or less is sufficient, for snow to fall to sea-level, on the coast...An easterly is an entirely different kettle of fish, however.

Yes, usually -9 here off northerly, -12 needed off any Atlantic air

[snowice]

Will the UKmo move in the 12z or will we have to wait till tomorrow anybody?? 

[stewfox]

2 minutes ago, snowice said:

Will the UKmo move in the 12z or will we have to wait till tomorrow anybody?? 

 

Can someone confirm the attached are the current out put times, ie we should see 12z before UKMO 

 

[Polar Maritime]

No more discussion on Meto forecasts please. There's a thread here for that

 

Edited December 30, 2016 by Paul
Added link

[SteveB]

10 minutes ago, snowice said:

Will the UKmo move in the 12z or will we have to wait till tomorrow anybody?? 

Still time for changes, and we've seen some massive changes before, you only have  to look at last months massive flip from cold to mild, so caution still needed.

I think the fact that the first Northerly is nailed on (finer details aside) and the second one is almost in the bag leads to think, as we are in a cold pattern then it gives us a good platform to continue a colder theme, it's just what version of cold that will be.

And as many have said, we are in a far better position than the last 2-3 Winters. We are still in the game, just need the UKMO to play ball..... not long until we find out

[Man With Beard]

Bit of time for a longer synopsis today...

UKMO - IS IT RIGHT?

Let's look at how it might be doing at the moment by looking at Monday's prospective charts for ECM/UKMO - first at T144, followed by the current outlook (T72)

  

  

The ECM had a separated Atlantic ridge at T144 and still has it at T72. The UKMO did NOT have a separated ridge at T144 (substantially joined to the tropical ridge), but its latest T72 looks much more like the ECM was at T144.

This is a GOOD TREND for those wishing the UKMO to be wrong on its current T144 in the Atlantic, as the difference between itself and the ECM is, once again, a matter of phasing Atlantic lows. A bit like the charts above, the UKMO combines them whilst the ECM (and GFS) have a separation between Atlantic energy. 

HOWEVER, the ECM did blow up the Azores low too much and has moderated it somewhat in its current output.

So, the UKMO cannot be completed discounted, as much as any T144 output is rather ropey at the moment due to the issues with how much energy goes under any Atlantic ridge.

But the UKMO is just one run. You would think it cannot be right if it opposes all of the GEFS (20 runs), GFS op, ECM op and ECM ens (51 runs)

GEFS T144 mean

ECM ensemble mean at T144

ECM op

GFS op

ROCK ROCK ROCK SOLID AGREEMENT on a separation of energy in the Atlantic and no route in for heights up the eastern seaboard of the US at this point. Euro heights do differ between GFS/ECM at this point but seem to make no significant difference in the outcome of later ensembles

VERDICT:

UKMO is 95% likely to be WRONG with the mid-Atlantic. Put it this way, if the UKMO had been broken this morning, we would have enough evidence from the ECM and GFS to make a confident judgement on the Atlantic with such agreement at just T144. However, it may be ahead of GEFS on Euro heights.

 

 

 

 

[fromey]

Is this in with what the ECM is seeing??

 

fromey

Edited December 30, 2016 by fromey

[weatherguy]

3 hours ago, SN0WM4N said:

Looks to me like cold rain for lower levels. The 6z doesn't bring the v cold air at all.

 

Obviously far out in FI and they share similar pressure patterns, but the deep low that comes down to give us the northerly feed throws warmer air in front of it. But the high pressure is further north and may give us a better chance of an easterly. Just variations in the theme.

 

Yes indeed, it would be very marginal as modelled there.  Should have emphasised "could" - was rather referring to the potential for how it might pan out, something to keep an eye on anyhow.

[bobbydog]

I see the latest met office update suggests an increased confidence in the model output we are seeing lately (even daring to mention the word "snow"). If the UKMO model is not following the trend so far, it would indicate that the Meto are giving more weight to the GFS and ECM solutions. If that is the case, we should see the UKMO leaning back towards the other two... we'll see...