Model Output Discussion

[nick sussex]

In a winter where we've discussed everything about shortwaves we're now turning our attention to the phasing of two lows! as we've seen and I think we discussed this a few days back a route to cold given the set up is with the Iberian Low becoming the dominant feature.

If this happens then the outlooks much more favourable, the 168hrs to 216hrs on the ECM looks wintry with snow on the northern flank of the low, shame its so far out but this IMO is the only plausible way out of the more expected slushfest of the other models.

[Nick F]

Fascinating and unusual synoptic evolutions tonight. 12z GFS seems to have fallen in line with the Euros, jettisoning its easterly positioning of the low by taking it S and now taking it SW towards Ireland.

Big uncertainty IMO beyond t+120-132 to where the low will go after, all depends on the shape and orientation of the upper trough that extends down from the NE, as the 500mb flow will ultimately determine the path of the surface lows. 12z ECM has the SW-NE 500mb trough further south, so the sfc low will end up further south too ... pulling in colder air across UK on its northern flank eventually.

[Polar Continental]

Fascinating prognostic charts at the moment. Practically the whole north Atlantic is being projected to shut down from the normal mobile west to east point of view. I have not seen anything like this for many years.

Very quiet Atlantic

I really hope we can scrape something very wintry out of this very unique pattern shown.

The 12z ECM at T168 is showing tentative signs that we could be heading in the right direction for a very cold mid month to end of month.

ECM T168

[cooling climate]

Before winter is over and by that I mean in a time frame where we can still see very cold

or severe winter weather(mid March probably in the south, end of march into April for Scotland,

Shetland Isles), I really hope and believe we will see a proper freeze again for at least several

days. Whilst seeing snow falling on everyday this week bar one it was still milder than what

many of us hoped and thought it would be. Going through this week there have been strong

signs from the stratosphere forcasts and hints from the synoptic charts that very cold and

wintry weather could return to the UK once again. The 12z ECM run today is the first run that

shows what a few of us have been indicating could happen synoptic wise over the next several

days IE the low from the north tracking south of the UK with blocking from the north building

height between Iceland and into Scandinavia. Then as the low moves east it will pull in a very

cold continental feed. Powder snow, ice days, and severe night frosts could be on the menu

once again. I for one would much prefer to see this outcome than perhaps heavy snow daytime

max temps of +3c and a steady thaw.

Of course this is just one run but imo it is the most plausible and likely outcome when you consider

the MJO, blocking to the north (very -AO and NAO) and yet to be felt impacts from the MMW for our

neck of the woods. Of course we need to see where this run lies in the ensembles plus what the

runs do tomorrow to see if this scenario has any validity.

[La Bise]

On the chart Polar posted, you can see so well that grim conveyor belt of LP that use to spend winter above our heads and is now holidaying in Southern Spain/Northern Africa. I don't miss them one bit...

[80sWeather]

well once again the ECM to brings the blocking to the party and the iberian low gives us a free bar for the night ! this would be the icing on the cake for an amazing winter of model watching.

[mcweather]

Still a good deal to play regarding the track of the sinking low early next week I wouldn't take any of the models as gospel at the moment. Although I must admit I do like tonights ECM solution.

[TEITS]

What I do like about the ECM and the same can be said for other models runs is the first hurdle towards a very cold spell in the UK is already in place. Some of you might be wondering what im on about but what im referring to is a bitter cold pool to our N/NE.

One of my gripes with this winter and the same can be said in recent winters is a general lack of extensive very cold pools to our N/NE. What we have been seeing is small pockets of cold pools around -10C/-15C. This is why the E,ly in Jan actually became warmer!

I have always said at times the synoptics prior to a cold spell are just as important as to the synoptics bringing the actual cold spell itself. For example Feb 05 E,ly was very weak because prior to this the continent was subjected to mild S/SW,lys. The other extreme is Jan 1987 when an incredibly cold pool spread S prior to backing SW across the UK.

So with this in mind the model output does suggest a cold pool will be to our N/NE so thats the first hurdle out of the way. The next hurdle is getting the right synoptics so this backs SW. Now the 12Z ECM is a very good run because we do see the colder temps back SW. However it could be better and it would only require the LP to track slightly further S to back an even colder E,ly flow. Also worth mentioning that the chance of a Scandi HP remains possible as has been shown on some of the GEFS ensembles.

If the ECM continues with this trend it could get very exciting. However this LP is reminding me of my ex girlfriend i.e extremely unpreditable!

[Frosty.]

It's very good to see how much the ecm has improved since this morning, the 00z showed the cold charts beginning to diminish by T+240 but tonight it's quite the opposite. There is still a lot of doubt on where the low moving down from iceland will end up though but it's safe to say next week will be very unsettled everywhere and at the very least, rather cold with a good chance of surprise snow events. Hopefully the ecm de bilt ensembles will show that the op run has support.

[Cheese Rice]

Is the next week going to be similar to the short break in between the Dec and Jan cold spell? I have read posters make reference to Dec 23rd.

[snowray]

i find it funny people still beleive in the models.

they didnt know their butt from their elbow last week for days on end.

in the end UKMO won out (with human intervention)

Not so sure if the UKMO has won out now, would have agreed a week or so back, but the correct position of our current HP further South and the Easterly just about clipping kent was consistently modelled by the GFS 18z, it stuck to its guns for 3 conecutive runs and then the ECM came on board 1st. The minor models like the Canadian, NOGAPS, etc, were way way out. UKMO being about in the middle.

[Duane S.]

Is the next week going to be similar to the short break in between the Dec and Jan cold spell? I have read posters make reference to Dec 23rd.

Here's a chart for 4 days time and here's one from Xmas day last year. Not exactly a million miles apart!

[nick sussex]

What I do like about the ECM and the same can be said for other models runs is the first hurdle towards a very cold spell in the UK is already in place. Some of you might be wondering what im on about but what im referring to is a bitter cold pool to our N/NE.

One of my gripes with this winter and the same can be said in recent winters is a general lack of extensive very cold pools to our N/NE. What we have been seeing is small pockets of cold pools around -10C/-15C. This is why the E,ly in Jan actually became warmer!

I have always said at times the synoptics prior to a cold spell are just as important as to the synoptics bringing the actual cold spell itself. For example Feb 05 E,ly was very weak because prior to this the continent was subjected to mild S/SW,lys. The other extreme is Jan 1987 when an incredibly cold pool spread S prior to backing SW across the UK.

So with this in mind the model output does suggest a cold pool will be to our N/NE so thats the first hurdle out of the way. The next hurdle is getting the right synoptics so this backs SW. Now the 12Z ECM is a very good run because we do see the colder temps back SW. However it could be better and it would only require the LP to track slightly further S to back an even colder E,ly flow. Also worth mentioning that the chance of a Scandi HP remains possible as has been shown on some of the GEFS ensembles.

If the ECM continues with this trend it could get very exciting. However this LP is reminding me of my ex girlfriend i.e extremely unpreditable!

The ECM ensembles for the Netherlands are quite interesting. The control run follows the operational run until the time that the low is expected to cross into that area, the control goes colder but still shows similar precip spikes. This suggests it takes the low further south and hence still wet initially or as the case maybe snowy.

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

[Cheese Rice]

Here's a chart for 4 days time and here's one from Xmas day last year. Not exactly a million miles apart!

Interesting, I hope very much it comes of as on the 23rd I got 10cm of fresh snow and on the 24th I got 5cm of fresh snow.

[Bolton67]

Interesting, I hope very much it comes of as on the 23rd I got 10cm of fresh snow and on the 24th I got 5cm of fresh snow.

It can do what it wants next week...

As for the 23rd we had rain which washed our snow away and the 24th was dull and wet.

So people in the east mids will hope this does NOT come off.

[swilliam]

The ECM ensembles for the Netherlands are quite interesting. The control run follows the operational run until the time that the low is expected to cross into that area, the control goes colder but still shows similar precip spikes. This suggests it takes the low further south and hence still wet initially or as the case maybe snowy.

http://www.knmi.nl/e...M_06260_NWT.png

The extended ensembles show the control run going mad

[damianslaw]

As others are saying a very cold pool is beginning to develop to our NE, teleconnections support advection of this very cold air our way eventually next week, the only place for this low to go is southwards, ECM is onto this pattern watch the others fall in line..

The jet is projected to be very southerly for the foreseeable future. This is the time of year the atlantic often goes into a slumber, patterns tend to stick around this time of year for a long time, I often associate the period mid-late Feb as a cold blocked non-atlantic dominated period.. the synoptics are better than we what we saw in early Jan for delivering potentially the coldest conditions we can get relative to the time of year, proper arctic continental, arctic high and all..

[nick sussex]

The extended ensembles show the control run going mad

Yes thats certainly an east to ne flow shown with the PV dropping south into western Russia! Given the later output is at the end of February that control run shows some pretty amazing temps. So it really is down to the phasing of the lows initially as I suspect the control run and operational would show similar synoptics but the control run dropping the low further south which allows the very cold air to back west over the top.

I think its safe to say that if people still want to see one last major freeze before the winter is out then its now or never. Of course we have seen snow and cold temps well into March but for ice days and true winter weather with no slush start praying for the ECM output with a trend further south.

[Cheese Rice]

It can do what it wants next week...

As for the 23rd we had rain which washed our snow away and the 24th was dull and wet.

So people in the east mids will hope this does NOT come off.

I think this shows how marginal the situation will be for most areas, as many places got rain on the 23rd of Dec and the upcoming synoptics are quite similar. looking at the GFS I would say a definite risk of snow only for the central spine of Northern England and Scotland, not exclusively for high ground either. On the 23rd Dec most places got rain apart from very central areas of northern England, this was the scene in the center of Leeds (30m ASL) on the 23rd where only a few miles east got rain

, and the scene on the morning of the 24th

more heavy snow which wasn't forecast .

[Snowyowl9]

Having just looked at december 24th again it was marginal but gave snow,unusual patteren this was.

http://www.wetterzentrale.de/archive/ra/2009/Rrea00120091224.gif

http://www.wetterzentrale.de/archive/ra/2009/Rrea00220091224.gif

[johnholmes]

There is of course going to be no major freeze next week. However, we do have the set up for a really interesting few days watching how the weather turns out. Certainly wintry for some, and as L-N posts about the Bolton episode, I think its going to be a case of the higher you are the more likely you are to see a decent fall of snow. Not exclusively though which is what I suspect is going to be the interest for many.

Its way too far to even speculate but the usual checks need to be done on whichever run you use.

is the rain more than slight for you-how long-any evaporative cooling likely as a result of the intensity?

what is the 850mb temperature when the precip is falling?

the 850-1000mb thickness?

the temperature and dewpoint along with the wet bulb?

zero isotherm

all will help give some guidance on what may fall out of the clouds.

DON'T expect to be at all clear about it much before 24 hours before its showing on the charts-area-time-intensity etc WILL change.

As to beyond, then as the blog in the forecasters link I've just put in then to me its a cold not a warm end to February and start of March it seems to me.

So for those wanting spring-it does look as though it may be on hold for a bit.

[cold snap]

Yes thats certainly an east to ne flow shown with the PV dropping south into western Russia! Given the later output is at the end of February that control run shows some pretty amazing temps. So it really is down to the phasing of the lows initially as I suspect the control run and operational would show similar synoptics but the control run dropping the low further south which allows the very cold air to back west over the top.

I think its safe to say that if people still want to see one last major freeze before the winter is out then its now or never. Of course we have seen snow and cold temps well into March but for ice days and true winter weather with no slush start praying for the ECM output with a trend further south.

Well looks like another week of fun.

I do agree with you there Nick about time running out.

One thing that does suprise if people remember the evolution of the last major freeze .this did take a slow timelaspe.and if that similar evolution was to appear now we would be hitting the month of March.Ive never been a fan of March .Marginal is one word that will crop up over and over again in that month.

However i pray to god we dont get stuck in no mans land again which is a route GFS might be thinking about again.

I think people would take one Snowy day or night now.Rather than another go a long cold snap.

Cant see there being much more cold pools being left to tap in.Surely the East is going to warm up soon.Its been in a deep freeze for so long.

ECM is very good tonight.but ECM has put us here before and then drop it runs later.At least this time all models are showing the same low.but they are placing it in different parts.

To end i dont think theres much point in trying to look for a long good evolution.Time is ticking so that low coming down from the north will either make us or break us.

[fazzafarrand]

I think this shows how marginal the situation will be for most areas, as many places got rain on the 23rd of Dec and the upcoming synoptics are quite similar. looking at the GFS I would say a definite risk of snow only for the central spine of Northern England and Scotland, not exclusively for high ground either. On the 23rd Dec most places got rain apart from very central areas of northern England, this was the scene in the center of Leeds (30m ASL) on the 23rd where only a few miles east got rain

, and the scene on the morning of the 24th

more heavy snow which wasn't forecast .

No offence but I am a few miles south / east of Leeds and we got a Good covering of Snow on both of the above occasions

[len]

As others are saying a very cold pool is beginning to develop to our NE, teleconnections support advection of this very cold air our way eventually next week, the only place for this low to go is southwards, ECM is onto this pattern watch the others fall in line..

The jet is projected to be very southerly for the foreseeable future. This is the time of year the atlantic often goes into a slumber, patterns tend to stick around this time of year for a long time, I often associate the period mid-late Feb as a cold blocked non-atlantic dominated period.. the synoptics are better than we what we saw in early Jan for delivering potentially the coldest conditions we can get relative to the time of year, proper arctic continental, arctic high and all..

It has seemed like an eternity as we watched Snowmaggedon Easterlies gradually evaporate to a short blast into France. Then we consoled ourselves with a real Northerly Arctic blast in the offing; this will now try to warm the Central Atlantic. We now face a messy & marginal Limbo.

But ECM still says real cold is just "yet another week away". It's always a week away.

I, for one, don't believe it.

[Liam J]

gfs still going for snow event next week imo, after the ppn falls as rain monday turns to snow from the north monday evening and night as the low brings down the 528 thickness and colder uppers falling onto surface temps of 0-3c.

we cant take any run as gospel i feel there will be more twists to this until sunday, so very close to wrapping even colder air into the low from the continent and from the north.

some places will get heavy snowfall next week it may be marginal but trending to be on the right side for many.

roll on tomorrows model outputs getting closer to nailing hopefully.