Model Output Discussion

[Eugene]

Pressure building from the south is becoming a very consistent feature now on GFS

Ths is just what you want to get any chance of a proper cold spell later on, looking blocked to our east

http://www.wetterzen...s/Rtavn1321.png - Very happy to see charts like this bringing an end to all the unsettled weather.

Edited December 5, 2009 by Eugene

[Eugene]

That is some cold pool developing just to our northeast

http://www.wetterzen...s/Rtavn2643.png

http://www.wetterzen...s/Rtavn2762.png

TEITS and i will be very happy with this run whilst the rest moan about warm 850`s aloft

Edited December 5, 2009 by Eugene

[loophole]

I'll take this

[Lincs Observation]

Morning all

just looked at the Christmas update and the trend is still there for a interesting period so very happy there, also the models this morning continue to hint at colder transitions around a week before festivities, however its my fav set of models for the jet that interest me the most and this morning im cocker hoop as the jet goes on holiday to Africa, how much further south could it get. For me this is very significant in the winter months and I like some on here can feel the taste of something quite special over the next few weeks.

LO

WARNING !!!!

Caution is STILL needed when looking at model outputs,EXCITEMENT MAY LEAD TO HEALTH PROBLEMS OR IN EXTREME CASES LOSS OF LIFE.

Edited December 5, 2009 by Lincs Observation

[Optimus Prime]

yes but as usual you're picking the charts to suite you NOT the charts that are most likely to come of. I'm almost certain now inversion high will be the outcome, IF we're lucky.

EXCITEMENT MAY LEAD TO HEALTH PROBLEMS OR IN EXTREME CASES LOSS OF LIFE.

Yeah I may end up shooting myself in the face if people don't listen for once.

[J07]

Even High pressure sitting over the country doesn't always guarantee an inversion, it's one of those things where it probably occurs as much by chance as it does owing to a specific set of conditions.

With a high over the country, there would always be an inversion at the top of the boundary layer.

[Snowmad79]

yes but as usual you're picking the charts to suite you NOT the charts that are most likely to come of. I'm almost certain now inversion high will be the outcome, IF we're lucky.

Yeah I may end up shooting myself in the face if people don't listen for once.

00z GFS is not a bad run for cold lovers. I think most people kind of agree that an Inversion High was always going to be the first step anyway. We still need more runs before we can tell if and how far that High will progress northwards.

Its good to see Iceland emsembles still showing the trend for HP there too.

[Iceberg]

The good news is that all of the models have the the Jet and WAA correctly for cold weather at 120Z.

i.e shooting up the west side of the UK.

From here it seems to be a question of

A potential cold anticyclonic spell or

A potential easterly.After a few days both ECM and GFS retrogress the High over to Greenland.

GFS is quite cold

ECM has a bit of an easterly then the regression.

Meto probably similar to the ECM.

GFS alternative is probably the warmest of the lot and goes for normal december settled conditions.

GFS ensembles support all of the above in equal measure.

Knowing that the models beyond 120Z don't tend to model in enough shortwaves, I am tempted to go with a blend of all three.

Starting next weekend we have settled weather which will turn progressively colder, with quite a bite to an easterly wind, particularly in the south and a possible few light snow grains on Monday.

Then the High starts to retrogress northwards and westwards, however shortwave features slow this progress down allowing for me of a NE feed to develop allowing maybe a few snow showers for eastern areas come mid week.

Detail is however a total guess and it's just fantastic the agreement we have at 120/144 which probably makes some form of below average weather a 75% chance now, with the severe cold still only a 25%

[Frosty.]

Very promising models this morning, a massive upgrade on the 00z runs yesterday. The models are in good agreement that the atlantic low pressure conveyor belt will run out of steam just after midweek with high pressure building strongly to the east, we will then lose the mild temps as we pick up a continental feed by the end of next week with frosty nights and temps by day struggling to reach much more than 3-5c and lower than that in some areas. Watching that deep cold wintry trough to the far northeast spilling it's bitterly cold air sw'wards towards the uk is fantastic to see although on this mornings runs we don't seem to feel the full force of it but the trend is key, I seriously thought the charts might have imploded overnight but we appear to be on track for a potentially very cold and possibly very wintry spell which is tantalizingly close to the reliable timeframe.

[winterof79]

Forget the UK, look how much cold goes into Greece on the 18z - that's astounding! In my opinion if the high pressure is going to occur, this is pretty much how it'll play out (in terms of pattern, not severity), and at one point the FI shows -24C in Northern Greece. It's all fairy tale stuff in terms of severity and has little to no chance of being that severe if it occurs but in terms of what it shows, it's quite entertaining!

Good morning all, still ploughing through last nights posts.Stephen,irrespective of what transpires,i was stationed in northern Germany in early 1987 and daytime temps were -16C for many days.Frostbite was common during that period.So it can happen,but it is a rareity.Any way i will finish my reading and hope we are still in the same position when i arrive at the last page

[Altostratus]

Some interesting outputs being shown this morning. I couldn't help but notice the similarity between this chart:

http://www.wetterzentrale.de/pics/Rtavn3361.png

and

http://www.wetterzentrale.de/pics/archive/ra/1982/Rrea00119820109.gif

Long way to go, but it at least looks like bceoming more settled and cooler before something potentially better beyound this.

[TEITS]

Some excellent charts on offer today.

Let me begin by saying that at +144 we have excellent agreement in the ensembles with the mean in Cambs at 1030mb.

http://charts.netweather.tv/ensimages/ens.20091205/00/prmslCambridgeshire.png

Now the next hurdle is can we get the cold airmass to our NE to advect SW. In recent Decembers when we have had a HP sitting over the UK there has never been an opportunity of the HP retrogressing due to LP systems running to our N. However take a look below at the Iceland ensembles and rather than there being a deep Icelandic LP we have higher pressure than the norm.

http://charts.netweather.tv/ensimages/ens.20091205/00/prmslReyjavic.png

So in summary there are 3 possible outcomes.

1. HP over the UK but the cold airmass to our NE moves S and doesn't reach the UK.

2. HP over the UK retrogresses and the cold airmass moves SW and reaches the UK.

3. HP over the UK retrogresses but only E areas tap into the cold airmass.

Over the next few days the models are likely to show all 3 outcomes but at the moment I wouldn't want to say which one it will be.

[nick sussex]

A good start to the day with generally good agreement in the models for at least the first stage to colder weather, just one small negative being the GEM which shows what can happen if things go wrong. A few pointers to look out for in future output, we want to see a strong southerly flow ahead of the trough piling into the arctic, this with the aid of WAA(warm air advection) will aid the building of high pressure to the ne and east of this.

You need to see the trough aligned north/south like the ukmo, although IMO we need a bit of insurance so with all the output the further west the trough the better.

http://www.wetterzentrale.de/pics/Rukm1441.html

You don't want to see the trough aligned ne/sw as this could see energy spill eastwards over the top and make the route to cold more difficult or in the GEM basically scupper things completely.

It's still going to be bite your finger nails time today if you're looking for cold, also in the early stages the more digging south of the trough the better, also we need to see the euro high extend as far north as possible.

Anyway here comes he gfs 06hrs run,let's hope it continues with the same pattern.

[mt-leinster-snow-drifts]

I have avoided getting carried away in this one , usually at any signs of an easterly i'd almost wet myself(not really). But I have a feeling that it will last about 36 hours and then something will plow in from the atlantic , i just have a bad feeling about this one.

[kold weather]

The important thing eye is that all those solutions have a very real chance of being quite cold as well...I'm very happy with how this is progressing at the moment, GFS is a great run, the ECM is very borderline and close to a stunning set-up though there may not be quite enough upper support to allow some real cold air towards us, may get diverted to the east but its still a good run out to 240hrs.

[nick sussex]

The important thing eye is that all those solutions have a very real chance of being quite cold as well...I'm very happy with how this is progressing at the moment, GFS is a great run, the ECM is very borderline and close to a stunning set-up though there may not be quite enough upper support to allow some real cold air towards us, may get diverted to the east but its still a good run out to 240hrs.

To be honest KW if it wouldn't have been for the GEM i would have been much happier with the output, this is a little concern this morning. It's impossible to ignore it so we should bear this in mind, any movement of the gfs 06hrs run to it IMO would be a bad sign, so we need this to stick to its guns.

[kold weather]

Yeah the GEM does show what can happen but to be fair its the only one and if the GEM does have a fault its that its not really at all good in blocking situations, a good model in progressive situations but if things start to slow down it can get caught out. I'd be more worried if the UKMO moved away, thats tends to be the first to throw a spanner in the works usually.

For now I think a colder few days under a inversion is very probable, beyond that its hard to say.

[cooling climate]

Excellent runs this morning. The ensembles should continue on their downward trend now.

I really can not see anything other than a very cold pattern developing across Europe and

the UK.

Their may possibly be the odd hic-up that may slightly delay the onset of very cold weather

but that is all.

Very good model watching to come I feel.

[londonsnow]

whilst the evolution to an easterly pattern starts in the fairly reliable timeframe, the detail remains firmly in the unreliable. the gfs is great in the proper fi, but this could clearly go up in smoke. as nick says the gem is a fly in the cold ointment. anyway, here comes the 6z

[Iceberg]

The 06Z has brought in an extra little shortwave at 132Z out in the atlantic, this should help to drag the High NW more, all in all upto 144 I think this is a good run.

I've got a feeling that as the 120-144 approaches the 96-120 timeframe we will see a few more of these and it will get a little better.

[cooling climate]

I noticed the GEM model has low pressure around Svalbard at t132 which would stop

the high ridging north and the WAA.

No other model agrees with this.

The 18z operational GFS had this last night but the 0z ditched it and so has the 06z.

[kold weather]

06z not as good at the moment IMO, got a strengthening low to our west that is moving northwards which on the 0z was the low that undercut the high and allowed us to drag in a colder flow...I think this run may just see the HP sit over the UK instead.

[nick sussex]

This so far is more in line with the majority of the ensembles at this time period but still okay and thankfully says no to the gem!

[Iceberg]

06z not as good at the moment IMO, got a strengthening low to our west that is moving northwards which on the 0z was the low that undercut the high and allowed us to drag in a colder flow...I think this run may just see the HP sit over the UK instead.

I think I would prefer to forgo the short term easterly if the high can ridge further northwards and allow the cold more into the continent.

But I am being really picky here, personally I like the 06Z.

[cooling climate]

The 06z looks like being a absolute cracker of a run.