General Model Output Discussion

[swilliam]

Definite changes in the overall pattern on this run in F1. Looking at the 00 run you can see mainly PV to the North of Scandinavia.

On the 06 run this is now replaced by an Arctic high as the WAA from the US Pacific coast is much more energetic and reaches the Pole region.

Will this make any difference to the length of our cold spell on this run?

[nick sussex]

It`s really small differences in the placement of the surface features on the 006z which hold the cold in place to T150hrs.

The general flow is much the same and these small but important features are going to be a nightmare to model untill close up.

Morning Phil

Yes its a nightmare forecast for next week with very messy synoptics but the key is the low to the sw, the uk by then would in a sense be developing its own localised cold pool and as long as we see this low track ne through France then a much better outlook would result for the uk.

Down here it looks like warming up but beforehand even this far south we're expecting some snow tomorrow.

[swilliam]

Definite changes in the overall pattern on this run in F1. Looking at the 00 run you can see mainly PV to the North of Scandinavia.

On the 06 run this is now replaced by an Arctic high as the WAA from the US Pacific coast is much more energetic and reaches the Pole region.

Will this make any difference to the length of our cold spell on this run?

The answer seems to be yes with a completely different evolution now. 00hrs

06hrs

Not sure if it was for the reason I mentioned previously but certainly a vastly different outcome and very interesting/welcome it is.

[phil nw.]

Morning Phil

Yes its a nightmare forecast for next week with very messy synoptics but the key is the low to the sw, the uk by then would in a sense be developing its own localised cold pool and as long as we see this low track ne through France then a much better outlook would result for the uk.

Down here it looks like warming up but beforehand even this far south we're expecting some snow tomorrow.

Morning to you Nick,

Yes the low res.shows what could happen if the jet buckles and the low complex to the South West elongates with higher pressure to the North.

It get`s milder near the south coast for a while but further north surface temps. remain low.

Yes i see from the 850`s you likely to be close to -10c there nick.

Time to put the woolies on mate.

[Yeti]

I'm still amazed by the sudden short-term changes on this run.

http://www.wetterzentrale.de/pics/Rtavn482.png

The -15 isotherm was expected to reach no further than East Germany yesterday. On the 6z it reaches into France and the Low Countries only 48 hours away! That's a monumental shift at this range.

[nick sussex]

Morning to you Nick,

Yes the low res.shows what could happen if the jet buckles and the low complex to the South West elongates with higher pressure to the North.

It get`s milder near the south coast for a while but further north surface temps. remain low.

Yes i see from the 850`s you likely to be close to -10c there nick.

Time to put the woolies on mate.

Hi again Phil

Well it's really a complex set up but so much relies on that low to the sw, i really hope it enters the festive spirit!

Down here is been cold all week and we're now into our second consecutive day below freezing, just shows you with 850's only near -5 what can happen with no sea modification and an easterly flow off the continent. The - 10's are expected later tomorrow so will be interesting to see what that produces, currently -1.7c here.

Edited December 17, 2009 by nick sussex

[Eugene]

It'll be a brave person who says with confidence what will happen next week I think

It will stay cold until at least Dec 25th, fairly confident about that too

Amazing GFS 06Z with no mild breakdown until the extreme reaches of FI, extraordinary run

[carinthian]

Hi , not as progressive on the latest GFS. Some sort of stalling situation likely to develop early next week into the Christmas period. Could end up with classic battle between the cold entrenched to the Northeast against the milder airmasses. This is a great winter set up to follow, normally you see in Mid Winter.

C

[cooling climate]

It will be interesting to see the updated OLR (outgoing longwave radiation charts) later on, but with

a increase in convection over and to the east of the date line this will pump stronger heights up the

west coast of America which should slow or delay the Greenland high retrograding (moving west).

This could well be a signal for more blocking over the Arctic and our neck of the woods which is all good

news.

In the near time excellent synoptics and weather to enjoy over the coming few days at least with post

t144 far from settled.

Edited December 17, 2009 by cooling climate

[Eugene]

I have some extremely bad news for you people.

http://91.121.94.83/modeles/gens/graphe_ens3.php?x=&ext=1&y=&run=6&lat=54.534412955465584&lon=-6.037735849056602

We may have to put up with 850`s only around -5C hPa on Dec 25th

[Wayneywoo]

I have some extremely bad news for you people.

We may have to put up with 850`s only around -5C hPa on Dec 25th

That in itself is not bad news. Dew points, surface temps, wind direction, continental surface temps etc..etc.. all play an important part also. Not to mention the fact that +T72 is changing beyond belief.

Take each model as it comes people and look for agreement between them to spot something that keeps appearing and has a high chance of happening.

Sorry Eugene, I may be misinterpreting what you say. Did you mean only -5º as good, getting colder or bad, getting warmer...

Edited December 17, 2009 by Wayneywoo

[phil nw.]

I have some extremely bad news for you people.

http://91.121.94.83/...037735849056602

We may have to put up with 850`s only around -5C hPa on Dec 25th

Yes the mean now dipping below 0c for Christmas.

A downward trend now starting to persist.

Edited December 17, 2009 by phil n.warks.

[swilliam]

I have some extremely bad news for you people.

http://91.121.94.83/...037735849056602

We may have to put up with 850`s only around -5C hPa on Dec 25th

Yes and look at the dip in 500HPa temps after the cold front comes through in a couple of days time. Now that is really cold true arctic air.

That in itself is not bad news. Dew points, surface temps, wind direction, continental surface temps etc..etc.. all play an important part also. Not to mention the fact that +T72 is changing beyond belief.

Take each model as it comes people and look for agreement between them to spot something that keeps appearing and has a high chance of happening.

Sorry Eugene, I may be misinterpreting what you say. Did you mean only -5º as good, getting colder or bad, getting warmer...

I think he was being sarcastic!!!

[sandstorm2]

The GFS is trying its hardest to bring in milder air from the atlantic but with a strong high to the northeast ridging into Scandi I would put my money on the cold air winning and giving us some really cold temps in the new year.

Haven't had a chance to look at the other models yet but hoping there is some agreement.

SS2

[Yeti]

Hi again Phil

Well it's really a complex set up but so much relies on that low to the sw, i really hope it enters the festive spirit!

Down here is been cold all week and we're now into our second consecutive day below freezing, just shows you with 850's only near -5 what can happen with no sea modification and an easterly flow off the continent. The - 10's are expected later tomorrow so will be interesting to see what that produces, currently -1.7c here.

The cold is cruel here Nick - temps refusing to get above -3 today, with -9 maxima predicted on Saturday!

http://www.wetterzentrale.de/pics/Rmgfs574.gif

That could definitely be one of the coldest days I've ever experienced, certainly at home.

Sadly the Euros still want to send the low further W atm and so it's GFS/GEM vs ECM/UKMO. Mind you, I believe the 6z was the first GFS run to send the low at this angle? I don't remember seeing it before because a warm up looked almost guaranteed here by next week with no models showing anything more favourable e.g. 6z.

[casparjack]

Only just had time to look at this, so apologies if it's already been talked about...

...but it looks like a really marginal situation for anywhere south of Manchester/Lincolnshire to me for Monday, I know there will be some decent surface cold air, but the source to the SW looks like it might spoil the party to an extent. Many changes possible between now and then though!

[MP-R]

Looking ahead (which is perhaps a bad idea at this point), what sort of weather conditions would we see with this evolution? Still has ESE/SE winds for Christmas Day but would this still be cold bearing in mind the surface temps of Europe etc. That low in the Atlantic really gets its act together by Boxing Day on this run.

Thursday 24th:

http://www.wetterzentrale.de/pics/Rtavn1681.html

Friday 25th:

http://www.wetterzentrale.de/pics/Rtavn1921.html

Saturday 26th:

http://www.wetterzentrale.de/pics/Rtavn2161.html

[summer blizzard]

Looks like a good FAX chart for central and northern England on monday, and does explain why the postcode forecast is showing heavy snow for me on monday, the important thing is that the front swings east or south east, and not north east.

[Frosty.]

Interesting 6z run but I doubt it has much support, the meto update is not so promising for southern britain with a rain & sleet mix by early days next week followed by a milder trend but the colder air hanging on in the north with sleet and snow.

[PB22]

Hi Karl,

The 06Z ensembles suggest a trend towards a colder Christmas now, with a lot of the runs at or just below -5C in 850hPa terms until the big day itself:

http://www.wzkarten...._London_ens.png

http://www.wzkarten....chester_ens.png

http://www.wzkarten...._Dublin_ens.png

http://www.wzkarten....berdeen_ens.png

The operational run was one of the milder options post Christmas in the south, colder in the north. :lol:

Edited December 17, 2009 by Paul B

[Frosty.]

Hi Karl,

The 06Z ensembles suggest a trend towards a colder Christmas now, with a lot of the runs at or just below -5C in 850hPa terms until the big day itself:

http://www.wzkarten...._London_ens.png

http://www.wzkarten....chester_ens.png

http://www.wzkarten...._Dublin_ens.png

http://www.wzkarten....berdeen_ens.png

The operational run was one of the milder options post Christmas in the south, colder in the north. :lol:

Thanks paul, hopefully the meto update tomorrow will change then as it currently looks fairly unpromising for the south.

[swilliam]

Hi Karl,

The 06Z ensembles suggest a trend towards a colder Christmas now, with a lot of the runs at or just below -5C in 850hPa terms until the big day itself:

http://www.wzkarten...._London_ens.png

http://www.wzkarten....chester_ens.png

http://www.wzkarten...._Dublin_ens.png

http://www.wzkarten....berdeen_ens.png

The operational run was one of the milder options post Christmas in the south, colder in the north.

That is certainly true for the 850s but is not so pronounced for the actual temps on the ground due to cold surface layer. This is shown on the progged temps where 5C is not reached until almost the New Year

[casparjack]

Thanks paul, hopefully the meto update tomorrow will change then as it currently looks fairly unpromising for the south.

I have no doubt that it will change, whether towards cold or mild, however, no one really knows.

The FAX chart for Monday that I posted earlier is a perfect example of how complex the situation is and frankly that's what makes it so interesting - isn't it!! ?

[Frosty.]

I have no doubt that it will change, whether towards cold or mild, however, no one really knows.

The FAX chart for Monday that I posted earlier is a perfect example of how complex the situation is and frankly that's what makes it so interesting - isn't it!! ?

Yes it's a very complex fax chart for monday with areas of precipitation all over the place and cold air across most of the uk, maybe some heavy snow in some areas on monday is likely, I would think that northern scotland is the most favoured area for disruptive snow from the weekend onwards though..just my opinion.

[Eugene]

I notice some ensemble members building HP over christmas, while others keep it rather cold and slack :lol:

http://91.121.94.83/modeles/gens/run/gens-5-1-228.png?6

http://91.121.94.83/modeles/gens/run/gens-0-1-264.png?6

http://www.meteociel.fr/modeles/gefs_cartes.php?code=7&ech=240&mode=0

　

Surprised i haven't read more about this must be bored of the cold weather by now :lol: