Model Output Discussion

[shuggee]

A fresh thread for today's 12Z outputs.

[kold weather]

Hopefully we won't see too much any more further southward adjustments of the high between 96-144hrs, however saying that it still looks very cold and actually wouldn't be a bad thing to get a decent few sunny days with good overnight frosts...

Best shot of snow away from the SE probably will be a 24hrs period after this where the upper high starts to re-develop further north and this opens up a cold easterly flow again, though that will run out of steam eventually.

[Yeti]

The extra solar input won't make the showers off the sea any heavier but it will allow us to 'grow our own' over land during the day to a limited extent. Best example is during the summer months where the showers fall inland whilst coastal areas can stay sunny all day.

Being early Feb the sun won't have a lot of strengh, but i suspect it will be just enough to cause some activity inland (as long as there isn't a sheet a grey low cloud).

Eh? If the sun enhances land convection then it must also enhance sea convection... both involve exactly the same mechanism, except that the sea has a lot more water so it produces a lot more activity.

Similarly, if the sun is strong enough, as some people are suggesting, to make a difference to daytime temps by heating the ground more, then it cannot NOT have effects in other areas... that just doesn't make sense. It's certainly true, though, that cold uppers are vital to decent convection which is why I suspect there won't be that much around before midweek. In fact, the upper profile doesn't look brilliant, all things taken into account - the core of the cold pool is now trending further S into Germany with more S and E areas still seeing some really decent 850 temps - still subject to upgrades/downgrades.

[Cheese Rice]

Eh? If the sun enhances land convection then it must also enhance sea convection... both involve exactly the same mechanism, except that the sea has a lot more water so it produces a lot more activity.

I'm pretty sure there was a North Westerly at the beginning of march last year and again there was talk of the sun been stronger so an increase in shower potential, but it didn't happen. I don't think the sun is strong enough yet to produce anything significant in terms of convective activity, however with a slightly stronger sun there obviously must be some impact on the shower activity, but nothing substantial.

[Eugene]

http://www.wetterzentrale.de/pics/Rtavn963.png - Nice pool of sub 510 dam air just to our east, this looks another good run

[Jason M]

Eh? If the sun enhances land convection then it must also enhance sea convection... both involve exactly the same mechanism, except that the sea has a lot more water so it produces a lot more activity.

Similarly, if the sun is strong enough, as some people are suggesting, to make a difference to daytime temps by heating the ground more, then it cannot NOT have effects in other areas... that just doesn't make sense. It's certainly true, though, that cold uppers are vital to decent convection which is why I suspect there won't be that much around before midweek. In fact, the upper profile doesn't look brilliant, all things taken into account - the core of the cold pool is now trending further S into Germany with more S and E areas still seeing some really decent 850 temps - still subject to upgrades/downgrades.

I take your point, but don't really agree.

At this time of year the relative warmth of the sea interacts with the colder air and you get convection as a result (ie coastal showers), in the summer months showers form more readily over land as the land heats quicker than the surrounding seas. The sun will have little impact on showers over the north sea at the moment as whilst its strong enough (just about) to heat the land for a few hours each day, it will have virtually no impact on sea temperatures. The main shower driver will still be the sea though as we are only in early Feb.

I agree with your comment about showers before mid week though! To get beefy showers cold uppers help greatly.

Jason

[Eugene]

http://www.wetterzentrale.de/pics/Rtavn1142.png - Fab blo*dy tastic

[LomondSnowstorm]

http://www.wetterzen...cs/Rtavn963.png - Nice pool of sub 510 dam air just to our east, this looks another good run

Slightly better ridging as well by the looks of it:

[J10]

The GFS very similar to previous GFS runs (out to T+120), slightly better for Ireland as the cold air gets further west quicker.

[Cheese Rice]

Am hoping the GFS will bring a stronger easterly flow as the snowfall potential doesn't look amazing. Interestingly the GFS has beens showing a trough (?) running down the whole of northern england and parts of the midlands and south on Wednesday, perhaps some decent snowfall, atm the precipitation doesn't look heavy but perhaps an upgrade?

[Eugene]

lol trust me if GFS 12Z was to verify it would produce persistent heavy snowfall for eastern areas into the midlands and south thursday night into friday, can't believe you are trusting snowfall charts that far out

http://www.wetterzen...s/Rtavn1381.png

Edited February 6, 2010 by Eugene

[J10]

The GFS very similar to previous GFS runs (out to T+120), slightly better for Ireland as the cold air gets further west quicker.

This for T+123 shows the contrast between the 06Hz and the 12Hz, and shows a better profile of the cold for the UK at T+123.

There is also more precipitation modelled on the charts for the 12Hz than the 06Hz at the T+123 time frame.

[LomondSnowstorm]

Am hoping the GFS will bring a stronger easterly flow as the snowfall potential doesn't look amazing. Interestingly the GFS has beens showing a trough (?) running down the whole of northern england and parts of the midlands and south on Wednesday, perhaps some decent snowfall, atm the precipitation doesn't look heavy but perhaps an upgrade?

Don't read too much into precipitation intensity - trust me, if the GFS had verified exactly during the last cold spell there would have been only 2cm accumulations at a time at most!

[nick sussex]

The UKMO although cold throws a shortwave between the high and the ridge to the east and stops the easterly until it finally appears at 144hrs, it does look a little strange though so we'll have to wait for the ECM to see where that goes, its not a bad run but looking at the 144hrs it develops the shortwave which drops south. I have my doubts about this run.

Edited February 6, 2010 by nick sussex

[Iceberg]

Certainly wouldn't trust intensity but GFS tracks a front in with the cold pool(thurs) through the south east (but also alot of other parts), it then brings another one in further north.

This really needs to be watched as it will be very easy for this to develop into a meso low IMO, with an active warm front(relatively speaking) which could produce some good accumulations and tighten the easterly.

very much worth looking at the kinks in the isobars.

The UKMO although cold throws a shortwave between the high and the ridge to the east and stops the easterly until it finally appears at 144hrs, it does look a little strange though so we'll have to wait for the ECM to see where that goes, its not a bad run but looking at the 144hrs it develops the shortwave which drops south. I have my doubts about this run.

Just seen the METO Nick, it seems to show the meso low I as talking about above, but it has created it in a strange place. I think the chances of a low moving from say the wash to the IOW, producing some good snow is high though.

[Eugene]

UKMO 12Z T+144 hrs doesn't look too shabby either.

http://www.meteociel...44-21.GIF?06-17

GFS 12Z really is an excellent run for the week ahead, just remember what the runs on wednesday morning were showing for the week ahead and then i dare you to complain

Could see snowfall into next weekend on GFS 12Z yeah i'm sure someone will mention oh the uppers are too mild but you don't rely on uppers for snowfall in an easterly flow after an intial cold blast

Edited February 6, 2010 by Eugene

[January Snowstorm]

UKMO 12Z T+144 hrs doesn't look too shabby either.

Could see snowfall into next weekend on GFS 12Z yeah i'm sure someone will mention oh the uppers are too mild but you don't rely on uppers for snowfall in an easterly flow after an intial cold blast

The uppers are -8 to -10, who would say that?

In the relable dry and frosty with a definite trend to something a bit more productive late in the week

[nick sussex]

Certainly wouldn't trust intensity but GFS tracks a front in with the cold pool(thurs) through the south east (but also alot of other parts), it then brings another one in further north.

This really needs to be watched as it will be very easy for this to develop into a meso low IMO, with an active warm front(relatively speaking) which could produce some good accumulations and tighten the easterly.

very much worth looking at the kinks in the isobars.

Just seen the METO Nick, it seems to show the meso low I as talking about above, but it has created it in a strange place. I think the chances of a low moving from say the wash to the IOW, producing some good snow is high though.

I'm really not sure about the UKMO, it looks more like something you'd expect to see from the GFS pub run! It drops the shortwave south developing it at the same time, it could produce quite a bit of snow but it's rare for me to say this but I think its gone AWOL this evening.

If the ECM backs this I'll go to mass at Lourdes tomorrow! That sort of suggests that I don't think it will!

[Guest FireStorm]

Where does one find the NMM models? Are they freely available?

[len]

Eh? If the sun enhances land convection then it must also enhance sea convection... both involve exactly the same mechanism, except that the sea has a lot more water so it produces a lot more activity.

Similarly, if the sun is strong enough, as some people are suggesting, to make a difference to daytime temps by heating the ground more, then it cannot NOT have effects in other areas... that just doesn't make sense. It's certainly true, though, that cold uppers are vital to decent convection which is why I suspect there won't be that much around before midweek. In fact, the upper profile doesn't look brilliant, all things taken into account - the core of the cold pool is now trending further S into Germany with more S and E areas still seeing some really decent 850 temps - still subject to upgrades/downgrades.

The sun enhances land convection only because it rapidly raises the temperature of surfaces.

This effect is much, much less over water, and even more reduced over open, moving wind-mixed water

[Eugene]

lol i just love how GFS 12Z FI loses the plot and hasn't a clue what to do with all that northerly blocking, hilarious

[Jason T]

I'm really not sure about the UKMO, it looks more like something you'd expect to see from the GFS pub run! It drops the shortwave south developing it at the same time, it could produce quite a bit of snow but it's rare for me to say this but I think its gone AWOL this evening.

If the ECM backs this I'll go to mass at Lourdes tomorrow! That sort of suggests that I don't think it will!

Nick...Well better keep your fingers crossed. I will be crying IF that ecm pulls off.

[LomondSnowstorm]

Where does one find the NMM models? Are they freely available?

For those down south you can get it on meteociel for free, but they've blurred the the UK so you can't see where your location is (bloody french!) http://www.meteociel...&map=0Otherwise, get Netweather extra - the best radar for the UK, it updates every 5 minutes and you can now zoom into your house!The NAE use (Scottish only joke there) is on weatheronline http://www.weatheron...=0&WMO=

Enjoy!LS

Edited February 6, 2010 by LomondSnowstorm

[Iceberg]

I'm really not sure about the UKMO, it looks more like something you'd expect to see from the GFS pub run! It drops the shortwave south developing it at the same time, it could produce quite a bit of snow but it's rare for me to say this but I think its gone AWOL this evening.

If the ECM backs this I'll go to mass at Lourdes tomorrow! That sort of suggests that I don't think it will!

I don't think the ECM will but only becuase it tends to be late developing these little meso lows. 18Z might do. However the 12Z ensembles might give us a clue.

[johnholmes]

Eh? If the sun enhances land convection then it must also enhance sea convection... both involve exactly the same mechanism, except that the sea has a lot more water so it produces a lot more activity.

I'm afraid your physics is a bit suspect Yeti-it does not have the same effect on water as it does on land.