Model Output Discussion:

[Methuselah]

Please carry on, folks...Previous:

[NorthNorfolkWeather]

34 minutes without anyone commenting, amazing.

Where do people think FI sits now? it seems certain that we will have a cold rather than a cool spell, although from the variation in the runs, we still cannot be certain where the snow, if any, will fall. The High having less influence in the last run enhances snow potential over a greater area than the South East/East Anglia, but no doubt variations will occur right up to the cold spell hitting us.

So FI for details? Probably T60, FI for the Cold spell T120-T144

[smich]

The lull before the storm! lol

We'll probably get a slight downgrade from the heady heights of yesterday's 12Z, but as we are nearer the event itself I wouldn't expect too much in the way extreme flip flops.

As I mentioned in the Mood thread, I'm looking more keenly at the fax charts at this sort of range.

smich

[loafer]

Quality, not quantity!

Mind you, I notice that the thread had 800 views over the first 40 minutes. I guess everyone is waiting for the 12Z...

Onto the models, the key seems, to my uninformed eyes, to be the extent to which the high over southern Sweden builds to push the warmer ridge over the Netherlands south quicker than the models are showing. First few slides from the 12Z look to be the reverse...

[nick sussex]

GFS upto 72hrs and very similar so far to the 06hrs run, although I'm slightly happier with the shortwave track on this run. Low forming in southern France and High near Iceland all looking very good, the high a touch further north.

[TEITS]

Magical +72 timeframe and its looking good.

Angle of the HP and SW look better than the 06Z.

[mountain shadow]

Pressure seems higher to the north again, could be a better easterly..

http://cirrus.netweather.tv/gfsimages/gfs.20100205/12/72/h500slp.png

[Bobby]

The HP is further North which is allowing a more potent NEly feed in which means more snow for the east.

[mountain shadow]

It seems to me as well, that the closer we get to the 'snowy' period the more precipitation is showing up on the GFS charts.

For reference and to show the vast improvement over the GFS 0z.

The 0z run did not shoe the 528 DAM line over Ulster until t+240, this has it at T+87

[loafer]

You are right that it seems to be similar, if not a slight upgrade.

Some cracking NEly's on this one...

http://cirrus.netweather.tv/gfsimages/gfs.20100205/12/87/h850t850eu.png

...and it's not in deep FI either!

[nick sussex]

Very good so far, trough disruption to the west sending shortwave se towards France will support the high, excellent run so far.

[mountain shadow]

Could be floodgates about to open on this run with -10 850s across the Uk and Ireland..

http://cirrus.netweather.tv/gfsimages/gfs.20100205/12/96/h850t850eu.png

[mountain shadow]

East coast hammered..................again!!

http://cirrus.netweather.tv/gfsimages/gfs.20100205/12/120/ukprec.png

[johnholmes]

For those of you with NW Extra comparing the GFS Wetter precip charts with, in my case, the skew-t for Doncaster and the skew-t clearly shows how the pale green fairly stable airmass is being converted into a showery style air mass over the period T+48 onwards.

For those in eastern England and with NW Extra take a look at the nearest site to you to see this being shown.

Over the past 2-3 days the 12z has tended to show rather more instability in its outputs and lower afternoon temperatures than the other runs in the period Monday-Thursday. It seems to be repeating this today.

How realistic this is is impossible to judge just from the GFS/Extra output. You have to read CAREFULLY the 3-5 day and 6-15 day outlook from UK Met. NAE obviously is not out far enough yet to make a direct comparison. Perhaps we may get an insight into their thinking if Ian F posts in sometime this afternoon or evening. They have, all along, tended to be more for showery than stability when compared to the GFS output at times and also that from ECMWF-again we have no direct precip outputs from there.

I would say a cold spell is 90% certain, how cold and how long is still open to some doubt or changes-GFS does appear to be extending it although its max temp ideas do appear to be getting shunted somewhat further on, both the start and end.

How unstable, let alone will there be any unsuccessful attempts to break the cold down from the SW is way out in la la land at the moment.

[mountain shadow]

Stunning run, lets get a good retrogression to Greenland now so the West can have a bit of the action...

http://cirrus.netweather.tv/gfsimages/gfs.20100205/12/132/h500slp.png

METO looks on board...

[Iceberg]

I have no fear over the GH retrogression, interesting METO 12Z, Showers rather limited, even with a better easterly flow, however for those in the SW the T72 precip chart from the METO has the bad just touching the cornish coast, if it moves a little further west things could be interesting down there.

[LomondSnowstorm]

Lovely 12Z. Everything a bit further west so a proper easterly even for eastern Scotland. http://cirrus.netweather.tv/gfsimages/gfs.20100205/12/120/h500slp.png

Very nice UKMO also, again with things a little further northwest http://www.meteociel.fr/ukmo/run/UW120-21.GIF?05-17

And note the uppers at just +72 http://www.meteociel.fr/ukmo/run/UW72-7.GIF?05-17

http://www.meteociel.fr/ukmo/run/UW72-21.GIF?05-17

Snow showers possible across most of the east of the UK by Monday.

As John says, it is a bit too early to call instabillity in this spell and we'll just have to wait for this to come into NMM territory/radar territory before we can make more accurate precipitation predictions but it doesn't look like it will be a completely dry spell to me.

LS

I have no fear over the GH retrogression, interesting METO 12Z, Showers rather limited, even with a better easterly flow, however for those in the SW the T72 precip chart from the METO has the bad just touching the cornish coast, if it moves a little further west things could be interesting down there.

I've never found the UKMO precipitation charts, or the GFS or ECM for that matter, to be all that accurate with easterly convective showers.

[Iceberg]

Yes too early for precip forecasts but interesting that GFS wants to introduce a band of precip coming down the country for most on Wed as the colder air digs in a trough is destabilised.

[Lewis]

This run is truely stunning. I would bank this one

I love how the GFS just upgrades and upgrades, it's a northerly, north easterly, easterly, northerly/north easterly, in 1 week.

Just need ECM to come on board with regards the high pressure, if it does... game on!!!

[johnholmes]

i'm not saying they are accurate-just trying to show how we can all get a better 3 dimensional picture by comparing basic model output, be it Wetter, NW, or Extra, if you then compare that with the nearest Extra skew-t to your own area?

[TEITS]

I love how the GFS just upgrades and upgrades, it's a northerly, north easterly, easterly, northerly/north easterly, in 1 week.

Which should that occur will benefit many locations.

Excellent medium range trend yet again at +192.

I noted on the UKMO that at only 48hrs away the colder E,lys are only just off the E coast.

[kold weather]

The 12z GFS is a very good run, of course where the upper high ends up is going to make a huge difference with regards to what actually happens!

Still this run is ver6y good, nice little frontal/trough feature that comes down with the upper cold pool at 120hrs but of course small shift of the high is going to make a huge difference with this one!

One thing looks certain now though, its going to get very cold once more!

[mountain shadow]

Meto 144..

[kold weather]

Thats a peach of a UKMO at 144hrs, nice easterly flow coming in there!

Of course it really is going to be very tight as to whether we get the showery flow or not, of course the SE is going to be best placed simply because its further away from any high but we shall see!

Equally, the 12z GFS has just about 9one of the most odd FI I've seen but because of that we sustain a very slack and probably bitterly cold flow throughout.

[Lewis]

This is a lovely chart, and Kold Weather, the UKMO is a peacher, also regarding the GFS in FI, it stays super cold throughout!

I like this chart: