Model Output Discussion

[grab my graupel]

Please continue :lol:

[kold weather]

Still very little agreement in the ensembles even out to 72hrs on the evolution of the models. Some runs have the snow threat for only the far north of Scotland after a brief spell of snow on the front edge of the front, most have a snow event for the Midlands of some kind, a couple have a big event for even the south.

[Nick F]

Yes KW, the detail, as always with where snow potential will be, will not be resolved beyond close range over the coming days, as the track of sfc lows varies widely beyond this weekend.

However, there is quite good broadscale agreement on the upper flow pattern looking at the 12z mean 500mb HGT comparisons, with a long-wave upper trough extending SW across the Atlantic, as the block over Sern Greenland edges west over the Davis Strait across NE Canada. This SW-NE aligned upper trough over the NE Atlantic will be the 'driving force' for the weather going into next week, with shortwaves ejecting NE on the forwardside of this trough developing lows to the SW which will move NE across the UK, though whos tracks will not be determined yet:

... these shortwave lows moving NE bumping into the cold air in place over the UK always trying to introduce less cold air from the south on their approach then pulling cold air back south across the UK as they exit NE. But only really looks like the Midlands southwards flipping between cold and less cold while the north remains cold. Wales, Midlands and N England look most favoured for snowfall as these lows move NE.

[J10]

I do think though the GFS is really overdoing those lows again as it is prone to do. but it could be very interesting next week in the cold side of the fronts.

[TEITS]

NAE suggesting another snow event for S England/Wales during Saturday.

http://expert.weatheronline.co.uk/daten/proficharts/en/nae/2010/02/18/basis18/ukuk/prty/10022012_1818.gif

http://expert.weatheronline.co.uk/daten/proficharts/en/nae/2010/02/18/basis18/ukuk/prty/10022018_1818.gif

Beyond this and taking all the model output I do feel a big snow event is going to occur. The trouble is this could hit either Scotland or the S coast of England. I suppose the favourite would be something inbetween so thats N Wales/Midlands/S parts of N England.

[yamkin]

NAE suggesting another snow event for S England/Wales during Saturday.

http://expert.weatheronline.co.uk/daten/proficharts/en/nae/2010/02/18/basis18/ukuk/prty/10022012_1818.gif

http://expert.weatheronline.co.uk/daten/proficharts/en/nae/2010/02/18/basis18/ukuk/prty/10022018_1818.gif

Beyond this and taking all the model output I do feel a big snow event is going to occur. The trouble is this could hit either Scotland or the S coast of England. I suppose the favourite would be something inbetween so thats N Wales/Midlands/S parts of N England.

BBC & Sky News are yet to pick up on the NAE ppn chart for the South on Saturday. Why is that?

[Rorky_Leicester]

BBC & Sky News are yet to pick up on the NAE ppn chart for the South on Saturday. Why is that?

On the latest BBC forecasts theres a hint of it from South Wales up to the Bristol area with snow graphics and alot of Rain coming from behind it so they are definitely aware of the threat.

[yamkin]

On the latest BBC forecasts theres a hint of it from South Wales up to the Bristol area with snow graphics and alot of Rain coming from behind it so they are definitely aware of the threat.

I suppose here in the SE, they will update their forecast after looking at the updated NAE.

[TEITS]

BBC & Sky News are yet to pick up on the NAE ppn chart for the South on Saturday. Why is that?

Probably due to the 18Z NAE coming out around 22.00. Also I feel the Met O will want to see the NAE consistently trend with this before issuing warnings. If tomorrows 0Z/06 NAE show the same then expect warnings to be introduced.

Speaking of warnings but if the fax chart remains the same tomorrow you can expect the Met O to continue with the warnings for Monday!

http://www.wetterzentrale.de/pics/brack3.gif

[yamkin]

Probably due to the 18Z NAE coming out around 22.00. Also I feel the Met O will want to see the NAE consistently trend with this before issuing warnings. If tomorrows 0Z/06 NAE show the same then expect warnings to be introduced.

Speaking of warnings but if the fax chart remains the same tomorrow you can expect the Met O to continue with the warnings for Monday!

http://www.wetterzentrale.de/pics/brack3.gif

Very interesting Fax chart. The WMC Moscow 12Z 850hpa is looking good at 96h and is the nearest to the fax chart 528 dam line.

[LomondSnowstorm]

Very interesting Fax chart. The WMC Moscow 12Z 850hpa is looking good at 96h and is the nearest to the fax chart 528 dam line.

The WMC is the definition of cannon fodder - it showed the relocation of the entire PV (-28 uppers and all) to the midlands for about twenty runs out of fifty, and each time it was in a shorter timeframe than before - it had me worried for a bit!

[kold weather]

Beyond this and taking all the model output I do feel a big snow event is going to occur. The trouble is this could hit either Scotland or the S coast of England. I suppose the favourite would be something inbetween so thats N Wales/Midlands/S parts of N England.

Looks that way to me, mind you I've been saying for some time we were entering a very snowy pattern and given what has occured since Tuesday and what the models show I'm happy with that call still...

What you say is true though, there is a good signal for several disturbances to come through England, exactly where will dictate so very much it seems.

Finally, that fx charts is going with the ECM...that means the ECM ensembles must be strongly agreeing with its op run rather then the 12z UKMO, now that is real interest to some!

[TEITS]

Very interesting Fax chart. The WMC Moscow 12Z 850hpa is looking good at 96h and is the nearest to the fax chart 528 dam line.

At +120 the WMC brings in bitter E,lys for Scotland.

Looking at the overall model output and im far from convinced of a return to milder weather. As I said this morning more of the same but with the chance of it turning even colder from the NE especially towards the end of the month. Anyone hoping for an early spring is going to be very disappointed IMO.

From a personal perspective im not that bothered either way. Would you believe im actually getting weary of following the models. Just shows what a fantastic winter we have had!

[summer blizzard]

Wow, wow, wow!!!

GFS18Z is an apsolutely epic snow run upto 170 hours out for most of England, my location alone is forecast to see snow on sunday, monday, wednesday and thursday and not just showers, but actual frontal snow all four times, meaning snow totals over England could be in the region of 30cm.

[Eugene]

Wow, wow, wow!!!

GFS18Z is an apsolutely epic snow run upto 170 hours out for most of England, my location alone is forecast to see snow on sunday, monday, wednesday and thursday and not just showers, but actual frontal snow all four times, meaning snow totals over England could be in the region of 30cm.

I didn't see GFS 18Z but GFS 00Z is wow wow wow too esp for you up in leeds/bradford area right into the early stages of FI with lots of snow potential for midlands northwards :lol:. UKMO 00Z looks great also, what a winter this has been

Not much hope for mild weather fans on the ensembles, the only hope is towards the end of GFS 00Z OP and its a big warm outlier then i`m afraid.

Edited February 19, 2010 by Eugene

[Eugene]

Very exciting output lots of rain to snow events in the next week for the midlands :lol:

Looks like rain on sunday afternoon turning to heavy snow overnight into monday

[Eugene]

http://www.wetterzentrale.de/pics/Recm1681.gif :lol:

I think some have underestimated our snow chances for next week totally doesn't look like widespread rain to me well not for long anyway

[SteveB]

Anyone looking for Spring, the latter stages of FI show +10 850's for the first time

http://www.netweather.tv/index.cgi?action=nwdc;sess=

[Nick F]

Well, it looks like cold and wintry is the form horse this winter, in contrast to recent winters where mild has been the form horse.

ECM is the best of the bunch for more widespread snow potential for the UK going into the medium range, with lows developing to the SW on a more southerly track as the move NE across they UK and a NE flow developing across northern areas.

In the shorter range, a trough feature looks like moving east across southern areas tomorrow PM, with outbreaks of showery rain turning to snow on the northern extent - probably S Wales and south central England. Sunday looks to see another trough swing E/NE across Ireland which may bring outbreaks of rain turning to snow across Wales, northern and parts of central England. Monday, we see that filling low over Bay of Biscay move NE across Sern UK, fairly good agreement between GFS/UKMO/ECM on this low tracking NE over SE England ... looks to bring rain initially but turning to snow from the NW across England and Wales as the low clears NE and colder air digs SE.

[kev238]

Well- next week does look potentially epic for some locations. The thing is with these low pressures- their track will vary which will play havoc with forecasts. The area of snow they produce will always be on the North and North Western flank of these lows-- but there could be a lot. Equally- some places 40 -50 miles south of heavy snow may get nothing.

It is quite often like this -- to get the heavy snow you need an element of risk which is in this case the warm air involved with fuelling these types of low pressures.

Favoured areas appear to be to the Midlands/ Northern England and Wales at the moment but with snow risks moving North and South at times.

[Paul T]

00Z again shows the potential. So, what have we got?

In summary

Two events coming into a slight more reliable time frame now, although every run is different with the positioning, the trend for 2 events is there.

From Monday morning through to the evening we have a low shooting through from the south west/channel up to the north sea. The question here is - will the milder section be over France? if so, as is currently being forecast, then a huge swath of Britain will see snow.

Here the warmer section is kept at bay: T84 enabling some very cold temps for mid day monday: T84 TEMPS with some big preciption totals.

The second event is the channel low developing for Tuesay night.

00Z show perfect positioning @ T117. This will have more precipitation and cause a massive event for the south if it is cold enough - will it be? Well, gfs is saying yes, which leads to this chart: T120

Watch these two events, around 78T and 112T of the 06z:

Along with the obvious quesion of will they be further north or further south? I would look out for the cold uppers staying a s low as possible in the build up to the event, the intensity of the precipiation, the timing of the event (@ 3pm or 3am?) and watch out for the 528 dam, it needs to be kissing the south coast throughout the lows i.e: 528dams

The very fact ive bothered to post means thats something is on the cards, as im usually pretty pessimistic!

I have been watching next week for some time, as im off to Longleat centre parcs (210m asl which is a bonus!) and i can say that the forecast for next week has varied so much; On Tuesday i told my party that it was going to be wintery showers, with overnight frosts, only 48hrs on we are looking at a much snowier or much wetter week; alot can still change 4-5 days off.

[TEITS]

Excellent summary Paul T.

Looking at just tomorrow using the NAE, which I hasten to add nailed yesterdays snow and we can see some more snow is possible during tomorrow afternoon across Wales and and parts of the Midlands/E Anglia.

http://expert.weatheronline.co.uk/daten/proficharts/en/nae/2010/02/19/basis00/ukuk/prty/10022018_1900.gif

Looking at the precip amounts and the timing of this means nothing too significant. I would say the chance of a few cm of snow.

Chilly night to come tonight with mins dropping widely to -3C. Some locations i.e Scotland could see mins below -10C.

http://expert.weatheronline.co.uk/daten/proficharts/en/nae/2010/02/19/basis00/ukuk/tmp2/10022006_1900.gif

Edited February 19, 2010 by THE EYE IN THE SKY

[cooling climate]

From what I can see there is very little continuity between the models or the model runs,

therefor it is very difficult to say exactly what is in store over the next three to four days

with any accuracy.

One point I would make is that I think the models are again overdoing the northward

movement of the low pressure systems.

[Eugene]

Yes good post paul t but you don't need the 528 dam line kissing the south coast for heavy snowfall in the midlands like yesterdays snowfall showed, just to the north of the midlands or through the midlands is fine and can deliver snowfall for the midlands.

I think monday is less marginal than yesterday and that really did deliver to quite alot of places in england and wales

[TEITS]

From what I can see there is very little continuity between the models or the model runs,

therefor it is very difficult to say exactly what is in store over the next three to four days

with any accuracy.

Yes which is why I personally can't be bothered to look into much of the details just yet. I feel someone is going to take a battering from snow but I have no idea where!

The pattern I am noticing is the return to mild is always outside the reliable timeframe. So far this winter the weather patterns have been the complete opposite to what we have become used to.