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Winter Model Discussion 12Z 15/1/13 onwards.

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As with all MODEL DISCUSSION THREADS the clue is in the title and with so much information, conjecture, analysis and forecast that can be discussed with the current models, there is no reason to post anything else in this particular area of the forum.

Enjoy this thread and treat your fellow contributors with respect and courtesy please. :good:

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For me the uncertainty is great in winter ie low pressure coming in and then waining.much better than the sometimes hit and miss easterlies.Today proves the point has sheff was forecast to be dry but we have moderate snow at the moment.24 hours seems to be a long time at the moment weatherwise never mind the weekend.12z awaited eagerly

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This potential setup over the weekend reminds me of when I was a kid in the 1980s.

On several occasions the bbc weather forecast would say snow spreading in from the west, turning to rain later on. But it never arrived and ended up staying cold for another week with Easterly winds.

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Away from the far south west and Ireland Friday is looking like a good bet for another snow event

gfs-2-66.png?6

gfs-2-72.png?6

gfs-2-78.png?6

Maybe some snow for a time later in the day for parts of Ireland

gfs-2-84.png?6

Into Saturday and that band of snow is still falling in the east

gfs-2-102.png?6

Snow totals by 15:00 Saturday

15011306105270010170-1.png

15:00 Sunday

15011306129270010170-1.png

And 15:00 Monday

15011306153270010170-1.png

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Yet more weather charts that made me think "Wow" this morning! The Atlantic attack again showing signs of edging south (with GFS being the main exception), and as many undercutting lows have gone further south than predicted recently, I can understand ideas that the cold may never leave for the foreseeable future.

However, there is another increasing trend - forecast 850 temps edging up in central-western areas as T0 approaches. The real cold sticking in north sea. This may make Friday's attack marginal for snow for many areas? And weakens the foundation of cold for when / if the Atlantic pushes through?

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Some posts are not linking to the models and are really for general discussion threads like this one

Let`s keep this thread informative and factual please folks.

Thanks.

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06z esembles starting to compare to the dec 12 ensembles at one time, in that it is likely to below avergage but wrong side of borderline down the line, still good for snow this weekend however with 850's not quite the be all and end all.

MT8_Manchester_ens.png

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Away from the far south west and Ireland Friday is looking like a good bet for another snow event

gfs-2-66.png?6

gfs-2-72.png?6

gfs-2-78.png?6

Maybe some snow for a time later in the day for parts of Ireland

gfs-2-84.png?6

Into Saturday and that band of snow is still falling in the east

gfs-2-102.png?6

Snow totals by 15:00 Saturday

15011306105270010170-1.png

15:00 Sunday

15011306129270010170-1.png

And 15:00 Monday

15011306153270010170-1.png

Quality charts there Gavin - It's such a fine line at the moment, some special I feel is brewing up come Friday & into the weekend with the Atlantic throwing these lows across the west country before easing over to the East. These types of setups are very good for the West and even the East as the preciptiation generally intensifies once it crosses the midlands / pennines to dump a load over them too. From a IMBY perspective this couldnt be far from great for us in the North West, with always the potential of stalling as the low's meet the block out in the East.

I think one thing for sure is, someone, somewhere is going to get an almighty dumping. I just hope it's in my back garden tease.gif

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h850t850eu.png

h850t850eu.png

h850t850eu.png

h850t850eu.png

h850t850eu.png

h850t850eu.png

Continuing my look at one point in time. I have to say that, although the GFS was moving the low southwards yesterday, it seems to have, at this stage, firmed up on its projection of where it passes through the UK. Still think the cold uppers to the North east look more capable of pushing down though compared to earlier runs

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the gefs are rock solid on a snow event across the country on friday. checking the last four runs yields decent precip with temps barely breakign zero across much of the uk

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The trend for more Atlantic energy going south continues with the 00z runs and as the trough disrupts near the UK many areas would be looking at some snowfall towards the weekend.

http://cdn.nwstatic..../h850t850eu.png

http://cdn.nwstatic....ecmt850.096.png

http://cdn.nwstatic....5/00/met.96.png

Further on the UK and ECM runs go for low pressure going into France which would renew the cold spell from the east whereas the GFS takes things further north introducing less cold conditions for many further south.

I wouldn`t even try to put detail on the outlook but the breakdown to any mild looks long odds now -maybe a less cold interval for those further south west but even that`s not a given.

The 2mtr ens graph for London continues with a cold picture.

post-2026-0-94945800-1358250682_thumb.gi

suggesting the GFS Op on the warmer side of the ens.

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It still looks good for widespread snow this weekend, maybe as early as friday as SSEly winds strengthen, the southwest and wales could have heavy snow on friday, probably rain for ireland and up into western scotland but the cold air not budging further east, feeling very raw as the winds strengthen across all parts of the uk by saturday, the snow in the sw of the uk probably turning back to rain but most of the uk is at risk of a spell of heavy snow, the snow threat probably becoming confined to NE Britain by sun/mon, then next week remains cold or rather cold with further snow in the n and e and widespread frosts continuing, probably becoming a bit less cold in the s and w but still cold enough for wet snow on hills and remaining cold at the surface, no sign of any mild weather reaching the BI in the next 7-10 days or probably much longer, infact, the colder air to the northeast will probably feed down across the uk again but on current evidence, the n and e, especially the northeast will probably end up being the most wintry part of the uk being furthest away from the atlantic influences, the sw and w probably less cold at times (as now) the temps in western scotland an w.isles together with western ireland will be nearer average in the next few days and miss out on the freeze but thats how I think it's looking for now. I don't think the gfs 06z will verify, i'm thinking more of a blend from the ecm and ukmo ops, the ecm 00z looked amazing for northern britain with lots of snow and always cold enough to avoid anything other than brief slight thaws but time will reveal all.smile.pngcold.gif

Friday is the critical day, the atlantic and cold block will lock horns and it will be a titanic struggle I think, and the cold will mostly win, especially the further north and east you are.

post-4783-0-42400100-1358254651_thumb.pn

post-4783-0-40368100-1358254673_thumb.pn

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Quality charts there Gavin - It's such a fine line at the moment, some special I feel is brewing up come Friday & into the weekend with the Atlantic throwing these lows across the west country before easing over to the East. These types of setups are very good for the West and even the East as the preciptiation generally intensifies once it crosses the midlands / pennines to dump a load over them too. From a IMBY perspective this couldnt be far from great for us in the North West, with always the potential of stalling as the low's meet the block out in the East.

I think one thing for sure is, someone, somewhere is going to get an almighty dumping. I just hope it's in my back garden tease.gif

I always take these snow depth charts with a bigger pinch of salt than the models themselves, but the potential for disruptive snow is certainly there on the models this morning. I've been musing over past charts from 78/79, this for me is a similar sort of set up, albeit without much ridging into Greenland at this moment in time. Two things that I keep musing over are the NAO, which refuses to play ball at this moment in time and the other is just how far North and East will any precipitation be. On the first point and concern is will we see heights build into Greenland thus promoting an - NAO, looking at the model out put we see the jet splitting and IMO this will gig further and further South, which will then allow height rises in that area. The second point regarding how far North and East we see any precipitation is slightly complicated ( understatement ), when I viewed the models first thing this morning I saw this digging further and further South, now I'm not so sure. I can see this getting as far North as the Borders and not really reaching Eastern parts of England at all before sinking back Southwards. This would mean a snow to rain event for those in the Midlands Southwards, though possibly not the North Midlands.

ZoomButt.gif

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It still looks good for widespread snow this weekend, maybe as early as friday as SSEly winds strengthen, the southwest and wales could have heavy snow on friday, probably rain for ireland and up into western scotland but the cold air not budging further east, feeling very raw as the winds strengthen across all parts of the uk by saturday, the snow in the sw of the uk probably turning back to rain but most of the uk is at risk of a spell of heavy snow, the snow threat probably becoming confined to NE Britain by sun/mon, then next week remains cold or rather cold with further snow in the n and e and widespread frosts continuing, probably becoming a bit less cold in the s and w but still cold enough for wet snow on hills and remaining cold at the surface, no sign of any mild weather reaching the BI in the next 7-10 days or probably much longer, infact, the colder air to the northeast will probably feed down across the uk again but on current evidence, the n and e, especially the northeast will probably end up being the most wintry part of the uk being furthest away from the atlantic influences, the sw and w probably less cold at times (as now) the temps in western scotland an w.isles together with western ireland will be nearer average in the next few days and miss out on the freeze but thats how I think it's looking for now. I don't think the gfs 06z will verify, i'm thinking more of a blend from the ecm and ukmo ops, the ecm 00z looked amazing for northern britain with lots of snow and always cold enough to avoid anything other than brief slight thaws but time will reveal all.smile.pngcold.gif

Friday is the critical day, the atlantic and cold block will lock horns and it will be a titanic struggle I think, and the cold will mostly win, especially the further north and east you are.

Is it just me or are these two charts showing the cold uppers moving WEST!? during the struggle?

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one thing to remember from precipitation charts is that they measure the amount of precipitation delivered, not the level of snowfall.

For example, where i am i would estimate that the measured amount of precipitation for yesterday would probably have been around 12mm or 12cm of snow. But although i saw that amount fall, I didn't see it settle!

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Is it just me or are these two charts showing the cold uppers moving WEST!? during the struggle?

It's really tricky, friday is the pivotal day, with a better undercut it will stay snowy for much longer but we still won't know for sure how this will play out, tomorrow will probably give us the answer regarding timings and undercut potential. I will say that I believe the gfs 06z is too progressive and is powering up the atlantic lows too much, as it tends to do, i'm still hopeful of a better jet tilt of nw/se with a good dig of very cold SEly winds ahead of the fronts as they make inroads.

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It's really tricky, friday is the pivotal day, with a better undercut it will stay snowy for much longer but we still won't know for sure how this will play out, tomorrow will probably give us the answer regarding timings and undercut potential. I will say that I believe the gfs 06z is too progressive and is powering up the atlantic lows too much, as it tends to do, i'm still hopeful of a better jet tilt of nw/se with a good dig of very cold SEly winds ahead of the fronts as they make inroads.

I don't generally say bin a run but the GFS 06z in my eyes is just to progressive in the way it handles Sat/Sun low, the ECM run looks nearer the mark but even that could be too far North or South. Fascinating model watching Frosty, regardless of who sees what, where, or when.

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I don't generally say bin a run but the GFS 06z in my eyes is just to progressive in the way it handles Sat/Sun low, the ECM run looks nearer the mark but even that could be too far North or South. Fascinating model watching Frosty, regardless of who sees what, where, or when.

Agreed, Binning is silly. However the 6z always seems progressive.

I put it down to two things:

1) Lack of data.

2) Too much data pertaining to the Atlantic. ( It wants to default to its usual synoptic )

15:30 is always a good run in my eyes.

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looks as tho the output is updating by the min?our bbc local weather just showed locally heavy snow sat-sun in sheff.Is the 06z overplaying it?something one will recieve heavy snow for certain but imo the front will fizzle out and drift back sse

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It seems the latest Met Office warning are very much in-line with the UKMO output.

For most of the country the ECM solution would be the most favourable.

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It's really tricky, friday is the pivotal day, with a better undercut it will stay snowy for much longer but we still won't know for sure how this will play out, tomorrow will probably give us the answer regarding timings and undercut potential. I will say that I believe the gfs 06z is too progressive and is powering up the atlantic lows too much, as it tends to do, i'm still hopeful of a better jet tilt of nw/se with a good dig of very cold SEly winds ahead of the fronts as they make inroads.

TBH I think we would all be better served if the jet takes the depressions into France as that would allow pressure to the north to build and we would no doubt get a good cold spell out the resultant easterly. Short term pain but a big long term gain! These undercutting situations can be good for initial snowfall but over the years I recall many more dissapointments than big snowfalls. The 06 run is renowned as being unreliable but setting that aside it seems to me that the ensembles have very strong agreement to bring in the Atlantic.

GFS shows a big snowfall later this week, but i'm far from convinced as GFS often overdoes these events. Also, as others have said you can end up with six inches of snow falling and next to nothing settling.

It may all change later this afternoon but a big 12z this afternoon and we need to see further adjustments south given that timeframes are getting a little tight for major changes. I personally think we will get the nudge south but thats based on gut feeling rather than anything else and as of now even the pro's would be hard pressed to be certain.

Jason

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A rare post from me. A question for the knowledgeable:

The Met Office have a snow warning for Friday in the south west:-

http://www.metoffice.gov.uk/weather/uk/uk_forecast_warnings.html?day=4

but the fax chart for 96 hours does not show this as far as I can tell.

http://www.netweathe...s;type=fax;sess=

Where am I going wrong?

Many thanks,

Mike.

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A rare post from me. A question for the knowledgeable:

The Met Office have a snow warning for Friday in the south west:-

http://www.metoffice...ings.html?day=4

but the fax chart for 96 hours does not show this as far as I can tell.

http://www.netweathe...s;type=fax;sess=

Where am I going wrong?

Many thanks,

Mike.

Not sure what you mean? The fax chart at 96hr as drawn is about as classic a "SW frontal snow" chart as you could get. If it happens like that of course, which is highly unlikely! Why do you think it isn't? SE winds, an occluded front heading into cold air and the trough disrupting and sliding under the block up the Channel!

However that chart has since been replaced by the 84hr chart (look at the forecast time, it is the same), which to my eye is much less favourable - it shows more of a straight-on attack rather than an undercut, although the trough is doing its best to disrupt. Also the cold air makes less inroads west, looking at the 528dam line.

Bear in mind that in this set-up, the 528dam line is not too critical.

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