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Model Output Discussion - The final stretch to Christmas


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Can you get snowfall with uppers above 0 but solid surface cold in place?

My understanding is there will need to be many favourable factors needled to be in place for snow to occur, but uppers usually need to be below 0 with negative dew points unless the rate of precipitation is heavy enough to cause evaporation cooling. I think snow grains might be the best bet but obviously cloud and moisture would be needed for that. I might be wrong of course.

Edited by Grimsby Snow Lover
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Mean while in the real world away from the MOD... A tragic accident has cost 6 lives in Glasgow. yes this is off topic but a timely reminder of just how unimportant the weather really is in our lives.

There is an enormous lack of respect for other people in this thread at the moment. I suggest that if one doesn't have something to add to the model discussion with a salient chart or pertinent inf

Model uncertainty throwing both operational and ensemble data into discontinuity has proved as rife as was expected a week ago - when AAM flipped to negative tendency along with GWO phasing that was i

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Don`t you remember that infamous forum statement? :-) I think the chart I posted is a good benchmark to get to and then go from there.

The trouble is that by then the game is already up. See the link below. Once the jet runs over the top of the high and the westerlies penetrate into Scandi, you might as well name the high 'titanic' because by that point she's going down! Very rare (not impossible though)to see anything other than a sinker from that point.

http://www.meteociel.fr/modeles/ecmwf.php?ech=96&mode=1&map=0&type=0&archive=0

This chart is an earlier timeframe than the one you posted because its really from this point that its game over.

Once that happens, the form horse is generally something akin to this

http://www.meteociel.fr/modeles/ecmwf.php?ech=168&mode=1&map=0&type=0&archive=0

Note also how the cold pool is obliterated by this stage

http://www.meteociel.fr/modeles/ecmwf.php?ech=168&mode=0&map=0&type=0&archive=0

In essence, for much of NW Europe we enter a mild weather pattern (at least in terms of upper air profile). From there its probably 10 days min for a full on cold spell to develop. What is slightly odd in my mind though is why we are seeing no real attempt to increase heights to our NE at this point (72 hours). http://www.meteociel.fr/modeles/ecmwf.php?ech=72&mode=1&map=0&type=0&archive=0 . Its probably too late to change now though given the strong agreement right across every model.

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Very poor charts this evening d can find very .Much like last winter, we don't even seem to be much in the way of eye candy with the deep FI charts. Any deep cold charts have been real collectors items this winter.Anyway, its Xmas so as the models are playing scrooge, off to find some cheer elsewhere....

Wide spread snow tomorrow on boxing day models confirm cold outlook upto FI with the odd freezing day with embedded surface cold. What has that got in common with last winter and 9c and floods ? Loads of eye candy this winter I'm stuffed.

Edited by stewfox
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The trouble is that by then the game is already up. See the link below. Once the jet runs over the top of the high and the westerlies penetrate into Scandi, you might as well name the high 'titanic' because by that point she's going down! Very rare (not impossible though)to see anything other than a sinker from that point.

http://www.meteociel.fr/modeles/ecmwf.php?ech=96&mode=1&map=0&type=0&archive=0

This chart is an earlier timeframe than the one you posted because its really from this point that its game over.

Once that happens, the form horse is generally something akin to this

http://www.meteociel.fr/modeles/ecmwf.php?ech=168&mode=1&map=0&type=0&archive=0

Note also how the cold pool is obliterated by this stage

http://www.meteociel.fr/modeles/ecmwf.php?ech=168&mode=0&map=0&type=0&archive=0

In essence, for much of NW Europe we enter a mild weather pattern (at least in terms of upper air profile). From there its probably 10 days min for a full on cold spell to develop. What is slightly odd in my mind though is why we are seeing no real attempt to increase heights to our NE at this point (72 hours). http://www.meteociel.fr/modeles/ecmwf.php?ech=72&mode=1&map=0&type=0&archive=0 . Its probably too late to change now though given the strong agreement right across every model.

 

For me though Jason, yes the charts and your thoughts make sense for what is shown but as I said get to Monday and go form there. Until this period in the next day or so is out of the way then I think even Monday that I posted is FI.

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Wide spread snow tomorrow on boxing day models confirm cold outlook upto FI. What has that got in common with last winter ? Loads of eye candy this winter I'm stuffed.

We will have to agree to differ then :-)

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Can you get snowfall with uppers above 0 but solid surface cold in place?

Yes, if the airs cold enough the warmer air rides over the top of the dense cold air, ie an inversion, and it can give snow. There was an instance of this in 1985, i was working and counting on the warmer air to enable us to carry on working but we ended up with snow.

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Yes, if the airs cold enough the warmer air rides over the top of the dense cold air, ie an inversion, and it can give snow. There was an instance of this in 1985, i was working and counting on the warmer air to enable us to carry on working but we ended up with snow.

Erm no u can't . Freezing rain yes . Snow , no . It can't fall from the clouds frozen if it's above freezing there can you? If there's a cold inversion the rain rain will freeze on impact if the air at ground level is below 0c .

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I think the lack of data is a red herring, there is no lack of data , it's not like the models have a holiday at the same time as we do...funny as the idea may be.

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Yep, fair enough Stuie :smiliz19:

 

Believe me, I really want to be wrong. Its much more fun to post epic / interesting charts.

Glad we agree to disagree. I am just treating these spikes of "milderish" air as cold dry days. Really looking forward to watching that air to the East.

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Cold uppers are not important next week, we will have surface cold, especially those areas lucky enough to get a good snow cover, notice how the timings have been rushed forward and instead of Saturday it's boxing day snow then fine and frosty with high pressure giving the UK a rest from Atlantic muck for most of the week ahead.

Smacks of inversion to me, and that means dull, overcast, raw cold in other words cold muck as opposed to mild....

Im far from sold on the snowcover either. From that direction mostwont settle but just be wet slushy muck. But maybe my altitude here isnt one that ttransfers more widespread. Think pm will get more then me just 20odd miles away.

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I think the lack of data is a red herring, there is no lack of data , it's not like the models have a holiday at the same time as we do...funny as the idea may be.

There actually is a lack of data Frosty, read Retron's post on TWO

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Erm no u can't . Freezing rain yes . Snow , no . It can't fall from the clouds frozen if it's above freezing there can you? If there's a cold inversion the rain rain will freeze on impact if the air at ground level is below 0c .

It happened in 85, its the first time i learned about inversions and thats what the man on the telly said had happened, however i dontknow what the upper air temps were, juzt that they were milder then the surface by quite alot.

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There actually is a lack of data Frosty, read Retron's post on TWO

This gets discussed every Christmas, especially when the models look rubbish but I seem to remember some of the experts on here saying it's a red herring.

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This gets discussed every Christmas, especially when the models look rubbish but I seem to remember some of the experts on here saying it's a red herring.

So you didn't read it? I think it is irrelevant what the charts look like, either there is some missing or there isn't.

 

Experts?

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I think the lack of data is a red herring, there is no lack of data , it's not like the models have a holiday at the same time as we do...funny as the idea may be.

p

One of the experts yesterday, think it was TEITS said that there is a lot less planes in the air Christmas day, in some areas 30% less flights so there is less data

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So you didn't read it? I think it is irrelevant what the charts look like, either there is some missing or there isn't.

 

Experts?

John Holmes for example. I will have a read of it though. :-)

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So you didn't read it? I think it is irrelevant what the charts look like, either there is some missing or there isn't.

 

Experts?

The effects would be fairly minimal given the vast amount of data is automated. Of course this doesn't explain the poor charts from yesterday of course.

To five days out it looks cold either by a brief burst of colder air or surface cold. The ECM brings a milder strong south-westerly flow in at day 6. So the two options seem to be a continuation of the surface cold or a more mobile westerly pattern.

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This gets discussed every Christmas, especially when the models look rubbish but I seem to remember some of the experts on here saying it's a red herring.

http://old.ecmwf.int/products/forecasts/d/charts/monitoring/coverage/dcover!aircraft!06!pop!od!mixed!w_coverage!latest!/ take a look at this, much less observations today but not sure if it is enough to cause a big difference for the run.

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Hopefully any alleged lack of data at this time of year is responsible for the stomach churning offerings of the 12z ecm. Even if zonal does look like becoming the keyword from midweek on wards, no full atlantic onslaught is evident owing to the ongoing persistence of generally high heights to the south. Glancing blows to the northwest of Ireland and Scotland, followed perhaps by pm incursions  at most. All a tad frustrating. :diablo:

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