Model Output Discussion

[yamkin]

I hope the blog I've done might answer the query about their Fax chart and the country being mainly in Polar Maritime showery air by late Tuesday.

Very good read John. Would the intensity of ppn in the S/SE have an influence of rain turning to snow? Reason I ask is because Peter Cockroft's graphic chart on Friday evening showed heavy snow for the SE on Tuesday.

[bluearmy]

Very good read John. Would the intensity of ppn in the S/SE have an influence of rain turning to snow? Reason I ask is because Peter Cockroft's graphic chart on Friday evening showed heavy snow for the SE on Tuesday.

yamkin - the T96 FAX from last night looked good for snow into the se on the occlusion. the updated T84 from this morning less so with a different direction of attack plus warm sector sstill present. the meto forecast was issued at 3 am which probably explains why it is more ppositive re snow.

i note from the NOAA discussion this morning that they refer to analogue years Feb 1963 and 1978 although they point out that '63 wasnt a nino year. given we look like having the 3 months of winter all below CET average, its amazing that we have managed to miss out on a prolonged freeze period in the southern half of the UK. we shouldnt dismiss what we have had - remarkable considering what some thought was possible.

[danm]

For me, once march comes I'd like to see it start getting warmer. Snow in march usually doesn't settle for long at all. If we don't see snow in the next couple of weeks then roll on spring and summer in my opinion. It has been a better winter than many of us could have hoped for.

[johnholmes]

Very good read John. Would the intensity of ppn in the S/SE have an influence of rain turning to snow? Reason I ask is because Peter Cockroft's graphic chart on Friday evening showed heavy snow for the SE on Tuesday.

Intensity would have an effect.

In any marginal situation IF the precip (rain) is moderate to heavy then evaporational colling comes into play. This has the effect of lowering the zero isotherm which in turn allows snow to fall to a lower level.

So watch for bright echoes on the radar upwind of you!

[Cheese Rice]

After looking at the GFS I still stick by next week will be very wintry, conditions are still favourable for snow, especially but not exclusively for higher ground. Monday and Tuesday snow doesn't look heavy so I would of though a wintry mix to lower levels, I doubt there will be 5cm of snow to lower levels, perhaps 5cm to higher ground.

[492]

Just been reading over on Eastern US and the with the AO index standing at -4.7 yesterday

(record tying 8th consecutive day) and another - 4SD reading expected today this will apparently

break the record set in 1969.

70% of the US is snow covered with a large swathe of snow around the 30 degree latitude

and snow forcast into Florida today and tomorrow.

Despite this amazing blocking to the north the UK have only seen rather cold weather

since the latest phase of the very negative AO with the very cold weather missing us to the

southeast.

I think we in the UK would have to be very unlucky to miss out on another very cold and wintry

spell of weather with the amount of blocking just to our north plus with the warming expected

to our north at the 30hpa level and the down-welling negative zonal winds from the MMW.

Maybe patience is the key and we will have to wait until nearer the months end but seeing the

way the Euro's are starting to trend I think the return of real winter weather will be sooner rather

than later.

I have noticed the developing high to our north on the actual circumpolar analysis chart. It is not difficult to see the eventual outcome that you have been suggesting and given the oddity of this winter and the way the pattern seems to keep resetting itself and also the fact that late winter is a more favourable time for blocking it seems all the more likely. As it is not even mid month there is plenty of time for more cold spells before the months end.

[snowray]

I agree with that. And perhaps it highlights how off kilter what we have experienced so far this winter is for the UK. That time we got lucky.

I was talking about luck on one of the other threads yesterday, and how most of time in the UK we seem to just miss out, only just mind you, but will suffice.

Of course this Winter we have got lucky twice, (3 tmes maybe for East Kent) but many people will just remember the extreme cold, ice, general wintryness, but the lack of deep snow, that something like a channel low would have produced, or last week's very unstable Easterly for the whole country that just missed in the end, only just.

It baffles me sometimes to see huge storms in the USA that dump snow for thousands of miles, or as we just saw again in Europe, Snow falling from Moscow to Madrid and Rome, and yet all we can manage are a few showers in the East that evaporate into nothing a few miles inland (aparts from East kent of course). Many of these showers have been of rain anyway, in spite of the North see being 2c colder than normal, and uppers being -6, -8c.

Even next week, here we are, a little group of Islands in the grand scheme of thigs with a small blob of mild air stuck to us like a magnate, and freezing pools of air all around, I dont get it!

We see this time and time gain, and then the mild blob just sits over us like its home.

Now there is a chance that this low will slip further South still as the ECM is hinting at, but nothing is ever simple in the UK even when in theory fundaments are the best we have seen in donkeys years, (AO, NAO, jet, MJO,etc etc) and yet things have got so good that the end result has gone full circle and we end up with bad.

I can see things very marginal next week for snow lovers, I think Wales and the NW will have see snow mainly above 150m, and the Northern half generally might do reasonably well but mainly on higher ground, the honey pot being, well, NE Scotland yet again of course.

But why cant we ever have a nationwide snow event, North to South, make everyone happy for a change, its always a case of, Snowed in Eastbourn but not in Brighton, or, snowed in Newcastle but not in Middlesborough, marginal in Liverpool but a dumping in Manchester. Like Its always snowing at Yamkins in Croydon about 10 miles away and bone dry here!!

Edited February 13, 2010 by snowray

[dubmuffin]

Snowray, that is such a good summing up. It is amazing how we are so small an island on the edge of europe that we manage to have our own special weather. Time and again I have watched FI getting closer and closer, only to find it lives up to its name once it is within touching distance. I'm beginning to think that the models tease us with the possibilities just to keeep us watching...

[snowray]

Snowray, that is such a good summing up. It is amazing how we are so small an island on the edge of europe that we manage to have our own special weather. Time and again I have watched FI getting closer and closer, only to find it lives up to its name once it is within touching distance. I'm beginning to think that the models tease us with the possibilities just to keeep us watching...

[/quote

Thanks Dubmuffin, a was kinda hoping for some positive responses as oposed to any gripeing that one sometimes reads on here or regionalism. And I know people will say that large land masses like the USA and Europe are always colder, etc, etc. But none the less I feel the points that I raise are valid. Its like when you see these massive snow streamers coming down from the North Sea for hundreds of miles into the Low coutries and France, when ours fizzle out a few miles inland, don't get it!

Anyway, theres still time for change, the low hasn't even formed yet up around Iceland so I await the 12z runs with an open mind.

Edited February 13, 2010 by snowray

[ribster]

Snowray, that is such a good summing up. It is amazing how we are so small an island on the edge of europe that we manage to have our own special weather. Time and again I have watched FI getting closer and closer, only to find it lives up to its name once it is within touching distance. I'm beginning to think that the models tease us with the possibilities just to keeep us watching...

Not sure I understand either of these posts, it's exactly because we are a small island surrounded by water that it is very easy for weather systems to miss us completely. I can't agree that everything has been FI, as obviously many events have verified this winter. If you want to look at winters where FI never materialised you would be better to go and look at some of the shockers of the 90s and 00s, snowmageddon just isn't going to visit our shores very often.

[snowingtequila]

I was talking about luck on one of the other threads yesterday, and how most of time in the UK we seem to just miss out, only just mind you, but will suffice.

Of course this Winter we have got lucky twice, (3 tmes maybe for East Kent) but many people will just remember the extreme cold, ice, general wintryness, but the lack of deep snow, that something like a channel low would have produced, or last week's very unstable Easterly for the whole country that just missed in the end, only just.

It baffles me sometimes to see huge storms in the USA that dump snow for thousands of miles, or as we just saw again in Europe, Snow falling from Moscow to Madrid and Rome, and yet all we can manage are a few showers in the East that evaporate into nothing a few miles inland (aparts from East kent of course). Many of these showers have been of rain anyway, in spite of the North see being 2c colder than normal, and uppers being -6, -8c.

Even next week, here we are, a little group of Islands in the grand scheme of thigs with a small blob of mild air stuck to us like a magnate, and freezing pools of air all around, I dont get it!

We see this time and time gain, and then the mild blob just sits over us like its home.

Now there is a chance that this low will slip further South still as the ECM is hinting at, but nothing is ever simple in the UK even when in theory fundaments are the best we have seen in donkeys years, (AO, NAO, jet, MJO,etc etc) and yet things have got so good that the end result has gone full circle and we end up with bad.

I can see things very marginal next week for snow lovers, I think Wales and the NW will have see snow mainly above 150m, and the Northern half generally might do reasonably well but mainly on higher ground, the honey pot being, well, NE Scotland yet again of course.

But why cant we ever have a nationwide snow event, North to South, make everyone happy for a change, its always a case of, Snowed in Eastbourn but not in Brighton, or, snowed in Newcastle but not in Middlesborough, marginal in Liverpool but a dumping in Manchester. Like Its always snowing at Yamkins in Croydon about 10 miles away and bone dry here!!

I would like to one know why one. model progs the low to go south and another one doesn't what are the signals that one is getting wrong?

this winter I remember a foot of snow on the ground for a long time after a brief interlude after 8 inches of snow had started to melt. A lot of the country did get snow just not the southeast it appears.

I imagine we will have another snow event before winter is out, it is very rare that I go through feb and march without some proper snow particulaly when such blocking is about

[full_frontal_occlusion]

Its like when you see these massive snow streamers coming down from the North Sea for hundreds of miles into the Low coutries and France, when ours fizzle out a few miles inland, don't get it!

Snowray, you answered your own question: Nowhere in Great Britain is more than 70 miles from the sea.

The North Atlantic Drift also plays a big role.

Then think about where streamers form and in which direction? There are few places where streamers form in the UK since the topology is right in but few places. And there you have it.

Smallish land mass on the extreme western edge of a continental land mass, with a warm sea current across our western and northern approaches and few topological features to induce such favourable snow conditions.

Continental Europe in winter is cold but mainly dry and when a snow event happens (don't forget Europe covers a large numebr of big compared to ours countries) wherever those weather systems meander, somwhere in Europe will get pounded.

So many more factors need to be in place for us than on the continent, that the probability of a major snow event dumping feet of snow is a twice a century occurrence for the British Isles.

Viola - marginality screams from the rooftops.

So yes it is down to luck when it finally happens. But then that's why we're so transfixed with snow as a nation.

ffO.

Edited February 13, 2010 by full_frontal_occlusion

[Duane S.]

Not sure I understand either of these posts, it's exactly because we are a small island surrounded by water that it is very easy for weather systems to miss us completely. I can't agree that everything has been FI, as obviously many events have verified this winter. If you want to look at winters where FI never materialised you would be better to go and look at some of the shockers of the 90s and 00s, snowmageddon just isn't going to visit our shores very often.

Quite Agree Ribster. It is no coincidence that through the ages we have been 'unlucky'. An island by default has its own 'micro climate'. Add to that our physical geographical location and its a wonder we ever get anything extreme in this Country, the southern half of it anyway.

[snowray]

Not sure I understand either of these posts, it's exactly because we are a small island surrounded by water that it is very easy for weather systems to miss us completely. I can't agree that everything has been FI, as obviously many events have verified this winter. If you want to look at winters where FI never materialised you would be better to go and look at some of the shockers of the 90s and 00s, snowmageddon just isn't going to visit our shores very often.

I think you should try reading it again then, its not rocket science like some of the more technicial posts.

Ok, well Sardinia is a much, much smaller Island, its snowed there on and off all Winter even in the Capital Cagliari on the extrme Southern Coast, and Corsica, and they are both in the middle of the Western Med.

At our latitude and with the Atlatic still well and truly closed for business what happens to us I ask? We end up getting mild air from the North, shoving the cold pool over us out East, then instead of contunuing South it just stops, end result bitter cold NElys end up in the Atlantic. It's madening stuff realy, like a bit of fiction, couldn't make it up if you tried.

Snowray, you answered your own question: Nowhere in Great Britain is more than 70 miles from the sea.

The North Atlantic Drift also plays a big role.

Then think about where streamers form and in which direction? There are few places where streamers form in the UK since the topology is right in but few places. And there you have it.

Smallish land mass on the extreme western edge of a continental land mass, with a warm sea current across our western and northern approaches and few topological features to induce such favourable snow conditions.

Continental Europe in winter is cold but mainly dry and when a snow event happens (don't forget Europe covers a large numebr of big compared to ours countries) wherever those weather systems meander, somwhere in Europe will get pounded.

So many more factors need to be in place for us than on the continent, that the probability of a major snow event dumping feet of snow is a twice a century occurrence for the British Isles.

Viola - marginality screams from the rooftops.

So yes it is down to luck when it finally happens. But then that's why we're so transfixed with snow as a nation.

ffO.

Great reply there FFC, cheers.

Guess I just get frustrated when these titchy Islands get snow at Sea level in the Middle of the Med which is much warmer then our chillier than normal North Sea. It also shocks me to see what a big modifying effect the North Sea can still have even at this time of the year.

Quite Agree Ribster. It is no coincidence that through the ages we have been 'unlucky'. An island by default has its own 'micro climate'. Add to that our physical geographical location and its a wonder we ever get anything extreme in this Country, the southern half of it anyway.

In theory the South sould do better I would have thought due to its proximity to the continent, lost count of the number of times I have left Dover white with chalk and arrived in Calaise white with snow right down to the beach. Its only 20 miles

Edited February 13, 2010 by snowray

[full_frontal_occlusion]

I would like to one know why one. model progs the low to go south and another one doesn't what are the signals that one is getting wrong?

this winter I remember a foot of snow on the ground for a long time after a brief interlude after 8 inches of snow had started to melt. A lot of the country did get snow just not the southeast it appears.

I imagine we will have another snow event before winter is out, it is very rare that I go through feb and march without some proper snow particulaly when such blocking is about

One of the first things in the modelling process is to mathematically interpolate grid point data (used to initialise the models) from the available raw data. By inspection alone, this process introduces some inaccuracy as blocking features cover large swathes of area with little to differentiate between grid points.

Solutions are then at the mercy of small scale features just above the noise floor (point at which a discernable signal is measured and not random) and thus affects outcomes as in the trajectory of weather systems.

This is akin to say correctly decoding deep space communications from probes, where the wanted signal needs to be transmitted many times in order that ground systems can differentiate it from the all swamping background noise.

Hope this helps.

ffO.

[snowmadchrisuk]

The 12z has the main Low further west and makes things much more favourable for back edge Snow of the main front . And Snow showers following . Nice to see with only a couple of days to go .

[Cheese Rice]

The 12z has the main Low further west and makes things much more favourable for back edge Snow of the main front . And Snow showers following . Nice to see with only a couple of days to go .

Yeah, looks like a small upgrade to me, more colder air around the low than previous runs, little upgrades like this will make a big difference as to whether you get snow or rain.

Edited February 13, 2010 by 10123

[cooling climate]

GFS 12z, post t96 going the same way as the 06z dropping heights over

northern Scandinavia with a portion of vortex energy moving back over

this area. Imo the model is wrong and we will see a building of heights

in this area not lowering.

Lets see what the Euro's have to say.

[Rollo]

GFS 12z, post t96 going the same way as the 06z dropping heights over

northern Scandinavia with a portion of vortex energy moving back over

this area. Imo the model is wrong and we will see a building of heights

in this area not lowering.

Lets see what the Euro's have to say.

It seems to be heading towards the ECM but kicking and screaming as it does,with synoptics like these who would want to be a weather forecaster.

[johnholmes]

I don't know Rollo-we may get it wrong at times but it sure is a challenge

oh I added a whole para and its gone walk abouts!

What I thought I posted was

i've done a comparison of the 850mb temps of the NAE and Extra, for the furthest out NAE goes, 06z Monday, and they are almost identical.

Pity NAE is not available out to about T+72.

Still it does allow us to compare the two models at that time and try to decide, if there are differences, which is more likely to be right with its precip type.

Edited February 13, 2010 by johnholmes

[Rollo]

I don't know Rollo-we may get it wrong at times but it sure is a challenge

oh I added a whole para and its gone walk abouts!

What I thought I posted was

i've done a comparison of the 850mb temps of the NAE and Extra, for the furthest out NAE goes, 06z Monday, and they are almost identical.

Pity NAE is not available out to about T+72.

Still it does allow us to compare the two models at that time and try to decide, if there are differences, which is more likely to be right with its precip type.

You are certainly right John in these situations being a challenge,I wonder in all your years forecasting how many times such winter synoptics came up?

[cooling climate]

UKMO at t120 and t144 very different to the GFS at these time frames, with much better

heights over Scandinavia due to the vortex being pushed away east.

I must admit the t144 UKMO chart looks very strange though with the low filling out and

becoming very flabby.

I would have thought the cold would undercut this and that the t144 is actually a cold

outcome for the UK.

[ANYWEATHER]

Its quite clear that the cold weather pattern will not change for the forseeable future and the word Mild will once again be made redundant for at least another week. The setup forthcoming will favour snow on any high ground even in the south but lowlevel southern snow will always be marginal but certainly not unlikely! Lots of ifs and buts ,wheres and whens coming up and lots of changes too in what is a rather unusual synoptic setup. Look what that center low from Iceland does next week near or over the BI. Kinda goes in a complete cirle across the uk:cc_confused: :lol: :lol:

[bluearmy]

UKMO at t120 and t144 very different to the GFS at these time frames, with much better

heights over Scandinavia due to the vortex being pushed away east.

I must admit the t144 UKMO chart looks very strange though with the low filling out and

becoming very flabby.

I would have thought the cold would undercut this and that the t144 is actually a cold

outcome for the UK.

certainly for n england and scotland - no question that any appreciable precip would be white under that slack cold nothingness.

i expect things will change a fair bit by t144 though CC. hoping that ecm continues its recent trend though i'd like to see that energy not go mid atlantic this run as it cuts off the cold uppers advecting into the north at an earlier stage. just have a feeling that north midlands/northern england could see a big snowfall week after this one.

[Grimsby Snow Lover]

Its quite clear that the cold weather pattern will not change for the forseeable future and the word Mild will once again be made redundant for at least another week. The setup forthcoming will favour snow on any high ground even in the south but lowlevel southern snow will always be marginal but certainly not unlikely! Lots of ifs and buts ,wheres and whens coming up and lots of changes too in what is a rather unusual synoptic setup. Look what that center low from Iceland does next week near or over the BI. Kinda goes in a complete cirle across the uk:cc_confused:

The one thing that screams out at me from those charts you have posted is the shear amount of cold just to the north of the low pressure. Would be great if we could tap into that before March.