Model output discussion - The run up to Christmas

[Chesil View]

The point being missed on the 06 GFS is that 100 mile south ward correction  just past 240 ( perfectly possible at that range gives you a Drc30/31st 1978 repeat.

[Anthony Burden]

GFS 06z showing northern blocking in fantasy island,Goodbye northerlies.

Welcome easterlies.60s winters here we come.

[sheikhy]

Beautyyy of a control at 250 hours!!!!!!

[ALL ABOARD]

5 minutes ago, snowking said:

There's been a lot of focus on 850mb temperatures over the last few days and will they/won't they support snowfall, so just wanted to create a post for any of the less experienced members who are probably left scratching their heads about the conflicting views amongst different members and want to know what to believe.

Let's start with why everyone looks for the -6c 850mb (or hPa) line and it's a bit of a history lesson I'm afraid. I believe in terms of these (and other) forums, the magical figure of -6c was really coined as the "snow line" back in the bad old days of the late 90's and early 00's over on the old BBC Snowwatch forums, when things were so desperate that we were crying out for any sort of 2 day northerly toppler just to look forward to (which is why I do find it amusing that some members can't see the potential in the upcoming period, I think unfortunately December 2010 distorted the expectations of some). Anyway, because back in those days we were primarily looking for Northerly topplers for any sort of cold, given an almost complete lack of Easterlies between 1996-2005, the 850mb temperature needed to be significantly below 0c for the airmass to be conducive for snow falling (this is a bit of an oversimplification, but let's keep it light!). Why? Well in the lower part of the troposphere we generally expect that as we travel from the clouds to the surface of the earth, the temperature increases. However we also have to remember that cold air falls, and so what we expect is the colder air from the 850mb level to fall down closer to the surface of the earth over time. The rate of this temperature increase (or "thermal gradient") varies hugely due to an overwhelming number of factors, however if we consider this in a simplified form again, the answer lies, for us at least, in the oceans.

Because from a North or North-Westerly airflow the air is travelling a long distance over a generally warm Atlantic ocean, there is more likelihood of warmer pockets of air close to the surface of any airflow from the N/NW cancelling out some of the colder air dropping from aloft than there would be from say the East, where the air is travelling a far shorter distance over the North Sea and so is less likely to include these warmer pockets of air. These warmer pockets of air can affect many of the parameters that we won't go into in this post, but the two that are worth calling out as they are mentioned a lot are the 2m temperature and the 2m dew point. 

So if we try and summarise the above two paragraphs, in a N/NWly airflow the air is travelling over warmer oceans and so warmer pockets of air can be expected to be found closer to the surface. To override these warmer pockets of air we need the cold air aloft (at the 850mb level) which falls down towards the surface of the earth to be cold enough to override these warmer pockets of air and make the air from cloud to surface cold enough throughout to support all of our lovely snowflakes falling from the clouds remaining as snowflakes rather than falling through a warmer pocket (or layer) of air and melting into horrible rain, which from experience is much more difficult to make snowballs from.

I think the primary reason we chose the -6c line was that back in those bad old days where Wetterzentrale was the choice of most members to consume their daily dose of GFS from, the dashed isotherm line which indicated the 850mb temperatures were spaced out at approximately every 5c (although for some reason I seem to remember Wettzentrale often showing -6c instead of -5c as one of the dashed isotherm lines, correct me if I'm wrong if anyone can remember), and so we would often look for the -5/-6c isotherm on the 850mb temperature charts as our guaranteed snow line, as it allowed for enough headroom for some warmer pockets of air at the surface to be overridden by the falling colder air from above. At this time I think it's fair to say that none of our collective weather knowledge was anything like it was today, and so looking for something simple like a single "snow line" helped us in our search for snow.

 

So, on to the next part, what exactly is the 850mb (or hPa - they both essentially mean the same thing) temperature chart. Again I will keep this as simple as I can, so apologies to anyone offended by the oversimplified statement I may be about to make. Well to answer the first part, it's exactly what it says - it is the temperature of the air at the point in the atmosphere where the air pressure is equal to 850 millibars (mb) or hectopascals (hPa). But the exact height above the surface of the earth of where pressure is equal to 850mb can change, and that is what all of the pretty colours on the "height" charts we see are. So we've been talking about the 850mb level of the atmosphere, let's take a jump to the other common charts we see - the 500mb charts, such as the one below:

The colours here represent how high above the earth the 500mb pressure level is. The more towards blue/purple the colour is, the lower the height (or closer to the surface of the earth) the 500mb pressure level is, and vice versa for the greens/yellows/oranges. This also has a knock on effect on how high/low the 850mb pressure level below it is.

So what we are saying in the context of our upcoming cold spell is that under that huge low pressure system, the height above the surface of the earth of both the 500mb and the 850mb pressure level is lower. What this means is that the colder air aloft, at the 850mb level, does not have as far to fall down towards the surface, and therefore more colder air is able to come down and help override any warmer pockets/layers of air towards the surface. This means that we don't necessarily need the 850mb temperature to be below -6c to support snow falling to the surface. We also then need to bear in mind that as that low pressure falls further South, and we change our feed of air from being from the North/North-West across the Atlantic ocean to instead coming from the East from the near continent, fewer of these warmer pockets of air are likely to exist.

Just to give you an example of this from the most recent 6z run, here are two 850mb temperature charts, the first one at +138 hours, and the other at +168 hours:

It would stand to reason that if it was as simple as colder 850mb temperature = colder surface temperature, then we would expect to see a lower 2m dew point temperature in the corresponding +168 chart right? Well see for yourself:

You can clearly see that despite the 850mb temperature being 1-2c warmer at +138 than at +168, the dew point temperature is 1-2c lower at +138c. 

You can again see the reason for this by looking at the 500mb height charts:

We can see here that the lower heights at +138 aid the cooler 2m dew point temperatures.

So in summary for what is a very long post, you do not require -6c or colder 850mb temperatures, even in a North-Westerly airflow sometimes, in order to guarantee all of the relevant parameters for snow being the right side of marginal, it is significantly more complex than that, and that is why the upcoming period could well deliver a lot of surprises - the word could being crucial in there!

What an outstanding post. 

[danm]

5 minutes ago, snowking said:

There's been a lot of focus on 850mb temperatures over the last few days and will they/won't they support snowfall, so just wanted to create a post for any of the less experienced members who are probably left scratching their heads about the conflicting views amongst different members and want to know what to believe.

Let's start with why everyone looks for the -6c 850mb (or hPa) line and it's a bit of a history lesson I'm afraid. I believe in terms of these (and other) forums, the magical figure of -6c was really coined as the "snow line" back in the bad old days of the late 90's and early 00's over on the old BBC Snowwatch forums, when things were so desperate that we were crying out for any sort of 2 day northerly toppler just to look forward to (which is why I do find it amusing that some members can't see the potential in the upcoming period, I think unfortunately December 2010 distorted the expectations of some). Anyway, because back in those days we were primarily looking for Northerly topplers for any sort of cold, given an almost complete lack of Easterlies between 1996-2005, the 850mb temperature needed to be significantly below 0c for the airmass to be conducive for snow falling (this is a bit of an oversimplification, but let's keep it light!). Why? Well in the lower part of the troposphere we generally expect that as we travel from the clouds to the surface of the earth, the temperature increases. However we also have to remember that cold air falls, and so what we expect is the colder air from the 850mb level to fall down closer to the surface of the earth over time. The rate of this temperature increase (or "thermal gradient") varies hugely due to an overwhelming number of factors, however if we consider this in a simplified form again, the answer lies, for us at least, in the oceans.

Because from a North or North-Westerly airflow the air is travelling a long distance over a generally warm Atlantic ocean, there is more likelihood of warmer pockets of air close to the surface of any airflow from the N/NW cancelling out some of the colder air dropping from aloft than there would be from say the East, where the air is travelling a far shorter distance over the North Sea and so is less likely to include these warmer pockets of air. These warmer pockets of air can affect many of the parameters that we won't go into in this post, but the two that are worth calling out as they are mentioned a lot are the 2m temperature and the 2m dew point. 

So if we try and summarise the above two paragraphs, in a N/NWly airflow the air is travelling over warmer oceans and so warmer pockets of air can be expected to be found closer to the surface. To override these warmer pockets of air we need the cold air aloft (at the 850mb level) which falls down towards the surface of the earth to be cold enough to override these warmer pockets of air and make the air from cloud to surface cold enough throughout to support all of our lovely snowflakes falling from the clouds remaining as snowflakes rather than falling through a warmer pocket (or layer) of air and melting into horrible rain, which from experience is much more difficult to make snowballs from.

I think the primary reason we chose the -6c line was that back in those bad old days where Wetterzentrale was the choice of most members to consume their daily dose of GFS from, the dashed isotherm line which indicated the 850mb temperatures were spaced out at approximately every 5c (although for some reason I seem to remember Wettzentrale often showing -6c instead of -5c as one of the dashed isotherm lines, correct me if I'm wrong if anyone can remember), and so we would often look for the -5/-6c isotherm on the 850mb temperature charts as our guaranteed snow line, as it allowed for enough headroom for some warmer pockets of air at the surface to be overridden by the falling colder air from above. At this time I think it's fair to say that none of our collective weather knowledge was anything like it was today, and so looking for something simple like a single "snow line" helped us in our search for snow.

 

So, on to the next part, what exactly is the 850mb (or hPa - they both essentially mean the same thing) temperature chart. Again I will keep this as simple as I can, so apologies to anyone offended by the oversimplified statement I may be about to make. Well to answer the first part, it's exactly what it says - it is the temperature of the air at the point in the atmosphere where the air pressure is equal to 850 millibars (mb) or hectopascals (hPa). But the exact height above the surface of the earth of where pressure is equal to 850mb can change, and that is what all of the pretty colours on the "height" charts we see are. So we've been talking about the 850mb level of the atmosphere, let's take a jump to the other common charts we see - the 500mb charts, such as the one below:

The colours here represent how high above the earth the 500mb pressure level is. The more towards blue/purple the colour is, the lower the height (or closer to the surface of the earth) the 500mb pressure level is, and vice versa for the greens/yellows/oranges. This also has a knock on effect on how high/low the 850mb pressure level below it is.

So what we are saying in the context of our upcoming cold spell is that under that huge low pressure system, the height above the surface of the earth of both the 500mb and the 850mb pressure level is lower. What this means is that the colder air aloft, at the 850mb level, does not have as far to fall down towards the surface, and therefore more colder air is able to come down and help override any warmer pockets/layers of air towards the surface. This means that we don't necessarily need the 850mb temperature to be below -6c to support snow falling to the surface. We also then need to bear in mind that as that low pressure falls further South, and we change our feed of air from being from the North/North-West across the Atlantic ocean to instead coming from the East from the near continent, fewer of these warmer pockets of air are likely to exist.

Just to give you an example of this from the most recent 6z run, here are two 850mb temperature charts, the first one at +138 hours, and the other at +168 hours:

It would stand to reason that if it was as simple as colder 850mb temperature = colder surface temperature, then we would expect to see a lower 2m dew point temperature in the corresponding +168 chart right? Well see for yourself:

You can clearly see that despite the 850mb temperature being 1-2c warmer at +138 than at +168, the dew point temperature is 1-2c lower at +138c. 

You can again see the reason for this by looking at the 500mb height charts:

We can see here that the lower heights at +138 aid the cooler 2m dew point temperatures.

So in summary for what is a very long post, you do not require -6c or colder 850mb temperatures, even in a North-Westerly airflow sometimes, in order to guarantee all of the relevant parameters for snow being the right side of marginal, it is significantly more complex than that, and that is why the upcoming period could well deliver a lot of surprises - the word could being crucial in there!

Outstanding post. Thank you.

[Jeremy Shockey]

GFS 06 z ensembles

lots of opportunity after the 27th !  ( and snow showers for the lucky few on 24th if precipitation occurs in the East )

[Djdazzle]

@snowking, one of the clearest explanations I’ve seen. Well done.

[Mikey Skins]

7 minutes ago, snowking said:

There's been a lot of focus on 850mb temperatures over the last few days and will they/won't they support snowfall, so just wanted to create a post for any of the less experienced members who are probably left scratching their heads about the conflicting views amongst different members and want to know what to believe.

Let's start with why everyone looks for the -6c 850mb (or hPa) line and it's a bit of a history lesson I'm afraid. I believe in terms of these (and other) forums, the magical figure of -6c was really coined as the "snow line" back in the bad old days of the late 90's and early 00's over on the old BBC Snowwatch forums, when things were so desperate that we were crying out for any sort of 2 day northerly toppler just to look forward to (which is why I do find it amusing that some members can't see the potential in the upcoming period, I think unfortunately December 2010 distorted the expectations of some). Anyway, because back in those days we were primarily looking for Northerly topplers for any sort of cold, given an almost complete lack of Easterlies between 1996-2005, the 850mb temperature needed to be significantly below 0c for the airmass to be conducive for snow falling (this is a bit of an oversimplification, but let's keep it light!). Why? Well in the lower part of the troposphere we generally expect that as we travel from the clouds to the surface of the earth, the temperature increases. However we also have to remember that cold air falls, and so what we expect is the colder air from the 850mb level to fall down closer to the surface of the earth over time. The rate of this temperature increase (or "thermal gradient") varies hugely due to an overwhelming number of factors, however if we consider this in a simplified form again, the answer lies, for us at least, in the oceans.

Because from a North or North-Westerly airflow the air is travelling a long distance over a generally warm Atlantic ocean, there is more likelihood of warmer pockets of air close to the surface of any airflow from the N/NW cancelling out some of the colder air dropping from aloft than there would be from say the East, where the air is travelling a far shorter distance over the North Sea and so is less likely to include these warmer pockets of air. These warmer pockets of air can affect many of the parameters that we won't go into in this post, but the two that are worth calling out as they are mentioned a lot are the 2m temperature and the 2m dew point. 

So if we try and summarise the above two paragraphs, in a N/NWly airflow the air is travelling over warmer oceans and so warmer pockets of air can be expected to be found closer to the surface. To override these warmer pockets of air we need the cold air aloft (at the 850mb level) which falls down towards the surface of the earth to be cold enough to override these warmer pockets of air and make the air from cloud to surface cold enough throughout to support all of our lovely snowflakes falling from the clouds remaining as snowflakes rather than falling through a warmer pocket (or layer) of air and melting into horrible rain, which from experience is much more difficult to make snowballs from.

I think the primary reason we chose the -6c line was that back in those bad old days where Wetterzentrale was the choice of most members to consume their daily dose of GFS from, the dashed isotherm line which indicated the 850mb temperatures were spaced out at approximately every 5c (although for some reason I seem to remember Wettzentrale often showing -6c instead of -5c as one of the dashed isotherm lines, correct me if I'm wrong if anyone can remember), and so we would often look for the -5/-6c isotherm on the 850mb temperature charts as our guaranteed snow line, as it allowed for enough headroom for some warmer pockets of air at the surface to be overridden by the falling colder air from above. At this time I think it's fair to say that none of our collective weather knowledge was anything like it was today, and so looking for something simple like a single "snow line" helped us in our search for snow.

 

So, on to the next part, what exactly is the 850mb (or hPa - they both essentially mean the same thing) temperature chart. Again I will keep this as simple as I can, so apologies to anyone offended by the oversimplified statement I may be about to make. Well to answer the first part, it's exactly what it says - it is the temperature of the air at the point in the atmosphere where the air pressure is equal to 850 millibars (mb) or hectopascals (hPa). But the exact height above the surface of the earth of where pressure is equal to 850mb can change, and that is what all of the pretty colours on the "height" charts we see are. So we've been talking about the 850mb level of the atmosphere, let's take a jump to the other common charts we see - the 500mb charts, such as the one below:

The colours here represent how high above the earth the 500mb pressure level is. The more towards blue/purple the colour is, the lower the height (or closer to the surface of the earth) the 500mb pressure level is, and vice versa for the greens/yellows/oranges. This also has a knock on effect on how high/low the 850mb pressure level below it is.

So what we are saying in the context of our upcoming cold spell is that under that huge low pressure system, the height above the surface of the earth of both the 500mb and the 850mb pressure level is lower. What this means is that the colder air aloft, at the 850mb level, does not have as far to fall down towards the surface, and therefore more colder air is able to come down and help override any warmer pockets/layers of air towards the surface. This means that we don't necessarily need the 850mb temperature to be below -6c to support snow falling to the surface. We also then need to bear in mind that as that low pressure falls further South, and we change our feed of air from being from the North/North-West across the Atlantic ocean to instead coming from the East from the near continent, fewer of these warmer pockets of air are likely to exist.

Just to give you an example of this from the most recent 6z run, here are two 850mb temperature charts, the first one at +138 hours, and the other at +168 hours:

It would stand to reason that if it was as simple as colder 850mb temperature = colder surface temperature, then we would expect to see a lower 2m dew point temperature in the corresponding +168 chart right? Well see for yourself:

You can clearly see that despite the 850mb temperature being 1-2c warmer at +138 than at +168, the dew point temperature is 1-2c lower at +138c. 

You can again see the reason for this by looking at the 500mb height charts:

We can see here that the lower heights at +138 aid the cooler 2m dew point temperatures.

So in summary for what is a very long post, you do not require -6c or colder 850mb temperatures, even in a North-Westerly airflow sometimes, in order to guarantee all of the relevant parameters for snow being the right side of marginal, it is significantly more complex than that, and that is why the upcoming period could well deliver a lot of surprises - the word could being crucial in there!

This is my first post but I have been visiting this page for a couple of years now. 

This post has really helped me and my knowledge of the upcoming cold spell greatly. The current charts are absolutely fascinating but I do get lost sometimes in the uppers, 850mb's etc. 

Cracking post and I for one am looking forwards to the evolutions of the charts moving forwards. 

 

 

[Speedbird]

1 minute ago, Djdazzle said:

@snowking, one of the clearest explanations I’ve seen. Well done.

Agreed.

Every once in a while there's a contribution which should be framed and pinned as a reference point for everyone.

This is such an occasion.

[MAF]

@snowking 's post is probably the post of the year  

[Ice Day]

Mods  please pin a link to Snowkings outstanding post to each and every MOD thread for the rest of time. Just brilliant. 

Talking of brilliant, this mornings runs are upping the ante, short, medium and long term. Best model watching for years.

Uppers seem a bit marginal to me though.

[sheikhy]

Seriously to hell with the gfs op if we thought that was good take a look at the control!!this is all happening at the best time of the year!!longest night shortest days!!!

[The4Seasons]

9 minutes ago, sheikhy said:

Beautyyy of a control at 250 hours!!!!!!

Can you post the image of the control chart mate. Be good for all to see . 

[sheikhy]

Im actually getting pretty worried now cos all this is gona affect my morning jogs!!cant be running on the snow and ice

[sheikhy]

1 minute ago, The4Seasons said:

Can you post the image of the control chart mate. Be good for all to see . 

 

[Allseasons-Si]

4 minutes ago, sheikhy said:

Seriously to hell with the gfs op if we thought that was good take a look at the control!!this is all happening at the best time of the year!!longest night shortest days!!!

Yes it's a beauty Shaky

 

3 minutes ago, The4Seasons said:

Can you post the image of the control chart mate. Be good for all to see . 

here you go mate

Meteociel - Cartes Ensemble GFS (ENS/GEFS)

WWW.METEOCIEL.FR

---

meteociel propose des rubriques météo temps réel, forums, modeles...

 

Edited December 22, 2020 by Allseasons-si

[ITSY]

2 minutes ago, sheikhy said:

Seriously to hell with the gfs op if we thought that was good take a look at the control!!this is all happening at the best time of the year!!longest night shortest days!!!

and may I just add what a marvellous and educational post that was from @snowking. Bravo 

[Severe Siberian icy blast]

19 minutes ago, snowking said:

There's been a lot of focus on 850mb temperatures over the last few days and will they/won't they support snowfall, so just wanted to create a post for any of the less experienced members who are probably left scratching their heads about the conflicting views amongst different members and want to know what to believe.

Let's start with why everyone looks for the -6c 850mb (or hPa) line and it's a bit of a history lesson I'm afraid. I believe in terms of these (and other) forums, the magical figure of -6c was really coined as the "snow line" back in the bad old days of the late 90's and early 00's over on the old BBC Snowwatch forums, when things were so desperate that we were crying out for any sort of 2 day northerly toppler just to look forward to (which is why I do find it amusing that some members can't see the potential in the upcoming period, I think unfortunately December 2010 distorted the expectations of some). Anyway, because back in those days we were primarily looking for Northerly topplers for any sort of cold, given an almost complete lack of Easterlies between 1996-2005, the 850mb temperature needed to be significantly below 0c for the airmass to be conducive for snow falling (this is a bit of an oversimplification, but let's keep it light!). Why? Well in the lower part of the troposphere we generally expect that as we travel from the clouds to the surface of the earth, the temperature increases. However we also have to remember that cold air falls, and so what we expect is the colder air from the 850mb level to fall down closer to the surface of the earth over time. The rate of this temperature increase (or "thermal gradient") varies hugely due to an overwhelming number of factors, however if we consider this in a simplified form again, the answer lies, for us at least, in the oceans.

Because from a North or North-Westerly airflow the air is travelling a long distance over a generally warm Atlantic ocean, there is more likelihood of warmer pockets of air close to the surface of any airflow from the N/NW cancelling out some of the colder air dropping from aloft than there would be from say the East, where the air is travelling a far shorter distance over the North Sea and so is less likely to include these warmer pockets of air. These warmer pockets of air can affect many of the parameters that we won't go into in this post, but the two that are worth calling out as they are mentioned a lot are the 2m temperature and the 2m dew point. 

So if we try and summarise the above two paragraphs, in a N/NWly airflow the air is travelling over warmer oceans and so warmer pockets of air can be expected to be found closer to the surface. To override these warmer pockets of air we need the cold air aloft (at the 850mb level) which falls down towards the surface of the earth to be cold enough to override these warmer pockets of air and make the air from cloud to surface cold enough throughout to support all of our lovely snowflakes falling from the clouds remaining as snowflakes rather than falling through a warmer pocket (or layer) of air and melting into horrible rain, which from experience is much more difficult to make snowballs from.

I think the primary reason we chose the -6c line was that back in those bad old days where Wetterzentrale was the choice of most members to consume their daily dose of GFS from, the dashed isotherm line which indicated the 850mb temperatures were spaced out at approximately every 5c (although for some reason I seem to remember Wettzentrale often showing -6c instead of -5c as one of the dashed isotherm lines, correct me if I'm wrong if anyone can remember), and so we would often look for the -5/-6c isotherm on the 850mb temperature charts as our guaranteed snow line, as it allowed for enough headroom for some warmer pockets of air at the surface to be overridden by the falling colder air from above. At this time I think it's fair to say that none of our collective weather knowledge was anything like it was today, and so looking for something simple like a single "snow line" helped us in our search for snow.

 

So, on to the next part, what exactly is the 850mb (or hPa - they both essentially mean the same thing) temperature chart. Again I will keep this as simple as I can, so apologies to anyone offended by the oversimplified statement I may be about to make. Well to answer the first part, it's exactly what it says - it is the temperature of the air at the point in the atmosphere where the air pressure is equal to 850 millibars (mb) or hectopascals (hPa). But the exact height above the surface of the earth of where pressure is equal to 850mb can change, and that is what all of the pretty colours on the "height" charts we see are. So we've been talking about the 850mb level of the atmosphere, let's take a jump to the other common charts we see - the 500mb charts, such as the one below:

The colours here represent how high above the earth the 500mb pressure level is. The more towards blue/purple the colour is, the lower the height (or closer to the surface of the earth) the 500mb pressure level is, and vice versa for the greens/yellows/oranges. This also has a knock on effect on how high/low the 850mb pressure level below it is.

So what we are saying in the context of our upcoming cold spell is that under that huge low pressure system, the height above the surface of the earth of both the 500mb and the 850mb pressure level is lower. What this means is that the colder air aloft, at the 850mb level, does not have as far to fall down towards the surface, and therefore more colder air is able to come down and help override any warmer pockets/layers of air towards the surface. This means that we don't necessarily need the 850mb temperature to be below -6c to support snow falling to the surface. We also then need to bear in mind that as that low pressure falls further South, and we change our feed of air from being from the North/North-West across the Atlantic ocean to instead coming from the East from the near continent, fewer of these warmer pockets of air are likely to exist.

Just to give you an example of this from the most recent 6z run, here are two 850mb temperature charts, the first one at +138 hours, and the other at +168 hours:

It would stand to reason that if it was as simple as colder 850mb temperature = colder surface temperature, then we would expect to see a lower 2m dew point temperature in the corresponding +168 chart right? Well see for yourself:

You can clearly see that despite the 850mb temperature being 1-2c warmer at +138 than at +168, the dew point temperature is 1-2c lower at +138c. 

You can again see the reason for this by looking at the 500mb height charts:

We can see here that the lower heights at +138 aid the cooler 2m dew point temperatures.

So in summary for what is a very long post, you do not require -6c or colder 850mb temperatures, even in a North-Westerly airflow sometimes, in order to guarantee all of the relevant parameters for snow being the right side of marginal, it is significantly more complex than that, and that is why the upcoming period could well deliver a lot of surprises - the word could being crucial in there!

What a fantastic post, showing your worth there my old boy

I'v came out the shadows after 2 years, I allowed my personal life to leak through and became nagative rather than constructive, so for the good of the forum I took a break! 

So after, a marriage break down, a mental break down, a bankruptcy, a house loss, I'm back lol, happier it's all over and as a single lad and know nagging wife behind my back I can come back and pick up my obsession of winter cold!!!! 

Promise to add meaning and illustration to my posts moving forward to a put a smile on you all and hopefully bring a 3 wk period of severe winter weather with disruption to travel

Edited December 22, 2020 by Severe Siberian icy blast

[Guest]

@snowking Take a bow, son. Wonderfully informative and so clearly explained  Thank you - I wish I could like your post a thousand times over! 

[sheikhy]

1 minute ago, ITSY said:

and may I just add what a marvellous and educational post that was from @snowking. Bravo 

Was a brilliant post and defo more towards the posters who keep banging on about cold 850s!!lot more complex than that peeps!!!

[Penrith Snow]

1 hour ago, That ECM said:

Upgrade in the 850’s. They are important right?

Excellent, there is a finger of -8c 850s about 50 miles wide centred over my house  

[The4Seasons]

Just now, Allseasons-si said:

Yes it's a beauty go

 

here you go mate

Meteociel - Cartes Ensemble GFS (ENS/GEFS)

WWW.METEOCIEL.FR

---

meteociel propose des rubriques météo temps réel, forums, modeles...

 

It is impressive. I will remain cautious that the low might go too west. Hopefully not. Although having said that the charts in the 6 hours might look totally different . However things are upbeat and moving in the right direction for ❄

[Ice Day]

3 minutes ago, Severe Siberian icy blast said:

Promise to add meaning and illustration to my posts moving forward to a put a smile on you all and hopefully bring a 3 wk period of severe winter weather with disruption to travel

Great to see you posting back here again SSIB

[snefnug]

33 minutes ago, General Cluster said:

Oh bugger! I guess the Road to Snowmageddon is lined with dog turds?

    

Turds hidden in the lying snow?

[Iceaxecrampon]

26 minutes ago, Broadmayne blizzard said:

The point being missed on the 06 GFS is that 100 mile south ward correction  just past 240 ( perfectly possible at that range gives you a Drc30/31st 1978 repeat.

Oh yes - we remember that one  - people were skiing round these parts.