Model Output Discussion - Christmas and New Year

[BlueHedgehog074]

Greetings all

A new thread for the festive period. Other thread started to slow down a bit.

With Christmas here, a lot of us weather-wise become flooded with excitement at the prospect of something cold and white. For a few, maybe you want something mild, stormy and/or dry. But what sort of weather will Santa be delivering for us I wonder?

From what the models are showing, we have chilly weather taking over from the North at the moment. Using various charts from the Netwx-SR/MR and GFS models, it shows a chilly Northerly invading the whole UK during Christmas Eve today and a toppling Atlantic High out West.

The whole UK under -5*C and colder 850 hPa temperatures. -10*C area not far off from Northern Scotland. It will be cold across Northern England and Scotland, freezing over higher ground. Pretty cold across the rest of the UK. 

Fine and dry for Central areas, maybe with an isolated shower. Otherwise showers likely down Western, Northern and Eastern Coasts. The 850 hPa temperatures and 500 to 1000mb thicknesses look supportive for showers to be wintry at times. More especially under heavier showers down the Eastern parts of the UK where the Netwx-SR model has the thicknesses as low as 520dam over parts of the Eastern Midlands and Lincolnshire. So a few flakes possible, though probably more marginal right out on the coast. 

 

The wintry mix of showers likely to continue overnight and through Christmas morning down some Eastern UK coasts. Dry and clearer everywhere else, perhaps the odd isolated shower or two down Western UK coasts. A bitter night and morning to come with frost for most places away from Eastern and Western coasts. Little less cold over Western Ireland.

Christmas Day will be another chilly day with some morning frost, which may persist for a while over Northern high ground areas and places sheltered from the Westerly winds. The  Atlantic High/ridge gets shunted back South-West to allow the Westerly flow to take over from the Atlantic. 

 

Few odd wintry showers may continue over some Eastern coasts. Most Eastern, Central and Southern parts staying fine and bright though. Could get some nice walks in. Some cloudy, windy and wet conditions will spill into the North-West of the UK later into the day. Wintry over the Scottish hills 

A less colder night compared to Christmas Eve/Christmas morning with some showers and rain over Western and North-Western areas. Heavier rain pushing into Western Scotland Boxing Day morning. Cold over South-Eastern areas of the UK with some frost possible.

 

Boxing Day looks unsettled as Low Pressure over Iceland drives a blustery Westerly flow over the UK. You will also see that the Azores High is re-amplifying out West, which leads to some compelling outcomes for cold weather fans further down the line. There will be showers and longer spells of rain for many places, which could be heavy at times. Perhaps drier towards the far North-East of the UK. Fairly mild over Southern areas, but cooler under the heavier areas of rain I’d imagine. Bit chillier further North where the rain is likely to fall as sleet or snow over some of the taller hills

 

Sunday 27th December sees the Atlantic ridge to our West becoming Highly amplified. The upper heights from this extending North-West through Greenland connecting with the ridge over the Siberia area. This sends the upper and surface Low South-East over the UK. We see a split in the Troposphere Vortex over the Northern Hemisphere. 

It will be a chilly day with further rain and showers circulating around the Low Pressure over the UK. South-Eastern areas clinging onto milder temperatures at first as some heavy rain via cold front clears South-East over that area. The rain and showers over the UK could become wintry on high ground, although with such low upper heights accompanying the deep Low Pressure, there could be some sleety precipitation down to lower levels. Particularly under heavy showers, and more so over Western and Northern areas where the Low wraps some colder 850 hPa temperatures from the North-West, South-Eastwards through Western UK

 

Some little changes to the details are possible over the next few days as to where and how wintry precipitation could be. This is just a general idea of what to expect. Some of this coming down to nowcasting. In fact, even on Sunday the exact depth of the Low and where the centre of it goes is not full-on settled yet. What looks certain is an amplified area of High Pressure over the Atlantic and a deep upper trough sent South over the UK

Looking at the Jetstream chart for Sunday on the latest GFS 18Z run would support the above scenario. Buckles and amplifies upstream in the mid and Western Northern Atlantic. Help to steer weather systems from the North-West down towards us

 

Onto 120 hours (Monday midday), the various 12Z operational runs while there are differences to some details, keep the Atlantic ridging rather strong to our West and Low Pressure over the UK.

12Z GFS



12Z UKMO

12Z ECMWF

12Z ICON

12Z GEM

In terms of that Atlantic ridge, the GEM seems the strongest. The upper ridging pushing the furthest North over Southern Greenland. The Low to the West of it in slightly of a less hurry to run over the ridge.

One thing that caught my eye, however, is the GFS is the most keen to try sink that upper UK trough to our South through Monday. Same is true on the latest 18Z GFS run for Monday below, so being quite consistent with this situation 

Other models above have the deep Low and upper trough more directly placed over the whole UK. ICON not too far off from the GFS in that it has the centre of the Low over South/South-Western UK. A variation in the shape of the surface and upper trough on the operational models above. Going for quite a stretch on the UKMO. Stretchy Lows tending to be better than rounded ones for wintry weather. The further South and East they also go, the better for pulling in a colder flow from the North and East.

With the way things are, there is a lack of particularly cold 850 hPa temperatures over the UK, despite the impressive setup. I think the issue is, the UK Low combined with the Russian block to our East is drawing up some milder 850 hPa Northwards through South-Eastern Europe and towards Scandinavia, meaning not much proper cold to tap into in that direction. This does vary a bit depending on the shape and position of the UK Low above at 120 hours. A little shift further East of Low Pressure at that time-frame, could mean dragging in some of the colder 850 hPa temperatures down from the North around Iceland. 

However, it’s not worth getting too nail-bitey over the 850 hPa temperatures. Plus it’s not like both Scandinavia and the UK, for example, are under positive 850 hPa temperatures. Depending on where the actual position and track the Low ends up, anywhere could see some rain, sleet or hill snow. There will likely be a wintry mix of showers about too away from the longer spells of wintry weather considering how unstable the air is. And with the upper 500mb heights being very low, this could drag colder air down to lower levels pushing the snow line down. Helped by precipitation being heavy to encourage evaporative cooling and the flow being slack. Which the outlook for Monday has real possibilities of doing since the Low Pressure, except perhaps away from the centre of it doesn’t look all that ‘stormy’. For snow, deep cold is not essential. It can help, but can get by without it. Sure though it would be nice to tap into some proper cold at some point. Some deeper cold quite easily be possible thanks to the blocked setups the models are currently showing. 

Would say the GFS is mostly on its own with the speed it sinks the trough on Monday, making me wonder if it’s being too quick with that evolution. Will see I guess. 

Further on towards 168 hours, the 18Z GFS, 12Z ECMWF and 12Z GEM, in that order below, continue with ridging in the mid-Atlantic. Between 120 and 168 hours, some Low Pressure tried to run over the top of the Atlantic ridging over Western Greenland attempting to somewhat knock it down South to our West. But struggled to make much impact. You can see there is, in varying forms, a pokey Low/shortwave over Iceland looking to swing South-East down towards the UK. Along with Low Pressure reasonably far enough West over the Newfound area to allow a good gap for the amplified Atlantic ridge to gain more Northwards latitude

Have highlighted on the GFS the usefulness of having separation between the UK/Eastern UK Lows and the ones to the West of that ridging

Too much of that Low Pressure riding over the top of the Atlantic ridge could flatten it, even though events downstream would likely prevent that ridge getting over to mainland Europe. And it’s not impossible for a North-West to South-East Jetstream to continue towards the UK. It does seem unlikely for it to run over the top. Models haven’t be that keen for that to happen. Not impossible, mind.

Both the ECMWF and GEM from 192 to 240 hours stretch that Newfoundland Low throwing up warm air Northwards towards South and Western Greenland and then drop the Low South into the Atlantic. At the same time Low Pressure to our North-West drops over (12Z GEM), or to the East of (12Z ECMWF), the UK. This forms some strong blocking to our North-West. GEM trying to build a cut off Greenland High while the ECMWF has more of a Western Icelandic one. The poor Icelandic ridge gets a big poke from the Northern Iceland Low at 240 hours on the ECMWF

12Z ECMWF

12Z GEM

The 18Z GFS, while it does try to get some ridging going over Greenland, has that Low further upstream exhibiting some different behaviour. Part of it does split against the Atlantic to Southern Greenland ridging - a small shallow area dropping South into the Atlantic with ridging building over the top. That little shallow part getting cut off. But a fair chunk of the Low mixes with other Lows upstream swirling around the increasingly deep upper low heights over North-Eastern Canada towards 240 hours

 

Puts pressure on the ridge, although it has no choice but to topple East over the South-Eastern UK Low Pressure towards Scandinavia. That run though does get as messy as getting covered in a big pile of mud!

A quick look at the 850 hPa temperatures from those 3 long range models at 240 hours, and they generally get some colder 850 hPa temperatures in over the UK

18Z GFS

12Z ECMWF

12Z GEM

Not mind-blowing, but too far out to pay much attention to. Yep, tis a shame they’re not colder. Considering it would have been staying cool to cold over the UK, especially across the North, they’re adequate. And provides some better chances of wintry weather.

The 12Z ECMWF ensemble mean between days 8 and 10 looks impressive for cold and blocked weather.

 

A signal for the Atlantic ridge to get up to Iceland with downstream European trough. Incredible for a 10 day mean. With operational models showing variations of blocking to our North-West, then it feels like the most preferred outcome. Both the Russian and Icelandic ridging giving the Vortex a good thrashing. No signs of it yet, coming back home to Greenland. 

Same is the case on the 18Z GEFS mean at 240 hours, except with a more positively tilted ridge of slightly lower latitude in the mid-Atlantic and a bit more in the way of purples to the North of Greenland. A little less great personally than on the ECMWF ensemble mean. But in no way terrible. No menacing blue and purple monster pushed over to Greenland, which would likely fire up the Jetstream upstream keeping things flatter 

 

One issue with the means is they can obscure other scenarios where ensemble members become tightly clustered towards differing solutions against the mean. As a quick example for London though, the 18Z GEFS average 2 meter temperature graph does maintain the chilly theme (not much scatter)... albeit there’s that odd milder blip just after Christmas Day

Both the 6 to 10 and 8 to 14 day NOAA 500mb anomaly charts are similar going for chilly conditions. Upper ridge combined with higher than average heights over Russia and the mid-Atlantic. Lower than average heights with upper trough South through the UK and into mainland Europe. A tendency for the upper trough to sink a little further South on the 8 to 14 day chart. Upper flow between the North-West and North over the UK. But is rather slack so the direction the weather comes from will likely depend on the surface features, though primary direction probably being from the Northerly sector. 

 

Definitely could support a wintry mix of weather at times, not necessarily over the Northern hills. An aspect that’s making these charts interesting at the moment.

If I had to be picky, would love for the Russian High to drift into a more desired position more directly to our North or North-East orientated in a West to East position. This would then draw some deeper cold air Westwards on its Southern flank towards the UK all the way from Siberia. The way it’s positioned isn’t the best for getting some real cold air in. Is funny really, the Russian High could assist in keeping the Vortex all bruised up, but in other ways, could be a big, fat, pain. The feeling of wondering if it’s better for it to get lost. 

To be honest, though, I think the cold weather fans have a lot to be happy with at the moment. Some of the best charts in a while. Some of the deeper cold could come with time, or as some covered before, some localised cold pools could develop. This sort of slow and blocky pattern has possibilities to lead to colder and colder weather, though not impossible for blocking to eventually migrate in an undesirable place. Depending in a way how the developments up in the Stratosphere continue to behave and what affect it could have in the lower down layers. No easy feat to get deep cold over the UK. For a cold weather fan during Winter, am grateful with what is showing at the moment. To me, the Atlantic looks sleepy. While it’s not impossible for things to become more flatter (guess blocked patterns don’t last forever), doesn’t seem much chance for the mild South-Westerlies to take over. 

On the whole, great outputs to bring some joy. And quite possibly some snow ️ 

It wanting something milder, just got to hope the models are overplaying amplification in the West and the blocking signals in general. Or the meridional/blocking patterns set up unfavourably for long lasting cold. Some understandably as well might just be happy with a High Pressure dominated outlook over the UK, or a variation of different things.

Additionally, thought it was worth including this king post by @snowking below to highlight that, although 850 hPa temperatures can be important for snow, this is just a reminder that it’s not the only thing required for wintry weather with various factors to take into account

Also going to include this by knocker. Contains some further useful information for factors regarding snowfall and a link by John Holmes (included below) covering these ingredients 

Will it snow? - John Holmes

Hopefully help calm some nerves, as things were getting quite heated over the 850 hPa temperatures in the previous thread. Which, to be fair, people are entitled to their opinion on as longs as it’s related to the Models. Not constantly full of moans and snipes, and doesn’t clog up the thread.

Speaking of which, please keep it to the models and keep it friendly in here. Rude and nasty behaviour is not tolerated. You can can expect these sort of posts to vanish, like magic!

If you spot any issues like the above, please report the post rather than responding to it. We’ll get it sorted. Thanks you! 

If you're wanting to chat more generally about Winter, maybe have a ramp or moan, please head off to the Winter chat thread:

Because we understand this thread is fast paced during Winter, a little bit of off topic content in ya post is okay, especially with the pandemic about, which doesn’t make things easy at the moment. Providing however your post is still mostly related to the models. Otherwise, the thread above is better suited for general Winter chat. Seeing as it’s Christmas we’ll allow Christmas messages in here, although you could also use the regional chat threads if you like.

For discussions about the Met Office UK outlook, use this thread here:

Wanna learn more about meteorology? Please take a look at the Learning and Research area: https://www.netweather.tv/forum/learning/

Model Output And Charts On Netweather:

UKV (Extra Subscribers)

GFS

GFS Hourly

GEFS Ensembles

ECMWF

ECMWF EPS

NetWx-SR (3km)

NetWx-MR (9km)

Met Office (UKMO)

Fax

GEM

Model Comparison

Global Jetstream

Stratosphere

Previous thread:

Lastly, with the ongoing pandemic, Christmas this year could feel different to a lot people. Whether you’re spending it with family, loved ones or on your own, I hope it is still a good one being able to make the best of the situation you’re in. For those where Christmas may lack joy, I trust you’ll be able to find the light within you to glow and flourish. We’re always by your side

I would like to thank everyone for making this site a fabulous place to be. All your great contributions, humour, rollercoaster moments and such that get the machinery of Netweather running like clockwork. Sure there are those times, where threads like these descend into discourtesy, although those moments are mostly few and far between. There’d would be no community if it wasn’t for you all. So many of you bringing something magical to the site. A lot great people I would love to name, but you should be proud of yourselves  

A healthier year may the New Year bring to us all. Let it shine like a brighter star than 2020. One where we’re taken back to the pre-Covid days... only better than ever before! Lots of great weather to excite all the enthusiasts from snow, rain, sunshine, warmth, storms or what ever else that gets ya boat floating 

A warm Christmas and New Year

[A Frayed Knot]

6 minutes ago, DiagonalRedLine said:

Greetings all

A new thread for the festive period. Other thread started to slow down a bit.

With Christmas here, a lot of us weather-wise become flooded with excitement at the prospect of something cold and white. For a few, maybe you want something mild, stormy and/or dry. But what sort of weather will Santa be delivering for us I wonder?

From what the models are showing, we have chilly weather taking over from the North at the moment. Using various charts from the Netwx-SR/MR and GFS models, it shows a chilly Northerly invading the whole UK during Christmas Eve today and a toppling Atlantic High out West.

The whole UK under -5*C and colder 850 hPa temperatures. -10*C area not far off from Northern Scotland. It will be cold across Northern England and Scotland, freezing over higher ground. Pretty cold across the rest of the UK. 

Fine and dry for Central areas, maybe with an isolated shower. Otherwise showers likely down Western, Northern and Eastern Coasts. The 850 hPa temperatures and 500 to 1000mb thicknesses look supportive for showers to be wintry at times. More especially under heavier showers down the Eastern parts of the UK where the Netwx-SR model has the thicknesses as low as 520dam over parts of the Eastern Midlands and Lincolnshire. So a few flakes possible, though probably more marginal right out on the coast. 

 

The wintry mix of showers likely to continue overnight and through Christmas morning down some Eastern UK coasts. Dry and clearer everywhere else, perhaps the odd isolated shower or two down Western UK coasts. A bitter night and morning to come with frost for most places away from Eastern and Western coasts. Little less cold over Western Ireland.

Christmas Day will be another chilly day with some morning frost, which may persist for a while over Northern high ground areas and places sheltered from the Westerly winds. The  Atlantic High/ridge gets shunted back South-West to allow the Westerly flow to take over from the Atlantic. 

 

Few odd wintry showers may continue over some Eastern coasts. Most Eastern, Central and Southern parts staying fine and bright though. Could get some nice walks in. Some cloudy, windy and wet conditions will spill into the North-West of the UK later into the day. Wintry over the Scottish hills 

A less colder night compared to Christmas Eve/Christmas morning with some showers and rain over Western and North-Western areas. Heavier rain pushing into Western Scotland Boxing Day morning. Cold over South-Eastern areas of the UK with some frost possible.

 

Boxing Day looks unsettled as Low Pressure over Iceland drives a blustery Westerly flow over the UK. You will also see that the Azores High is re-amplifying out West, which leads to some compelling outcomes for cold weather fans further down the line. There will be showers and longer spells of rain for many places, which could be heavy at times. Perhaps drier towards the far North-East of the UK. Fairly mild over Southern areas, but cooler under the heavier areas of rain I’d imagine. Bit chillier further North where the rain is likely to fall as sleet or snow over some of the taller hills

 

Sunday 27th December sees the Atlantic ridge to our West becoming Highly amplified. The upper heights from this extending North-West through Greenland connecting with the ridge over the Siberia area. This sends the upper and surface Low South-East over the UK. We see a split in the Troposphere Vortex over the Northern Hemisphere. 

It will be a chilly day with further rain and showers circulating around the Low Pressure over the UK. South-Eastern areas clinging onto milder temperatures at first as some heavy rain via cold front clears South-East over that area. The rain and showers over the UK could become wintry on high ground, although with such low upper heights accompanying the deep Low Pressure, there could be some sleety precipitation down to lower levels. Particularly under heavy showers, and more so over Western and Northern areas where the Low wraps some colder 850 hPa temperatures from the North-West, South-Eastwards through Western UK

 

Some little changes to the details are possible over the next few days as to where and how wintry precipitation could be. This is just a general idea of what to expect. Some of this coming down to nowcasting. In fact, even on Sunday the exact depth of the Low and where the centre of it goes is not full-on settled yet. What looks certain is an amplified area of High Pressure over the Atlantic and a deep upper trough sent South over the UK

Looking at the Jetstream chart for Sunday on the latest GFS 18Z run would support the above scenario. Buckles and amplifies upstream in the mid and Western Northern Atlantic. Help to steer weather systems from the North-West down towards us

 

Onto 120 hours (Monday midday), the various 12Z operational runs while there are differences to some details, keep the Atlantic ridging rather strong to our West and Low Pressure over the UK.

12Z GFS



12Z UKMO

12Z ECMWF

12Z ICON

12Z GEM

In terms of that Atlantic ridge, the GEM seems the strongest. The upper ridging pushing the furthest North over Southern Greenland. The Low to the West of it in slightly of a less hurry to run over the ridge.

One thing that caught my eye, however, is the GFS is the most keen to try sink that upper UK trough to our South through Monday. Same is true on the latest 18Z GFS run for Monday below, so being quite consistent with this situation 

Other models above have the deep Low and upper trough more directly placed over the whole UK. ICON not too far off from the GFS in that it has the centre of the Low over South/South-Western UK. A variation in the shape of the surface and upper trough on the operational models above. Going for quite a stretch on the UKMO. Stretchy Lows tending to be better than rounded ones for wintry weather. The further South and East they also go, the better for pulling in a colder flow from the North and East.

With the way things are, there is a lack of particularly cold 850 hPa temperatures over the UK, despite the impressive setup. I think the issue is, the UK Low combined with the Russian block to our East is drawing up some milder 850 hPa Northwards through South-Eastern Europe and towards Scandinavia, meaning not much proper cold to tap into in that direction. This does vary a bit depending on the shape and position of the UK Low above at 120 hours. A little shift further East of Low Pressure at that time-frame, could mean dragging in some of the colder 850 hPa temperatures down from the North around Iceland. 

However, it’s not worth getting too nail-bitey over the 850 hPa temperatures. Plus it’s not like both Scandinavia and the UK, for example, are under positive 850 hPa temperatures. Depending on where the actual position and track the Low ends up, anywhere could see some rain, sleet or hill snow. There will likely be a wintry mix of showers about too away from the longer spells of wintry weather considering how unstable the air is. And with the upper 500mb heights being very low, this could drag colder air down to lower levels pushing the snow line down. Helped by precipitation being heavy to encourage evaporative cooling and the flow being slack. Which the outlook for Monday has real possibilities of doing since the Low Pressure, except perhaps away from the centre of it doesn’t look all that ‘stormy’. For snow, deep cold is not essential. It can help, but can get by without it. Sure though it would be nice to tap into some proper cold at some point. Some deeper cold quite easily be possible thanks to the blocked setups the models are currently showing. 

Would say the GFS is mostly on its own with the speed it sinks the trough on Monday, making me wonder if it’s being too quick with that evolution. Will see I guess. 

Further on towards 168 hours, the 18Z GFS, 12Z ECMWF and 12Z GEM, in that order below, continue with ridging in the mid-Atlantic. Between 120 and 168 hours, some Low Pressure tried to run over the top of the Atlantic ridging over Western Greenland attempting to somewhat knock it down South to our West. But struggled to make much impact. You can see there is, in varying forms, a pokey Low/shortwave over Iceland looking to swing South-East down towards the UK. Along with Low Pressure reasonably far enough West over the Newfound area to allow a good gap for the amplified Atlantic ridge to gain more Northwards latitude

Have highlighted on the GFS the usefulness of having separation between the UK/Eastern UK Lows and the ones to the West of that ridging

Too much of that Low Pressure riding over the top of the Atlantic ridge could flatten it, even though events downstream would likely prevent that ridge getting over to mainland Europe. And it’s not impossible for a North-West to South-East Jetstream to continue towards the UK. It does seem unlikely for it to run over the top. Models haven’t be that keen for that to happen. Not impossible, mind.

Both the ECMWF and GEM from 192 to 240 hours stretch that Newfoundland Low throwing up warm air Northwards towards South and Western Greenland and then drop the Low South into the Atlantic. At the same time Low Pressure to our North-West drops over (12Z GEM), or to the East of (12Z ECMWF), the UK. This forms some strong blocking to our North-West. GEM trying to build a cut off Greenland High while the ECMWF has more of a Western Icelandic one. The poor Icelandic ridge gets a big poke from the Northern Iceland Low at 240 hours on the ECMWF

12Z ECMWF

12Z GEM

The 18Z GFS, while it does try to get some ridging going over Greenland, has that Low further upstream exhibiting some different behaviour. Part of it does split against the Atlantic to Southern Greenland ridging - a small shallow area dropping South into the Atlantic with ridging building over the top. That little shallow part getting cut off. But a fair chunk of the Low mixes with other Lows upstream swirling around the increasingly deep upper low heights over North-Eastern Canada towards 240 hours

 

Puts pressure on the ridge, although it has no choice but to topple East over the South-Eastern UK Low Pressure towards Scandinavia. That run though does get as messy as getting covered in a big pile of mud!

A quick look at the 850 hPa temperatures from those 3 long range models at 240 hours, and they generally get some colder 850 hPa temperatures in over the UK

18Z GFS

12Z ECMWF

12Z GEM

Not mind-blowing, but too far out to pay much attention to. Yep, tis a shame they’re not colder. Considering it would have been staying cool to cold over the UK, especially across the North, they’re adequate. And provides some better chances of wintry weather.

The 12Z ECMWF ensemble mean between days 8 and 10 looks impressive for cold and blocked weather.

 

A signal for the Atlantic ridge to get up to Iceland with downstream European trough. Incredible for a 10 day mean. With operational models showing variations of blocking to our North-West, then it feels like the most preferred outcome. Both the Russian and Icelandic ridging giving the Vortex a good thrashing. No signs of it yet, coming back home to Greenland. 

Same is the case on the 18Z GEFS mean at 240 hours, except with a more positively tilted ridge of slightly lower latitude in the mid-Atlantic and a bit more in the way of purples to the North of Greenland. A little less great personally than on the ECMWF ensemble mean. But in no way terrible. No menacing blue and purple monster pushed over to Greenland, which would likely fire up the Jetstream upstream keeping things flatter 

 

One issue with the means is they can obscure other scenarios where ensemble members become tightly clustered towards differing solutions against the mean. As a quick example for London though, the 18Z GEFS average 2 meter temperature graph does maintain the chilly theme (not much scatter)... albeit there’s that odd milder blip just after Christmas Day

Both the 6 to 10 and 8 to 14 day NOAA 500mb anomaly charts are similar going for chilly conditions. Upper ridge combined with higher than average heights over Russia and the mid-Atlantic. Lower than average heights with upper trough South through the UK and into mainland Europe. A tendency for the upper trough to sink a little further South on the 8 to 14 day chart. Upper flow between the North-West and North over the UK. But is rather slack so the direction the weather comes from will likely depend on the surface features, though primary direction probably being from the Northerly sector. 

 

Definitely could support a wintry mix of weather at times, not necessarily over the Northern hills. An aspect that’s making these charts interesting at the moment.

If I had to be picky, would love for the Russian High to drift into a more desired position more directly to our North or North-East orientated in a West to East position. This would then draw some deeper cold air Westwards on its Southern flank towards the UK all the way from Siberia. The way it’s positioned isn’t the best for getting some real cold air in. Is funny really, the Russian High could assist in keeping the Vortex all bruised up, but in other ways, could be a big, fat, pain. The feeling of wondering if it’s better for it to get lost. 

To be honest, though, I think the cold weather fans have a lot to be happy with at the moment. Some of the best charts in a while. Some of the deeper cold could come with time, or as some covered before, some localised cold pools could develop. This sort of slow and blocky pattern has possibilities to lead to colder and colder weather, though not impossible for blocking to eventually migrate in an undesirable place. Depending in a way how the developments up in the Stratosphere continue to behave and what affect it could have in the lower down layers. No easy feat to get deep cold over the UK. For a cold weather fan during Winter, am grateful with what is showing at the moment. To me, the Atlantic looks sleepy. While it’s not impossible for things to become more flatter (guess blocked patterns don’t last forever), doesn’t seem much chance for the mild South-Westerlies to take over. 

On the whole, great outputs to bring some joy. And quite possibly some snow ️ 

It wanting something milder, just got to hope the models are overplaying amplification in the West and the blocking signals in general. Or the meridional/blocking patterns set up unfavourably for long lasting cold. Some understandably as well might just be happy with a High Pressure dominated outlook over the UK, or a variation of different things.

Additionally, thought it was worth including this king post by @snowking below to highlight that, although 850 hPa temperatures can be important for snow, this is just a reminder that it’s not the only thing required for wintry weather with various factors to take into account

Also going to include this by knocker. Contains some further useful information for factors regarding snowfall and a link by John Holmes (included below) covering these ingredients 

Will it snow? - John Holmes

Hopefully help calm some nerves, as things were getting quite heated over the 850 hPa temperatures in the previous thread. Which, to be fair, people are entitled to their opinion on as longs as it’s related to the Models. Not constantly full of moans and snipes, and doesn’t clog up the thread.

Speaking of which, please keep it to the models and keep it friendly in here. Rude and nasty behaviour is not tolerated. You can can expect these sort of posts to vanish, like magic!

If you spot any issues like the above, please report the post rather than responding to it. We’ll get it sorted. Thanks you! 

If you're wanting to chat more generally about Winter, maybe have a ramp or moan, please head off to the Winter chat thread:

Because we understand this thread is fast paced during Winter, a little bit of off topic content in ya post is okay, especially with the pandemic about, which doesn’t make things easy at the moment. Providing however your post is still mostly related to the models. Otherwise, the thread above is better suited for general Winter chat. Seeing as it’s Christmas we’ll allow Christmas messages in here, although you could also use the regional chat threads if you like.

For discussions about the Met Office UK outlook, use this thread here:

Wanna learn more about meteorology? Please take a look at the Learning and Research area: https://www.netweather.tv/forum/learning/

Model Output And Charts On Netweather:

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GFS Hourly

GEFS Ensembles

ECMWF

ECMWF EPS

NetWx-SR (3km)

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Fax

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Model Comparison

Global Jetstream

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Previous thread:

Lastly, with the ongoing pandemic, Christmas this year could feel different to a lot people. Whether you’re spending it with family, loved ones or on your own, I hope it is still a good one being able to make the best of the situation you’re in. For those where Christmas may lack joy, I trust you’ll be able to find the light within you to glow and flourish. We’re always by your side

I would like to thank everyone for making this site a fabulous place to be. All your great contributions, humour, rollercoaster moments and such that get the machinery of Netweather running like clockwork. Sure there are those times, where threads like these descend into discourtesy, although those moments are mostly few and far between. There’d would be no community if it wasn’t for you all. So many of you bringing something magical to the site. A lot great people I would love to name, but you should be proud of yourselves  

A healthier year may the New Year bring to us all. Let it shine like a brighter star than 2020. One where we’re taken back to the pre-Covid days... only better than ever before! Lots of great weather to excite all the enthusiasts from snow, rain, sunshine, warmth, storms or what ever else that gets ya boat floating 

A warm Christmas and New Year

Nicely posted, long strolling though on a phone but well illustrated. Hate using my phone. 

[Zak M]

@DiagonalRedLine

One word... WOW. What a post!!

I would have thought it took you a ton of time writing that and it was certainly worth it! Thank you so much to you and everyone else that takes the time out of their day to post to this site.

As it's almost 3am, and I'm one of the few people browsing Netweather at this time... I decided to look at the models for something to post - so the first model I looked at was the JMA. After viewing the whole run, I didn't decide to look at the other models any further!

   

A ton of people would be happy if this came off. It's certainly what we need in these difficult times!

Have a great Christmas and New Year lads. All the best. 

Edited December 24, 2020 by Zak M

[Allseasons-Si]

Before i go to noddyland,what a fabulous opening to start a new thread @DiagonalRedLine,bravo

things are starting to look up for a potential cold spell,and not a cold snap,how long it will last,who knows but certainly over the next week or so somewhere i would of thought would get a dumping of snow starting as early as the 27th-28th

i am off for now and i will catch you lot in the morning for another bout of model roller-coaster rides

the 18z gefs ens for my local and for London,they look good don't they and to be honest there isn't much between them

take care everyone. 

 

[Dave Kightley]

The low maybe slightly further west compared to 18z and up to 171h looks better around Greenland  

[Dave Kightley]

I dunno but I think it is better upto 195 h around Greenland though less cold uppers around in comparison.. should be happy about the first part 

[Dave Kightley]

210 hours build of heights to the South West building north towards the Block.. I dunno if that is a good thing. Very good I hope!!!! That is nerve racking.. 

hmmm looks good up to 275 abit to far east maybe.. way different to 18z so no doubt will change again.

 

that low to the South west goes more Ne when more high pressure joins up with Greenland then North and then NWly..getting  pushed around quite easily that low like a wave crashing through lol

Edited December 24, 2020 by Dave Kightley

[Radiating Dendrite]

Looking like being a fantastic run.

Initially cold and cyclonic (could be a lot of snow for some places). Then we get a griceland high > Omega Block, similar to recent mean charts, with a cold NE looking likely to set up past +300.

Yum yum  

[Dave Kightley]

That low over the Atlantic is going Nw or W direction... unusual.. not helping the block go the direction we want! The way that low has behaved I am not taking the run that seriously from the start looks funny to watch from 200h

Edited December 24, 2020 by Dave Kightley

[Griff]

2 minutes ago, Radiating Dendrite said:

Looking like being a fantastic run.

Initially cold and cyclonic (could be a lot of snow for some places). Then we get a griceland high > Omega Block, similar to recent mean charts, with a cold NE looking likely to set up past +300.

Yum yum  

Interesting, seems to be further towards a shift west initially with the low at the start of next week not as elongated. To my eye the earlier opportunities for snow seemed to have diminished a little, a sacrifice as you say that actually improves the outlook in deepest darkest FI for some eye catching charts. 

I think temperature and precipitation for Monday are still questionable, beyond that the signal remains but yet another example of the uncertainty and how potentially marginal this could be. 

Not looking beyond 180, just for fun...

These will catch people's attention regarding the 'mashing' of the spv. 

I mentioned last night that blocking according to many yesterday across the pond is strongly signalled towards Greenland, and these would lend support to that. 

 

[Griff]

I should add moving forwards the majority of the purple is moving over the Arctic, which I've been told is potentially excellent for our winter prospects, as opposed to over Canada and continental North America. 

[SLEETY]

Think Greenland high will be the big player eventually, with the trough and bitter uppers dropping down over Scandinavia and hopefully towards the UK, the gfs was close to that in this run, until the very end. Very interesting model watching in the days ahead 

[Griff]

10 minutes ago, SLEETY said:

Think Greenland high will be the big player eventually, with the trough and bitter uppers dropping down over Scandinavia and hopefully towards the UK, the gfs was close to that in this run, until the very end. Very interesting model watching in the days ahead 

I wouldn't dream of, but there might be some here that comment that everything keeps shifting a bit into the distance...  

[Dave Kightley]

fI is actually more interesting going from 382 hours to 300 hours..on the 500 height charts.. check it out before you know it is going backwards!

Edited December 24, 2020 by Dave Kightley

[Ali1977]

Morning everyone, I took a few days in the hope that good looking FI charts would make it into the reliable and they certainly have. What a great period of model watching coming up, hopefully you don’t get in too much trouble having a quick peek on Xmas day rather than opening presents etc...

Day 10 GFS is a belter , I think a prolonged cold spell is nailed on with the potential for it to be substantially long. Nothing mJor cold modelled yet but that’s only a matter of time.

Merry Christmas to everyone

[Griff]

1 minute ago, Ali1977 said:

Morning everyone, I took a few days in the hope that good looking FI charts would make it into the reliable and they certainly have. What a great period of model watching coming up, hopefully you don’t get in too much trouble having a quick peek on Xmas day rather than opening presents etc...

Day 10 GFS is a belter , I think a prolonged cold spell is nailed on with the potential for it to be substantially long. Nothing mJor cold modelled yet but that’s only a matter of time.

Merry Christmas to everyone

Yes, my thoughts too. Colder but not a big freeze initially. Are we looking at a belated post new year party? 

[SLEETY]

Think start of next year is when the really cold weather will begin, this is just the starter incoming.! 

[drm]

12 minutes ago, Griff said:

Yes, my thoughts too. Colder but not a big freeze initially. Are we looking at a belated post new year party? 

Definitely looking like a January of much interest ahead ,a dusting of snow in Aberdeen and snowing as I type

[Ravelin]

2 hours ago, Allseasons-si said:

certainly over the next week or so somewhere i would of thought would get a dumping of snow starting as early as the 27th-28th

As @drmjust indicated, NE Scotland has had snow overnight. Its a bit dark to tell exactly but I'd say I have a couple of cm at least lying outside, so if that's  "dumping" we've got it in early. Should manage to lie through to tomorrow so a white Xmas for us, even if not technically one. 

[That ECM]

T120 for all 3. Similar

[Griff]

1 minute ago, That ECM said:

T120 for all 3. Similar

 

[Weather-history]

Northern hemisphere on GEM 0z op run at the start of New Year. Haven't seen a chart like this at the start of a new year for some time, the lack of blues and purples on our side.

 

 

 

 

[Captain Shortwave]

ECM wins the “Please circle the U.K.” competition

very low heights, slack flow across most of the U.K. and 850s of -3/4c. A lot of good ingredients there for snow to reach low levels. Beyond that, increasing confidence of getting into a better position longer term with consistency across the board of a high latitudes block forming in the very north of the Atlantic.

[That ECM]

2 minutes ago, Captain Shortwave said:

ECM wins the “Please circle the U.K.” competition

very low heights, slack flow across most of the U.K. and 850s of -3/4c. A lot of good ingredients there for snow to reach low levels. Beyond that, increasing confidence of getting into a better position longer term with consistency across the board of a high latitudes block forming in the very north of the Atlantic.

Indeed. That not a bad at T192.

[swfc]

5 minutes ago, That ECM said:

Indeed. That not a bad at T192.

Morning. Yes it's OK but a bit to far west imo. Bit of a throw of the dice going further into fi. Shows how good the projected charts have been recently when this is a slight downgrade. That said it's still fluid and has the output gets nearer tends to moderate.