Nick F

No point squabbling over how dry it will be, too far away to pin down where troughs, convergence zones or lows will track next week that may bring snow I think the key to the longevity of next weeks cold spell will be how long the TPVs over Canada and N/NE Europe are kept apart by ridging mid-N Atlantic and Greenland. GFS/GEM ops are more bullish to merge to 2 TPVs over the Atlantic later next week, turning the flow more zonal / milder / unsettled. While EC det keeps the two upper vortices apart. However, as already posted, the mean of both GEFS and EPS do join the two together by day 10, with the more zonal look taking over. But the smoothed out mean may not be the best guidance at handling upstream developments and how the upper flow and surface lows over the Atlantic interacts with the cold air entrenched over northern Europe Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5006538

Looking at the extended EPS spread, the 00z det was on the cold side later on but by no means without support, the TWO and meteociel graph makes it look like an outlier, but it's not really on the wetterzentrale spread. The mean does rise though towards day 10 and after, so we have to assume, for now, that it will turn milder after next week for a time, as the Canadian and north European TPV lobes merge to cover the far N Atlantic in low heights driving a more westerly flow. This ties in with background larger scale teleconnections e.g. MJO motoring through 'warmer' phases at decent amplitude. Still a decent spike in precipitation for Weds 17th on London EPS, so still suggest a good chance of precip and likely snow with the T850 mean below 0C, in 1st chart posted above. Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5006604

00z UKMO 'current laying snow' chart animated through next week until Thursday suggests northern areas look to see greatest chance of laying snow, probably from that low that forms near Iceland and drops SE and also from showers, but also a chance in the southeast as one or two lows track east close to the south. Although it's too far off to forecast snow for now, seems a reasonable assumption, for now, to think Scotland, N England and N Ireland stand to see greatest chance of snow, lower chances further south, unless the Atlantic lows track further north, but the low from the southwest more likely ending up further south into France. Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5006567

Looking at the extended EPS spread, the 00z det was on the cold side later on but by no means without support, the TWO and meteociel graph makes it look like an outlier, but it's not really on the wetterzentrale spread. The mean does rise though towards day 10 and after, so we have to assume, for now, that it will turn milder after next week for a time, as the Canadian and north European TPV lobes merge to cover the far N Atlantic in low heights driving a more westerly flow. This ties in with background larger scale teleconnections e.g. MJO motoring through 'warmer' phases at decent amplitude. Still a decent spike in precipitation for Weds 17th on London EPS, so still suggest a good chance of precip and likely snow with the T850 mean below 0C, in 1st chart posted above.

00z UKMO 'current laying snow' chart animated through next week until Thursday suggests northern areas look to see greatest chance of laying snow, probably from that low that forms near Iceland and drops SE and also from showers, but also a chance in the southeast as one or two lows track east close to the south. Although it's too far off to forecast snow for now, seems a reasonable assumption, for now, to think Scotland, N England and N Ireland stand to see greatest chance of snow, lower chances further south, unless the Atlantic lows track further north, but the low from the southwest more likely ending up further south into France.

No point squabbling over how dry it will be, too far away to pin down where troughs, convergence zones or lows will track next week that may bring snow I think the key to the longevity of next weeks cold spell will be how long the TPVs over Canada and N/NE Europe are kept apart by ridging mid-N Atlantic and Greenland. GFS/GEM ops are more bullish to merge to 2 TPVs over the Atlantic later next week, turning the flow more zonal / milder / unsettled. While EC det keeps the two upper vortices apart. However, as already posted, the mean of both GEFS and EPS do join the two together by day 10, with the more zonal look taking over. But the smoothed out mean may not be the best guidance at handling upstream developments and how the upper flow and surface lows over the Atlantic interacts with the cold air entrenched over northern Europe

Morning. Great EC det this morning, cold throughout and ends with a cold high. Snow event for central Scotland on Tuesday as that secondary low that develops in the polar flow near Iceland drops southeast. Then another potential snow event across the far south mid-week, as an Atlantic low tracks east, but still uncertainty over its track for now. UKMO looks really good too up to Thursday, looks like a cold NE flow developing after then. GFS looks rather too bullish to turn it mobile, unsettled and milder off the Atlantic. GEM looks like it goes down a similar turning mobile / milder route to GFS Stick with the Euros IMO. Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5006453

Potential for 2 lows tracking east close to southern Britain Weds and Thurs/Fri, but they may end up tracking further south into France on current trends, so could end up dry for much of next week for England and Wales, though Scotland, N. Ireland and N England could see a snow event early week plus snow showers in the north and coasts.

Morning. Great EC det this morning, cold throughout and ends with a cold high. Snow event for central Scotland on Tuesday as that secondary low that develops in the polar flow near Iceland drops southeast. Then another potential snow event across the far south mid-week, as an Atlantic low tracks east, but still uncertainty over its track for now. UKMO looks really good too up to Thursday, looks like a cold NE flow developing after then. GFS looks rather too bullish to turn it mobile, unsettled and milder off the Atlantic. GEM looks like it goes down a similar turning mobile / milder route to GFS Stick with the Euros IMO.

The difference between GFS vs UKMO and ICON are quite stark at t+144, so probably not worth fretting over mild vs cold boundary snow events next week at the moment. Best not over analysing beyond 6 days IMO. T+144 GFS T+144 UKMO and ICON UKMO and ICON similar in having the straight northerly that digs further south, a stronger mid-Atlantic ridge north and east of the Azores low, which is kept more at bay and thus doesn't phase with the N / NE European trough. Not sure who my money's on until the EC comes out though ... but suspect GFS maybe a tad too progressive with upper flow energy over the N Atlantic, particularly as it's pretty much a cut off low near the Azores that tend to be a sign of a weakening jet that disrupts. 12z GEM does follow a similar route to GFS, which makes me a little nervous to call UKMO and ICON more likely correct for now, but could it be the great N American wx models vs European wx models battle this evening? Original post: https://community.netweather.tv/topic/99706-model-output-discussion-into-2024/?do=findComment&comment=5003476

The difference between GFS vs UKMO and ICON are quite stark at t+144, so probably not worth fretting over mild vs cold boundary snow events next week at the moment. Best not over analysing beyond 6 days IMO. T+144 GFS T+144 UKMO and ICON UKMO and ICON similar in having the straight northerly that digs further south, a stronger mid-Atlantic ridge north and east of the Azores low, which is kept more at bay and thus doesn't phase with the N / NE European trough. Not sure who my money's on until the EC comes out though ... but suspect GFS maybe a tad too progressive with upper flow energy over the N Atlantic, particularly as it's pretty much a cut off low near the Azores that tend to be a sign of a weakening jet that disrupts. 12z GEM does follow a similar route to GFS, which makes me a little nervous to call UKMO and ICON more likely correct for now, but could it be the great N American wx models vs European wx models battle this evening?

Morning. Now the models seem to be settling on the cold northerly next week, thought I might start to post some thoughts. 00z GFS looks a bit too bullish with the Atlantic encroachment from the SW next week, also it blows up a low south of Iceland early next week which phases with the Atlantic low system to the south - which the other models don't have. Be interesting how well the models handle how far the south the deep cold gets and how far north milder air gets - the boundary bringing a high risk / high reward of heavy snow or rain wherever it sets up. Lots for the models to resolve next week, but think the 00z GFS looks a little too bullish with the Atlantic push, has a habit of blowing up lows too much. Original post: https://community.netweather.tv/topic/99706-model-output-discussion-into-2024/?do=findComment&comment=5002793

Morning. Now the models seem to be settling on the cold northerly next week, thought I might start to post some thoughts. 00z GFS looks a bit too bullish with the Atlantic encroachment from the SW next week, also it blows up a low south of Iceland early next week which phases with the Atlantic low system to the south - which the other models don't have. Be interesting how well the models handle how far the south the deep cold gets and how far north milder air gets - the boundary bringing a high risk / high reward of heavy snow or rain wherever it sets up. Lots for the models to resolve next week, but think the 00z GFS looks a little too bullish with the Atlantic push, has a habit of blowing up lows too much.

Certainly the models are beginning to converge on the idea of a few snow shower streamers setting up Monday PM. EC, ICON and Arpege below for Monday early evening: ICON T850s Not only because a pool of deeper cold moves through but also likely to do with breeze convergence creating lift. These convergence zones marked on the wind map below

The ridge butting in across Iberia in response to low over Azores bit of a concern - really need to see lows track east from the Azores into western Med, otherwise the deep cold coming south next weekend could be stalled across the north or worse. But still so much to resolve over the Atlantic this far out, so alarm bells not ringing yet. Original post: https://community.netweather.tv/topic/99706-model-output-discussion-into-2024/?do=findComment&comment=4998056

The ridge butting in across Iberia in response to low over Azores bit of a concern - really need to see lows track east from the Azores into western Med, otherwise the deep cold coming south next weekend could be stalled across the north or worse. But still so much to resolve over the Atlantic this far out, so alarm bells not ringing yet.

Well, it's low pressure in general over Norway pulling down the deep cold air, not really a shortwave issue, though disturbances in the northerly flow could bring a few surprises. Too far away to discuss that though, lets get the deep cold to arrive first!

Day later than ICON, but the Troll from Trondheim arrives in Scotland on 12z GFS. GEM quicker than GFS too.

Looks like there could be a chance of snow showers Monday evening / night, as a cold pool moves west and some wind convergence develops to provide lift. 3 different models

From the Met Office app 14 day outlook, make see a few flakes with the easterly ...

06z GFS highlights what may happen if there isn't sufficient undercut of troughing beneath the block, to keep it at a decent latitude to keep the cold air advection going. Without the undercut the high just sinks back south. Not saying this more likely to happen, but this lack of energy going underneath blocks often a stumbling block in trying to get sustained cold air advection from the east or northeast in winters these days. Original post: https://community.netweather.tv/topic/99706-model-output-discussion-into-2024/?do=findComment&comment=4996142

06z GFS highlights what may happen if there isn't sufficient undercut of troughing beneath the block, to keep it at a decent latitude to keep the cold air advection going. Without the undercut the high just sinks back south. Not saying this more likely to happen, but this lack of energy going underneath blocks often a stumbling block in trying to get sustained cold air advection from the east or northeast in winters these days.

Didn't this happen in December 2022? Big Greeny block modelled initially with bitter NE'ly flow and everyone got excited, then it vanished into thin air and we got the Atlantic in instead. But still too early to be worrying about this possibility. But there is a risk the block drifts too far west or weakens to the NW.

It's like children in a candy shop who've been told by the owner they can help themselves to as many sweets as they want in here. Sugar rush over day 10+ charts showing deep cold and snow. Maybe after watching and discussing the models for 20+ years I've got a bit weary of the excitement of cold and snowy nirvana past day 7. I'll join in when it's still showing below 7 days. Original post: https://community.netweather.tv/topic/99706-model-output-discussion-into-2024/?do=findComment&comment=4994977

Not for now, we have a lot of consistency from models and their ensemble guidance which is a plus, but been burnt too many times at that range!