johnholmes

Dry and fairly cloudy with a temperature currently of 2.3 C; it dropped to 0.1 C with ground frost 0300-0400

Not got time to post the full set of charts I use but they are along similar lines to yesterday. So deepish cold to start next week before the upper flow on NOAA and ECMWF turns more westerly cutting off the deep cold. Also borne out by UK met at 144h. Just where snow will fall and settle still seems uncertain but the low shown on Met Fx charts is the system that is the cause so watch how UK Met deal with it over the next 3-4 days and their forecasts/warnings for where snow is most likely. Certainly looks to become less cold/milder into next weekend I feel. ps obviously coastal areas from Monday into perhaps Wednesday are likely to see coastal snow showers, with a small risk of these being more extensive on any troughs that form, little advance warning of these, say 6-12 hours at most. Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5010067

Not got time to post the full set of charts I use but they are along similar lines to yesterday. So deepish cold to start next week before the upper flow on NOAA and ECMWF turns more westerly cutting off the deep cold. Also borne out by UK met at 144h. Just where snow will fall and settle still seems uncertain but the low shown on Met Fx charts is the system that is the cause so watch how UK Met deal with it over the next 3-4 days and their forecasts/warnings for where snow is most likely. Certainly looks to become less cold/milder into next weekend I feel. ps obviously coastal areas from Monday into perhaps Wednesday are likely to see coastal snow showers, with a small risk of these being more extensive on any troughs that form, little advance warning of these, say 6-12 hours at most.

Almost totally clear sky for a change, white ground frost with a low of 0.6 C

Cloudy with 0.2 mm since midnight, current low is 4.6 C; seeing the sun will be a plus whenever that happens!

Thursday same charts The NOAA chart now shows all contours into UK are from a westerly point but also still from a cold source, (NW Canada/Alaska) and about 528 DM maybe just above.The upper trough has moved west, from between Iceland and nw Scotland to be nearer Iceland. There is little indication of any troughing into Europe for the third chart in succession. ECMWF just looking at the -5 C 850 MB line, (period 17-21 Jan) starts S Wales to the Thames and ends up over the northern tip of Scotland, with a general WNW 500 MB flow from the initial N’ly Finally the T+144 to 168h Met O upper air and surface charts, (15-17 Jan) show the upper ttrough extending to some extent into southern Europe but not as sharp as the issue I showed on Tuesday a N’ly on the first day changing to a deepish surface feature with a SW;ly flow for all but the far north of Scotland by the end (17 th=Wednesday) So what can we suggest for the surface weather in the 6-10 day and then the 8-14 period some of these charts cover? Deepish cold to start by the end of this weekend over pretty much all of the UK. Dry for most but mini troughs are quite possible in the N’ly (they do often feature in these flows), a few snow showers around coasts early next week, enhanced over any area affected by a trough. There is a probability of the low shown on the Met O T+144 of spreading some snow into areas, say Midlands south possibly turning to rain in the SW. How far north this gets is difficult to suggest and best to wait to see how the synoptic models deal with it, by Sunday this should be getting clearer! The fact that NOAA charts show a westerly by the end of the 6-10 day period coupled with this being shown on the 8-14 (this is the third consecutive such chart,) does suggest to me a more unsettled and rather cold westerly with lows eventually succeeding in moving less cold air, perhaps only temporarily in the 10-14 day period. Beyond that, not for these charts Climate Prediction Center - 6-10 Day 500mb Outlook WWW.CPC.NCEP.NOAA.GOV Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5006868

Thursday same charts The NOAA chart now shows all contours into UK are from a westerly point but also still from a cold source, (NW Canada/Alaska) and about 528 DM maybe just above.The upper trough has moved west, from between Iceland and nw Scotland to be nearer Iceland. There is little indication of any troughing into Europe for the third chart in succession. ECMWF just looking at the -5 C 850 MB line, (period 17-21 Jan) starts S Wales to the Thames and ends up over the northern tip of Scotland, with a general WNW 500 MB flow from the initial N’ly Finally the T+144 to 168h Met O upper air and surface charts, (15-17 Jan) show the upper ttrough extending to some extent into southern Europe but not as sharp as the issue I showed on Tuesday a N’ly on the first day changing to a deepish surface feature with a SW;ly flow for all but the far north of Scotland by the end (17 th=Wednesday) So what can we suggest for the surface weather in the 6-10 day and then the 8-14 period some of these charts cover? Deepish cold to start by the end of this weekend over pretty much all of the UK. Dry for most but mini troughs are quite possible in the N’ly (they do often feature in these flows), a few snow showers around coasts early next week, enhanced over any area affected by a trough. There is a probability of the low shown on the Met O T+144 of spreading some snow into areas, say Midlands south possibly turning to rain in the SW. How far north this gets is difficult to suggest and best to wait to see how the synoptic models deal with it, by Sunday this should be getting clearer! The fact that NOAA charts show a westerly by the end of the 6-10 day period coupled with this being shown on the 8-14 (this is the third consecutive such chart,) does suggest to me a more unsettled and rather cold westerly with lows eventually succeeding in moving less cold air, perhaps only temporarily in the 10-14 day period. Beyond that, not for these charts Climate Prediction Center - 6-10 Day 500mb Outlook WWW.CPC.NCEP.NOAA.GOV

Max balloon data is 00Z and 12Z Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5005196

Found this about weather balloons; certainly in my time world-wide ascents main times were 00 and 12Z for all data including balloons. Currently, the global radiosonde network includes about 900 upper-air stations, and about two-thirds make observations twice daily (at 0000 and 1200 UTC). The network is predominantly land-based and favours the Northern Hemisphere. Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5005208

Found this about weather balloons; certainly in my time world-wide ascents main times were 00 and 12Z for all data including balloons. Currently, the global radiosonde network includes about 900 upper-air stations, and about two-thirds make observations twice daily (at 0000 and 1200 UTC). The network is predominantly land-based and favours the Northern Hemisphere.

Max balloon data is 00Z and 12Z

Is it me, perhaps I'm seeing something that is not correct? Most avid followers seem in despair after each 00z GFS run, fairly elated then after almost each 06Z and 12Z runs?

A snap answer would be possibly! Like my post mentioned I need a couple more outputs to make a definite prog

Not got time to post charts etc but 10-14 day NOAA shows a westerly into the UK, still a bit below 500 MB temperatures for UK, 6-10 shows pattern I posted yesterday. ECMWF also v slightly downgraded in its time frame, shows very slack COL situation by end of its period which is a similar time frame to 6-10 NOAA. I prefer to see 2-3 charts being consistent before making any forecasts.

dry with mainly large amounts of CuSc after 1 or 2 light rain showers; 0.4 mm since midnight; current low is 2.3 C

no ppn forecast of snow is accurate even at short times scales. Not that different to the summer forecasts of rain if you look back. How often even at T+24 or less was the ppn not in the right place/not the correct intensity etc. With snow there are further 7 or 8 parameters to consider! Original post: https://community.netweather.tv/topic/99706-model-output-discussion-into-2024/?do=findComment&comment=5003580

no ppn forecast of snow is accurate even at short times scales. Not that different to the summer forecasts of rain if you look back. How often even at T+24 or less was the ppn not in the right place/not the correct intensity etc. With snow there are further 7 or 8 parameters to consider!

UK Met rarely, as far as I am aware, rarely make use of this model for UK forecasting

First practice day for the Lauberhorn races taking place today; nice backdrop! https://www.jungfrau.ch/webcams/lauberhorn/#/

Tuesday 9 th Jan NOAA 6-10==15-19th, in other words inside the approximate date of ‘deep’ cold predicted some time ago.the 6-10 chart keeps the meridional flow across the chart, the shape is not the classic one but no signal for a developing mobile Atlantic, not on the 8-14 really. As usual the high +ve anomaly is much reduced but this is normal. IF this persists and the upstream becomes less conducive to another trough-ridge downstream then a change could be signalled but not so far and the 8-14 takes us to 17-23rd Jan? ECMWF has never been as +ve about the deep cold scenario and its latest output for 15-19 Jan is pretty similar. The 850’s show the -5C extending during the period to cover all of the UK by the 15th then it is moved north again so that by the 19th is is predicted be N Wales to about the Wash area. This as the 500 flow backs more west or even south of west with time. UK Met of course only shows surface and 500MB outputs for 3 days (13-15 th) but it looks to be on the same page for just prior to the two above from the 15 th. Ridge dominated both 500 and surface, over/just NW of the UK to a more trough dominated by the end of its run, again surface and upper air. So overall then, after a temporary slight warming at the surface and height, over the weekend a deeper colder spell seem likely to occur. The direction of flow, initially, being N’ly not E’ly. Looking on Extra at the skew-T diagrams, the colder air seems to start arriving over Doncaster by 14 Jan and much colder air continues to advect into the area from a N’ly direction as far as the run goes=T+180. All the time with limited convection, to around 6000 ft. So even well inland it is ‘possible’ for snow to fall. This is way ahead of any reliability from the synoptic models so patience is needed as to just what will happen over the UK regarding snowfall. Be that from showers and any possible troughs in the flow or from the Atlantic trying to move in giving more general ppn. To me it seems unlikely that milder air is unlikely to make much, if any, real progress against the cold airmass in the period under discussion on this post. All really interesting though to see just how the actual weather will turn out. Original post: https://community.netweather.tv/topic/99706-model-output-discussion-into-2024/?do=findComment&comment=5003095

Tuesday 9 th Jan NOAA 6-10==15-19th, in other words inside the approximate date of ‘deep’ cold predicted some time ago.the 6-10 chart keeps the meridional flow across the chart, the shape is not the classic one but no signal for a developing mobile Atlantic, not on the 8-14 really. As usual the high +ve anomaly is much reduced but this is normal. IF this persists and the upstream becomes less conducive to another trough-ridge downstream then a change could be signalled but not so far and the 8-14 takes us to 17-23rd Jan? ECMWF has never been as +ve about the deep cold scenario and its latest output for 15-19 Jan is pretty similar. The 850’s show the -5C extending during the period to cover all of the UK by the 15th then it is moved north again so that by the 19th is is predicted be N Wales to about the Wash area. This as the 500 flow backs more west or even south of west with time. UK Met of course only shows surface and 500MB outputs for 3 days (13-15 th) but it looks to be on the same page for just prior to the two above from the 15 th. Ridge dominated both 500 and surface, over/just NW of the UK to a more trough dominated by the end of its run, again surface and upper air. So overall then, after a temporary slight warming at the surface and height, over the weekend a deeper colder spell seem likely to occur. The direction of flow, initially, being N’ly not E’ly. Looking on Extra at the skew-T diagrams, the colder air seems to start arriving over Doncaster by 14 Jan and much colder air continues to advect into the area from a N’ly direction as far as the run goes=T+180. All the time with limited convection, to around 6000 ft. So even well inland it is ‘possible’ for snow to fall. This is way ahead of any reliability from the synoptic models so patience is needed as to just what will happen over the UK regarding snowfall. Be that from showers and any possible troughs in the flow or from the Atlantic trying to move in giving more general ppn. To me it seems unlikely that milder air is unlikely to make much, if any, real progress against the cold airmass in the period under discussion on this post. All really interesting though to see just how the actual weather will turn out.

I suppose I will be talking to myself but comparing 06 to 00 at extended distances really is a waste of time. Compare like with like and you will get a better idea of where the particular model seems to be heading. I'm in the middle of doing my usual 500MB output, will post it before long but they seem to agree with the overall outlook of cold returning over the coming weekend, but with differences in how cold. re the how far north will any low get. Almost always IF the cold has been in place for 3 days or more then the initial modelling suggesting the Atlantic pushing the ridge/cold air away is very often too quick. The direction of travel of the depression at the surface and in the 3 dimension is fairly critical and is usually only seen accurately 24-48 hours out. Even then it can be several days before there is a real breakdown into genuinely milder gets there. Original post: https://community.netweather.tv/topic/99706-model-output-discussion-into-2024/?do=findComment&comment=5003059

I suppose I will be talking to myself but comparing 06 to 00 at extended distances really is a waste of time. Compare like with like and you will get a better idea of where the particular model seems to be heading. I'm in the middle of doing my usual 500MB output, will post it before long but they seem to agree with the overall outlook of cold returning over the coming weekend, but with differences in how cold. re the how far north will any low get. Almost always IF the cold has been in place for 3 days or more then the initial modelling suggesting the Atlantic pushing the ridge/cold air away is very often too quick. The direction of travel of the depression at the surface and in the 3 dimension is fairly critical and is usually only seen accurately 24-48 hours out. Even then it can be several days before there is a real breakdown into genuinely milder gets there.

Dry with about half cover of shallow CuSc much of time, some sunshine, cold with a low of 0.9C, with what I call a 'dry' ground frost. no windscreen scraping and nil white showing on the grass.

Dry and mainly cloudy with a low of 2.0 C, no visible ground frost at all