Cambrian

Little point ducking the issue. A quacking weekend in store… 0z ECM op for day 4, as another low pressure system finds us with impressive timing! Further ahead, some more positive signs - once we start seeing this type of “super-meridional” pattern - ambitious building of heights up through the Atlantic and more spectacularly, through all the S’s - Sahara-Sweden-Svalbard-Siberia-Seguam like here at day 6 on the 0z ECM op… …it’s only a matter of time before we start seeing the trough becoming over-extended with the cutting off of the low at the base of the trough, it sinking south, the heights linking up through the UK and Ireland like here at day 8… Yes, add Skegness and Sandymount to your list, spectacular super-meridional S thing! After that, a weaker version of the trough tries to reassert itself from the northwest, which the GFS op has been keenest on, though looking at the 0z ensemble mean, the pressure never really falls away again, a steady rise to a respectable 1020mb for Birmingham by the end of week 2… …which is consistent with the ECM charts and the pincer movement of heights weakening the polar trough at its stem - so though nothing wall to wall by any means, the chance of a somewhat more promising setup emerging into early May. I’ll post again around then. All the best. Original post: https://community.netweather.tv/topic/99814-model-output-discussion-spring-has-sprung/?do=findComment&comment=5060751

Little point ducking the issue. A quacking weekend in store… 0z ECM op for day 4, as another low pressure system finds us with impressive timing! Further ahead, some more positive signs - once we start seeing this type of “super-meridional” pattern - ambitious building of heights up through the Atlantic and more spectacularly, through all the S’s - Sahara-Sweden-Svalbard-Siberia-Seguam like here at day 6 on the 0z ECM op… …it’s only a matter of time before we start seeing the trough becoming over-extended with the cutting off of the low at the base of the trough, it sinking south, the heights linking up through the UK and Ireland like here at day 8… Yes, add Skegness and Sandymount to your list, spectacular super-meridional S thing! After that, a weaker version of the trough tries to reassert itself from the northwest, which the GFS op has been keenest on, though looking at the 0z ensemble mean, the pressure never really falls away again, a steady rise to a respectable 1020mb for Birmingham by the end of week 2… …which is consistent with the ECM charts and the pincer movement of heights weakening the polar trough at its stem - so though nothing wall to wall by any means, the chance of a somewhat more promising setup emerging into early May. I’ll post again around then. All the best.

Not very often we see a low pressure system romp so triumphantly west from Scandinavia through the UK and Ireland to the Atlantic, as here on the 12z UKMO but there are some very intricate handovers of pockets of low heights that drive the whole process and give it some considerable elegance. The first pocket drops south to join the Scandinavian low at day 2, deepening it. The second drops out of the trough at the tip of Greenland at day 3, joining the melee at day 4 and drawing the system west over the UK and Ireland for the weekend. Thanks A third pocket drops southeast via the same route at day 6, pulling the system west out over the Atlantic. Looks like an “atmospheric” weekend awaits to round off this very mixed April, ripe for savoury evening treats washed down with a sumptuous glass or three of your favourite ale or wine. The late spring fitness effort can wait until some suitable conditions are laid on. And from there, let’s grab all the potential silver linings. Though not seemingly immediately on offer, there are at least some emerging signs that this remarkable retrogression, as a part of wider adjustments occurring within the generally very static hemispheric pattern, might eventually lead to sufficiently consistent heights building over the near continent to bring us a better chance of some warmer interludes as May progresses.

@Josh Cool Stundon Hi Josh, I think that we have to look at each event on its own rather than necessarily seeking a sub-classification of the classic Spanish plume. I have looked at the archive charts for June 28th 2012. What is striking about that event is the dramatic west-east temperature gradient that developed that day and how the contrasting air masses interacted in the circulation of the developing low pressure system. I have examined the pressure charts and the T850 charts, relevant here because the 850 hPa temperature, at altitude about 1.5 km, is above the atmospheric boundary layer and so is a very good measure of the relative temperatures of the air masses. At 0z that day, the low pressure at around 1000mb, was centred about 800 km to the southwest of Ireland. The pressure was around 1005mb over southwest Ireland. The T850 was around 11 degrees over Limerick and around 14 degrees over southeast England, though the 16 degree isotherm of the plume was over the English Channel coast. The surface circulation over Ireland was a southeasterly, drawing in warm, humid air from that region. By 6z, the low pressure had extended northeast, and the pressure over southwest Ireland had fallen to 1000mb. The centre of the low was by then around 400 km to the west of Kerry. The T850 over Limerick was around 9 degrees, and the 16 degree isotherm had arrived in southeast England. The surface flow into southwest Ireland was still from the southeast, continuing to feed in warm, humid and unstable air. By 12z, the deepening of the low pressure, to around 995mb had pulled in colder air from the northwest, so that the T850 over Kerry and West Cork was only 6 degrees and this knuckle of much cooler air was pushing in from the southwest behind a developing front, into the very warm humid air to the east of it. The T850 over Kent was around 17 degrees, so two things had happened. Firstly, over 12 hours, the difference in T850 between southwest Ireland and southeast England had risen from 3 degrees to an 11 degree difference, so the temperature gradient had become extremely steep. The atmospheric instability through that zone would have become profound. Secondly, the centre of the approaching low pressure had more or less stalled, still several hundred kilometres to the southwest of Ireland but the low was deepening in situ, so all of Ireland was by then below 1000mb as the system grew. The winds would have been slight and variable within this cyclonic circulation but with the dramatic west-east temperature contrasts within the system, and the peak convection of the afternoon, severe thunderstorms would have formed through the frontal zone, fed by the growing instability and making only very slow eastward progress. As the front approached, the wind would have backed southerly running along the front, so a local effect of air getting lifted over the Cork and Kerry mountains, enhancing the updrafts, might have been an additional factor for the Limerick area. Limerick was in effect stuck in the trigger zone for several hours with the growing temperature contrast of the air masses and increasing convection of the day feeding a growing instability that resulted in the severe thunderstorms. I hope this helps look at the question in another way. The precise setup for each instance of this type of event is naturally different, but I was hoping that by looking at the dynamics of this particular event, the requisites might be identified.

Keeping abreast of the models, here’s a notable pair of ECM means, in near perfect hemispheric symmetry around day 9 / 10, persistent heights reinforcing the cleavage. The sheer indecision of it all - sure to be amongst the abiding mam…oops, memories of spring 2024.

We’ve been quite lucky this morning, it has been absolutely beautiful, steadily warming up from a -1.2 degrees frost around dawn, 1026mb and no wind. April mornings don’t come much better. A very reasonable looking few days ahead, through the weekend and into early next week, the 0z EPS chart for next Monday morning at day 4 is a cracker. The MSLP chart shows a high pressure of 1036mb over the UK and Ireland, part of a “bar” of higher pressure extending through to the Siberian Arctic. But make the most of it! Even with this setup, though it is nigh impossible for our high to be shifted east by anything off the Atlantic, it instead gets undermined by trough development to the east. There were good hints of this in the models yesterday, and though still a fair way off, the subtle hints of yesterday for day 10 have grown into clear suggestions today for day 9, the trough notably deeper and further west. This is the kind of evolution I love to see, not necessarily for the weather it will bring, but for the phenomenon itself. The 0z ECM op at days 6-10 shows the potential, the Scandinavian trough spawning a little low pressure system running down through the Norwegian Sea, joining with another more active one coming out of Greenland and sweeping down through Iceland… …the two merging and swivelling down into the UK and Ireland, with the cold air reasserting itself in the process. With the seasonal timing, probably not at all welcome, though I keep the faith that one of these years we’ll get this kind of thing a couple of months earlier and enjoy it a lot more. As it stands in the current modelling, it’s a spring ambush!

This appears to be quite a telling moment in the development of this spring. The Atlantic jet stream is heading very decisively north before fragmenting, here on the 0z ECM op for the next 10 days. The 0z ECM mean anomaly shows an impressive build in heights not only north through the Atlantic but also west into Greenland. The low pressure over the pole is lost as heights link up through the Arctic to the Siberian side. So the pattern is getting locked down. From the meridional 5-wave hemispheric pattern we’ve been looking at recently, we might have seen the next stage involving injection of some energy to incorporate a couple more waves, reduce the amplification and introduce a more mobile setup, but instead we’re seeing the opposite happen - the Atlantic build is so substantial that it serves to carve out one of the waves altogether. This is shown nicely by the 0z GEFS jet stream charts, the 5-wave starfish at day 5 being replaced by a 4-wave cross at day 10, the jet stream actually bending back on itself with a northeasterly component as it dives south towards the UK and Ireland. The surface flow will be very much in the northeast for several days, following the contour lines in the mean heights charts (below) from around day 5 onwards. So we’re moving towards a more static setup towards the end of the month, drier than it has been, but with suppressed temperatures. The stronger sunshine when on offer could make for some pleasant weather all the same, especially further west with shelter, though as discussed, the onshore breeze could be quite the dampener in eastern parts at times. One more thing, looking through to day 10, the upper trough remains uncomfortably close by to the east, even steadily working its way further west - so small systems beginning to run down the western flank of the trough, picking up moisture through the Norwegian Sea, might well become an added complication later on next week. Original post: https://community.netweather.tv/topic/99814-model-output-discussion-spring-has-sprung/?do=findComment&comment=5058638

This appears to be quite a telling moment in the development of this spring. The Atlantic jet stream is heading very decisively north before fragmenting, here on the 0z ECM op for the next 10 days. The 0z ECM mean anomaly shows an impressive build in heights not only north through the Atlantic but also west into Greenland. The low pressure over the pole is lost as heights link up through the Arctic to the Siberian side. So the pattern is getting locked down. From the meridional 5-wave hemispheric pattern we’ve been looking at recently, we might have seen the next stage involving injection of some energy to incorporate a couple more waves, reduce the amplification and introduce a more mobile setup, but instead we’re seeing the opposite happen - the Atlantic build is so substantial that it serves to carve out one of the waves altogether. This is shown nicely by the 0z GEFS jet stream charts, the 5-wave starfish at day 5 being replaced by a 4-wave cross at day 10, the jet stream actually bending back on itself with a northeasterly component as it dives south towards the UK and Ireland. The surface flow will be very much in the northeast for several days, following the contour lines in the mean heights charts (below) from around day 5 onwards. So we’re moving towards a more static setup towards the end of the month, drier than it has been, but with suppressed temperatures. The stronger sunshine when on offer could make for some pleasant weather all the same, especially further west with shelter, though as discussed, the onshore breeze could be quite the dampener in eastern parts at times. One more thing, looking through to day 10, the upper trough remains uncomfortably close by to the east, even steadily working its way further west - so small systems beginning to run down the western flank of the trough, picking up moisture through the Norwegian Sea, might well become an added complication later on next week.

Please continue to use the reporting facility in the usual way. If you have a specific issue regarding moderation, or in general, that you would like to raise with the team, then please do so via here: https://www.netweather.tv/other/contact-us We greatly appreciate this feedback. Please remember that the moderators are keeping an eye on the shape of the forum across many threads. If you have reported a post and no action has been taken, it’s invariably because it has been reviewed and the decision was to leave the post as it is. For instance, at quieter times, when there is little possibility of the thread becoming derailed by a marginal post, some leeway is sometimes given in order to keep the threads moving along and as engaging as possible. A blustery and chilly morning here, showery with plenty of hail. Not great, but a 1030mb+ high building through the UK and Ireland by day 6 on the 0z ECM op, day 0-6 here, the rise in pressure and its convenient location now well inside the reliable and for once, coinciding with the weekend! Many a lawn will get mowed…. An impressive build in heights to the west and north. No doubt some fresh and chilly nights and mornings as it works its way in and settles down. Consistent signs of the high pulling back west thereafter, but for a fair few days, this is going to feel much, much better!

Shiver me timbers! Looks like we have a retrogressing high before our very eyes, ha ha haar (and other pirate noises) - even before it’s properly arrived. Whether ‘twill be as shivery as 6z GFS op at day 9, where it withdraws far enough to the northwest to allow a proper cold blast down the frontage with some snow a fair way south, and settling on the hills… or holds close enough nearby to keep the old lunger a bit further east like on the 0z GEM op at day 10 (beware that sea serpent beyond the pole, haar)… the retrogression and European trough are definitely looking to be features of week 2 - ‘tis here too on the 0z EPS at day 11. Aar. The CFS weeklies (weeks 1-3) show the Euro trough by week 3 being reinforced by its maritime buddy that’s come romping through the Azores in weeks 1 and 2, while to the north, the Atlantic heights hint at wobbling back east, a tad back our way again… …the big concern for us island landlubbers looking for something to warm our jellies is that rather than a generally quiet but cool outlook, the pattern in the event all heads just that bit further north bringing us back into chilly cyclonic influences that just judder your rafters. More pirate noises…. Original post: https://community.netweather.tv/topic/99814-model-output-discussion-spring-has-sprung/?do=findComment&comment=5057987

Shiver me timbers! Looks like we have a retrogressing high before our very eyes, ha ha haar (and other pirate noises) - even before it’s properly arrived. Whether ‘twill be as shivery as 6z GFS op at day 9, where it withdraws far enough to the northwest to allow a proper cold blast down the frontage with some snow a fair way south, and settling on the hills… or holds close enough nearby to keep the old lunger a bit further east like on the 0z GEM op at day 10 (beware that sea serpent beyond the pole, haar)… the retrogression and European trough are definitely looking to be features of week 2 - ‘tis here too on the 0z EPS at day 11. Aar. The CFS weeklies (weeks 1-3) show the Euro trough by week 3 being reinforced by its maritime buddy that’s come romping through the Azores in weeks 1 and 2, while to the north, the Atlantic heights hint at wobbling back east, a tad back our way again… …the big concern for us island landlubbers looking for something to warm our jellies is that rather than a generally quiet but cool outlook, the pattern in the event all heads just that bit further north bringing us back into chilly cyclonic influences that just judder your rafters. More pirate noises….

The end of the coming week looking settled sooner and for longer now on the models. We’ve been watching this change develop for several days now, but it’s always good to see a signal: a) firm up b) come forward in time And this one’s really beginning to look very good. 0z EPS for next Thursday (18th) from last Monday for day 10, and today at day 5, showing the two sides of the coin becoming more clearly imprinted - the bubble to the west of the UK and Ireland gaining in modelled heights and steadily being modelled further north, and the low heights earlier focused over Scandinavia, now modelled as a deeper trough extending down into southeast Europe. Typical of how these models often work as they firm up, we can see the uncommitted, white gaps and softer shades getting gradually taken up by stronger signals, Atlantic heights growing stronger and more expansive, while a fully-fledged polar trough becomes marked out running down into Europe, the most notable synoptic difference being the development of the small low pressure to the east of Greenland that aids the link-up of low heights. Though some colder, less settled conditions are slowly departing to the east, for the UK and Ireland, the more relevant feature is the decisive edging east of the modelled ridge, and more noticeably into southern Greenland and Iceland too, which sets up the prospect of an earlier arrival of a much quieter end to next week, and combined with the better build, dare we say it (!), hints at this being followed up by several back-to-back usable days… ….this positively illustrated by the EPS MSLP charts for day 7, with the high pressure edging in from the west at day 7, gradually establishing itself slap bang over the UK and Ireland by day 10. Rightly being picked up on is the Atlantic becoming sealed off, but this looks a more substantial block than just that, with high pressure extending from the Azores through our stretch of Western Europe to Siberia, so by that stage it’s not only a block to weather off the Atlantic but also a block to further troughs running down through Scandinavia - with the added benefit that with the removal of the threat of the colder air to the east, in the gentle and variable circulation of the high pressure, daytime temperatures should be building to much more encouraging levels into the last week of the month - drier and warmer - good news for those yearning to give their spring freckles an airing. Have a great weekend.

Historybuff They appear to be the old Beaufort letters, used up until around that time, but replaced very swiftly thereafter. e.g. ogm at Lerwick is o = overcast, m = mist and g = gale (mean speed 34-47 knots over a period of 10 minutes or more). cq at Stornaway : c = cloud covering 6 to 7 oktas (eighths of the sky); q = recent squall They are listed in this document here: https://www.metoffice.gov.uk/binaries/content/assets/metofficegovuk/pdf/research/library-and-archive/library/publications/factsheets/factsheet_11-interpreting-weather-charts.pdf The really useful bit for these Beaufort letters gets going around page 29-30. There are some others relating to cloud cover on page 18. It looks like you have many happy hours of meteorological detective work ahead! Best of luck.

Blimey. Outstanding choreography from the ridge dance troupe, lining up to really sock it to the PV on the NH dance floor over the next 10 days on the 12z ECM operational run. Let’s watch the elaborate performance as successive waves of heights push north. Starting from where we are today, PV centre stage, coordinating Atlantic, Scrussian and Bering Sea troughs in a whole hemisphere twirl. Keep an eye on that little pocket of heights over the Canadian seaboard with the hook north, because…. …first up is the Atlantic ridge by day 3, still with the northward extension of heights, now extending well up through Baffin. By day 5, the PV still holding centre stage, but the Atlantic ridge has been joined by the Alaska ridge, a sweet little link-up of heights pushing the lower heights east. But about to join in is a nascent ridge pushing up the east of Japan towards eastern Russia, and there are hints of a naughty little squeeze from Kazakhstan. By day 9 / 10, the Kazakh squeeze is maintained, well and truly heating up that floor, while the Japan surge goes all-out Siberian, joining their friends from the west in a hemispheric Cha Cha that ultimately congas its way right through the heart of the Arctic. PV exit stage left, arrivederci. A good few days respite for the UK and Ireland. Yeah, sign up everyone (if you’re not totally exhausted), the moves are awesome. Original post: https://community.netweather.tv/topic/99814-model-output-discussion-spring-has-sprung/?do=findComment&comment=5057123

Blimey. Outstanding choreography from the ridge dance troupe, lining up to really sock it to the PV on the NH dance floor over the next 10 days on the 12z ECM operational run. Let’s watch the elaborate performance as successive waves of heights push north. Starting from where we are today, PV centre stage, coordinating Atlantic, Scrussian and Bering Sea troughs in a whole hemisphere twirl. Keep an eye on that little pocket of heights over the Canadian seaboard with the hook north, because…. …first up is the Atlantic ridge by day 3, still with the northward extension of heights, now extending well up through Baffin. By day 5, the PV still holding centre stage, but the Atlantic ridge has been joined by the Alaska ridge, a sweet little link-up of heights pushing the lower heights east. But about to join in is a nascent ridge pushing up the east of Japan towards eastern Russia, and there are hints of a naughty little squeeze from Kazakhstan. By day 9 / 10, the Kazakh squeeze is maintained, well and truly heating up that floor, while the Japan surge goes all-out Siberian, joining their friends from the west in a hemispheric Cha Cha that ultimately congas its way right through the heart of the Arctic. PV exit stage left, arrivederci. A good few days respite for the UK and Ireland. Yeah, sign up everyone (if you’re not totally exhausted), the moves are awesome.