Met4Cast

A plume of very warm theta-e 850hPa (>45C) will begin to destabilise along an occluded frontal wave associated with a broader upper trough sat across France/Belgium. Very high CAPE values in excess of >2000J/KG of CAPE look to be achieved by mid afternoon triggering rapid development of thunderstorms. These are likely to become severe in nature across France and towards the Belgium border with the potential for large or very large hail & significant rainfall amounts. The frontal wave will continue backing westwards into the evening drawing the plume of air northwards and with that, the thunderstorms, helped along by a shortwave sat to the SW of the UK. Thunderstorms will become increasing elevated above the 900mb level with a significant inversion developing. Frequent or very frequent lightning will push into the southeast of England extending into central southern England as the night progresses. Rough estimates place the highest risk between midnight and 3am Thursday morning with the risk getting later the further northwest you head. Moderate wind shear suggests a small likelihood of large hail, particularly across the far SE closest to the highest instability. Sampled AROME soundings suggest CAPE in the region of 1500-2000J/KG just off the Kent coast with diminishing values the further north and west, albeit still enough to sustain on-going thunderstorm activity. The greatest risk across the UK will be on the eastern extent of the rain band, model consensus is quite poor overall but the highest risk of thunderstorms & prolific lightning looks to be just east of the IoW across Kent, Sussex and extending northwest towards south London & the M4 corridor, perhaps extending into parts of the south Midlands later in the night although confidence on this is lower.

Mapantz Not surprising - Any rainfall will move through relatively quickly, storms are elevated so cloud-ground lightning strikes aren't really a concern and it's happening in the middle of the night so naturally the likelihood of impacts is quite low.

AROME sampled Skew-T continues to signal >2500J/KG of CAPE moving up into the SE area before expanding (and weakening) westwards with the shortwave trough. Assuming these values are realised we could be looking at a prolific lightning event tonight moving up into the southeast and extending northwest through CS England and perhaps even as far as Wales. I suspect the AROME is overcooking things slightly but regardless, potential for significant amounts of lightning tonight accompanying the likely torrential rainfall. Large hail looks to be a slightly higher likelihood compared with yesterdays thinking too, albeit probably reserved further southeast. This really is an impressive setup for the time of year.

This is an impressive skew-T sampled just off the Kent coast tomorrow evening; CAPE approaching 2,000J/KG with strong elevated convection coupled with strong DLS suggests the potential for some very active elevated thunderstorms into the SE tomorrow night, likely travelling NWards into the Midlands region (albeit weakening). I suspect AROME is overcooking the values here slightly. Don't be fooled by the precipitation further west, bulk of any activity will be on the eastern side of any precipitation field.

CoventryWeather Really difficult to say at this stage. UKV is probably too far west, AROME 12z has shifted west slightly but still favours broadly the same areas as before, i.e SE into CS Eng perhaps the Midlands. Whether there will be much in the way of lightning further NW though remains to be seen. Very tricky forecast but impressive amounts of CAPE being shown for the time of year.

ChannelThunder Seems to be on the western end of the envelope compared with other models at the moment, EC/AROME for example have been consistently further east. I wonder if this is a case of the UKV underestimating elevated convection further east and instead running with the broader rain band associated with the warm front/trough. Not buying it's output currently, would like to see some support from other models first.

A plume of very warm theta-e 850hPa (>40c) will destabilise and track NWards across northern France behind a broader warm front tomorrow. Initially surface based, these storms will become increasingly elevated as they track northwards into southern England. 800-1000J/KG of CAPE combined with 30-35kts of deep layer sheer will allow storms to become organised & sustained as they cross the English Channel. Locally severe weather is possible across northern France with severe wind gusts, heavy rain & large hail associated with possible supercell storms and a broader tornado risk. For the UK, the elevated nature of storms suggests a reduced severe weather risk however heavy rain & frequent lightning can be expected. There remains a lot of model variation on where these storms will track. SE/CS remains the most likely outcome with landfall probably east of the IoW but west of Folkestone as a rough estimate. Some modelling (UKV in particular) suggests a much further westward track into SW England/up into Wales but this remains on the extreme western end at the moment with models such as AROME/EC remaining consistent with a more eastern track.

alan.duckers The Shannon Radar should be re-added to the composite data by late April, whilst it's now operational additional data for calibration is still required, there are also an additional 5 radars being put up. So, hopefully by the end of April the dark spot across southern Ireland will be gone & we'll have a fully functional radar system again.

Unsurprisingly the blocked model outputs from a week or so ago didn’t really materialise, here was a run for today vs how things actually looked today; The teleconnections are sometimes rubbished on this forum if it doesn’t snow in X location but once again they’ve proved a very useful tool in viewing NWP outputs with added context, as they have done for the majority of this winter. It seems instead we’re in for a fairly prolonged period of above average temperatures with the March CET likely coming out above average if the current direction of travel continues. Perhaps signs of something a little colder thanks to Atlantic ridging late March/early April as the MJO continues to progress eastwards through the Maritimes & into the Pacific with AAM tendency fairly positive at the moment as a result.

Background forcing has been against the idea of colder weather since the mid January cold spell, a marker divergence appeared around the 22nd January when I (and others) noted the likelihood of a cold February was diminishing. Indeed, background forcing remains unfavourable for strongly blocked/colder patterns with the Iberian high continuing to play a larger role in the broadscale patterns (despite major SSW) April however does show some tendency towards higher latitude blocking as the MJO continues to progress into phase 7-8 but by this point does anybody really want colder blasts of air? Probably not.

Frigid Unfortunate really because it’s the first good deterministic run for a while I said a week ago now that there’s no sign of anything notably cold or warm and that remains the case going forward through this month. Quite a bog standard affair, boring from a weather perspective but also from a wanting to get out and do things perspective.

RJBingham Yup. I've struggled to see the enthusiasm for anything properly cold to be honest, besides some deterministic runs/outlier ENS members modelling has been pretty consistent with predicting temperatures remaining around average for the foreseeable with very little sign/support of anything significantly colder. Later in the month will likely see some renewed high latitude blocking as the MJO cycles into more favourable phases in the context of rising AAM but by and large, it's game over for cold chasers.

Going back to this post from the 26th February we are now seeing this broader evolution play out within modelling. High pressure forming across Scandinavia but increasing support that it’ll be too far NE to really drive energy SEwards & advect cold west across Europe. The pattern flattening out is now well advertised. I think it’s probably fairly safe to rule out any cold weather through the first half of March & probably beyond now.

The det seems to fall off a cliff in terms of the cold pooling into the UK. Synoptically the det is quite well supported but in terms of cold pool positioning etc, very little support.

Metwatch I don’t think using the BFTE, which was one of the most extreme SSW responses on record is really a fair comparison. The continent warms very quickly through March (typically), direct northerlies are often a much stronger source of cold by late March/April.

Mike Poole The EC46 has been spectacularly poor this year. I wonder if the now daily updates just highlight this more, was a little harder to keep track when the model only updated twice a week. I don't think i'll be putting much weight into it in the future, it's inability to drop a signal that it's latched onto when it's clear the trend has changed isn't great. I think 1-2 weeks it can be helpful to provide support for current trends within other models but as an isolated long-range forecasting tool it's poor.

KTtom Good summary! Rather amusing that we ended up seeing the mildest February on record after a lot of promise during early winter of a backloaded cold one

Total AAM tendency has been strongly negative of late thanks to the MJO decaying into COD, this re-emergence into the Indian Ocean and quick progression eastwards through the Maritimes though has begun to reverse this with AAM tendency now slightly positive. I do wonder just how much overall +ve AAM will rebound to though, a fast MJO progression as is currently predicted would suggest less westerly momentum being injected into the atmosphere, I'd be surprised if we reached values seen through late January/most of February again, especially with El Nino beginning to fade. The recent abrupt decline in AAM tendency combined with the SSW is likely generating the blocking to the NE of the UK across Scandinavia and we are seeing a regressive signal towards Greenland within NWP modelling, the only real issue is the lack of cold across Europe to advect into the UK, I do also think, as stated previously, the high might end up being too far NE to really drive Atlantic energy to the south of the UK and the means are now showing this with winds broadly S/SErly across the UK rather than true easterly, this essentially stalls the low across the UK bringing yet more rain.. wont that be nice. The direction of +AAM anomalies is equally important and we're seeing +AAM anomalies moving poleward as the previous cycle completes, this is suggestive of a stronger jet and is further evidence of a quicker flattening of the pattern. I do think we've probably missed the boat here in terms of anything colder, at least through the first half of the month. Continued MJO progression into phase 7/8 later this month could potentially allow for another attempt late March/early April but honestly but that point we'd need a very direct northerly to produce, an easterly at that time of year is very unlikely to cut it. For those wanting one last bite of cold/snow, the outlook is poor. For those wanting some early spring warmth the outlook is equally poor.

Despite the blocked charts there's very little cold on offer to tap into, ensembles across all models are generally sticking to climatology (average) with temperatures gradually rising a little throughout the forecast period. Blocking to the NE may well retrogress towards Greenland but MJO moving through typically zonal phases and rising AAM suggests a flatter pattern, rather than a blocked one. My expectations are still for the pattern to flatten out rather quickly, at least across the Atlantic sector with a west based -NAO seemingly the direction of travel following retrogression with nothing notable in terms of cold or snow potential, despite the SSW tropospheric drivers are not favourable to produce proper cold weather across the UK. Impressive looking synoptic patterns but sadly, no cold.

GFS det was a rather obvious outlier unfortunately. There continues to be a complete lack of support for colder/notably colder weather into the UK with the majority of ensembles favouring milder weather (at least at the 850hPa level) This comes as no surprise really given the MJOreturning to the Indian Ocean and progressing eastwards through phases not typically supportive of blocking.

Absolutely no support for the GEM det unfortunately, seems to have gone off on one and then some.

Despite a few interesting looking det runs the means are generally against the idea of anything cold/snowy. In fact, could end up being quite mild with southerly winds taking hold!

Addicks Fan 1981 They show the recent decayed MJO signal & expected start of the next cycle over the Indian Ocean, albeit they have been a little inconsistent of late, largely down to modelling struggling with the MJO (SSW related I presume). Can certainly see the uptick in Pacific trade winds.

Yesterday’s CPC MJO update suggests a return to the Indian Ocean before progression through the Maritimes as the cycle resets so further away from the typical “blocking” phases than originally anticipated, having said that the SSW early March could have some impacts on the MJO & thus forecasts are more uncertain than usual. Assuming this is the direction of travel though, the next surge in momentum is fairly predictable with an uptick in frictional torque followed by a return to positive mountain torque values adding westerly momentum to the atmosphere thanks to the MJO progressing eastwards. With that in mind, it continues to seem less likely that’ll we’ll see colder patterns establishing for the UK with high pressure early March likely to be too far NE of the UK with a rather active Atlantic jet hitting that road block, it could potentially be quite wet, especially in the north & west depending on exactly where any blocking highs set up before the patter, I suspect, quickly flattens out coinciding with this next momentum push. I see the Met Office extended is more inline with this & indeed with my thoughts posted yesterday morning a page back. Any blocking is a result of the recent abrupt drop in AAM tendency as westerly winds are scrubbed, i.e increasing easterly trade wind strength. El Niño is on very thin ice now.

I think the separate threads serve well for more prolonged conversations but I don’t see an issue with highlighting various teleconnections or the strat in this thread given the role & importance they play in the weather & the modelling that this thread is for.