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An extract taken from a post last week, as means for continuity analysis Much of the discussion in that wider post detailed the "pull and push" effects on the synoptic pattern of the decelerating and accelerating wind-flow inertias, respectively, within the atmospheric circulation. With the comparisons of that last post in mind, and following the downturn of a week back that led to the latest cool and wet weather conditions - we are now in the new uptick phase in momentum and the re-setting of the downstream ridge and Atlantic trough over the coming days - a very close match to what was seen in the first week of April and to what was hinted at may evolve in the first week of May in the previous post. One key difference this time is, as observed already by others in this thread, the final warming of the stratosphere has occurred and this will play a part in determining how the mid latitudes and and polar field interact over the coming month - much less of a factor obviously during April. I think its important to put this in perspective however - it is not inevitable that any tropospheric blocking response at higher latitude extrapolates outwards for weeks and weeks on end, and somehow is an omen for the rest of spring and then summer as a whole. Clearly, with that said - various factors come into play here and it is true that these factors do have to be watched over coming weeks - more on that later. The Global Wind Oscillation, which is a phase plot depiction of wind -flow inertia and its effects on angular momentum tendency within the atmosphere, show a lovely symmetry with the previous tropical and extra tropical cycle in April. The GWO has orbited through the falling momentum phases 8/0, much as it did in late March, and is progressing into increasing tendency Phase 4 - the signal, synoptically, for the start of re-set back to the downstream anticyclonic pattern. At least for a time. This GWO symmetry was discussed previously and it was anticipated that the present cool and unsettled spell would respond once the ENSO "mini cycle" embarked on its next eastward cycle and started adding some westerly inertia back into the atmospheric circulation. Such westerly inertia now creating the latest increase back in angular momentum tendency. In the short term, this uptick in momentum re-sets a more +NAO profile in the Atlantic and adjusts ridging back to our nearby mid latitudes - this ensures that much of next week looks quite pleasant once more, and though no heatwave looks likely, it will feel very nice by day with more sunshine to enjoy once more. That is, once the trough to the SW edges away early in the week. Thereafter NWP is advertising the next fall back in momentum in tandem with the tropospheric effects of that final warming - the falling momentum augmenting the more -AO/-NAO profile returning suggested around the days 8 to 10 period and beyond for a time. As alluded to above, some caution is best interpreted with this signal and wise not to over extrapolate its duration and extent this far out in time - suffice to say a further cool and unsettled phase may well follow which would take the time out to the mid month period. Long term some of the uncertainties remain surrounding speed of continued downwelling of e/QBO regime - still a very weak signal to recently, and also how quickly the ocean/atmosphere relationship might lean towards a growing La Nina signal. There is evidence for the latter from various proxy data (not included in this post to prevent it becoming too long). Both of these signals taken together (at face value) are often not the best of portends for a very good summer at this latitude. This does not though, via late Spring and early summer at least, preclude the chances of further warm settled weather to come

What wonderful mammtus clouds

Everythings a Supercell You guys do know whats needed to actually make a Supercell ?? Seriously not everything is a supercell because it has a white core on radar

We just had some pretty potent showers with Hail move through and they had some incredible looking sky's and structures

Sunset heavy showers in Stoke Newington, London. Rumble of thunder also heard. Glorious colours

The general theme going on the models suggest a settled spell next week and largely dry with sunny spells.. Perhaps similar to back in April... Beyond that the signs of a general cool down and at times unsettled.. Exeter hinting at a warming up towards the final 3rd and more settled again.. I think singularity also hinted at this in an earlier post.. So if that's the way it's gonna be... I will take it.. In the shorter term some decent weather to come one hopes.

Okay so this was a Risk in the Texas Panhandle last Season where we saw a Tornado at Sunset. Picture 1 is from the Baron System which does not have a great Resolution more like the Uk Radar - White Brick is my car/Position Picture 2 is from GRLevel3 which shows Dopplar Radar and better resolution again the white circle is my position Picture 3 is showing the Velocities Picture 4 is showing what was in front of us As you can see we need much better radar to call Supercells from radar alone

Good afternoon all, happy first day of May! The GFS 06z has a high developing over the British Isles on day 5, so hopefully we will see some settled and perhaps warmer weather for a time.

The line looked promising from here but it fizzled out into just light-moderate rain once the sun went down, but i'll still take it over this morning's grey and dull skies.

Some great cloud tops to my West right now from that line of showers! I've posted these before but seems as we're on the topic of UK Supercells, why not have them again! 28th June 2012: Some great info and pics on these 2 links https://www.stratusdeck.co.uk/28th-june-2012 https://hinckleyweatherblog.wordpress.com/2013/06/25/leicestershire-supercell-storms-of-28th-june-2012/ Massive hail in Leicestershire The multi-cell cluster and the classic flying eagle Supercell to the right Said Supercell went on to produce the Sleaford tornado, that's probably the most defined Supercell ever seen on UK radar? Satellite image Lightning total

When In the USA I dont really overcook things as I find if you look at too many variables you can actually do more harm when picking a target. These are the things I will always look at which we can actually find on our Uk Storms in the next 5 months upto the end of September. First thing I look at is obviously shear and I am looking for at least 30-35knts of Deep Layer Shear. Ideally you want your 2m winds out of the east of South East, your 850mb winds out of the south and at least 25knts of speed on those. Your 500mb winds out of the South West or West and again around 40knts so storms are not moving at warp speeds. Once you look at your Hodograph that should yield winds turning with height (Shear) and then look at your T'Td Spreads. In the Uk a few years back we had those Supercells in the Midlands with temps of 75 and Dewpoints of 66. That is an amazing Spread even in the USA that would make you sit up and take notice. Notice I have not even mentioned Cape yet ? It is not the be all and end all of Supercell formation and I have seen Tornadoes with as little as 500jkg of Cape. One thing the USA has that is quite rare in the Uk is the LLJ (low Level Jet) and this really helps to get storms spinning and gives that extra spin to Mesocyclones in the early evening, although rare in the Uk we have seen the LLJ nosing up from France before. When we get a decent Set-Up in the Uk in the next few months it will be good for us to all look at the charts to see if any or all of these ingredients come into play.

Yes we do get Supercells in the Uk and as another poster said how many low topped Supercells go unnoticed due to the lack of Doplar, remember Cold Core Supercells only really reach levels of 20-27k feet which is attainable by quite a few UK Storms in our Spring and Summer Months. Most Uk Single Cell Storms hang out at around 15-18k feet but we have had Storms above 40,000 feet before

Cant see that myself, no plume of Theta air makes it further north than Central France - Cape is almost at zero (MU & SFC) In fact I will apologise now to everyone, this is the first May I will be in the Uk since 2004 and I know you guys have had some humdingers over the past Mays, but going on the latest GFS alone it looks devoid of any sort of Plume outbreak for the Entire run upto the 15th May and Cape gets to 200jkg on 1 day at the end of the run. Sorry again

Outlook - the story over the next few days is essentially one of the positively tilted upper trough, currently aligned across the UK, splitting under pressure from the amplifying subtropical high zones and creating a cut off low to the south west. From this point it is about the movement of the latter and the energy flows around the amplifying European ridge north west towards Greenland At the moment the country is still under the influence of the trough as the above process gets underway so another day of showers and sunny intervals,not so frequent as yesterday, but still heavy at times and more concentrated in northern and eastern regions with the SW and S having a quite pleasant day with less wind The showers in the east will tend to fade away tonight but still a few in the north and north west, otherwise a dry night By Saturday the UK is between troughs, so to speak resulting in a generally dry day with sunny intervals but some showers in the north and east courtesy of a stray occlusion By Sunday the cut off upper low to the south west is established with the UK in a slack gradient and another day of sunny intervals and showers On Monday the now influential high cell is centred near the Hebrides so a generally sunny day but with some marked regional temp variations courtesy of the North Sea and the onshore wind By Tuesday the high pressure has become quite elongated as the trough to the south west pushes north and the associated front brings rain the south and generally a much cooler day

Some great cloud tops to my West right now from that line of showers!@ChezWeather From the decaying line of cells crossing central England

This is the York one, taken from Garforth, near Leeds, about 15 miles away. Would have loved to be under that!

Brace yaself for some sunning next week, get the lawns cut, perhaps chill and have a beer of the evening... Then get ya ice scrapers ready for the following week, wouldn't be surprised to see a bit of wintryness over those mountains with that set up... Alot can change though.. So let's just see how it unfolds... Do take care.

Sleaford, Lincolnshire on the 28/06/12. Actually looks like a classic supercell. This is the same cell that gave the tennis ball hail over Leicestershire. At the beginning, note the rapid moving inflow jet, and at the end of this video, the tornado is clearly visible. A rare day where conditions were as if it was tornado alley. Very high wind shear (increased wind speed with height) overlapping a high amount of CAPE and instability. We very rarely get both combined here. Usually one or the other!

Just found some more videos of that 28th June 2012 storm, good god!!

But then the end of March and 1st week of April hardly suggested what much of April turned out to be

That sure is a decent ECM 0z ensemble mean once we’re through the next few days with a more settled look to our weather next week..fingers crossed!

Seems the "Gab of May " (spelling ? ) is on its way around the 9th of May according to some of the models with some fairly cold weather. With all this dry weather young Mr. Northernlights has been getting the neep ground ready but I have said we will wait till after mid May to sow them as they can "bolt" (they are perennial plants developing a bulb in their first year and setting seed in their second year, bolting makes them set seed in their first year and therefore no bulb for feeding the cattle) if they germinate, emerge and get a sharp frost.

A truly historical day. Also I forgot to mention, the clear deviation to the right is also a prime sign of a supercell. I believe that one highlighted became a splitter over the Warwickshire area. Remember seeing it undergo rapid intensification after it broke off and moved more NE as opposed to N-NNE earlier that day. The lightning track also shows this clearly. That was when the huge updrafts would have started and then started dropping golf balls and tennis balls over Hinckley and underwent tornadogenesis. This storm would have been enough to warrant sirens in the Midwest and the weather channel have the chopper following it! That’s how dangerous that one really was. All we got however was the BBC saying there would be a few thunder showers...Majorly caught off guard there! Lastly, another day I forgot to mention, the El Brumo day of 28th July 2005. There was even 2 confirmed tornadoes in Peterborough and Moulton near Spalding. Large hail also fell from that storm! That was one epic day too

Strong compatibility between the models today not just within the reliable either. Next few days high pressure back on the scene ridging in from the NW to settle over the UK, whilst a trough lingers to the SW giving the chance of showery rain far SW early in the week. As we move further through the week, signal heights will advect NW, drawing in a cooler feed from the N/NE, but still dry probably under quite a stable airstream. Temperatures by day reaching mid-high teens, possible very low 20s in one or two spots, very pleasant but nothing especially warm for the time of year, nights conversely could be quite chilly with risk of frost in sheltered spots. Longer term, a classic negative NAO/AO synoptic, strong heights over Greenland joining hands with arctic high - true northern blocking, trough through scandi and low pressure to the SW, with southerly tracking jet - eventual outcome possibly cyclonic and cool for May.

Evening all Another day of April showers in lowland East London - not quite as sharp as yesterday but we're a long way from summer yet. So, what of this evening's offerings from the models as we head further into the new month? The T+240 charts tonight from ECM, GEM, GFS OP and GFS Control The first thing to say is the GFS OP looks out on its own tonight but even that has some heights over Greenland whereas both ECM and GFS Control have very strong blocking over Greenland so it becomes a question of modelling the trough. ECM has the kind of chart which, if it was at T+6 in early January, would have many salivating uncontrollably. It's a uniformly cold and bleak chart for the British Isles with a strong NE'ly flow bringing plenty of rain or showers. GFS Control has the trough rather further north over Scandinavia so the NE'ly becomes a N'ly or NNW'ly with pockets of -8 850s over Scotland which suggests snow for the mountains. GEM plays a different game with more extensive blocking from Greenland to the north of the British Isles so the flow is more E or ESE over most parts so dry and fine conditions with decent temperatures by day but a risk of frost at night (for both ECM and GFS Control there would also be a strong likelihood of rural ground frost under any clear skies). As for the GFS OP, the key difference is the core of heights never becomes established over Greenland but sinks SE back toward the British Isles and by T+240 there are weak heights over us keeping the weather fine and dry. Again reasonable day time values but chilly evenings. As I've stated before, none of this is unusual for May - as Michael Ventrice points out, the collapse of the PV often allows for a negative NAO/AO regime in May. In some years, the block is over Scandinavia as we saw last week and the British Isles benefits from clear skies and warm sunshine but if the block retrogresses to the NW, the air flow shifts to the north-east or north and that just draws in the cold air from north Scandinavia or the Arctic. In addition, we see lower pressure over Europe in response and that either leaves us in the ECM situation (at the sweet spot between the pressure systems) or under the influence of the trough to the east. Either way, it's cool if not cold and unsettled but this is the Buchan cold spell which we often see in early May. It lasts 7-10 days and what often happens is the Atlantic moves back in before the summer pattern asserts.

Only a few spits here, dodging a drenching from the NW. Very nice sunny spells peaking at 14.5c with minimal wind so perfectly pleasant. A good day to get into the garden and earn my keep. I’d make a class landscape gardener Rhododendron tree in full bloom now, a glorious Deep pink

Yep @ Kirkcaldy Those 28th June Storms were the ones I was thinking about, Baseball sized hail in Leicester and a Classic Supercell with Tornado in Sleaford. The conditions were absolutely superb on that day, everything pointed to Supercell Storms, 40knts of Deep Layer Shear and low LCL's. Lets hope for more of those this year

Just in from a 45 min walk mostly in sunshine but with very heavy dark clouds to the West and North which are edging this way. 13C with the rain just starting now. In fact it is bouncing hailstones! oops duplicated post and photo!

What a great sky

Time lapsed the squall line as it passed through Hayward’s Heath. Slight splitting of the cell was observed with a small inflow area seen on radar and some very weak rotation on the left hand side. Lots of lightning loud thunder and hail.

Some beautiful convective skies here!

April confirmed as 10.4c https://www.metoffice.gov.uk/hadobs/hadcet/mly_cet_mean_sort.txt

Beautiful cumulus tower developing to my SE.

Oh dear i suspected this would happen and some of the ens inc the op and control have been showing this for the last few runs BBQ it is then.

A good drenching few hours of rain early this morning and already the garden is looking the better for it - if for no other reason than to wash off all the dust encrusted on the foliage from the last few weeks of dry weather. After the damp morning, drier in the afternoon with a few glimpses of the sun. Light winds and feeling cool if not cold, with a max of 10c. Every year have a mystery here in that you suddenly see a lot of House Martins for a day or two (as was the case last weekend) then they disappear completely before reappearing en masse a week or two later. This year is proving no exception with none seen since Saturday. Regarding traffic, roads round here are definitely busier than previous weeks; people are not taking things as seriously and the situation is going to get worse again with the muppets in London declaring this evening that the worst is over and all is well.

Been a while since there has been some decent convection here

Oooolalala

We've had one shower this morning and have cells passing parallel to us (as always happens). Southwest view... Northwest view... And the radar image.. As you can see, this happens Every. Single. Time. Meanwhile my friend in Edenbridge is enjoying the storm of his life. I'm happy for him, but I'm wondering when it's going to be my turn.

I don't count hearing a couple of distant rumbles. It has to be a direct hit or nothing at all.

Hi Mark, just seen this sorry. The surface wind looks to be generally from the east and drawing in air that's at fairly typical temps for the time of year. Generally mid-teens to low 20s depending on how much sunshine there is, but may only be low teens on eastern coasts.

Got some lovely cumulus clouds this morning, also had a heavy shower that lasted about 5 mins

Very dry here in April too. In fact a very dry March too. No swallows or martins here yet (their nests all seem to have been adopted by sparrows) although I've seen them in other places I have visited in the last week.

Looks more promising now, reports are that it has reached naked eye visibility

Good morning, peeps...But the GFS 00Z isn't all that summery, temperature-wise, it has to be said, though there should be quite a lot of sunshine; and the scrag-end 'offers' some, very limited, suggestion of an eventual break in the easterlies...? T+96: T+240: T+312: T+384: And, worse still, the operational run is on the warm side of the ensembles!

We were in Inverurie yesterday for the first 'big shop' in exactly 2 weeks (local co-op shop last weekend). I'd say it was slightly busier in and around the shops, but still very quiet in the main town centre. Had a moment of inspiration and finally picked up flour, how exciting is that, lol. JG Ross bakery up near Morrisons is bagging up thier bulk supply into 1kg bags and selling in the small shop there. The wet weather yesterday was a welcome change, enough rain to have hopefully soaked in to the borders and grass. Would prefer warm rain if possible as at 7C it felt like we were back in Dec/Jan. First day I haven't done anything in the garden for weeks. I'm back in work (school) this morning for the first time since the schools closed, which is going to feel very strange. No idea what pupils I'll be supporting so I will be 'winging it' for 3hrs.

Day 2 Convective Outlook VALID 06:00 UTC Fri 01 May 2020 - 05:59 UTC Sat 02 May 2020 ISSUED 20:24 UTC Thu 30 Apr 2020 ISSUED BY: Dan A cold pool will reside over the British Isles on Friday, associated with a multi-centred upper low. In general, one low will be located over the North Sea, with another near Northern Ireland, and therefore slight ridging aloft over England between these two upper lows. Diurnal heating will gradually yield 200-500 J/kg CAPE, with numerous showers likely to develop - several will already exist first thing in the morning due to occlusion debris drifting southeast in the mean flow, but the coverage of showers is expected to increase by the afternoon. For the most part, shear is relatively weak and instability lower than Thursday, suggesting that lightning will be fairly isolated and hence the risk is considered just below SLGT threshold (20-25%). Convection may become particularly focussed during the afternoon and early evening along a pronounced low-level convergence zone stretching from SW Scotland across northern England towards Lincolnshire. Profiles from south Wales / south Midlands southwards into southern England will be drier and increasingly subsided, suggesting any showers here will be more isolated and generally not as deep. However, shear will increase here later in the afternoon and into the evening, and so any showers that do manage to develop could still produce a few isolated lightning strikes - particularly in SE England - but it will be somewhat of a fight between increasing shear and gradual reduction in convective cloud depth. Showers will weaken and reduce in number during Friday night, but are still likely to persist in places due to both proximity to the upper low and old occlusion debris. Convective Weather WWW.CONVECTIVEWEATHER.CO.UK Forecasting thunderstorms and severe convective weather across the British Isles and Ireland for up to the next 5 days.

I'm certainly not gonna lose any sleep over this 18z run.. Ntly??? Pull the other one... Thats about as likely as a 1 legged bloke at an ar@e kicking contest. I've not viewed the 18s for some time til now, and you know what... I'm glad... Its the same far fetched story as ever, the garden path is the only place it will ever lead us. I look forward to those heights being gone come the 0z runs.. Don't have nightmares...

Hello Looks like the SE has seen some lively weather today. Similar in Prague, gone are the blue skies and have had thundery showers, strong, cool winds and plenty of cloud. An active front is sweeping through as I type, with rain and wind lashing the windows. Hope all are safe and well, including loved ones. Mine are all ok, apart from one friend that works for the NHS. She’s now recovering well from the virus but had a very nasty few weeks and she never makes a fuss (typical Scorpio ️). Makes me take social distancing and hygiene seriously.

You nailed it Zak. Cracking ECM.. plenty of warm sunny spells at this stage looks a good call... Could be time to fire up the barbi again next week, which in this household is a big occasion BIG UP ALL FRONTLINE WORKERS... LOTS OF LOVE AND RESPECT. Keep safe...

Storm passing over combined with the evening light giving a lovely double rainbow here - just in time for the NHS clap!