Ian Fergusson

..... and looking decidely ominous on M25 cams underneath it!!!

Here's how it looks via Netweather's own feed a few mins ago.... still developmental. Could go pop.

It's got potential to get lively.... still developing on radar. I'm watching it live-time on Highways Agency video from the southern section of the M11..... nothing like 'virtual' storm chasing, eh?!!

Recent radar below for Chigwell and environs...

Yup, there's some genuine stuff on radar developing right now into that part of Essex. Diurnal showers for now (as opposed to the main action later) but they've got potential to go skywards pretty quickly, as you've clearly noted beneath one of them!

PS: I checked out the most lively looking area on radar near Burnham-on-Sea using HANET, but it's not looking like much is gettiing down to the ground (see dry scene below directly beneath it)

It can indeed do so - a more typical scenario is for the radar to pick-up on genuine PPN falling, for example, from mid-level clouds but then evaporating through a dry, warm boundary layer and never materialising at ground level. There's all manner of similar artefacts to by wary of, including the radar over-reading at it's extreme range; or for that matter some of the useful little clues it can offer, such as 'spiking' from hail production aloft in CB cells. If I spot any intteresting such stuff later today, I'll highlight 'em for you.

Hi guys, It's a weak(ening) feature, seemingly fed also by a bit of surface convergence focus into Somerset.... the SREWS it's passed over have shown zilch, despite radar hinting at that little line of PPN being squeezed from it. The upper forcing will sttart to show it's hand from now onwards into the SW.... we'll see how it all pans-out from now!

Hi Chris - that's very unlikely to be actual PPN. It's almost certainly the radar picking-up reflectivity from the growing Cu / TCu cells. You'll note a scattering of similar returns elsewhere (including W & N of London).... but it's a start, for sure!!

For those interested - - One study example from last year (straying a tad off-topic on this one occasion, but posted here to save doing so on another area of the forum!) = http://news.bbc.co.uk/1/hi/health/7931945.stm

I refer you to the recent compelling research linking migraines to thunderstorms and falling atmospheric pressure.....!

Yes. Especially as we're expecting some convergence-driven influences up across Herts northwards. And this is one weekend when I decided not to return to Welwyn Garden City. Lucky me (not).

Indeed so - hope the hill walking fraternity are being sensible under those conditions. We've already seen how dicy things can get, with those multiple casualties a few weeks back in Cumbria.

Yeah - having said all that, and albeit it I can't paste the modified NAE frames here to show you, it's a fairly strong shower signal from around 1900BST this evening in the likes of N Somerset, Bristol, up northwards through much of E Wales, Glos, W Mids etc., but I stress how the prognosis delivers the heavier / thundery stuff further to the east / NE. In broadcasts yesterday morning, on the basis of the model output at that stage, I'd indicated that some BBQ's held here in the West Country on Saturday evening could get a bit of a hosing and I've no reason to modify that opinion, albeit not a widespread risk!

Well, GFS had always wanted a more westerly solution for the plume engagement. There's a prospect for showers from the unstable mid--level (ACCas) cloud that'll spread into the SW later, but actually we're expecting a fair bit of the PPN in the West/SW to be dynamic in nature, rather than convective. Having said all that, the NAE signal for PPN is notably low across most SW/western England districts today and tonight; the main action will be in the east/SE, as earlier noted. Tomorrow has a far wider showery signal generally; however higher chance of CB/TS activity in these parts is early next week(Tues/Wed).

PS: For lightning aficonados, the ATDNet system has just picked-up the first SFERIC for the day - in the growing cell that's now turned thundery just offshore from Osgodby, near Scarborough.

"For some" being the key phrase. As the Chief F/C at UKMO Ops Centre has been at pains to stress in our briefings today, confidence in the evolution later today / overnight still remains low and our expectations are, of course, based increasingly now on the signal from the high resolution (UKV) products. This destabilisation process today is a really complex cocktail and the overall level of regional - let alone local - forecast detail remains low. Worth emphasising this at the outset! The primary area of upper forcing will edge into the SW during this evening (note the conspicuous plume on Vis / IR imagery out of Brest northwards with some PPN at the edge of radar range); the forcing then transfers northeastwards, to sit across Lincolnshire and environs by around 08z on Sunday. As you'll note from the raw (unmodified) product available on some websites, NAE is keen to develop thundery PPN associated with this, across a fairly wide area, which then - with time - effectively morphs into a back-bent occlusion. Meanwhile, the heavy rain associated with the plume edging northwards over the Channel to parts of SE England will become a cold front. Albeit closer to the SE quarter in the early phase of this complex evolution, we expect it to then move back across into the continent. Worth also stressing that UKMO cautions a 50 to 100NM error bar (east-west) on the location of this plume engagement (it's been very variable run-to-run and inter-model, as many of you will doubtless have noted). There's some impressive-looking modelled ascents in this plume for the SE.... assuming it finally shows-up (roughly) where expected! As for the rest of today, we'll see diurnally-driven showers developing in some well-signalled convergence zones, most notably from parts of eastern England up to Scotland (some very untable ascents for E Scotland). NAE is keen to throw-up 20 to 30mm peak values around Lincs and the Humber; with 25mm in a convergence zone expected to form over SW Scotland during Sunday morning. Cheers, Ian See my last post.... you are in one of the best spots today / this evening, for sure.

Agreed. UKMO-GM also yet to be convinced on the E-W positioning (sizeable error margin) and a more westerly bias for plume engagement wholly plausible. We'll await the next runs with interest. Timing of the breakdown also open to major uncertainty (Saturday evening onwards seems a reasoned punt for some districts...stress 'some')

Folks along the SE coast (especially here, but not exclusively so) might want to keep an eye out for embedded TS - tomorrow, Tuesday.... the split frontal progression is likely to generate instability in the shallow moist zone in various districts but more notably through areas of the eastern English Channel, based on latest UKMO high-res modelling and modelled profiles. Best, Ian

Interesting..... in a med-range briefing, UKMO Ops Centre advised us earlier today about some corruption to the overnight GFS ensemble products online (not sure if it's still an issue??), as follows: "00z model comments: .....EC ensemble has 29 out of the 51 ensemble members with a cyclonic circulation in the trend period, while MOGREPS 15 has a more anticyclonic theme, but still establishes a westerly in the trend period. Unfortunately GFS ensemble data is corrupt on websites, but on the few frames visible seems to support EC."

Their 10-15d briefing does talk of a return to milder (i.e. average) temperatures; this transition to a westerly cyclonic influence occurring around or between 15-17th. So the final departure of the cold easterly / NE influence can be fairly described as 'warmer' (especially after this winter!!)

Note my blog update reflecting current UKMO concerns re sting jet.

You'll doubtless be unsurprised that the UKMO's Med-Range guys totally agree with you..... to cite their latest briefing - - Re entire 6-10/15 day period: "Hazards & potential warnings - - Mainly nil, but low probs of heavy rain in W’ern and S’ern regions, mainly early in the forecast period. Also low probs of occasional snow, mainly in N’ern, E’ern and Central regions." Re Wed-Thurs next week: "Many areas fine and dry, but risk of some more persistent rain affecting W’ern, S’ern and, perhaps, some central regions at first, PPN wintry also perhaps at times over higher ground...... Confidence high for a transition to drier, more settled conditions, and for temperatures remaining below normal." Re Thurs-Sun: "....Increasing confidence for largely settled type persisting and high for temperatures remaining below normal...." Re Trend beyond that to 15 days ahead: "Good signal for a blocked pattern, anticyclonic circulation bias and bias towards weather types from the broadly E’ly quarter...." In other words, as you say, it's looking like mostly dry, rather settled but somewhat cold (against the norm) early spring weather for the next 2 weeks once we're past Wednesday (which in itself looks rather iffy at this stage - at least on the UKMO-GM - for any meaningful PPN moving eastwards).

Yes, albeit of course the seasonal bias v. the '87 Great Storm helps in this particular case (i.e. general lack of leaves on trees, helping ameliorate the risk of widespread uprooting, albeit ground will surely be sufficiently saturated to enable this to happen quite readily in exposure)

Rather cold signal / blocking both strongly signalled for first half of March in the detailed UKMO med-range guidance, but really nothing 'wow' that I've read in their documents today re snow threat in any southern areas especially. But unfortunately (for those now tired of winter), any warmer theme remains on hold for now. Conversely of course, with each passing day, the ever-increasing insolation steadily helps mitigate against any 'wintry' longevity lying around across much of southern UK especially, excepting any heavier snow threats (if indeed any even materialise, which looks currently unlikely).