Ian Fergusson

Hi Paul, and apologies for the delayed reply. I'm up again at 0300hrs for work and hence my 'day' (effectively a misnomer) tends to become somewhat obscured by strange dinner times, bedtimes and such-like! Firstly - I'm by original qualification a (chartered) biologist, not a meteorologist. My initial route to the BBC, many moons ago, was ironically through academia / field research studying sharks and their distribution/behavioural ecology, not the likes of severe convective events (albeit I undertook the latter informally, ever since constructing an ill-conceived - but effective - bamboo and galvanised steel 70ft 'lightning tower' in my parent's driveway in Jo'Burg, 1975, and yes, it worked..... rather well. Far too well, for my Dad's liking)! I won't bore you with the circuitous route I've taken to now broadcasting in my other lifelong passion (i.e., weather, as opposed to sharks, with aviation coming a close 3rd) but suffice to say that I've had MetO training and do maintain a semblance of the BBC/MetO tradition in employing scientists of one guise or another. After all, my former BBC (now GMTV) colleague Kirsty McCabe was a research geophysicist by original trade (including for NASA), but for sure, she sure knows her Met stuff, big time, after re-training at UKMO! Now, re your query: This clearly nonsensical term "mini tornado" is not one I've ever seen cited as either (a) scientifically valid nor ( an agreed piece of BBC or any other broadcast weather terminology. If someone spoke of a 'weak tornado' then fair enough: that's cited against a globally agreed scale of definition (i.e., Fujita's, versus the potentially confusing TORRO bespoke version). But ultimately, a tornado is a tornado: the use of 'mini tornado' makes little sense to me; much like talking of a 'mini Cumulonimbus calvus' is irrelevant if endeavouring to separate a UK summer cell reaching 26000ft from a towering, growing giant reaching 50,000ft in the tropics. I'm not sure where you've heard the term broadcast, but I'd doubt it's from an actual meteorologist? Best Ian My ultimate achievement was slipping "line convection", "frontolysis" and "tornadic" into three BBC TV forecasts a fortnight ago (with proper explanation, I hasten to add). Rich needs to beat this, so ANA-front is a good start. But he didn't reckon on me being back in work tomorrow at 0400hrs. Can I outdo him? It's possible..... ;-) Francis also talked of tornadic storms (sic) yesterday in the Midlands on his Sky gig.

SFERICS unlikely Paul - latest MetO NAE and high-res modelling suggest embedded tops on the ANA-front up to only FL 12-14 so we're not expecting a thundery feature to any great degree (if at all). The wind / squall-line / tornadic potential remains the primary interest (as well as rainfall obviously). The prefrontal conveyor will be blowing a steady 60+ kts; marked wind shift as the front passes and there's good agreement in the last NAE / severe weather diagnostic runs for marked low-level vorticity. General rainfall expectations range at 5-10mm under each hour across the front but more for Wales (15mm in 3 hours) . MO high-res model suggests classic ANA-front (rear-sloping) for this one tonight and some lively line convection elements with fairly wide swathe of 50-ish knot squally gusts inland and >60 coastally. In the likes of Bristol / Weston / Glos, you'll find these pick-up markedly between 2100-2300hrs; Swindon along M4 to Reading around 00Z-01Z Wed, with the NAE runs today all consistent in bringing the heaviest precip across Bristol at or soon after midnight. By 05-06Z we expect the whole show will be clearing out of East London and indeed nearly out of Kent (heavy and perhaps thundery showers then tomorrow at times for the south coast and indeed some other areas). Cheers Ian

Indeed I did - not least as the Met Office severe weather diagnostics (and yes, we do see them when there's a specific tornadic potential highlighted from the high-res modelling) are suggestive of a very lively scenario as the ANA-front passes through tonight. I've no qualms with mentioning tornadic potential in my TV forecasts if the data is unambiguously suggestive of such a set-up and have done so before. Moreover, perhaps contrary to popular belief, there's no corporate communication 'block' enforced either from BBC or MO in discussing such stuff on-air, so long as done responsibly; in keeping with specific MO Chief Forecaster guidance (as per today) and with a proper, rational scale of emphasis (indeed I was able to add extra detail on local radio this morning across the West). Clearly this is far removed from issuing formal warnings in the strict sense; that's a whole different problematic area of public communication in the UK (and indeed on mainland Europe, where supercell events are more common for some countries).... especially when stressing to a (non-specialist) public the differences in accurately forecasting or nowcasting supercell-spawned tornadic events over, say, the US Great Plains, versus accurately calling - at a local level - the more typical microscale / short-duration / non-supercell / non-visible / non-damaging events we more frequently encounter here, not least when any visible sign of such (funnels etc) is shrouded in both the darkness and likely heavy rainfall, such as will accompany tonight's ANA-front passage. We'll often thus talk in more generic terms of 'very squally winds, possibly damaging in places', which covers all bases for the public audience and sensibly so, in my estimation. Much like shouting 'shark' on a Mediterranean beach, often the public can't differentiate (nor frankly care: a fin is a fin) between a white shark or basking shark. Ditto, to most British public, the word 'tornado' - especially if spouted on BBC TV in a formal warning sense - conjurs-up a stereotypical image of a looming F5 beneath a wall cloud, demolishing some part of Wichita or wherever on Discovery Channel, and being replicated somewhere in the UK. The Brum 'wedge' event aside (and some historical equivalents), such conspicuous events are exceptionally rare in the British Isles.... fact. In other words, the warning would create undue panic and not least given how the nowcasting / spatio-temporal accuracy of forecasting such 'gustanados' (as the US dub them) and non-supercell tornados is generally poor at the best of times. Best Ian

Exactly right. Still a risk of severe t-storms but next model output might downplay the thundery element; we shall see. In any event, it's the rainfall that remains the key (and perhaps disruptive, for some) feature.

Sure do. I'm up in the NW (Bradley Stoke area).

(and of course I mean air mass )

Yes, it's been hit and miss, for sure. We had neat little thundery airmass cell pop-up just south of Bristol over the weekend, which inspired some nice viewer photographs taken after dark of CG's near Long Ashton, but the main action was the line of intense cells which 'grazed' Glastonbury Festival on Friday night and heralded a busy spell for the Fire & Rescue Service down that way, tackling lightning-induced structural damage and lightning-ignited property fires in parts of Dorset and Bridgwater, Som. I suspect they might be equally busy in some (maybe the same!??) districts tomorrow, too. Oh yes, and on the topic of local convective weather recently, we had the interesting funnel cloud in South Wilts on Friday evening, formed from some non-thundery and very low-precip convergence cells near Stonehenge. I received good photos of this one from different witnesses (I showed them on TV in our Saturday evening bulletin).

Certainly still a chance anywhere across West Country and Wales. Bristol included. Sorry to be unspecific but the nature and intensity of this feature has flip-flopped so much in recent model runs. But we're still suggesting possibility of some localised downpours perhaps touching 30-50mm. I stress localised. Either way, the surface run-off from lesser accumulations could become pretty bothersome for some areas; localised flooding certainly possible. Could be an interesting morning but I only get hyperventilated once I'm actually seeing reality real-time on the radar and hundreds of CG's on our ATDNet system!

Hmmm.....more NNW track really; current PPN prediction takes it up towards Plymouth and environs towards dawn, then an easterly shift with some heavy pulses feeding northwards into Cornwall / Devon /Dorset / Somerset; more of a weaker, showery signal trailing northwards up in Bristol and Glos by mid to late morning onwards, but take it all with a (major) pinch of salt re local detail, as the next model output will undoubtedly see some modifications as we try to understand the shape of the upper trough and how this will drive the areal and temporal extent of forcing. Certainly the risk of some potent localised downpours, but where, exactly....? Yup, welcome to my world at 0400-1130 tomorrow. But for best guess, I'd hope the culverts are suitably cleared of debris in Crewkerne, for example. Cheers Ian

Hi Andy, re (1) The PPN (MCS) across the channel, yes, current thinking takes it on a trajectory more towards SW peninsula rather than due north, as you suggest; re (2) Actually, Rich is a Netweather subscriber now too, after I convinced him earlier this week I'll try to update the forum with the NAE's spatial and temporal handling of the PPN intensity here in the SW once I see the new run..... after I'm back at our weatherdesk at 0400 tomorrow morning and who knows, it might all have changed complexion by then.... again!

Indeed so, Steve, a definite case of wait and see. But yes, the latest MO's (NAE) output suggests the focus being a tad further westwards, through the likes of Taunton northwards to the Bristol Channel (plus anywhere west of here during the morning; e.g., Exmoor, N Devon etc), before it all shifts north and somewhat eastwards, weakening as the upper feature over-runs. But there's been some considerable run-to-run variance in the regional detail, plus GFS is still eager to beef-up the collective totals beyond those indicated in the latest NAE..... all symptomatic of the problems in nailing this one down with any certainty, re the areal extent of any genuinely severe weather. It could be that you still get a real deluge in W-s-M; let's see what the next model output and high-res PPN prognosis offers. The risk indicated by the MO's regional advisory certainly remains valid. Best Ian