SimonP

UKASF's forecast is out for 4th July: http://www.ukasf.co....m-forecasts/188

MetO have updated warnings again: http://www.metoffice.gov.uk/weather/uk/uk_forecast_warnings.html?day=1 Whilst the image doesn't reflect it, just about everywhere in the UK is covered now...

Interesting. Laura Tobin on the News at 1 also only mentioned heavy rain, no t-word mentioned... Talk about painting a confusing picture!

Can't help but notice that the MetO have removed the word 'thunder' from just about every kind of text and warning regarding tonight's potential...

I also noticed that the MetO changed their textual forecast for the overnight period Weds into Thurs - they went from "thundery rain probably affecting southern Britain" to "thunder rain possibly affecting southern Britain" yesterday, and now they have removed any mention of thundery activity Bah!

Couldn't help but notice this from the MetOffice's forecast for Wednesday: Thundery rain as opposed to showers and probably, not "possibly" Countryfile forecast did mention it too with a low moving northwards from the near continent, but with it being further east, affecting Benelux area etc. Perhaps subsequent model runs have pushed this further west, which is only a good thing... One to watch maybe?

There will be no UKASF forecasts until the 21st June as forecasters are chasing in the US currently...

ESTOFEX forecast is out and they've gone with a level 1 severe:

Today's ESTOFEX forecast has a chunk of the south covered by a 15-% t-storm risk area. Marginal, to say the least: http://www.estofex.o...ormforecast.xml BTW, there will be no UKASF forecasts until the 21st June, due to forecasters chasing in the US...

I see the MetO have removed the yellow warnings for today for everywhere except N. Ireland.... Wondering if this has something to do with the fact sferics were headed for landfall a short while ago, just to the west of IoW, yet (as usual) have died a death?

This was posted by Matt D over at UKww: ---- A glance at the 00z (1AM BST) soundings for Trappes (Paris) and Herstmonceux (Sussex) is quite revealing, demonstrating why N France received so many active storms overnight and why Sussex did not. As can be seen on the (modified) Trappes ascent, there is a warm nose of temps at ~850mb followed by steep lapse rates between there and 500mb. I have analysed a most unstable, elevated CAPE situation which demonstates the HUGE amount of CAPE available to a parcel of air rising from the 850mb plume. The boundary layer (lowest 1km or ~150mb) near Paris was already much cooler by 00z (probably cooled by rain/outflow from earlier storms) and storms were therefore decoupled from the boundary layer. However, this did not prevent storms forming and persisting as they were growing from out of the plume above. This situation does happen in the UK too, explaining how we (sometimes!!) get active overnight storms. Now looking at Herstmonseux, Sussex - a sounding which is likely to be quite typical of an ascent over SE England. For an appreciable storm risk we really needed to advect some of the warm 850mb plume in from the south to generate the necessary instability to maintain storm cells that were travelling up from France. There is a very slight warm bulge at 850mb but it is very insignificant compared with the Trappes ascent and crucially we don't have those steep lapse rates between 850mb and 500mb to help create that store of elevated CAPE. It was always going to be a knife edge scenario last night as the very unstable air was sneaking right past the far SE of the UK and there was a small risk (accounted for in my forecast) that some of this instability could get advected over the far SE for a time. It is far easier to predict thunderstorms when all the forecast parameters are 'red lining' and the only thing that can go wrong is that the storms are slightly less numerous or active than you forecast. The position of the UK relative to the Atlantic and France/Spain often means we are clipped by the edges of these plumes and a slight shift west or east in the plume can make a HUGE amount of difference to the weather experienced and forecast success. The extensive (and largely unforecast 12 hrs before) raft of elevated thunderstorms that affected the SE and East Anglia on Tuesday 28th June this year is an example where the plume was slower to clear than forecast, with an approaching upper trough rapidly destabilising it creating many thunderstorms over a short time period.

UKASF have updated their forecast for tonight, moderate risk area: http://ukasf.co.uk/storm-forecasts/81

UKASF have gone with a moderate risk for much of southern England and Eire for Sunday (map of areas affected at http://www.ukasf.co....rm-forecasts/64): Areas Affected: Southern Britain and southern Ireland. Synopsis: A complex, multi-centred area of low pressure will be present across much of Britain allowing for large scale ascent and unsettled conditions. An occluded front across northern Britain will be the focal point for a large area of heavy rain which may produce some localised flooding, but no lighting / deep convection is expected with this. However, the warmer, more unstable air further south will have the potential to produce thunderstorms. Discussion: Low pressure as stated in the synoptic discussion will allow for unsettled conditons and suffient SBCAPE values of 500-700j/kg are possible in the moderate zone during the afternoon. ELTs in the range of -40C indicate suffiently deep enough convection for plenty of lightning and also, the risk of moderate hail. Both LLS and DLS values are relatively weak, so sustained updrafts won't be likely, meaning storms will be of the pulse variety, but could produce some brief gusty winds. Funnels are also unlikely except for near topographcially (Wicklow Mountains) or coastline enhanced (south coast of England) boundaries.

hehe, I'll certainly try A good couple more rumbles now - thunder is reasonably distant - probably somewhere towards MK? Unsure, to be honest. Came back from MK about an hour ago and there was certainly some decent TCu, but they've developed into Cb quite quickly.

Thunder just heard! Amazing cloudscapes!

Ah, this old bean again.... The storm chance stuff is purely derived from GFS data. Modelling is not an exact science, otherwise forecasting would be clear-cut. A 51% chance of storms still gives a 49% chance of storms *not* happening. In fact, so many people moan about it, I wonder whether it's worth Netweather actually dropping this. I am not a meteorologist, you're not a meteorologist, and this I know from your comment. Don't get me wrong, I understand your frustration, because I anticipate 90% of people who visit these storm threads actually want to see storms (myself included!), but such comments are pointless. The UK is a small nation, yet can yield very changeable conditions dependant on location. A level 1 severe was issued for a lot of southern England by Estofex, which didn't see anything. I'm not going to slate their forecast though, namely because [a] that's within 40km of a point and check out the team of forecasters, with their Masters in meteo and PhDs in various meteorological (namely severe weather) subjects. Take, for example, Johannes Dahl's paper on lightning frequency - it certainly makes interesting reading, and plenty of fascinating equations for your perusal: http://edoc.ub.uni-m...hl_Johannes.pdf This is by no way anything personal, but such comments really get on my nads. Cheers, Simon

Estofex haven't yet issued their forecast for Saturday.

Thunder is getting closer now; I am being patient, was seriously considering heading east, but may well sit this out a little longer and see what happens...

No worries - and I can empathise, as I was sure a couple of other knowledgeable people also posted their post mortems - but, alas, couldn't find them. Perhaps I just thought I'd read others' views on the situation Amazing that four entire threads were filled for yesterday's potential - there was plenty of anticipation! Cheers, Simon

Has already been explained; Roger J Smith's post mortem, for example: http://forum.netweat...ost__p__2098264

Likewise. Didn't witness any lightning either as per Snow Obsession's post. (I'm actually just outside of Dunstable, in Bucks, FWIW.)

Had some thunder here (distant, no lightning witnessed) and raining - cold front passing through?

UKMO have updated their advisory area; it's now a much slimmer eastern portion of England than it was previously: http://www.metoffice...t_warnings.html Issued at - 27 Jun 2011, 22:48 Valid from - 28 Jun 2011, 00:00 Valid to - 28 Jun 2011, 20:00 Heavy showers and thunderstorms on Tuesday have the potential to bring localised rainfall totals of 20-40 mm in a few hours, with a risk of flash flooding and large hail.

From PJB on the UKWW forums: None of the 12Z Models HIRLAM, GFS or NAE break out much in the SE overnight as the forcing has moved N and E. However cloud growth appears to be occuring over the SW at present... However % chance of storms in the SE overnight appears to be receding. Though Kent and E Anglia remain at risk

A quick look at the Estofex archives reveal they can issue storm forecasts quite late in the day, early hours even. Perhaps they want to see 18Z/00Z model runs before issuance of a forecast.