[RichC]

Christ, the runs for France look absolutely spectacular. I can see the whole of France being covered in a mass of MCS tonight and tomorrow. Some of those locations get a decent thunderstorm every day and night for weeks on end.
If only there was a road that shuffles south over a bridge to span the channel!!!

[JohnG]

RichC, on 27 June 2012 - 10:10, said:

Christ, the runs for France look absolutely spectacular. I can see the whole of France being covered in a mass of MCS tonight and tomorrow. Some of those locations get a decent thunderstorm every day and night for weeks on end.
If only there was a road that shuffles south over a bridge to span the channel!!!

Yes but then a lot of France will be under an inversion tonight and Thursday. Still a risk of isolated strong storms kicking off in central areas tomorrow but I think northern France and into Benelux stands a much better chance.

The models are looking very good for the UK on Thursday. I wouldn't be suprised to hear of one or two strong (for the UK) tornadoes and hail of ~3cm being reported before the day is out!

[Matt D]

RichC, on 27 June 2012 - 10:10, said:

Christ, the runs for France look absolutely spectacular. I can see the whole of France being covered in a mass of MCS tonight and tomorrow. Some of those locations get a decent thunderstorm every day and night for weeks on end.
If only there was a road that shuffles south over a bridge to span the channel!!!

Yes some very impressive CAPE over France and Low Countries tomorrow, even taking into account of the GFS over-the-top dew points of 22-24C. Nevertheless, dew points this morning over N France and UK are not too far off the GFS expectations so 22C over N France tomorrow is easily attainable. It is VERY humid.

With steepening mid-level lapse rates from the Spanish plateau overspreading this very moist boundary layer overnight and through into tomorrow, and with cold advection above this from the west tomorrow as the upper trough approaches, this maximises the CAPE. It is as close as NW Europe gets to a Great Plains 'ingredients mix' as far as the temperature/moisture profile is concerned!

There will be a fairly strong cap in place over NE France/Low Countries for much of tomorrow though (as John mentions above) and, additionally, the synoptic scale lift here tomorrow is much weaker than we have over the UK. However, with very strong surface heating through the day, increased low level wind convergence/confluence as a surface trough approaches in the evening, increased 850mb flow by 18:00 and with a gradual cooling of mid/upper level temperatures, I would be surprised if a sig MCS feature did not form over NE France/Low Countries by evening as the cap breaks down from the NW.

For the UK, we have the stronger forcing and better wind shear too (especially from SW England, Wales, Midlands and N England) during tonight and tomorrow as at least one short wave upper trough pushes NE in the strengthening SW mid/upper flow. We could well have our own MCS forming later tonight and then expanding NEwards quickly during tomorrow. Parts of SW England and W Wales tonight are likely to see a risk of mid-level storm clusters breaking out, as well as further east along the south coast too. S Wales, S and E Midlands across to north-western parts of East Anglia and Lincs looks a good bet for some lively activity on the southern side of any MCS that does form during tomorrow daytime.

Further north and west from this, turning very wet tomorrow with a few embedded storms possibly too. I think there will be a south-easterly 'cut off point' to storm activity tomorrow though (e.g. weaker forcing, combined with only moderate instability and also a freshening SW flow up through the Channel killing off the surface moisture). Therefore, southern coastal counties up through to London and Essex *may*(!) quickly have a reduced risk of storms tomorrow morning.

These are just thoughts at the moment....models classically struggle to handle MCS development and propagation amazingly well and once an MCS forms, it starts to heavily influence the flow patterns, surface temps/moisture and also vertical velocities in the surrounding areas too. If a model misses an MCS development at say T+15hrs, its output is pretty much useless thereafter.

This post has been edited by Matt D: 27 June 2012 - 10:51

[Mike Adams]

owen3371, on 25 June 2012 - 20:46, said:

We had a great show of lightning last monday in northern ireland(lough foyle co;derry)(18th) with several c-g,s one of which i caught on camera,the storm moved to within 1 mile of me so i left for my own safety!

Within a mile? I would have left before that! Don't forget if you can hear thunder, you can get struck. But then nobody would storm chase I guess :-)

[PaulKn]

Posted my current thoughts in the forecast thread - an interesting 36 hours to come I think!

[Nigel Bolton]

Might be worth pointing out that Spanish Plumes very rarely, if ever produce tornadoes, though to be fair there is the odd exception, i.e. 7th June 1996.

Might be worth saying that there may be a sig 'BWE' event on Friday.

N.

[PaulKn]

Nigel Bolton, on 27 June 2012 - 11:21, said:

Might be worth pointing out that Spanish Plumes very rarely, if ever produce tornadoes, though to be fair there is the odd exception, i.e. 7th June 1996.

Might be worth saying that there may be a sig 'BWE' event on Friday.

N.

These days they seem to be rare, full stop! I think what you allude to is the fact that the chances of having a plume in place whilst strong insolation is occurring is pretty slim, given the small size of our islands - they have a much higher chance of not coming through during the afternoon simply because there are only a few favourable hours of strong heating.

Another reason is that MCSs often develop on the back side of the plume, and they are not conducive to tornadoes, especially if elevated.

The difference, at least at the moment, as far as tomorrow is concerned is that there may be a relatively unworked area of the plume across portions of eastern England, at the time of peak heating.

However, there is plenty that can happen to change that!

[JohnG]

If I am not sorely mistaken, the Birmingham tornado of 28th July 2005 formed in similar conditions.

[PaulKn]

There was certainly a small EML present on that day, but I'm not sure it was such a marked one as this set-up.

[JohnG]

PaulKn, on 27 June 2012 - 11:37, said:

There was certainly a small EML present on that day, but I'm not sure it was such a marked one as this set-up.

I was trying to find some case studies on the Birmingham tornado online but couldn't find any.

[Nigel Bolton]

JohnG, on 27 June 2012 - 11:29, said:

If I am not sorely mistaken, the Birmingham tornado of 28th July 2005 formed in similar conditions.

Brum tornado formed in warm, moist, heavily modified rPm, where a trough intersected with a warm front to its north. Storm moving northwards up the trough was then forced over the warm front, the juxta-positioning of trough, plus strong easterly flow beneath warm front gave rise to exceptional helicity for a time, causing the storm to rotate. Spanish Plume on this event was well away to the east.

N.

[JohnG]

Nigel Bolton, on 27 June 2012 - 11:43, said:

Brum tornado formed in warm, moist, heavily modified rPm, where a trough intersected with a warm front to its north. Storm moving northwards up the trough was then forced over the warm front, the juxta-positioning of trough, plus strong easterly flow beneath warm front gave rise to exceptional helicity for a time, causing the storm to rotate. Spanish Plume on this event was well away to the east.

N.

Thanks Nigel

[PaulKn]

The airmass was of tropical or subtropical origin, given the dewpoints on the day. The trouble with the term 'Spanish Plume' is that there is no real definition. The Birmingham tornado developed, as Nigel said, as a storm moved across the warm front - this is something which happens quite regularly in parts of the Great Plains, and it's widely understood that tornadoes like to develop just on the cool side of a boundary, where LCLs are lower, and backed flow increases low-level shear and helicity.

[ChaserUK]

well my fingers are crossed and I got a half day today too! DP cuurently 18.1c - very oppressive.

[staffsstormspotter]

Mike Adams, on 27 June 2012 - 10:46, said:

Within a mile? I would have left before that! Don't forget if you can hear thunder, you can get struck. But then nobody would storm chase I guess :-)

Whilst what you say is true Mike, there are plenty of reports of people being struck without hearing any thunder. The lighning stroke can travel many, many miles from initiation to grounding.

Chris

[Mike Adams]

Is it starting?...........

http://www.meteox.co...soort=lightning

[Mike Adams]

staffsstormspotter, on 27 June 2012 - 14:02, said:

Whilst what you say is true Mike, there are plenty of reports of people being struck without hearing any thunder. The lighning stroke can travel many, many miles from initiation to grounding.

Chris

I didn't know that! I will stay in when the clouds look dark then

[Lightningfox92]

Is there a chance that I might actually see something good tonight? If so then what time is my best chance in catching a storm in the next 48 hours please? Thanks.

[lakes]

JohnG, on 27 June 2012 - 11:29, said:

If I am not sorely mistaken, the Birmingham tornado of 28th July 2005 formed in similar conditions.

its the same weather for when we had the Thurrock one in August 2010,

[lakes]

ChaserUK, on 27 June 2012 - 12:41, said:

well my fingers are crossed and I got a half day today too! DP cuurently 18.1c - very oppressive.

DP 17.5 here and 1016.6

I Have a very bad head right now....tend to get them about an hour before a storm so i live in hope lol