This is from UK Weather Scientific who used to be Met Monkey I think? What are thoughts on this?
DANGEROUS THUNDERSTORM STATEMENT for Wednesday 21st June 2017 from 15:00 until 06.00am Thursday 22nd for the potential of dangerous supercells.
There is a risk of dangerous supercells developing today across Northern England, North East England (Newcastle) and surrounding areas with a slightly lower risk for the Midlands. The situation is highly complex and a little uncertain due to the number of potential limiting factors however it is expected that a few supercell thunderstorms exhibiting rotation will form later this evening (dependant on heat and trigger locally).
Thunderstorms that develop in conditions present today will be capable of producing large or very large damaging hail, damaging straight line winds and moderate strength tornadoes, not too dissimilar to those that form in the states. In addition usual severe characteristics typical with storms such as frequent lightning and flash flooding will be observed.
Severe thunderstorms are also possible across the N Midlands and into E Anglia although the threat is more uncertain and isolated due to the presence of upper ridging drying out the vertical profile. Nevertheless any storm that does manage to fire will most certainly become severe and dangerous.
It must be stressed that any storm that does develop today will need extremely close monitoring and we advise the public to be very weather aware and on high alert. The main risk is considered to be later this afternoon with focus more on the evening when heat and cap breaking is most probable. Please share this post with as many people as possible and rest assured through the day further updates will be provided. A potentially dangerous day of weather locally. As is always the case with set ups like these many places will remain dry or could miss the core of any storms but regardless the violent nature of today's storm potential warrants utmost vigilance and awareness. Stay aware and stay safe.