Unexpected thunderstorms; September 1st, 2017.

[LetItSnow!]

The early hours of September 1st, 2017 brought unexpected but very severe thunderstorms to the south-east of England. Not only was it the intensity that makes them memorable to me but also the fact that (as far as I remember) they were largely unforecast and occured in a cool pattern. Proof you don't need heat to get big storms.

After a brief warm spell, the closing days of August 2017 were cool/very cool with a slack NW flow. As high pressure built in from the mid Atlantic, a shallow trough became embedded in the mix and brought instabillity into the 1st. You can see the trough develop and pass into the low countries on the synoptic charts.

 

I remember vividly being at home during the evening listening to music with my headphones in minding my own business when a flash from behind distracted me, only to my surprise there be a vivid lightning show. I checked the radar and a rash of severe thunderstorms were clung onto the south-east. Over the course of a couple hours the storms remained slow moving with torrential rain practically staying in place as storms back-built, dumping copious amounts of rainfall and causing localised flooding (coming after a locally exceptionally wet summer too). Most notably however was that despite it being night I could make out that there seemed to be a tornadic element with the clouds rotating and I did see what looked like a funnel cloud/tornado develop in the sky out my bedroom window, but didn't end up coming to much. It remains one of the most intense thunderstorms I've witnessed along with June 25th, 2016 (unbeaten to this day) and October 23rd (or 24th), 2022.

Do you have any memories of these storms? Were they as intense in your area or was it a New Ash Green special? 

[Metwatch]

3 hours ago, LetItSnow! said:

Proof you don't need heat to get big storms.

Not related to September 2017 but 9th May 2023 another great example, a day i'll always remember.

[LetItSnow!]

 Metwatch A lot of notoriously bad summers had a lot of convective episodes and severe storms.