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I can't help wondering what it would be like to be under it in a boat. Presumably the cockpit would instantly fill to the coamings. There would be nothing much left of the sails. The mast might or might not come down. The hull would be driven down somewhat but would bob up again. Anyone in the cockpit would be severely injured and would be lucky to survive. The hatches might be stove in but I don't think the boat would fill.
The terminal velocity of a standard raindrop is ~= 10m/s.
Purely on the basis of that video, I estimate the downspeed of the parcel to be about 40m/s. Area of a 30ft boat is 22msq. so v approx 1.1 tonnes of rain arriving in one lump at speed at very nearly 90 mph. Think of a small fast car hitting the boat
I know climate change is happening, but I rather think that if that starts happening in the Solent, the danger of being being caught in it in one's boat would be the least of our worries. Item number 1,452 on my "this is why I like living where I do" list