Well its happened to me too...though I suspect it was some sort of wind shear rather than any sort of tornado.. water spouts I have seen aplenty and it was not one of those.
Anyway, about 45m off the coast of GA, heading North to Southport, NC, a large front passed.. seas built to 14ft and winds to 40kt+ from N.. eventually, wind veered from N>NE>SE and reduced to 15-18kts and seas subsided to 5-6ft quite quickly.. a few puffy clouds was all that remained so we put out full sail and felt relieved after a tough 14hrs...we spent an hour moving along nicely on a broad reach on starboard tack heading about 015....made coffee, all was well with the world...even had foulies drying on the rails.
Without warning, or visible signs on the water, in an instant the wind was 45-50kts from NW, backing both Genoa
and Main.. boat had stbd rail, one lifeline and cabin
side in the water, but luckily it didn't make its way down the companionway
.. after that one second of WTF in disbelief, I simply let both the mainsheet and genoa sheets
fly... the boat bobbed up and leaving the main to its own devices,, tried to tame the genoa with the stbd sheet and furl it as fast as humanly possible.
Really don't know what I could or even would, do different.. with the boat heeled like that and the prospect of water free falling down below there want much time for niceties.