My Lucy, who interestingly is also a tortie, does the same thing.
It's erie, even if there are no storms forecast, if one's coming she
sits on the back of the couch where she can see out the west-facing
window.  She ordinarily doesn't sit there, because the a/c vent blows
there and she doesn't like the breeze, I suppose.  At the first sign
of storm, she either runs for my bed and gets underneath or hits the
floor and dives under the couch.  Getting under the couch is a bit
tough for her but really enjoyable for me to watch her.  She's a
little big to be getting under there but she just ducks her head and
keeps pushing with her hind legs until she pops under!

Some people can smell a thunderstorm coming often before you see it and before a
human can hear it.  Should be pretty easy for cats.

--
Jo Firey

"Life is not measured by the number of breaths we take, but by the moments that take
our breath away."

I don't remember who it was, but someone here once suggtested that it
may be that they can feel the change in pressure that comes with the
storm. Whatever it is, I also have a couple weather cats - more
accurate than the local TV channel. I used to let Little Bit out when
I went to work. She won't go out if it's going to rain, or get too
hot. And Sammy, who is scared of thundeerstorms, also hides well
before the storm arrives.

Of course I now have Rocky, and he's a total loss as far as weather
warnings go. Rocky lived as a feral, and weather doesn't bother him in
the least. As far as Little Bit and Sam are concerned, he just doesn't
act as a proper cat should. If it's hot and there's a mud puddle,
he'll lay in the mud - nevermind that he's mostly white and will this
be a muddy brown for several days. He'll sit in the middle of the lawn
and give himself a bath during a light rain, a kind of kitty shower.
Last night I let him inside for a little while, like I do most nights.
When he was ready to go, the fact that a storm had blown in didn't
faze him, he just wandered over to his favorite spot on the patio and
laid down, half in and half out of the rain.

my tortie, Emily, does this, too.
Brenda