Why does my cat do this?

[Coughee]

At 9.30 every evening my 13 year old cat goes out on to our driveway and meows really loudly, like a loud WOWING noise. We call her in and sometimes she runs in gratefully (as if she doesn't have a cat flap and was stuck out there), other times she takes some persuading to get back inside. Within minutes she's back out the cat flap and doing it again.

She's been fed, she's been watered. She's neutered so can't be calling for toms and hates other cats so I can't imagine it's some attempt to gather a little cat gang either.

I love her but it's tedious and so loud I worry about the neighbours! What's it all about?!

She's singing.
(I have no idea really)
But all of my cats who do this super loud wowing noise are calling to someone.
Has she always done this or is it new behaviour?

The going outside and doing it is new. The wowing was something she used to do if she caught something - Never animals as she's not a hunter, usually she was letting us know she'd 'caught' a hair bobble and as soon as we acknowledged it and told her well done she'd stop 😁

Ah yes, we always knew if our old cat had caught something because of the WOW WOW WOW!
Although 13 isn't that old, I wonder if she's experiencing a bit of confusion? The selective use of the cat flap/requiring you to open the door.
Long summer nights drives them all a bit potty too.

Yes we had wondered about confusion before. Her behaviour has definitely changed as she's got older. She doesn't go out in the winter but spends all her time outside in the summer so maybe she is just singing with happiness! Thank you