suddenly vocal kitty

Question
just sent this question to another "expert", but would like to hear your response as well...
I have a 7 and a half year old fixed female cat named Tippy.  I have always bragged about the fact that my cat is so quiet.  She's not mute or anything, but mostly she uses a sort of squeaky purr sound, unless she is stuck somewhere. My co-workers and friends complain about their cats keeping them up at night and I always tell them I will never get another cat because I don't think there will ever be one as quiet as mine (I've probably had 13 cats in my life, and she's the quietest...I cannot stress this enough).
2 days ago she started in at 6:30am with the kind of yowling you only hear from a cat in heat or in a cage.  She is neither, and seems very healthy.  She hasn't had any recent lifestyle changes... no moves or new people/pets, and she is quite keen on litterbox use.  No fleas, no earmites (as far as I can see), no stomach tenderness or loss of appetite.
She has been having these episodes frequently throughout the day accompanied by pacing, tail flicking, and getting on the table/counter, which she has never been in the habit of doing.  She is still affectionate if you pet her during these episodes, but she seems so...desperate.  She kneads like crazy and can't sit still, and she's quite tense...not like her usual eyes-half-closed self.  I'm quite distressed by all of this, especially with how desperate she sounds...   Any ideas?

Answer
Hi
umm it's a puzzle, you sound very knowledgeable yourself about cats so for you to be worried it really must be something unusual. the only thing i can think of is that she has spotted or heard or can even smell a new cat outside somewhere and this is making her feel threatened and uneasy.

Apart from that i cannot think what else to tell you, if the behavior continues over the next week and you can't spot another cat, maybe it would be a good idea to get her checked out by the vet in case their is something medically wrong.

Sorry i could not be of more help.

Best wishes
Kate