Ritzy does this too...it usually means "Mom, I'm bored and it's time to play!". Her typical time for this is in the evening after we are home from work...if I don't engage in "chase mousie" or some other game, she walkes over to the kitchen door, sits there in "bowling pin" pose and engages her top lung capacity in a meow aria
mmmeeeoooww, MEOW!, meeeeooooowwwwwWW, meowwwwwwww, mEOWW , MEEEOWW!

If I call to her and say 'Ritzy, come on' she will stop....if I go and attempt to pet her or pick her up, she will scurry away just as I reach her, and take the position at the living room door waiting for me to throw the mouse.

As noted in other posts, she has ME trained pretty well!