Helen was last seen around 1300 this afternoon in the area of Upper Bennett street in the city.
A police spokesperson said: “Helen is currently wearing a beige coat, lime green trousers and white shoes.
“She is described as having a head of white hair and walks with a stoop in her shoulders.
“We have no direction of travel.
“Helen is very vulnerable as she is currently in the early stages of dementia and which would affect her memory and her ability to navigate.
“Our eye in the sky is doing its thing but we could always use the help of the eagle eyed community.
“Please report any sightings on 101 quoting CC1447 of 16/09/19.”