Amber Ferns was last seen at around 4.30pm in Hercules Road on Monday 10 January 2022 when she left the area unexpectedly.
Amber is described as white, approximately five feet four inches tall and of average build with long straight purple hair. She was last seen wearing a fluffy grey coat and knee-high black boots.
Chief Inspector Stuart Pitman, of Dorset Police, said: “We are becoming concerned for Amber’s welfare and are keen to locate her as soon as possible to make sure she is all right.
“I would urge anyone with information as to her whereabouts, or who sees a girl matching the description given, to please contact us.
“I would also like to make a direct appeal to Amber if you read this – please make contact with us or your family and let us know where you are as we just want to check that you are safe.”
Anyone with information or knowledge as to Amber’s whereabouts is asked to contact Dorset Police at www.dorset.police.uk, via email email@example.com or by calling 101, quoting incident number 11:193.