Mariah Carey is saying goodbye to Summer with a sexy bikini photo. On Tuesday, the 49-year-old singer posted an Instagram snap of herself in a black two-piece and matching heels, and holy abs! "From the summer to the fall, we migrate #bye," she captioned it. Naturally, Mariah's sultry shot caught the attention of several fans, including Brandy, who left a sweet comment. "@MariahCarey you look stunning and happy. Always love you. Love #brandyLamb," Brandy wrote. Technically, the first day of Fall isn't until Sept. 23, but if Mariah says it's here well then hello, Pumpkin Spice Latte!