The broken line showings in all views are for the purpose of illustrating environment and forms no part of the claimed design. The broken lines of text, numbers, icons, and boxes demonstrating portions of a display screen with a transitional graphical user interface for a mobile device in all views form no part of the claimed design. The areas filled in with pixels illustrate contrasting appearance, within the display screen with a transitional graphical user interface for a mobile device, and form a part of the claimed design. The areas filled in with vertical fill lines illustrate an additional contrasting appearance of a background fill, within the display screen with a transitional graphical user interface for a mobile device, and form a part of the claimed design.
The appearance of the image transitions between images shown in