The ornamental design for a trenchcoat with an umbrella pocket, as shown and described.
FIG. 1 is a top front perspective view of a trench coat with an umbrella pocket showing my new design;
FIG. 2 is a bottom rear perspective view thereof;
FIG. 3 is a left elevational view thereof;
FIG. 4 is a right elevational view thereof;
FIG. 5 is a top plan view thereof;
FIG. 6 is a bottom plan view thereof;
FIG. 7 is a front elevational view thereof;
FIG. 8 is a back elevational view thereof; and,
FIG. 9 is a top front perspective view thereof, showing the trench coat storing an umbrella.
The broken line showing an umbrella in FIG. 9 is included for the purpose of illustrating environmental structure and forms no part of the claimed design.