Concatenate line 1 to the end of line 2

[C0ppert0p]

When the pattern of line one is ^[OAT][OAT][OAT]:
and pattern of line two is ^......13

I want to be able to concatenate line 1 to line 2:
eg:

OTA:
10/12/13

becomes:
OTA:10/13/13

I can do this in two steps but I'd like to do it in one

[ben_josephs]

Find what: ^([OAT]{3}:)\n(.{6}13)
Replace with: $1$2

[C0ppert0p]

The perfect solution.
and a teachable moment

Thanks Ben