1. Ignore the error and proceed to run the tool.2. Perform the 2 step process of projecting the raster - NAD_1927 to NAD_1983 using the "NAD_1927_to_NAD_1983_NADCON" transformation - Project resulting NAD_1983 raster to NAD_1983_HARN using the "NAD_1983_to_HARN_<state>" transformation