Dear Joe,
It is easy to specify wind input to FAST v8 with step changes by using “uniform wind” files. See the documentation supplied with the InflowWind module for instructions: wind.nrel.gov/nwtc/docs/InflowWind_Manual.pdf. In older versions of FAST, the “uniform wind” files were called “hub-height” wind files and were entered in the AeroDyn input file instead of an InflowWind input file.
Best regards,