Do you use WRF as an input? I think graphcast uses some kind of NWP input (qhich in my mind i've equated to WRF). Thank you for offering to answer questions!
We use a commercial meteorology service (aka Openweathermap with resolution 500m x 500m ) as one input so they might use WRF data (and indirectly my model as well).
OWM was chosen, because they provide an easy api for providing general weather data.
Last I checked the AI models still used the same initial conditions used in models like the GFS and ECMWF which is a combination of a previous forecast adjusted with observations.