I always wondered how they generate their in house models as well. Something like weather models are extremely demanding and actually really need to be done using quantum computers, NOAA just got a upgrade last year to their super computer which is cool to see. What I think probably happens is they have some sort of program that allows them to import some generated model. After it's imported they can then adjust certain things like wind direction and thats what you see them using. They can do this on their computers since they are't trying to predict the weather, they are basically telling it what they want.