Those are very good questions. My post above attempts napkin math, so it could probably be off by a factor of 10, but probably not by a factor of 100. Also, I

Those are very good questions. My post above attempts napkin math, so it could probably be off by a factor of 10, but probably not by a factor of 100. Also, I Am Not A Weather Forecast Scientist, just working in a related field (fluid dynamics). So I could be wrong about stuff here. As for shared models and data: I know Norway and the UK do a lot of this. I imagine so does the US and Canada/Mexico. Also, keep in mind that weather modelling relies heavily on running an ensemble with random variations in initial/boundary conditions. So a lot of the computational cost comes from running hundreds of these simulations. My guess is that you don't run the large area 100 times, just a few times and then perturb it for all your local area simulations.