They're using a graph neural network. From the article - "The team leveraged Google DeepMind's GraphCast model as an initial foundation and fine-tuned the model using NOAA's own Global Data Assimilation System analyses".

> so what’s AI about this that wasn’t AI previously?

The weather models used today are physics-based numerical models. The machine learning models from DeepMind, ECMWF, Huawei and others are a big shift from the standard, numerical approach used for the last decades.

AI refers to whatever would have been called "Machine Learning" five years ago.

This ambiguity resulted in some very funny drama on Bluesky: https://bsky.app/profile/nws.noaa.gov/post/3ma754dbtuj2t

> Presumably weather models have been using all sorts of advanced machine learning for decades now

This isn't actually true, unless you're considering ML to be just linear regression, in which case we have been using "AI" for >100 years. "Advanced ML" with NN is what's being showcased here.