A barometer will give you surface pressure, but that's a field that tends to vary relatively slowly over the surface of the Earth. The calibrated weather stati

A barometer will give you surface pressure, but that's a field that tends to vary relatively slowly over the surface of the Earth. The calibrated weather stations that exist at every airstrip do a reasonable job of providing these conditions over land, and the residual of "pressure from phones" probably won't help all that much. The data that would be most valuable to initial conditions is upper-atmosphere winds -- this is the kind of data given by weather balloons. In clear air there's no great way to measure this from either the ground or from space. One important supplemental data source here are aviation reports, from planes flying at altitude and particularly trans-oceanic routes. When air traffic was largely curtailed during the early phase of the Covid pandemic, weather forecasting suffered a bit for the lack of data (see eg https://www.ecmwf.int/en/about/media-centre/news/2020/drop-aircraft-observations-could-have-impact-weather-forecasts https://www.ecmwf.int/en/about/media-centre/news/2020/drop-a...).