The Physics of Forecasting

Modern numerical weather prediction (NWP) is applied physics at planetary scale. Chop the atmosphere into grid cells — the ECMWF's flagship model resolves cells around 9 km across, stacked through dozens of vertical levels — write down the equations for fluid flow, heat, moisture, and radiation, then integrate them forward in time.

Every six hours, data assimilation folds in tens of millions of fresh observations — satellites, balloons, buoys, aircraft — to pin down the planet's current state. It's among humanity's most demanding scientific computations, and it runs twice a day like clockwork.