Ensemble Weather Forecasting 2D — Spaghetti Plot & Predictability

Real weather models don't run once — they run dozens of times from slightly different starting conditions, because the atmosphere is chaotic: any two runs that begin almost identically will drift apart at a roughly exponential rate until they saturate. This simulator builds a small numerical weather model from scratch — a pressure field advecting itself across a periodic grid via its own geostrophic wind — and renders it as a pannable, zoomable top-down contour map with live wind vectors. A handful of ensemble members launched from near-identical initial states run alongside one deterministic "control" run: watch their small thumbnail maps peel away from the control as simulated forecast days pass, while a scrolling spread chart and live readouts track the ensemble spread and estimate the model's predictability horizon — the same diagnostic operational centers like ECMWF use to decide how far out a forecast can be trusted.