But beyond two or three days the world's best forecasts were speculative, and beyond six or seven they were worthless. The Butterfly Effect was the reason. For small pieces of weather—and to a global forecaster, small can mean thunderstorms and blizzards—any prediction deteriorates rapidly.
It's said that everything is connected to everything. The butterfly effect. You drop a pebble into a pond and the ripples radiate outward, affecting everything. Until finally a fish grows arms and legs and crawls out of the water, and picks up a rock and smashes the next two fish over the head, and we have the first serial killer.