Beyond（在…的那边） two or three days, the world's best weather forecasts（预测） are speculative（ 推理的） and beyond（在…的那边） six or seven, they are worthless. The butterfly effect is the reason. For small pieces of weather and to a global forecaster（预报员）, small can mean thunderstorms and blizzards. Any prediction deteriorates（(使)恶化） rapidly（快）. Errors and uncertainties（无常） multiply, cascading（像瀑布般大量倾泻下来） upward through a chain of turbulent（狂暴的） features. From dust devils（魔鬼） and squalls, up to continent-size eddies（旋转） that only satellites（卫星） can see.

  The modern weather models work with a grid（网格） of points of the order of 60 miles apart.