Error Sources in Weather Forecasts

1.  Inaccurate model assumptions (usually necessary oversimplifications)

2.  Excessively coarse grid (in latitude, longitude and/or altitude)

3.  Excessively large time steps (Δt)

4.  Non-global nature of most models, imperfect knowledge of boundary conditions

5.  Uneven grid points; sparse data in some locations, especially at sea

6.  Exclusion of small weather systems (e.g., small thunderstorms)

7.  Oversimplification of terrain

8.  Chaotic nature of atmosphere

9.  Observational errors