THE MAIN REASONS WHY MODELS HAVE FORECAST PROBLEMS
THE CURRENT STATE OF THE ATMOSPHERE MAY NOT BE DEPICTED ACCURATELY ENOUGH. BAD QUALITY CONTROL OR LOST DETAIL MAY BE IMPORTANT.
SMALL ERRORS IN THESE INITIAL CONDITIONS WILL LEAD TO LARGE FORECAST ERRORS OVER TIME.
THE MODELS MAY NOT HAVE SUFFICIENT HORIZONTAL OR VERTICAL RESOLUTION TO DEPICT TERRAIN AND WEATHER SYSTEM INTERACTIONS (OR TOO MUCH RESOLUTION!).
THE MATHEMATICAL CALCULATIONS IN THE MODEL ARE APPROXIMATIONS
*THE MODELS HAVE STRENGTHS, WEAKNESSES & BIASES