how accurate are the weather models for a 3-day forecast?

Question

need this for school. my classmates say after 3-days its like 50%. i need websites and proof please.

Answer 1

I'm afraid this is not an easy question to answer. When you say "50%," what does that mean? I think the forecasts these days are better than that. Skill improved dramatically during the decade of the 1990's. For actual numbers, you can go to the website

http://www.emc.ncep.noaa.gov/gmb/STATS/STATS.html

which evaluates weather forecasting model performance and you'll have to slog through numbers and graphs and try to understand what terms like "anomaly correlation" mean, because that's how accuracy in forecasting is measured. Sorry I can't explain more, but it's a complicated subject.

Answer 2

What I would recommend is two good books on the subject. The first is a popular science book written by James Gleick in 1987 entitled Chaos: Making a New Science. Although a little dated it addresses the limitations on numerical forecasting very well. The second book "Calculating the Weather" by Brederik Nebeker, written in 1995 covers the entire history of numerical forecasting in a very readable manner including the accuracy of various models.