I guess historically there were fewer weather stations/buoys in the Southern Hemisphere. But satellites provide global coverage today, hence accuracies merging in year ~2000
Reinsurance majors - Lloyd’s of London, Munich Re, and Swiss Re - use longer term forecasts to asses weather risks. One factor why parts of Florida are incurring a real estate crash as flood insurance coverage becomes more difficult to obtain or afford.
That increase in accuracy seems to be tailing off seven years ago. Do you not have the figures up to 2024? A lot has happened with the weather in the mean time.
The chart here shows the difference between the forecast and the actual weather outcome for forecasts 3, 5, 7, and 10 days in advance. The metric used here is the “500 hPa geopotential height”, a commonly used meteorological measure of air pressure — which dictates weather patterns.
The biggest improvements we’ve seen are for longer timeframes. By the early 2000s, 5-day forecasts were “highly accurate” and 7-day forecasts are reaching that threshold today. 10-day forecasts aren’t quite there yet but are getting better.
This data comes from the European Centre for Medium-Range Weather Forecasts (ECMWF), which produces global numerical weather models and publishes analyses of its errors over time.
While national weather agencies use much higher-resolution processing to get local forecasts, these global models provide a crucial input into those more local systems.
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but I guess I'm the only person nit picky enough to care
Three-day forecasts have been pretty accurate since the 1980s, and have still gotten a lot better over time. Today the accuracy is around 97%.