DAVID MIDDLECAMP / San Luis Obispo Tribune

World - How Well Can You Predict a Storm? Accuracy of Numerical Weather Models Varies

In late October, a numerical weather model advertised the possibility of gale-force winds, rain, and high sea and swell on Friday through Sunday.

Sure enough, stormy weather developed. It was remarkable that a model could predict these unsettled conditions eight days in the future.

The European Centre for Medium-Range Weather Forecasts (ECMWF) model called for rain, while the National Oceanographic and Atmospheric Administration’s Global Forecast System (GFS) model did not until just a few days before this fall’s first rain event arrived.

This led to a few readers asking why do these numerical models differ so much in their predictions?

To start, the United States pioneered the groundbreaking science of computer numerical modeling. These numerical models are collections of mathematical formulas, usually run on powerful computers, which produce forecasts for a specific location over several time intervals.

These models are almost indispensable in giving guidance to forecasters.

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