Ensembles

Timmead · April 19, 2008

Why do the " GFS operational" data often differ so greatly from the ensembles, especially with precipitation, and what data do they actually use? Is the GFS generally seen as the most accurate?

Thanks.

**Paul** · April 20, 2008

Hi Tim, the gfs operational and the ensembles are two different models, although they have the same starting data. The GFS up to 180 hours is at a higher spacial resolution (0.5 degrees) than the ensembles (1 degree) so it will show more local detail. Beyond 180 hours the GFS goes out to 2.5 degrees resolution, with the ensembles staying at 1 degree.

Hope that helps..

Paul

Gibli · April 20, 2008

Worth adding to Paul's explanation is that the operational model also has much more resolution in the vertical than the ensemble model, currently 64 to 28 levels I think.

Is the GFS generally seen as the most accurate? No, over the longer term the ECMWF is generally the most accurate but much of its output is restricted to the national weather services of the member states. The GFS and the UK Met Office model are about the same in terms of accuracy, but only the GFS stuff is widely available, which is why we see it in so many forms on so many sites. There are some graphs comparing various models but can't find them at th moment.

Gibli