Twin States Weather Blog

More on Computer Models

There are 3 major U.S. computer models. Each uses a different set of complex equations to analyze and forecast weather. Here's a breakdown of each U.S. model:

GFS -- Global Forecast System - This is the primary mid to long-range American model. It goes out 16 days (384 hours). It's primary strength is that it goes out so far. The main weakness however, is that the model solutions beyond about 7-8 days are not very reliable.

NAM -- North American Mesoscale - This is the primary short to mid-range American model. It goes out 3.5 days (84 hours). It runs on a higher resolution, which means it incorporates more data than the GFS. Therefore, in theory, it is more accurate in the short term than the GFS.

NGM -- Nested Grid Model - This is an older American model. It uses old equations. Its primary purpose is to serve as a comparison for the other model.

There are more American models, each serving a different purpose:

MM5 -- Short term model, uses the highest resolution. Generally considered to be very accurate. It doesn't go out as far into the future as the GFS or ETA.

NOGAPS -- This is the Navy's special weather forecast model.

Also, there are a variety of models used to forecast tropicsl systems. I'll write a blog entry on those as we get closer to hurricane season.

In addition to the American models, we use several models of international origin. We use the UKMET (United Kingdom), the ECMWF (European model), and the Canadian weather model, among others.

So, as you can see, we must often wade through a LOT of data to make our forecast.

I'll post again tonight with an update on the weekend/early week rain for next week....AND I'll talk about some very interesting possibilities for the rest of the month!

posted by WTOK Weather Staff @ 5:21 PM