Global Forecast System (GFS) Model Previous called the Aviation (AVN) and Medium Range Forecast (MRF) models. Global model and 64 levels Relatively primitive microphysics. Sophisticated surface physics and radiation Run four times a day to 384 hr. Major increase in skill during past five years derived from using direct satellite radiance in the 3DVAR analysis scheme. T382 (~35 km) over the first 180 hours (7.5 days) of the model forecast and T190 (70 km) for 180 through 384 hours--major implications for resolution change!

GFS Just changed vertical coordinates from sigma to hybrid sigma/pressure… sigma at low levels to pressure aloft.

Vertical coordinate comparison across North America

GFS Data Assimilation Has a later data cut-off time than the mesoscale models…and thus can get a higher percentage of data. Uses much more satellite assets..thus improve global analysis and forecasts. Major gains in southern hemisphere Based on 3DVAR

Skill Improvements (ECMWF) Useful skill until: - day 5 2000 - day 7 2003 - day 8

GFS