Abstract
Several astronomical observatories are currently in operation in Chile. They need accurate weather forecasts in order to have a better observational scheduling and reduce operational costs. The Global Forecast System (GFS) model produces global weather forecasts four times per day and its outputs are freely available on the web. Preliminary results in the estimation and forecasting of several atmospheric properties over APEX and Paranal observatories using the GFS model are presented in this work. The GFS model shows a very good agreement in the prediction of PWV (precipitable water vapor) at APEX, particularly in the PWV range from 0-1 mm using a PWV calculated from water vapor mixing ratio (q_v) profiles. The GFS model can also be used with some confidence to predict near-surface variables over astronomical sites with the implementation of a Kalman filter. PWV estimated from GOES data could be used as a diagnostic tool although it is best recommended the use of numerical models anytime they are available.
