Meteorological forecasting for the European Southern Observatory in Chile

The potential of numerical weather prediction to supply a useful support to flexible scheduling of astronomical observations is investigated. We appli ed some common tools presently used in numerical meteorology at regional sc ale in order to evaluate the ability to forecast local meteorological condi tions (cloud cover, air temperature and wind speed) at Cerro Paranal and Ce rro La Silla in Chile, where telescopes of ESO (the European Southern Obser vatory) are sited. The first part of this paper is devoted to evaluating th e accuracy of analysis and forecasts of the ECMWF (European Center for Medi um-range Weather Forecast) general circulation model for ESO needs. With th is aim, analysis and 24-48 hour forecasts from ECMWF are systematically com pared with observations at the ground meteorological stations of Paranal an d La Silla, and with vertical profiles of radiosounding launches at Antofag asta and Quintero. The second part of this paper is aimed at improving the ECMWF forecasts at telescope sites by means of Kalman filter statistical po st-processing and meteorological limited area modeling. Encouraging results are obtained concerning temperature, whereas much less satisfactory result s are obtained for wind field and cloud cover. The most critical aspects of atmospheric dynamics affecting the local forecast are discussed within the limits of available information.