This article only describes one highly specialized aspect of its associated subject. Please help improve this article by adding more general information. The talk page may contain suggestions.(August 2009)
The term prognostic is given to some values or variables that are directly predictive by the model, such as temperature, water vapour, salinity, depth in atmospheric or ocean models; variables that can be directly obtained as a model outcome. On the other hand, there are some other variables that need to be calculated separately as derived variables, such as relative humidity which may be a diagnostic variable obtained from the model's prognostic variables, temperature and water vapour.