COSMO stands for COnsortium for Small-scale MOdelling. The general goal of COSMO is to develop, improve and maintain a non-hydrostatic limited-area atmospheric model, the COSMOmodel, which is used both for operational and for research applications by the members of the consortium. The consortium was formed in October 1998 at the regular annual DWD (Germany) and MeteoSwiss (Switzerland) meeting. A Memorandum of Understanding (MoU) on the scientific collaboration in the field of non-hydrostatic modeling was signed by the Directors of DWD (Germany), MeteoSwiss (Switzerland), REMET(Italy, formerly USAM) and HNMS (Greece) in March/April 1999. The MoU has been replaced by an official COSMO Agreement, which was signed by the Directors of these four national meteorological services on 3 October 2001. Recently a new COSMO Agreement aiming at future challenges in high resolution regional numerical weather prediction as well as climate and environmental applications was accepted by the Directors of the COSMO members and was signed on 19 June 2014.
In 2002, the national weather service of Poland (IMGW) joined the Consortium in effect from 4 July. The National Institute of Meteorology and Hydrology (NMA) of Romania and the Federal Service for Hydrometeorology and Environmental Monitoring of the Russian Federation joined the Consortium in effect from 21 September 2009.

Currently, the following national meteorological services are COSMO members:
Germany DWD Deutscher Wetterdienst
Switzerland MCH MeteoSchweiz
Italy REMET Reparto per la Meteorologia
Greece HNMS Hellenic National Meteorological Service
Poland IMGW Institute of Meteorology and Water Management
Romania NMA National Meteorological Administration
Russia RHM Federal Service for Hydrometeorology and Environmental  Monitoring
Israel IMS Meteorological Service of Israel

These regional and military services within the member states are also participating:
Germany AGeoBw Amt für GeoInformationswesen der Bundeswehr
Italy CIRA Centro ItalianoRicercheAerospaziali
Italy ARPA-SIMC ARPA Emilia Romagna Servizio Idro Meteo Clima
Italy ARPA Piemonte Agenzia Regionale per la Protezione Ambientale Piemonte
Italy ARPA Friuli Venezia Giulia Agenzia Regionale per la Protezione Ambientale Friuli Venezia Giulia

In 2017 eight national meteorological services, namely Botswana Department of Meteorological Services, INMET (Brazil), Brazilian Navy (DHN), Namibia, Meteorological Service, DGMAN (Oman), NCMS (United Arab Emirates), Turkmenistan and Center of Excellence for Climate Change Research (King Abdulaziz University, Saudi Arabia) use the COSMO model in the framework of an operational licence agreement including a license fee.  

National meteorological services in developing countries (e.g. Egypt, Indonesia, Kenya, Mozambique, Nigeria, Philippines, Rwanda, Tanzania, Vietnam) can use the COSMO model free of charge.