who governs it?
Convention of the World Meteorological Organization
World Meteorological Organization
The WMO was established by the Convention of the World Meteorological Organization, signed 11 October 1947 and ratified on 23 March 1950. The Convention serves as the constituent treaty of the WMO, setting forth its purposes, governance, and general framework. 
what time of year is hail most likely In North America it occurs between  March and October,with the bulk of the occurrences from May through September. what does it refers to? Hail is a form of solid precipitation. It is distinct from ice pellets (American English "sleet") what are the factors favoring it? Movement of dry air into strong thunderstorms over continents can increase the frequency of hail by promoting evaporational cooling which lowers the freezing level of thunderstorm clouds giving hail a larger volume to grow in. what cases of it are recorded? Megacryometeors, large rocks of ice that are not associated with thunderstorms, are not officially recognized by the World Meteorological Organization as "hail," which are aggregations of ice associated with thunderstorms, and therefore records of extreme characteristics of megacryometeors are not given as hail records where is this mentioned organization based? UNANSWERABLE
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World Meteorological Organization [SEP] Governance
The WMO was established by the Convention of the World Meteorological Organization, signed 11 October 1947 and ratified on 23 March 1950. The Convention serves as the constituent treaty of the WMO, setting forth its purposes, governance, and general framework. The WMO hierarchy: The annually published WMO Statements on the status of the World Climate provides details of global, regional and national temperatures and extreme weather events. It also provides information on long-term climate change indicators including atmospheric concentrations of greenhouse gases, sea level rise, and sea ice extent. The year 2016 was the hottest year on record, with many weather and climate extremes, according to the most recent WMO report.