A nasty storm is brewing over the meteorological heart of Los Angeles. A decision by government forecasters to relocate downtown L.A.’s official weather observation station from USC to Dodger Stadium is generating extreme heat and wind gusts from some local climate experts. They insist the move will cast fog on local efforts to document the effects of climate change. “It contaminates the record,” said Jan Null, a veteran California meteorologist who runs the Golden Gate Weather Service. “It changes the ballgame.” The station — a curious array of poles, metal boxes and shiny cylinders that weather wonks know affectionately as “KCQT” — is slated to move from USC to the Los Angeles Fire Department’s training center on the south side of the stadium in Elysian Park on Monday. The last time the key monitoring station moved was 25 years ago.