Metrology is the science of measurement. (From http://en.wikipedia.org/wiki/Metrology)Meanwhile,
Meteorology is the interdisciplinary scientific study of the atmosphere. (From http://en.wikipedia.org/wiki/Meteorology)So while certainly, meteorologists practice some form of metrology when they take a scientific approach in their measurements of the properties of the atmosphere, metrologists do not know as much about weather forecasting outside of what they hear from weather forecast shows (e.g. local TV news) and services (e.g. newspapers, websites).
When you encounter someone say or spell metrology when they really mean meteorology, know that it is most likely only a miss on their part.