GNSS technology provides a very specific atmospheric application: the estimate, with very high temporal resolution, of the atmospheric water vapor column above a receiving station. The basic principles behind this technology are briefly presented here. The high temporal resolution of GNSS water vapor measurements, the fact that it works under all weather conditions and its low cost constitute a great advantage compared to other water vapor measurement techniques. A relatively dense network of GNSS stations (~100 stations) already exists in Colombia, but has not been used yet for atmospheric applications operationally. Making use of an extreme precipitation case at the Sabana de Bogota, this paper illustrates this technology’s huge potential regarding research in tropical atmospheric convection.