Synergetic use of GPS water vapor and Meteosat images for synoptic weather forecasting

The use of integrated water vapor (IWV) measurements from a ground-based global positioning system (GPS) for nowcasting is described for a cold front that passed the Netherlands during 16 and 17 May 2000. Meteosat water vapor (WV) and infrared (IR) channel measurements are incorporated to analyze this weather situation. A cloud band with embedded cumulonimbus clouds (Cb) preceded the cold front. The GPS IWV showed a clear signal at the passing time of the embedded Cbs over the GPS sites. After the frontal passage a dry intrusion occurred. By comparing Meteosat WV observations collocated in time and space with GPS IWV observations, a rough reconstruction of the vertical water vapor distribution can be made. The case described here shows that, in addition to Meteosat WV/IR images, GPS IWV contained information for nowcasting of the probability of the occurrence of thunderstorms and heavy precipitation.