During November and December 1998, ten cyclonic disturbances over the NorthAtlantic and Mediterranean area were studied. Features in potentialvorticity (PV) fields were tracked in the analyses and short-range forecastsof the Spanish version of the HIRLAM model (HIRLAM-INM) and the ECMWFmodel. They were superimposed on the corresponding Meteosat water vapour(WV) images with the aim of ascertaining the qualitative relationshipbetween Meteosat WV imagery and PV fields that might be used to assessNWP model behaviour. Two cases predicted incorrectly by HIRLAM-INM werestudied in detail: a rapidly deepening depression over the Atlantic(26–27 November 1998) and a cut-off low process over the westernMediterranean (3–4 December 1998). For evaluating HIRLAM-INM modelbehaviour, absolute vorticity at 2 PVU surface, positive PV anomaliesat 500 hPa as well as pseudo WV images were compared with Meteosat WVpictures. Being synthetic products of the numerical model, the pseudoWV images were used to indicate the strength of the relationship betweenthe Meteosat WV imagery and the PV fields, and to indicate whether anymismatches correspond to real NWP model errors. It is demonstrated thatthe HIRLAM-INM phase error at 3–4 December 1998 was clearly seen in thecomparison between Meteosat and pseudo WV images.