Concerning the forecast of the conceptual model "Rapid Cyclogenesis" in the SatRep Menu, a button "Vorhersage" = forecast has to be clicked and then the relevant menu appears. As can be seen, two kinds of forecasts and forecast times are presented:

The very short range forecast VSRF (06.00 - 18.00 UTC, 12 hours)

For the very short range forecast, six-hourly forecasts from ECMWF are used and those parameters which are key parameters of a conceptual model are prepared as overlays on the satellite image in three different colours representing the three points of time 06.00, 12.00 and 18.00 UTC:

• yellow: 06.00 UTC
• green: 12.00 UTC
• blue: 18.00 UTC

In the case of the conceptual model "Wave", the thermal front parameter (TFP), the height contours of 1000 hPa, warm advection (TA>=0) and the maxima of positive vorticity advection (PVA500>=2) are taken into account.

Nowcasting (0-2 hours)

For this forecast time atmospheric motion vectors (AMVs) are used which extrapolate the cloud systems for the next two hours. These nowcasts are renewed half-hourly or hourly and are not discussed here. All three key parameters show an eastward propagation towards Ireland with good agreement for the next two points of time; there are minor deviations between the WA maximum which is fastest and the surface low centre which is slowest. The images for the 12 hours period show very clearly the typical stages of cloud development in the case of a Rapid Cyclogenesis (compare Conceptual Models: Rapid Cyclogenesis - Cloud structure in satellite images ).

For the diagnosis stage additional parameters like PV have been discussed and it was concluded that a low isentropic level does not contain any stratospheric air in the area under consideration and that a higher isentropic level shows some typical features in this key parameter but somewhat displaced to the south (compare Rapid Cyclogenesis: Diagnosis for 17 April 06.00 UTC ). Bearing this result in mind, the forecast fields of PV can be understood in the same manner.

For the lower 305K and 310K levels, the very small isolines representing PV unit 1 close to the cloud spiral may be interpreted as indicating that a Rapid Cyclogensis process is taking place in higher layers. These higher layers represented by the 320K level show indeed PV values of 2 units but compared with the images, especially with the dark stripes in the WV imagery, a southward shift can also be observed in the forecasts.

This is a case of Rapid Cyclogensis, where the numerical model of ECMWF is not completely ignoring this process but should be corrected at least in respect to the position.