Synoptic Situation: Satellite images and derived numerical parameters
In order to consider the whole physical background derived model parameters are needed, too. The numerical field of thermal advection in 500 hPa, vertical motion in combination with KO-index and the vorticity advection in 300 hPa will be discussed. Because NWP-fields of frontogenesis and of PV are only available with a time increment of 12 hours we are not able to consider these parameters accordingly.
IR-imagery and vorticity advection at 300 hPa: time sequence
In this part we check if a correspondence between the cloud structures and the dynamical forcings exists and put that into relation to the wind speed in 300 hPa for a better understanding of the physical processes (
synoptic situation).
IR-imagery combined with KO-index and vertical motion 500 hPa: time sequence
When we combine the satellite image with the NWP-fields of Omega and KO we see where upward motion and potential instability occured.
IR-imagery and temperature advection in 500 hPa: time sequence
The temperature advection in relation to the vortcity advection gives us a better insight about the relevant dynamical processes for vertical motion.
Summary of the investigations in this chapter
The following results will be emphazised:
- At 00 and 06 UTC the patterns of most intense convection were super-imposed by strong warm air advection east of the surface warm front and positive vorticity advection in the right entrance region of the jet.
- Both advections led to a strong vertical motion near-by the most intense convection.
- The NWP-field exhibits the transition zone between conditional instability and stability (KO-index) at the area of maximum convection. However, the radiosoundings showed for the pseudopotential temperatures that within the lowest 4 to 6 kilometres a conditional instability existed. It could be found that the fontal contrasts were slightly smoothed out by the numerical fields. In reality, the KO-index was lower near the convective complex yielding a higher risk to convection.