Basic parameters like surface pressure and geopotential height of 500 hPa do not reveal the whole physical background of the case, and can therefore not explain neither the details seen in the cloud features of satellite images nor the different conceptual models.
Parameters and parameter combinations which can be helpful in the diagnosis of the deepening low and the frontal features are:
Geopotential height (in black) and Isotachs at 300 hPa (orange 30 m/s, cyan 40 m/s, green 50 m/s, blue 60 m/s) show the distribution of the wind speed and the location of the jet streak, PVA (in red) at the same level contributes for upward motion. The typical configuration is a maximum of PVA at the left exit region of the jet streak. Isotachs and positive vorticity advection at 300 hPa are displayed and described in a 12-hourly sequence.
Geopotential height (in black) and Equivalent Potential Temperature (red, magenta, blue) at 850 hPa show the location of atmospheric fronts at lower troposphere.
Geopotential height (in black) and Temperature Advection (WA in red, CA in blue) at 850 hPa show the the contribution of Temperature Advection to the vertical motion and deepening of the low pressure.
Investigation of the derived parameters helps us to understand the reasons for deepening of the low and the vertical motions.
In Finland the most intensive events are connected to the passing of the Cold front. The derived parameters indicate that the Cold front was quite intensive, but for the further investigations the diagnosis of Vertical Cross Sections is necessary. These will be dealt in detail in the next chapter.
In Lithuania the intensive rain was a result of both upper level PVA and WA contributing for ascending motion. Moreover, when the system started to slow down, the occlusion cloud band remained stationary over Lithuania for a relatively long time. The location of the occlusion is easy to define with the help of satellite images overlaid with the equivalent potential temperature.