Pseudopotential Temperature, Time Sequence: 27 July 2006

This chapter presents the wind barbs (measured 10 m above ground) and the pseudopotential temperature (tpspot). For information on pseudopotential temperature and how to interprete the values click here.

The wind barbs indicate zones where convection has to be expected or started already. Some convergence zones which can be identified by the data are marked by the arrows.

The pseudopotential temperature exhibits the two different air masses which are marked by the circles. Dry and hot air (blue) are found in eastern parts of Germany while warm and moist subtropical air masses (red) are approaching from Southwest. The transition zone between the two different air masses coincide with the "dark stripe" in the water vapour image (WV 13 UTC).

The wind barbs indicate surface convergences over central and western Germany. Both are connected to convective clouds. Tpspot-values between 60° and partly more than 70°C occurred which is equivalent to thunderstorms and severe thunderstorms, respectively.

In the meanwhile the two separate convergence zones began to merge. The wind barbs indicate clearly a convergence extending from northwestern Germany to southern Germany which fits rather well with high extending convective clouds. Tpspot values above 60°C show a risk of partly severe thunderstorms.

The convergence line is marked yellow.

The surface convergence (marked yellow) is still revealed well by the wind barbs. At the rear of the squall line mean wind speeds from the Southwest with up to 20 knots were measured. According to the diurnal cycle tpspot decreased over eastern Germany that was still influenced by dry air (below 50°C). In cloudy areas over Germany tpspot decreased, too (around 60°C). That is a hint to a reduced risk of severe thunderstorms.

Severe winds could be measured near the gustfront at the leading edge of the squall line (orange line).

The surface convergence moved slowly to the East and weakened (less clear structure, lower wind speeds).

The squall line reached the line Berlin-Dresden and continued weakening. We see over eastern Germany increasing tpspot due to approaching of more humid air to this region.