ThetaE 850 hPa

30th July 2005: 06UTC
A second way of describing the stabilty of the atmosphere is by making use of Theta E fields at 850 hPa

Why is Theta-E field chosen at 850 hPa?

Answer

High Theta-E values are an indication for instability. A Theta-E ridge or tongue is often the burstpoint for convective activity.
A pronounced Theta-E maximum is found over Poland. Its instability is reflected in IR10.8 by some Cbs. Further south a secondary maximum gives indication of an unstable atmosphere over Croatia. (Un)fortunately this is not seen in IR10.8, maybe because of a strong capped inversion that hampers convective development.

30th July 2005: 12UTC
Just ahead of the front a Theta-E ridge is seen south of the Baltic States. This is a potential area for convective development. Further south a pronounced Theta-E maximum is found just south of the Alps. Both of these areas are indicative and should be looked at in the following hours.

30th July 2005: 18UTC
A nice line of prefrontal convergence has appeared over the past 6 hours. The regions that were dicussed before as conditionally unstable have showed tremendous development of Cbs. Except for the two convective cells over Poland all the cells are characterised by Theta-E maxima.

31st July 2005: 00UTC
Two convective areas are found in connection to the case study. A MCS over Central Europe which is amrked by a weak Theta-E ridge and further north over Russia a second MCS which is characterised by a pronounced Theta-E ridge.

31st July 2005: 06UTC
The previous discussed MCS over Poland has decreased in both size and IR signal and shifted east. No pronounced Theta-E values accompany it.