Global Instability Index

30th July 2005: 09UTC
The K-index derived using the algorithms of GII is presented in a resolution of 5 x 5 kilometres in these set of images. In the contrast to the satellite pictures we have seen before the GII should give you a better insight in where potential TS may develop.
Most of Europe is pictured in blue, so some TS may be expected in the region. More interesting however is the yellowish region with K-index values over 30, which is seen stretching from Northern Italy over Austria, the Czech Republic towards the Baltic States. This line is where we will see 6 hours later the prefrontal convergence line!

K-index	TS probablity
<20	Thunderstorms unlikely
20 to 25	Isolated thunderstorms
26 to 30	Widely scattered thunderstorms
31 to 35	Numerous thunderstorms
Above 35	Thunderstorms very likely

30th July 2005: 10UTC
The region with K-index values over 30 stretching over Central Europe is still distinct. In Poland and Slovenia even values over 40 are seen. Further east over the Carpathian Mountain in Bulgaria the orographic induced convergence is about to start. Values over 30 and 40 accompany it.

K-index	TS probablity
<20	Thunderstorms unlikely
20 to 25	Isolated thunderstorms
26 to 30	Widely scattered thunderstorms
31 to 35	Numerous thunderstorms
Above 35	Thunderstorms very likely

30th July 2005: 11UTC
Over Central Europe values with K-index over 30 give rise to the assumption of thunderstorms. South of the Alps the first convective cells are already observed. Over Croatia the K-index even depicts values over 40!

K-index	TS probablity
<20	Thunderstorms unlikely
20 to 25	Isolated thunderstorms
26 to 30	Widely scattered thunderstorms
31 to 35	Numerous thunderstorms
Above 35	Thunderstorms very likely

30th July 2005: 12UTC
Over France, Switzerland and Southern Germany we can recognise the clouds of the frontal system. At the prefrontal side the K-index reveals values over 20 and in the area of interest even over 30. In the Eastern part of Austria ahead of the front the K-index shows some unstable pixels. At this location the next hour the first cell will start. In the correspondent IR image only a small sign of an onset to convection is seen.

K-index	TS probablity
<20	Thunderstorms unlikely
20 to 25	Isolated thunderstorms
26 to 30	Widely scattered thunderstorms
31 to 35	Numerous thunderstorms
Above 35	Thunderstorms very likely

30th July 2005: 13UTC
Within the prefrontal area (with K-index of >30) some more small patches (red pixels) which are highly unstable are observed. There orientation aligns in accordance to the prefrontal convergence line that develops these hours.

K-index	TS probablity
<20	Thunderstorms unlikely
20 to 25	Isolated thunderstorms
26 to 30	Widely scattered thunderstorms
31 to 35	Numerous thunderstorms
Above 35	Thunderstorms very likely

30th July 2005: 14UTC
Within the prefrontal area (with K-index of >30) some more small patches (red pixels) which are highly unstable are observed. There orientation is in accordance to the prefrontal convergence line that develops these hours.

K-index	TS probablity
<20	Thunderstorms unlikely
20 to 25	Isolated thunderstorms
26 to 30	Widely scattered thunderstorms
31 to 35	Numerous thunderstorms
Above 35	Thunderstorms very likely

30th July 2005: 15UTC
At this timestep most convection has already started. The cells are pictred in white (e.g. GII only works in cloudfree conditions!) and surrounded by yellow colours indicating K-indeces of 30 to 40. Some of the cells are also flanked by even higher values indicative for the further development of thunderstorms there.

K-index	TS probablity
<20	Thunderstorms unlikely
20 to 25	Isolated thunderstorms
26 to 30	Widely scattered thunderstorms
31 to 35	Numerous thunderstorms
Above 35	Thunderstorms very likely

30th July 2005: 16UTC
The prefrontal convergence has further developed. At the leading edge still an unstable line with K-index over 30 is recognised. Within the next few hours also in these areas thunderstorm should be reckoned with.

K-index	TS probablity
<20	Thunderstorms unlikely
20 to 25	Isolated thunderstorms
26 to 30	Widely scattered thunderstorms
31 to 35	Numerous thunderstorms
Above 35	Thunderstorms very likely

30th July 2005: 17UTC
The prefrontal convergence has further developed. At the leading edge still an unstable line with K-index over 30 is recognised. Within the next few hours also in these areas thunderstorm should be reckoned with.

K-index	TS probablity
<20	Thunderstorms unlikely
20 to 25	Isolated thunderstorms
26 to 30	Widely scattered thunderstorms
31 to 35	Numerous thunderstorms
Above 35	Thunderstorms very likely

30th July 2005: 18UTC
The prefrontal convergence has further developed. At the leading edge still an unstable line with K-index over 30 is recognised. This area has however decreased over the past hour.

K-index	TS probablity
<20	Thunderstorms unlikely
20 to 25	Isolated thunderstorms
26 to 30	Widely scattered thunderstorms
31 to 35	Numerous thunderstorms
Above 35	Thunderstorms very likely

30th July 2005: 19UTC
The prefrontal convergence has further developed. At the leading edge still an unstable line with K-index over 30 is recognised. This area has however decreased over the past hour.

K-index	TS probablity
<20	Thunderstorms unlikely
20 to 25	Isolated thunderstorms
26 to 30	Widely scattered thunderstorms
31 to 35	Numerous thunderstorms
Above 35	Thunderstorms very likely

30th July 2005: 20UTC
The prefrontal convergence has further developed. At the leading edge still an unstable line with K-index over 30 is recognised. This area has however decreased over the past hour.

K-index	TS probablity
<20	Thunderstorms unlikely
20 to 25	Isolated thunderstorms
26 to 30	Widely scattered thunderstorms
31 to 35	Numerous thunderstorms
Above 35	Thunderstorms very likely

30th July 2005: 21UTC
The prefrontal convergence has further developed. At the leading edge still an unstable line with K-index over 30 is recognised. This area has however decreased over the past hour.

K-index	TS probablity
<20	Thunderstorms unlikely
20 to 25	Isolated thunderstorms
26 to 30	Widely scattered thunderstorms
31 to 35	Numerous thunderstorms
Above 35	Thunderstorms very likely