High humidity content in the Bay of Biscay indicate convective development there (A). Dark region behind it is already an indication of dry air coming from upper levels. This intrusion is even better seen in Isentropic Potential Vorticity charts.
The region of higher humidity content is getting larger. Small white dots behind it indicate development in the cold air. Attention should be focused also on the dark stripe across Spain connected to the jet that will later on play a big role in the cyclogenesis in the Mediterranean.
In the region of south France on the Mediterranean coast humidity content is getting higher. The dak stripe flowing across Spain and the Baleares indicate the location of the incoming southwesterly jet. The cyclone from the Bay of Biscay is getting stronger.
3 hours later the cyclone has moved further towards the mainland and is situated over southern France. The jet is now hawing more westerly component and in this time step no noticable change is seen in the Mediterranean.
Humidity content is geting higher in the Mediterranean, near the Baleares. The first cyclone is getting into mature stage with a well developed occlusion cloud spiral.
Notice a very pronounced dry area in the Genoa Bay (marked by an arrow). This is a sign of dry air protruding downwards, a process which is in many cases connected to cyclogenesis.
The development in the Mediterranean is now clearly seen. The location of the dark stripe indicates that the development is taking place on the left-hand side of the jet.
Humidity content in the Mid Mediterranean is getting higher and convective development is clearly seen.
Clouds in the Mediterranean are getting a spiral shape. Notice the two dark stripes: the southern one flows around the whole system and the most intensive clouds are found left of the end region of that stripe. The northern stripe (the left-hand one) flows directly into the presumed centre of the newly formed cyclone.
Cloud spiral of the newly formed cyclone is getting more intense, whereas the humidity connected to the first cyclone is getting much lower.
At this point in time the WV image indicates the new development in Mid Mediterranean, while the main cyclone has moved to the north towards the Adriatic basin.
The first cyclone, now already in the mature stage, moves further to north-east. Convective clouds in Mid Mediterranean are forming a shape of a comma (C).
Further development of a cyclone can be followed. Notice a very nicely pronounced dark stripe indicating a Jet flowing accross the eastern Mediterranean towards Eastern Europe. A small low over Italy is now clearly indicated by a spiral shape of the clouds in the WV image. Across Spain, entering the Mediterranean near the Baleares, there is another branch of jet stream indicated by a dark stripe, but not as intensive as the first one.
In the far north, on the coast of Denmark, you can also see an indication of the development of a cloud spiral.
Both lows develop further. Over mid Italy WV image suggests that convective developmnet in the cold air is taking place. This area is also connected to the exit region of the jet coming across Spain.
The centre of the bigger low can now be seen over Northern Serbia (B), while the small low (C) is located in the Adriatic.
Notice also a nicely developed WV spiral west of Denmark
Convective development due to cold advection on the southern side of the cyclone intensifies.
The centres are moving further to NE and the whole system is starting to dissipate.