RGB combination of Meteosat-8 HR VIS and IR 10.8μm images

At this stage the cyclone in the Bay of Biscay is already very active. Open and closed cells in the cold air are seen on the Atlantic as low clouds (yellow in the image), whereas white-bluish colour of the clouds near the centre of the cyclone indicates much colder tops i.e. stronger convective development. The same can be seen within the cloud head of the occlusion. Blue clouds on the leading edge are mainly high transparent (cirrus) clouds. In the Mediterranean there are still only low clouds visible.

The well developed cloud spiral moves towards the inland of southern France. The clouds in the Meditteranean are still only low clouds, now overlayed with some blue cirrus clouds, but there is still no development there.

At this stage the development starts in the Mediterranean with several convective cells seen near the Baleares. The cyclone over south France and north Spain is in the mature stage.

Notice how the low clouds west of Portugal on the Atlantic are lined up because of the jet stream.

See also the nice lee waves over Italy, forming behind the Apenines in the southwesterly stream.

This is now the situation next morning, 18 hours later. The cyclone is now already above mid Italy with some strong convective development taking place in the cold air over the Mediterranean.

6 hours later two centres can be seen - one over Adriatic and the other over Italy.

Notice also fibrous clouds over the Eastern Mediterranean, connected to the jet streak there.

The cloud head consists of both low (yellow) and high clouds (blue). Convective clouds over the Mediterranean are lined up because of the strong wind.