The axis of the main trough at 500 hPa is situated over France and eastern Spain. A small trough in 500 hPa pressure field over western France and southern England indicates the development in this region.
27 February 2004, 00 UTC
Six hours later the small upper level trough is getting deeper. Clouds developing here already reveal a spiral structure. The region of the Mediterranean is under strong south-westerly flow.
27 February 2004, 06 UTC
The trough connected to the low in the Bay of Biscay is more pronounced, whereas the main trough axis has moved to Mediterranean, near the Baleares.
27 February 2004, 12 UTC
The trough axis is now over the Bay of Biscay, whereas the cloud band has already moved to the mainland of southern France.
27 February 2004, 18 UTC
The trough from the Bay of Biscay has moved to France. The region of the Mediterranean where the second low is developing, is in very strong south-westerly flow.
28 February 2004, 00 UTC
The region of mid-Mediterranean is still under south-westerly flow. The upper level trough is connected to the dissipating low. The new developing cyclone is on the leading side of the upper-level trough.
28 February 2004, 06 UTC
Six hours later the cloud spiral of the first cyclone has already dissipated, but there is still a trough in 500 hPa pressure field. The new development is on the leading side of the trough.
28 February 2004, 12 UTC
The upper-level trough axis is moving towards Italy. Looking closely into the region north-east of the trough axis, it can be seen how the stong warm advection forms a shallow ridge in the upper-level pressure field.
