Appearance in Satellite Data

In this study 12 cases of Back Bent Occlusions were investigated. In most cases the cloud band related to the occluded front is long and broad, but there are also cases, especially in cold air masses, where the cloud band is short, narrow and not very striking in the satellite image.

In the initial stage there is a quite straight or only slightly cyclonically curved occluded front. The movement of the occluded front stops, and after that the whole front or a part of it begins to move backwards. In most cases the occluded front is bent back by a cold advection originating from another low (usually Upper Level Low; see Upper Level Low ) in a polar airmass.

On the 21st of November 2000 at 12.00 UTC, there is a long, broad occluded front over the Atlantic and an upper level low over England and Scotland:

21 November 2000/12.00 UTC - Meteosat IR image
21 November 2000/12.00 UTC - Meteosat VIS image
21 November 2000/12.00 UTC - Meteosat WV image

The bending of the occluded front can clearly be seen in a sequence of satellite images. Part of the occluded front bends backwards, and the occluded front forms an s-shaped cloud band:

21 November 2000/09.00 UTC - Meteosat IR image
21 November 2000/15.00 UTC - Meteosat IR image
21 November 2000/21.00 - Meteosat IR image
22 November 2000/03.00 UTC - Meteosat IR image

On 18.00 June 2001 at 09.00 UTC there is a short, narrow Occlusion southwest of Iceland and a small upper level low between Iceland and Greenland with only slight cloudiness:

18 June 2001/09.00 UTC - Meteosat IR image
18 June 2001/09.00 UTC - Meteosat VIS image
18 June 2001/09.00 UTC - Meteosat WV image

The movement of the occluded front backwards can be seen in a sequence of satellite images. In this case the bending is not very pronounced:

18 June 2001/09.00 UTC - Meteosat IR image
18 June 2001/18.00 UTC - Meteosat IR image
19 June 2001/06.00 - Meteosat IR image