Secondary Low Centres In Occlusion Cloud Bands - Typical Appearance In Vertical Cross Sections
by FMI
- Isentropes:
The structure of an Occlusion is seen in the isentropes. As the Occlusions can be fairly old, however, the v-shaped structure with warmer isentropes above may not always be as clear as in younger systems. - Divergence:
As in a typical deepening low, there is convergence at low levels and divergence at high levels over the secondary low. - Positive vorticity advection:
There is a maximum on PVA ahead of the developing low in the lower troposphere.
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17 April 2008/10.00 UTC - Meteosat 9 IR image; position of vertical cross section indicated
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17 April 2008/12.00 UTC - Vertical cross section; black: isentropes (ThetaE), magenta thick: convergence, magenta thin: divergence
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17 April 2008/12.00 UTC - Vertical cross section; black: isentropes (ThetaE), green: positive vorticity advection (PVA
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