Typical Appearance In Vertical Cross Sections

  • 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.

17 April 2008/10.00 UTC - Meteosat 9 IR image; position of vertical cross section indicated
17 April 2008/12.00 UTC - Vertical cross section; black: isentropes (ThetaE), magenta thick: convergence, magenta thin: divergence
17 April 2008/12.00 UTC - Vertical cross section; black: isentropes (ThetaE), green: positive vorticity advection (PVA)