Key Parameters

  • Equivalent thickness
    Gradient zone of equivalent thickness:
    • Ana Cold Front: within the cloud band
    • Kata Cold Front: behind the cloud band
  • Thermal front parameter (TFP)
    The maximum of TFP accompanies the cloud band:
    • Ana Cold Front: within the leading area of the cloud band
    • Kata Cold Front: within the rear area of the cloud band
  • Temperature advection
    There is relatively weak warm advection ahead of the Cold Front, and pronounced cold advection behind it.
    • Ana Cold Front: cloudiness usually lies within CA, TA=0 ahead of cloud band
    • Kata Cold Front: cloudiness usually lies within WA, TA=0 within the cloud band
  • Positive vorticity advection (PVA) in upper levels
    PVA maxima can be found near the rear edge of the cloud band indicating the propagation of the upper level trough and/or the approach of a jet streak (see Front Intensification By Jet Crossing).
  • Isotachs at 300 hPa
    • Ana Cold Front: the jet runs behind the cloud band and parallel to it. The jet crosses the frontal system in the area of the occlusion point. The front is on the anticyclonic side of the jet.
    • Kata Cold Front: the jet crosses the Cold Front at a sharp angle; according to the jet crossing point the cloud band can be on the anticyclonic or cyclonic side of the jet.
    As already mentioned, there are similarities between Kata Cold Fronts and Split Fronts (see Split Front ). The main difference is the orientation between jet and front: in the case of a Split Front the jet approaches from the rear nearly at right angles.
  • Shear vorticity at 300 hPa
    Zero line of the shear vorticity:
    • Ana Cold Front: the zero line is close to and parallel to the rear cloud edge
    • Kata Cold Front: the zero line crosses the Cold Front; usually it accompanies the transition of the lower cloud tops on the cyclonic side to higher tops on the anticyclonic side of the front.

Equivalent thickness and Thermal Front Parameter (TFP)
04 October 2005/12.00 UTC - Meteosat 8 IR 10.8 image, Ana front; blue: thermal front parameter (TFP) 500/850 hPa, green: equivalent thickness 500/850 hPa

19 September 2005/12.00 UTC - Meteosat 8 IR 10.8 image, Kata front; blue: thermal front parameter (TFP) 500/850 hPa, green: equivalent thickness 500/850 hPa

Temperature Advection and Positive Vorticity Advection (PVA)
04 October 2005/12.00 UTC - Meteosat 8 IR 10.8 image; red: temperature advection 500/1000 hPa, green: vorticity advection 500 hPa

19 September 2005/12.00 UTC - Meteosat 8 IR 10.8 image; red: temperature advection 500/1000 hPa, green: vorticity advection 500 hPa

Isotachs and Shear Vorticity 300 hPa
04 October 2005/12.00 UTC - Meteosat 8 IR 10.8 image; yellow: isotachs 300 hPa, magenta: zero line of shear vorticity

19 September 2005/12.00 UTC - Meteosat 8 IR 10.8 image; yellow: isotachs 300 hPa, magenta: zero line of shear vorticity