Numerical Parameters

Useful Parameters:
For the identification of an occlusion cloud band the parameters thickness and temperature advection as well as the Thermal Front Parameter (TFP) are most relevant. Look into the parameters and answer the following questions.

Some Questions:

• Is the cloud band under discussion an occlusion and why?
  • What is the typical configuration of the thickness and how well is it developed on this case?
  • Is there a distinct TFP and if yes what is the relation to the thickness?
  • What is the typical quality of the temperature advection? Are these features also well developed in this case?
  • The involved countries England, The Netherlands and Belgium are they under Warm or Cold advection and during which time periods?

Useful Parameters:
For the discussion under this topic look into the fields of height on 1000 and 500 hPa. The 1000 hPa height filed can be regarded as very close to the surface.

Some Questions:

• What is the configuration in the 1000 hPa height field?
  • How many low centres do exist?
  • Are there changes or developments in the time period of the 12 hours?
  • What is the relation of the surface lows to the cloud band and the cloud features within the band?
• What is the configuration in the 500 hPa height field?
  • Is there an upper level trough and if yes how is its relation the surface trough?
  • Is there a change or evelopment during the period of the 12 hours
  • What is the relation of the upper level trough to the cloud configurations?

Useful Parameters:
For the identification of jet streaks and accompanying PVA maxima look into the parameters of isotachs at 300 hPa as well as into the PVA (Positive Vorticity Advection ) in the same upper level.

Some Questions:

• Is a Jet streak involved in this Conceptual Model?
  • At which levels and with which wind strength? Is it a thick jet streak?
  • If you look into 300 hPa, where is it located in relation to the cloud band?
  • In which relation to the jet streak at 300 are S-England, The Netherlands and Belgium?
• If there is a jet streak is there also a pronounced PVA maximum in the left exit region and if yes, with which strength?
  • What is the relation to the cloud configuration within the cloud band?
  • Is there any relation to the conceptual model which should be detected?

Useful Parameters:
Vorticity consists of a shear and a curvature part. The dominance of one of the two parts or the equal ness of the two through a light on the processes taking place. Look into the relevant parameters of shear and curvature vorticity at 300 hPa; ev. also on 500 hPa.

Some Questions:

• Are there in the area of the cloud band under discussion and its substructure cyclonic centres of shear and curvature vorticity. If yes:
  • Which kind of vorticity is dominant in the beginning ?
  • Does this change during the period of the 12 hours
  • What physical process is prevailing?

Useful Parameters:
The height of Potential vorticity > 2 units indicates the height of tropopause and indicates the existence of PV Anomalies. The latter is correlated with triggering secondary cyclogenesis. Consequently look into the parameter of Height of Potential vorticity > 2 units

Some Questions:

• Is there a PV anomaly in the area under consideration and if yes, how far down into the troposphere has the stratospheric air protruded?
• Is there any relation with the cloud band and its substructures?