Numerical Parameters

Useful Parameters:
For this topic the height contours of 1000, 500 and 300 hPa are available and very useful. With appropriate superposition you can answer the following questions.

Some Questions:

1. Describe the situation of the surface (height of 1000 hPa) in the time period
   • Is there a deepening of the surface low?
   • How much is the deepening in the different 6 hourly periods (00 - 06, 06 - 12 etc)?
2. The case shows the development of two surface lows:
   • Is the second surface low also recognisable in the fields ? From when on?
3. Describe the situation of the height contours (500 and 300 hPa)
   • Is there an upper level trough and does it deepen?
   • Is this recognisable in both height 500 and 300 hPa or are there differences?
   • What is the relation between the surface low and upper level trough?
4. Is the double structure of the surface low also indicated in the upper level fields?

Useful Parameters:
For the characterisation of the frontal situation the parameters thickness, TFP (Thermal front parameter) and temperature advection are useful. You can get ideas about the severity, the distinctness and the type of the front. In this regard make up your mind about the following questions and topics.

Some Questions:

1. Looking into thickness gradient and TFP: how can you describe the frontal situation
   • Is the front well developed or rather weak?
   • Where is the thickness gradient and the TFP located in relation to the frontal cloud band?
   • Does the situation change during the time period?
   • Is there a front dissolution in the area of the racy and if yes, is it reflected in the TFP?
2. The field Temperature advection (TA) is characterised by:
   • Strong or weak signals? How is the answer compared to typical situation in a racy?
   • Is the development of the double structure of clouds spirals and surface lows also mirrored in the TA field? If yes how?

Useful Parameters:
For evaluating the situation of the jet streak, the following parameters are very useful: Isotachs and Positive vorticity advection at 500 and especially at 300 hPa for getting an idea about the orientation of the jet streak in relation to the front as well as about the intensity and depth. For this relation the TFP (Thermal Front Parameter) might also be useful. In this regard make up your mind about the following questions and topics.

Some Questions:

1. Is this case of rapid cyclogenesis accompanied by a distinct jet situation in upper levels? Answer this question in looking into the following questions
   • Is the jet streak only in high levels or does it extend over more levels?
   • What is the relation between the jet axis and the WV and IR images?
   • The racy development takes place in which area of the jet streak?
2. Has the development of a double structure of surface lows something to do with the jet streak configurations? For this question compare the position of the PVA maxima in relation to each other and in relation to the cloud formations and it sequence throughout the time interval.
   • The PVA maximum in which height is in closer relation to the area of the first low centre the rapid cyclogenesis?
   • The PVA maximum in which height is in closer relation to the second low centre of the rapid cyclogenesis?
   • Does this relation change during the time period?

Useful Parameters:
For evaluating PV anomalies, the following parameters are very useful: Height of Potential Vorticity > 2 units for getting an idea if there is stratospheric air protruding downward into the troposphere. In this regard make up your mind about the following questions and topics.

Some Questions:

1. Rapid cyclogenesis developments are usually connected to PV anomalies. How is this in this case?
   • Is there already a distinct PV anomaly in the first time of point?
   • How does it change during the development?
   • Does it deepen?
   • Is there any relation of the development of a double structure of the surface lows to the distinctness and position of the PV anomaly?