Case Study: 19 February 1997

• I. Frontal Diagnosis - 19 February 1997/00.00 UTC
  • Overview of satellite imagery for 00.00 UTC
  • Key parameters on isobaric surfaces for 00.00 UTC
  • Use of vertical cross sections for 00.00 UTC
• II. Frontal Diagnosis - 19 February 1997/06.00 UTC
  • Overview of satellite imagery for 06.00 UTC
  • Key parameters on isobaric surfaces for 06.00 UTC
  • Use of vertical cross sections for 06.00 UTC
• III. Diagnosis of Rapid Cyclogenesis and Upper Level Trough Feature - 19 February 1997/00.00 UTC
  • Overview of satellite imagery for Rapid Cyclogenesis 00.00 UTC
  • Key parameters on isobaric surfaces for Rapid Cyclogenesis 00.00 UTC
• IV. Diagnosis of Rapid Cyclogenesis and Upper Level Trough Feature - 19 February 1997/06.00 UTC
  • Overview of satellite imagery for Rapid Cyclogenesis 06.00 UTC
  • Key parameters on isobaric surfaces for Rapid Cyclogenesis 06.00 UTC
  • Relative streams and conveyor belts for Rapid Cyclogenesis 06.00 UTC
• V. Very Short Range Forecast
  • Very Short Range Forecast for the frontal system
  • Very Short Range Forecast for the Rapid Cyclogenesis and the Comma feature
  • Verification of Very Short Range Forecast

19 February 1997 - Relative Streams And Conveyor Belts For Rapid Cyclogenesis 06.00 UTC

19 February 1997/06.00 UTC - Meteosat IR image; position of vertical cross section indicated	19 February 1997/06.00 UTC - Vertical cross section; black: isentropes (ThetaE), orange thin: IR pixel values, orange thick: WV pixel values

The right image shows again the vertical cross section which is perpendicular to the cloud shield of the Rapid Cyclogenesis and to the Cold Front band (compare left image). In the ideal case there are typical relative streams connected with a Rapid Cyclogenesis, with a different appearance on low and high isentropic surfaces. In this case the 290K surface represents a low surface close to the bottom of the frontal zone, while 310K is a high surface on the top of the frontal zone.

19 February 1997/06.00 UTC - Meteosat IR image; magenta: relative streams 290K - system velocity 231° 19 m/s, yellow: isobars	19 February 1997/06.00 UTC - Meteosat IR image; magenta: relative streams 310K - system velocity 231° 19 m/s, yellow: isobars

Relative streams on both surfaces can be seen in the left (290K) and right image (310K); indeed, they contain a lot of the typical features of an ideal case. On the low surface a splitting of a rising relative stream from south-south-east accompanies the cloud head of the Rapid Cyclogenesis, on the high surface a sinking relative stream from behind transports dry air across the cloud shield of the Comma to the area of the Rapid Cyclogenesis.

Summarizing, one can say that even in cases where a complicated structure with several conceptual models superimposed exists, an evaluation and estimation of all relevant key parameters helps to localize and separate the single conceptual models. This is the basis for a useful Very Short Range Forecast (compare Very Short Range Forecast).