Frontal System across Europe with Wave Development - Case Study 12 - 13 November 1997

• I. Synoptic Situation for 12 November 06.00 UTC
• Overview and frontal diagnosis
• Wave development in the area Sardinia - Corsica
• Intensification of frontal cloudiness and activity by jet streak crossing
• Cloudiness over Italy and the Balkan peninsula in front of the Cold Front: Relative Streams
• II. Development During the next 12 Hours
• Frontal displacement with help of the Thermal Front Parameter
• Displacement of the Wave
• Front Intensification by Jet Crossing
• III. Synoptic Situation for 12 November 12.00 UTC
• Overview and new aspects
• Diagnosis of front and Wave(s)
• Relative streams: Cloudiness over the Balkan peninsula
• IV. Synoptic Situation for 12 November 18.00 UTC
• Comparison of cloud configurations between 12.00 and 18.00 UTC
• Overall situation and frontal diagnosis
• Relative streams
• V. Synoptic Situation for 13 November 00.00 UTC
• Introduction for 13 November 00.00 UTC
• Overview and frontal situation
• Relative streams: Frontal and pre-frontal situation
• VI. Development of Thunderstorms and MCSs During the Whole Period
• Introduction for the diagnosis of conceptual modles for convective developments
• The period 12 November 05.00 - 07.00 UTC
• The period 12 November 11.00 - 12.00 UTC
• The period 12 November 14.00 - 18.30 UTC
• The period 12 November 21.00 UTC - 13 November 00.00 UTC
• Some summarizing ideas

Relative streams

12 November 1997/18.00 UTC - Meteosat IR image; position of vertical cross section indicated	12 November 1997/18.00 UTC - Vertical cross section; black: isentropes (ThetaE), orange thin: IR pixel values, orange thick: WV pixel values
12 November 1997/18.00 UTC - Meteosat IR image; black: shear vorticity 300 hPa, magenta: relative streams 312K - system velocity 232° 11 m/s, yellow: isobars

Few if any changes took place involving different relative streams (left image bottom). The most important facts can be summarised as follows:

• The rising Warm Conveyor Belt is responsible for the cloudiness over the Balkan Peninsula in front of the frontal system;
• Both relative streams from behind the front are involved in the frontal cloud band;
• A dry air stream connected with the crossing jet streak on its cyclonic side penetrates into the area in front of the frontal cloud band over Tunisia and the adjacent Mediterranean Sea.