Summary and references
The pre-frontal Convergence Line of this case study develops to the rear of an equivalent thickness ridge, as a pronounced Cold Front approaches from the west. A well developed Warm Conveyor Belt, containing very warm air, is located ahead of the Cold Front. As solar radiation heats the air of the Warm Conveyor Belt further during the day, the air column ahead of the Cold Front becomes clearly potentially unstable. Hence strong convection starts in the afternoon, triggering several cells of deep convection with heavy rain and thunderstorms. This development is seen very well in both the Meteosat and NOAA satellite images, but the NOAA images provide much more detail. The convergence ahead of the Cold Front reaches from the surface up to 800 hPa, which is a typical property of such a Convergence Line. The omega field, on the other hand, differs from the typical case, as upward motion is seen reaching throughout the whole troposphere. The triggering mechanism releasing the potential unstability remains unclear, but the most important contributor in this case seems to be the strong differential heating by solar radiation in combination with a pronounced Warm Conveyor Belt.
References
- Puhakka T., 1995: Pilvifysiikka. Lecture notes, University of Helsinki