Convective line

The development of convective lines in connection with cyclones during winter time is likely when the following conditions are fulfilled:

• Potential instability (humid air), especially in the case of high extending potential instability
  This enables deep convection. In the case of strong wind near the surface the convective line reveal bow form and/or line orientation.

• Strong convergences of air different airmasses
  Due to the strong horizontal temperature contrast a strong thermal direct cirulcation (upward motion of relatively warm air and downward motion of relatively cold air) establishes yielding a front intensification.

• Strong wind shear and low level jet
  Strong wind in higher and middle levels causes a fast movement of the cold front. Corresponding wind shear might lead even to tornados.

• Cold front's movement perpendicular to prefrontal warm air advection
  A high angle between the cold front's movement and the pre-frontal warm air advection leads often to a line orientated chain of convective cells.

• Positive vorticity advection on the frontal side of an upper air trough
  This causes upward motion which implies front intensification, increasing potential instability and finaly intensifying thunderstorms.