Which stage happens first in the life cycle of a middle-latitude cyclone?

The main weather producers in the mid-latitudes are wave cyclones or mid-latitude cyclones. These are the systems of low pressure, which travel towards the east from west and remains for a week or even longer. The life-cycle of a mid-latitude cyclone can be differentiated into six stages, of which the initial stage is the stationary front with the opposing shear across the front.