Meted: Satellite feature identification: Cyclogenesis
Extratropical cyclone developement
Cyclones tend to delope along preexisting fronts when an upstream perturbation approaches in the mid- or upper-troposphere. The surface baroclinic zone kinks, creating a cyclonic perturbation.
One should look for cyclongesis in the surface baroclinic zone. This region is associated with a frontal band cloud pattern.
Cyclogenesis can occur in many ways, based on the different orientations and strengths of the precursor structures. A strong upper-level amonaly (X) requires very little (or no) baroclinicity (F) to generate a cyclone, whereas a very baroclinic atmosphere requires only a weak forcing.
On the other hand, if both aspects are strong, then they need not overlap in space as strongly to still generate a cyclone.
Example: X and F comparable.
As the forcing nears the band of baroclinicity, layered cloud emerges from F ahead of X, indicating the beginiing of cyclongesis. It emerges from near the inflection point on the poleward side of F as F becomes more S-shaped. E begins as warmer, lower-topped couldswhich expand backwards towards X. E cools and expands further while cyclogensis continues. It will then merge with the clouds associated with X to form a comma shape.
Example: X <<F.
The spjhere of influence of X is much smaller than that of F. X will need to be essentially within F for cyclogenesis to begin.
Example X>>F. If the baroclinicity is weak, the driving anomaly must be large to generate a cxyclone. “COld air cyclogenesis” has cyclone development occuring entirely within the cold airmass.
Multiple cyclones are always present in various stages of developement across the globe. Detection from satellite imagery is aided by identifing
1: The frontal cloud band (F)
2: The upstream perturbation (X)
3: An emerging layered cloud (E)