Cyclogenesis Enhancement Factors

Cyclones develop most rapidly and become strongest if the following
conditions, listed in roughly the order of importance, are present:

• Upper-level support (under the jet stream with strong divergence aloft).
   

• Cold air aloft (relative to the surface temperature; the colder, the greater the enhancement).
   

• Baroclinic conditions (see sample upper level chart for 4/30/2004).
   

• A moist air mass.

It should be noted that favorable conditions for vigorous cyclogenesis are more likely with a meridional circulation than with a zonal pattern.  It should also be noted that a baroclinic upper level circulation pattern (non-parallel isobars and isotherms) is much more favorable for strong cyclogenesis than a barotropic pattern (parallel isobars and isotherms).  Also favorable conditions are associated with a high level of vorticity.