The difference in temperature between the poles and the equator is the main source of large-scale atmospheric motions around the globe and in particular the atmospheric mid latitude cyclogenesis. It is well known that, at these latitudes, the temperature gradient is maximum during winter and over land-ocean interfaces and is at the onset of upper-tropospheric atmospheric jet streams.

These jets are propitious to the forming of extra tropical cyclones that gather momentum from what is known as baroclinic interaction or baroclinic instability. Even though this mechanism responsible for cyclogenesis is well known, it is nonetheless true that other parameters can strongly modulate the properties of extra tropical cyclones. For example, latent heating processes may increase their amplitude but other phenomena such as the barotropic interaction related to horizontal wind shears may have the opposite effect. The impact of these phenomena on mid latitude cyclogenesis is still the subject of intense research.

Subsections

• Introduction and main ideas (2 articles)

  
  

• Coherent structure climatology (1 articles)

  
  

• Potential Vorticity Inversion (3 articles)

  
  

• December 1999 wind storms (2 articles)

  
  

• The 2009 January 24th windstorm (1 articles)

  
  

• Other extreme events (1 articles)