Figure 9. 0000-hr UTC, 28 October 1991, surface analysis 



Vortex Interaction 



In terms of intensification and movement, the early genesis stages of the 

 Halloween storm followed the classical description of extratropical cyclone 

 formation (e.g., Palmen and Newton (1969)), but also exhibited characteristics 

 consistent with results of recent studies which indicate both upper-level forcing 

 and lower-level moisture can be important contributors to cyclogenesis (Krietz- 

 berg 1991). The interaction of a surface low with an upper-level trough 

 located to the west which results in rapid intensification has been elegantly 



14 



Chapter 3 Halloween Storm 



