8 Summary and Conclusions 



The primary focus of this report is the determination of meteorological 

 factors which can be used to identify the population of storms similar to the 

 Halloween Storm and the storm of 4-5 January 1992. Identification of these 

 populations is necessary in order to arrive at a determination of frequency of 

 occurrence. The limitations and possible consequences of relying upon com- 

 monly available operational analyses for identifying and selecting candidate 

 events to include in these populations have been presented and discussed. A 

 synoptic analysis of the Halloween Storm is included and the storms is com- 

 pared with two similar events, one of which (the ERICA IOP-4 event) was 

 extremely well-documented. Meteorological factors which appear common to 

 all three events have been cited. The factors are based upon both observations 

 and theoretical investigations. A synoptic analysis of the 4-5 January 1992 

 storm which affected Ocean City, MD, also is presented. 



The following conclusions have been reached regarding factors affecting the 

 occurrence of storms similar to the Halloween Storm. It has been shown that 

 the values of at least two of the factors used to identify this type of storm, 

 (size and intensity as measured by the minimum central pressure) are depen- 

 dent upon the depiction of the events. Given the sparse data typical of the 

 marine environment, it may not always be possible to retrieve an accurate 

 estimate of these factors for every candidate event. Moreover, it appears prob- 

 able that certain pre-existing conditions are necessary for the formation of 

 large, long-duration, Halloween Storm-like events regardless of the subsequent 

 track the system may take. Common characteristics involved in the formation 

 and duration of Halloween Storm-like events appear to be: 



a. The presence of a strong anticyclone in the vicinity of the Hudson Bay 

 region of Canada. 



b. The presence of strong temperature contrast (20 °C or greater) between 

 the Canadian anticyclone and the maritime surface low at both the 

 surface and mid-troposphere levels. 



c. The presence of a mid- to upper-level low to the west of the maritime 

 surface low, typically over the Great Lakes region of the United States 

 during the early (formative) stages of the event. 



Chapter 8 Summary and Conclusions 



45 



