Winter Season Cold Front Variability in the Southern United States.

• Main Author: Hardy, Jeffrey W
• Format: Text
• Language: English
• Published: LSU Digital Commons 1998
• Subjects: Physical geography; Physics; atmospheric science; Alabama; Canada; Pacific; North Atlantic; North Atlantic oscillation
• Online Access: https://digitalcommons.lsu.edu/gradschool_disstheses/6779; https://doi.org/10.31390/gradschool_disstheses.6779; https://digitalcommons.lsu.edu/context/gradschool_disstheses/article/7778/viewcontent/9909821.pdf

The variability of southern United States cold fronts was examined for 29 winter seasons, with particular emphasis placed on the identification of the upper-air circulation patterns associated with months when the region experienced extremes in cold front frequencies and intensities. The influence of atmospheric teleconnection patterns on cold front variability was first examined. For the Pacific/North American (PNA) teleconnection pattern, cold front passage frequencies in Florida were found to be significantly higher (lower) during meridional (zonal) months. An examination of the North Atlantic Oscillation (NAO) revealed that cold front passage frequencies were significantly higher (lower) in western and eastern Texas and in Georgia and South Carolina during months when the Icelandic Low and Atlantic Subtropical High were weaker (stronger) than normal. The upper-air circulation patterns associated with extremes in cold front passage frequencies in the southern United States were also identified. Texas was found to experience a high (low) frequency of cold front passages during months when an upper-air ridge (trough) was present over the northeastern North Pacific and an upper-air trough (ridge) was located over western North America. Cold fronts were found to frequently pass over southern Arkansas, Louisiana, Mississippi, and Alabama when the upper-air circulation was characterized by a trough over northwestern North America, a ridge extending from the southwestern United States into Canada, and a trough over eastern North America. In Georgia and South Carolina, extreme cold front passage frequency months were found to be associated with the NAO. The PNA teleconnection pattern was found to be present during the extreme cold front passage frequency months in Florida. An examination of the months when the southern United States experienced extremes in cold front intensities revealed the importance of the presence of a strong upper-air ridge over northwestern North America during months when strong cold fronts ...