Electronic Theses and Dissertations



Document Type


Degree Name

Master of Science


Earth Sciences

Committee Chair

Dorian Burnette

Committee Member

Dorian J Burnette

Committee Member

Arleen A Hill

Committee Member

Youngsang Kwon


Recent research has shown tornado activity over portions of the U.S. is impacted by internal ocean-atmospheric forcing. Impacts of seasonal and annual precipitation on tornado activity have also been assessed in previous studies, but no published research has included a full assessment of the soil moisture balance despite the known influences of soil moisture on thunderstorm activity. Therefore, this research explores the influence of soil moisture balance on tornado activity over Arkansas, Louisiana, Mississippi, and the western portion of Tennessee. Two measures of the soil moisture balance were used, the Palmer Drought Severity Index (PDSI) and the Palmer Z-Index. Tornado day counts were computed from tornado path data and transformed into percent of normal values for comparison with the two drought variables and various ocean-atmospheric teleconnections (e.g., El Niño-Southern Oscillation). Results suggest the impact of soil moisture balance on tornado counts over the Southern Mississippi River Valley is mostly during the warmer months from late winter into the spring. Forward and backward stepwise regression modeling identified the Z-Index and the winter (December-January-February) Oceanic Niño Index as the most important variables influencing tornado day variability over the Southern Mississippi River Valley during the spring season (March-April-May).


Data is provided by the student.

Library Comment

Dissertation or thesis originally submitted to ProQuest


Open Access