Date of Award

May 2015

Degree Type


Degree Name

Master of Science



First Advisor

Clark Evans

Committee Members

Sergey Kravtsov, Kyle Swanson


Altlantic Basin, Hurricanes, Season Length, Tropical Cyclones


Atlantic tropical cyclone (TC) seasons vary yearly in length with some seasons significantly shorter or longer than normal. Kossin (2008) suggested that from 1980 to 2007, the Atlantic TC season increased in length; however, their study only considered a subset of the Atlantic basin south of 30°N and east of 75°W. It is uncertain whether this trend holds over the entire Atlantic basin or continues into the present. It is also unclear as to whether meaningful sub-seasonal variability in the environmental factors necessary for TC formation exists between early- and late-starting and -ending seasons.

Quantile regression is used to evaluate long-term trends in Atlantic TC season length. No statistically-significant trend in Atlantic TC season length exists for the years 1979 to 2013 independent of the subset of the basin considered. No trend in Atlantic TC season length between 1979 and 2007 – the period studied by Kossin (2008) – exists when considering the entire Atlantic basin. Linear regression, as applied to June and November monthly-mean reanalysis data, is used to examine sub-seasonal environmental variability between early- and late-starting and -ending TC seasons. Early-starting and late-ending seasons are associated with environmental conditions that promote an increased likelihood of TC development along the preferred genesis pathways for such events.

While confidence in these results is relatively high, they only explain a small portion of the total variation in Atlantic TC season length. More research is needed to understand how variability on all scales influences season length and the predictability of Atlantic TC season length.