Abstract
African easterly waves are the precursor to most Atlantic tropical cyclones, yet we still do not understand why certain waves develop into menacingly powerful hurricanes while others dissipate just as quickly as they formed. The goal of this work is to identify how specific large-scale environmental conditions affect the development of Atlantic tropical cyclones from African easterly waves, particularly for the record-breaking 2020 Atlantic hurricane season. This is the first study of its kind to utilize our objective wave tracking technique to investigate the relationship between relative humidity and wind shear as they influence tropical cyclogenesis. Our tracking technique reveals that African easterly wave development depends on the direction of vertical wind shear rather than the magnitude. The greatest differences between waves that develop into tropical cyclones and those that do not is that a higher percentage of non-developers experience westerly shear over the Atlantic, whereas a greater portion of developers experience southerly shear throughout the entire basin. We also identify that mid-level relative humidity and African easterly wave strength are positively correlated. Comparing the most recent hurricane season to climatological means reveals that July through September 2020 experienced anomalously high wind shear over much of northern Africa that did not deter the formation of over 50 African easterly waves. By uncovering these relationships between African easterly waves, relative humidity and wind shear, our unique tracker can be extended to help forecasters assess the likelihood of a wave developing into a tropical cyclone.