While mid-latitude dynamics and numerical weather prediction captured the attention of most research meteorologists in the immediate post-WWII period, Herbert Riehl and Joanne Simpson ventured into research that explored the subtropical and tropical atmosphere. As an assistant professor of meteorology at University of Chicago in the late 1940s, Riehl offered a course in tropical meteorology that stemmed from his experiences as a teacher and researcher at the Tropical Institute of Meteorology in Puerto Rico during the war. This course inspired several exceptional graduate students including Joanne Simpson. Simpson worked under Riehl for her doctorate (granted in 1949). The student-adviser relationship (Simpson-Riehl) eventually reached the collegial level. Riehl did not encourage scientific debate with his protégés, in Simpson's case he accepted it since he knew less about tropical cumulus than she did, and he suspected they were important sub-components of the general circulation. Together they investigated the physical aspects of the trade-wind circulation, tropical cumuli, and hurricanes. And although they were tenacious in their quest, there was a contentious aspect to the interaction but it only served to strengthen their contributions. Their scientific legacy is clarified by examining several key contributions while the nature of their interaction comes from information contained in several of Simpson's unpublished documents and an in-depth interview with her by the lead author in 2009.