Floridian Heatwaves and Extreme Precipitation. Part I: Observations and Trends

There exists broad scientific consensus that heatwaves are increasing in frequency, duration, and intensity in a warming world, and are generally the most strongly linked extreme weather event to anthropogenic climate change. Due to its predominantly maritime climate, few studies have examined heatwaves in Florida. However, Florida’s older-skewed population and increasingly urban land areas make it particularly susceptible to the impacts of heatwaves on human life and health in the twenty-first century. This project for the first time established an objective heatwave metric, climatology, and trend analysis for major cities in Florida from 1950–2015. Using a percentile-based heatwave definition applied to station daily average temperature data, trends in the frequency, intensity, and duration of heatwaves at each location were investigated. It was found that the frequency and duration of heatwaves have increased in Florida over the past 65-years, but the intensity of heatwave events have not changed significantly. Because heatwaves are generally associated with blocking high-pressure systems that act to warm and moisten the incipient air mass (particularly in maritime tropical climates like Florida), it was hypothesized that anomalously heavy precipitation events occur at the end of a heatwave event. The synoptic evolution of, and physical mechanisms responsible for extreme precipitation events in the three days following a heatwave were investigated. Results showed that anomalously large subtropical moisture transport and the position of the Bermuda High were key features in determining whether an extreme precipitation event will follow a Floridian heatwave.