Investigating the Correlation between Heat Waves and Tropical Storms for Broward County:

In the last decades, due to climate change, heat waves have increased in frequency and intensity, being considered the most lethal weather-related phenomenon in the United States, with tropical storms that develop into hurricanes not far behind in terms of lethality and strengthening from a changing climate. In the United States, Florida is the state amid the top options for domestic migration, especially for elderly people who are in search of sun, warmth, and rest. However, with an increasing population looking for a comfortable climate, urban areas are expanding as well, arising concerns related to the inherent risks associated with heat waves in those sectors due to the urban heat island effect, as well as the risks linked with hurricane activity. Amongst the highest populated metropolitan areas in the state, Broward County (25.96N, 80.88W; 26.36N, 80.02W), which has tropical climate characteristics, presents the highest number of heat-related deaths from the state and is among the topmost hurricane-vulnerable counties in the nation. Given the limited number of studies focusing on heat waves on cities with tropical climate characteristics, how extreme temperature events in Florida have not been investigated extensively, and how heat waves and hurricanes share common ground in terms of the need of high temperatures and humidity to thrive, and the risks that they pose to the population of Broward County, the first part of this research focuses on determining the number of heat waves through the application of a bivariate Extreme Value Analysis in Broward County, Florida. Thus, daily maximum and minimum temperature values from the ECMWF Reanalysis v5 (ERA5) hourly data, in addition to ASOS data for validation purposes, were retrieved for the 4 sites where the stations are located. Dates of occurrence and number of days for each heat wave event were also determined. A maximum of 13 heat wave events were identified in one of the sites, with only three of them occurring simultaneously at the 4 locations. The second part of the study focused on identifying whether any tropical cyclone activity took place before or after the three simultaneous heat wave events occurrences. For this, the historical hurricane tracks provided by NOAA were utilized, retrieving those who had impacted the southern part of the peninsula on the years of the simultaneous heat wave events. Out of these 3 heat waves, one of them ended one day prior to Hurricane Katrina’s landfall near the border of Miami-Dade and Broward counties on August 25^th, 2005, and another one ended 5 days before the impact of Tropical Depression Nineteen (later Hurricane Sally) made landfall near Culter Bay, Miami-Dade County, on September 12^th, 2020. Subsequently, possible connections with ENSO phases were examined. It was seen that a positive ENSO phase began to develop nearing the end of 2005 and towards the middle of 2020, years that correspond to the heat wave events that presented hurricane activity in Florida. Moreover, Mean Sea Surface Temperatures (MSST) from Nasa Earth Observations were obtained to gain a clearer view on the conditions of the North Atlantic Ocean (NAO) for each of the events. An initial analysis of MJO was considered, which presented a weak oscillation event for August 2005, however it is associated to more cyclostrophic possibility, which is related to an intensification of vorticity in case of tropical storms and hurricanes development. Thus far, deeper analysis is needed in order to gain a better understanding of the possible connections between heat waves and hurricanes, which is the focus for future investigation.