Challenges Associated with Extreme Rainfall Measurement during Hurricane Maria

The 2017 hurricane season was unprecedented, with Hurricanes Harvey, Irma, and Maria causing over $300 billion in damage and thousands of fatalities. The impacts to the built environment and loss of life were particularly severe in Puerto Rico from Hurricane Maria – ostensibly the result of multiple intersecting geophysical hazards impacting the island. In response to the Hurricane Maria disaster, the National Institute of Standards and Technology (NIST) has launched a multidisciplinary technical investigation of Hurricane Maria’s impacts on Puerto Rico. The components that comprise this post windstorm investigation integrate the fields of meteorology, climate science, engineering, social science, economics, and epidemiology, in an effort to produce a holistic understanding of Hurricane Maria’s impacts, and provide scientifically-based recommendations across a spectrum of relevant standards, codes, and practices, aimed at strengthening the future resilience of Puerto Rico, and the Nation.

Anchoring the investigation is a multi-hazard characterization, the goal of which is to provide objective hazard-specific guidance to the other investigation components, while contributing to the advancement of hazard measurement science in its own right. While most engineering-based post windstorm investigations focus primarily on wind impacts, recent experience demonstrates that extreme rainfall is comparable to wind as the progenitor of weather disasters. For example, extreme rainfall in U.S. landfalling hurricanes causes more than twice the number of fatalities on average, when compared to wind. Accordingly, analyzing the spatial and temporal evolution of extreme rainfall in landfalling hurricanes, and placing those measurements in their proper historical context, is highly relevant for a post windstorm investigation of Hurricane Maria, given the direct role of extreme rainfall in producing landslides and inland flooding, both of which contributed to the thousands of fatalities and catastrophic damage to infrastructure, critical facilities, homes, and businesses across Puerto Rico, including long term implications for social and economic recovery mechanisms.

Ironically, much of the ground-based rainfall measurement network was compromised by the impacts of extreme wind and rainfall during Hurricane Maria, making a robust rainfall analysis elusive, as current precipitation estimates vary significantly. Accordingly, there is a critical need to improve current measurement practices by conducting a space-based multi-sensor rainfall assessment to better understand the range of extreme rainfall measurements and their potential influence in rainfall induced geophysical hazards. The discussion will offer a brief overview of the NIST Hurricane Maria interdisciplinary technical investigation, highlight the unique rainfall measurement science issues and remotely sensed precipitation characteristics, and explore implications for future multi-hazard characterization challenges in landfalling hurricanes.