Extreme Precipitation from 2018 Hurricane Florence: Timeline, Postanalysis, and Communication of Rarity

Hurricane Florence produced record breaking tropical cyclone precipitation in the Carolinas in September 2018. Prior to landfall as models started to converge, it became apparent that excessive rainfall amounts were imminent. Quantitative Precipitation Forecasts (QPFs) from the Weather Research and Forecasting (WRF) and European Centre for Medium-Range Weather Forecasts (ECMWF) models were translated into Average Recurrence Intervals (ARIs) and supplied to emergency managers in South Carolina to aid with resource allocation. Once the bulk of the precipitation had moved northward beyond the Carolinas, a more detailed post-storm analysis was performed. Utilizing thousands of rain gauge reports and high-resolution Dual-Polarization radar data, the final comprehensive re-construction of the storm rainfall indicated large areas of 1000+ year rainfall had occurred over parts of North and South Carolina. The storm center, located between Fayetteville and Wilmington, North Carolina, had 96-hour precipitation values over 40”.

From the initial forecasted ARI analysis through the final post-storm analysis, results were shared with the public through social media. Based on comments and questions received, it’s clear that there are still many misconceptions when it comes to precipitation frequency. In an era of information overload and complex statistics, it is easy to get lost in or overlook the details. This event provided another important data point when it comes to lessons learned communicating precipitation frequency to the public.

This presentation will step through the timeline of this monumental storm detailing the precipitation average recurrence interval from forecasts to observations as it tracked up the east coast. It will also highlight lessons learned communicating the precipitation frequency through social media, such as common misconceptions and the role climate change will play in future studies.