Improving Flood and Flash Flood Forecasts Across South Florida

The objective of this project is to better understand the parameters and meteorological conditions necessary for flood and flash flood events in South Florida and better predict when they may occur. The mean meteorological conditions associated with flash flood events in South Florida are determined using Storm Data reports of flooding and flash flooding from February 1997 - February 2015 in South Florida. Upper air soundings from site KMFL for all flood and flash flood events are used to create a mean composite sounding. The RAwindsone OBservation (RAOB) program is used to analyze the different soundings and determine what meteorological characteristics and parameters are associated with these events. Events are also broken down into warm season and cool season to better reflect seasonal changes in parameters and atmospheric conditions. Events are then classified based on the synoptic conditions leading to flooding and flash flooding. Anomaly charts are created for various meteorological characteristics to show the anomalies that are present on flood and flash flood event days as compared to the 30 year climatological normal from 1981-2010. The study has recently been completed in partnership with the University of Miami Student Exchange Program with the National Weather Service Office in Miami. Preliminary results indicate cool season flooding and flash flooding episodes focus on eastern sections of South Florida, whereas western areas have episodes generally confined to the warm season. Nearly all events occur in urban or suburban locations, rather than rural. Anomalous southerly and easterly flow at various heights, anomalous deep-layer moisture, and warmer low-level temperatures combined with cooler upper-level temperatures are a few of the generalities discovered to favor flooding and flash flooding in South Florida. This paper will present the detailed results of this study identifying critical thresholds to look for among key ingredients, which will be incorporated into Weather Forecast Office Miami operational guidelines to improve the accuracy of flood and flash flood forecasts for its area of responsibility.