Variability and Trends in Florida's Synoptic-Scale Sea-Breeze Regime Distribution

Interactions between the synoptic-scale flow and the daily sea-breeze fronts that form along Florida’s extensive coastline influence precipitation probabilities throughout the state during the summer months. While the National Weather Service previously defined nine sea-breeze regimes resulting from variations in the synoptic-scale vector wind field near Tampa, Florida, these regimes were developed using a shorter 18-yr period and examined primarily for the purposes of short-term weather prediction. We extend this earlier work by employing recently released reanalysis data to develop a full 30-year climatology of the Florida sea-breeze regime distribution and analyze the composite mean atmospheric conditions associated with each regime. Further, given that 1) the synoptic-scale wind primarily varies as a result of movement in the western ridge of the North Atlantic subtropical high (NASH), and 2) previous studies suggest long-term shifts in the summertime mean position of the NASH western ridge, we also examine interannual variability and trends in the sea-breeze regime distribution and its relationship to rainfall frequency over a longer 60-year period, 1961—2020. Results indicate that synoptic-scale flow from the west through southwest, which enhances precipitation probabilities along the eastern half of the peninsula, has increased in frequency, while flow from the east through northeast has decreased in frequency. While our results suggest that changes in the sea-breeze regime distribution may in part explain increases in rainy-day frequency during June–August over northeastern Florida, it appears that other factors likely contribute to interannual variability in precipitation across the southern peninsula. Given these results, future work will assess the subseasonal predictability of theses sea breeze regimes and explore alternative methods of defining the regimes to better account for rainfall variability over the southern Florida peninsula.