Signatures of Oceanic Wind Events in Convection Resolving WRF Model Simulations

Abstract

Analyses of cloud top temperature and lightning characteristics of 48 Weather Research and Forecasting (WRF) model simulated ocean-based wind events, with 1 min temporal and 0.5 km horizontal resolution, revealed signatures similar to the corresponding 13 observed events detected by buoys and Coastal-Marine Automated Network (C-MAN) stations as shown in prior research on ocean-based wind events by the first author. These events occurred in the eastern Gulf of Mexico and in the Atlantic Ocean from Florida northward through South Carolina. The coldest WRF cloud top temperature (WCTT) and peak WRF-estimated lightning flash rate values of the model simulated events, where each event was required to have a negative vertical velocity of at least 10 m s-1 in the lowest 2 km associated with a convective storm, occurred at an average of 4.2 and 1.1 min prior to the events, respectively. With 36 of the events, the peak estimated flash rate occurred within 5 min of the coldest WCTT. Cloud depth typically increased as the WCTT decreased, and the maximum depth occurred at an average of 2.9 min prior to the events. Thermal cooling and precipitation loading provided negative buoyancy needed to help drive the wind events. Environmental characteristics of the model simulated ocean-based wind events also resembled those associated with land-based wet downbursts, including moist air near the surface, lapse rates near moist adiabatic, and low cloud bases.