Explicitly simulated lightning within Medicanes: comparisons with observations

The characteristics and morphologies of lightning activity within tropical–like Mediterranean cyclones (Medicanes) are presented using a sample of 7 Medicanes over the 2005-2016 period. Observations from a long–range lightning detection system show that lightning activity within Medicanes is generally less pronounced than in their baroclinic counterparts and peaks about 24 hours prior to maximum intensity within a 200 km radius (R) from the estimated storm center. Maximum flash density is observed in the inner core (R=50–100 km) with the largest variability seen in the outer region (R=150–200 km). Sudden peaks in lightning activity were often associated with increasing wind shear, primarily post landfall. Akin to tropical waves, recent studies have shown that deep convection played a pivotal role in the intensification of these systems.

This study also employs a recently implemented explicit lightning forecast module within the Weather Research and Forecasting model (E-WRF, Fierro et al., 2013) to investigate the relationships between lightning rates and the evolution of Medicanes. The performance of E-WRF in reproducing the spatial and temporal evolution of lightning activity is evaluated against observations. Cloud scale simulations (dx = 2 km) show a general over-prediction of lightning activity, which may be associated with an underestimation of the intensity of these systems, as measured by minimum sea-level pressure and maximum sustained 10-m wind speed.