Forecast of Convective Events and Its Verification against Atmospheric Electricity Observations

Abstract

A regional system of a short-term forecast of hazardous convective phenomena within WRF-ARW is described. It is shown that major maxima of errors in prognostic temperature and vertical velocity correlate with intense convective events, which indicates the need for additional verification procedures. A new method is proposed for forecasting hazardous convective events based on analyzing the simulated spatiotemporal distributions of the radar reflectivity of an event and comparing them with characteristic parameters (the duration, area, and maximum radar reflectivity) of intense convective events. Threshold values of the area and duration of the event are selected using field observations of powerful convective clouds, while the threshold of the maximum radar reflectivity in the vertical column is tailored for regional features. The method is verified against World-Wide Lightning Location Network (WWLLN) data and ground-based field measurements of the quasi-static electric field. It is shown that, for selected thresholds of duration (20 min) and area (50 km2), the optimal threshold of maximum radar reflectivity for Nizhny Novgorod oblast is 55 dBZ, in which case the Pierce skill score and the Heidke skill score take values of 0.61 and 0.62, respectively.