Аpplying prediction models for short-term hail forecasting in Southern Ukraine

Abstract

Formulation of the problem. Often natural disasters cause significant damage to the economy and the population, having a devastating nature, especially when a complex of dangerous weather conditions are created, which mutually reinforce their negative impact: storm rains accompanied by storm winds, thunderstorms with hail, etc. Increasing the validity and timeliness of storm warnings about hail occurrence is one of the main urgent tasks of operational meteorological support. The geographical position of Ukraine, the diversity of climatic conditions and the features of the synoptic processes on its territory contribute to the complex spatial and temporal distribution of the occurrence of natural meteorological phenomena (NMP). In recent years, the frequency of extreme weather phenomena has increased due to significant climate fluctuations. Often natural disasters cause significant damage to the economy and the population, having a devastating nature, especially when a complex of dangerous weather conditions is created. These weather conditions mutually reinforce their negative impact: storm rains accompanied by storm winds, thunderstorms with hail, etc. Increasing the validity and timeliness of storm warnings about hail occurrence is one of the main urgent tasks of operational meteorological support. The purpose of the article to study the synoptic and thermodynamic conditions of large hail occurrence in the territory of southern Ukraine, as well as the possibility of using forecasting models for short-term forecast of hail. Methods. Using of high spatial resolution forecasting models and GFS objective data or other resources. Results. The conditions of occurrence of two cases of hailstorms in the territory of the south of Ukraine in 2017-2018 are determined. In the first episode hail was not forecasted by the weather forecasters, due to the lack of daily radio-sounding data and a rare network of aerological observations, in the other one, an extraordinary hail (D = 65 mm) was observed. As predictors in forecasting of hail and other convective phenomena it is rational to use quantitative characteristics of the atmosphere instability. Possibilities of applying different convective storm indices, as well as the use of the Global Forecast System (GFS) numerical simulation forecast data with a grid step of 0.25o × 0.25o meridians were evaluated. It has been found that the forecast of moving hail clouds is effectively implemented by using the Bunkers method. Scientific novelty and practical significance. The most informative parameters of the thermodynamic state of the atmosphere the day before hail formation have been identified - Severe Weather ThrEAT Index (abbreviated SWEAT), Convective Available Potential Energy (abbreviated CAPE), Li (Lifted Index), BRN (Bulk Richardson Number), and VI (Boyden I). Recommendations are given to improve the quality of short-term hail forecast, taking into account numerical simulation data.