О НОВОМ ПОДХОДЕ К ПРОГНОЗИРОВАНИЮ СМЕРЧЕОПАСНЫХ СИТУАЦИЙ И ДРУГИХ ОПАСНЫХ КОНВЕКТИВНЫХ ЯВЛЕНИЙ

Abstract

In many studies indices of convective instability (hereinafter simply indices) are used to analyze and predict tornado-dangerous situations. For calculating the meteorological fields from which indices were subsequently calculated, the WRF-ARW version 3.4 was used – the non-hydrostatic, regional weather forecasting system. In the works (Novitskii et al, 2016; 2018) as an example of the calculation of 10 tornadoes that occurred at different times in the European territory of the Russian Federation, we show that the most informative from the point of view of forecasting tornado-dangerous situations and providing a minimum number of false warnings is the STP (significant tornado parameter) index. The characteristic time, during which STP index exceeds threshold value, is within the order of an hour, the size of the regions of localization of the values of the indices above the threshold is within the order of several tens kilometers. We proposed along with the STP index to involve the vertical velocity field, calculated in the WRF model, in the analysis and forecast of tornado-dangerous situations. We show that the value of the STP index above the threshold leads within the WRF model to the formation of a localized intense convective cell in the vertical velocity field in the vicinity of the maximum value of the index and at the moment of reaching this value. The possibility of using the STP index to predict tornado-dangerous situations with a lead time of up to three days with an accuracy of 150 km in space and several hours in time is demonstrated. A new approach to short-term forecasting of tornadoes is proposed. It is based on calculating the fields that are visible on the radar screen, using the WRF model forecast. Such fields are the fields of maximum radar reflectivity, upper cloud boundary and integral vertical water content. The comparison of the prognostic fields with the real fields that the radar sees allows us to specify a real convective system at the time of its formation in which the STP index will subsequently reach a threshold value and a tornado will appear. This can enlarge a lead time of tornado warnings to several hours, which currently averages 13 minutes. The approach can also be used for forecasting other dangerous convective phenomena, as well as in any other forecast models for current forecast correction by using incoming radar (satellite) information.