The coupled influence of instability indices and DWR data in estimating the squall speed of thunderstorms

Abstract

The specific forecast of occurrences and the associated consequences of thunderstorms is still a difficult task for both NWP models and professional weather forecasters due to the small spatial and temporal scales involved. In operational forecast, many indices are being used to assess the stability of the atmosphere and predict the possibility of thunderstorm development. It is also well established that the Doppler weather radar (DWR) has the capability of capturing the fast developing convective systems such as thunderstorms. The instability indices as well as the DWR data are utilized in the present study to estimate the speed of squall associated with thunderstorms during the pre monsoon season over Kolkata (22° 32′N, 88° 20′E), India. The ranges of the selected indices and the DWR data are estimated using the normal probability distribution function. The statistical skill score analysis is implemented to select the instability indices relevant for estimating the squall speed of thunderstorms over Kolkata. The threshold ranges of the selected indices and the DWR data are used as the inputs while the target output being the squall speed associated with thunderstorms. The method of rough set theory is adopted in this study to identify the best combination of the instability indices and DWR data for estimating the squall speed. The method of rough set theory is capable of dealing with inconsistency in the data set, if any, while simulates the condition — decision support system. The certainty factor of the rough set theory is computed in this study for the condition which is the coupled influence of the instability indices and DWR data on the decision that is, the squall speed associated with thunderstorms. The results are validated with the observations of 2010.