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2 Acta Geophysica

2 2023

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The capability of NOTHAS in the prediction of extreme weather events across different climatic areas

Spiridonov Vlado, Grcić Marija, Sladić Nedim, Ćurić Mladjen, Jakimovski Boro

Acta Geophysica

2023

Vol. 71, no. 6

3007--3024

Climate changes are accelerating and leading to climate and weather extremes with the most destructive impacts and negative consequences on the planet. For these reasons, precise forecasting, and announcement of weather disasters of a convective nature, from local to synoptic scales, is very important. The Novel Thunderstorm Alert System (NOTHAS) has shown outstanding results in forecasting and early warning of different modes of convection, including local hazards in mid-latitudes. In this study, an attempt has been made to apply this tool in the prediction of different atmospheric systems that occur in different climatic regions. The upgraded prognostic and diagnostic algorithm with adjusted complex parameters and criteria representative of tropical storms and tropical cyclones showed good coincidence with the available observations. NOTHAS showed skill and success in assessing the dynamics and intensity of Hurricane Ian, which hit the west coast of Florida on 30 September 2022 and caused great material damage and human losses. This advanced tool also detected the most intense-extreme Level-5 on 1 September 2021, over New York, when catastrophic flooding occurred within the remnants of Hurricane Ida. Likewise, the upgraded model configuration very correctly predicted the trajectory, modifications, and strength of super typhoon Nanmadol over Japan (19 September 2022), 24-48 h in advance, and super typhoon Noru over the Philippines (25 September 2022). The system showed the temporal and spatial accuracy of the location of the heavy rainfall and flash flood. In general, the obtained results for all evaluated cases are encouraging and provide a good basis for further testing, verification, and severe weather warnings and guidance for weather services worldwide.

Assessment of the WRF model in simulating a catastrophic flash flood

Spiridonov Vlado, Ćurić Mladjen, Grčić Marija, Jakimovski Boro, Spasovski Milosh

Acta Geophysica

2023

Vol. 71, no. 3

1347--1359

The present study examines the ability of the forecast (WRF) model to reproduce a heavy rainfall flash-flood event that hit the urban area of Skopje City, on August 6, 2016. A series of numerical experiments were carried out to evaluate the model’s performance in the simulation of this catastrophic event, which caused great material damage and the loss of 23 human lives. The simulations with the triple-nested WRF-ARW runs as well as the experiment using WRF-NMM dynamic core with the initial data of FNL GDAS showed better skills in a more precise qualitative and quantitative assessment of the total 24-h accumulated precipitation, the location and the relative intensities of rainfall. Explicit treatment of convection without parameterization significantly improves forecast accuracy and reduces forecast errors. The verification results, using standard tests, showed the model’s ability to reproduce the occurred flood. The correlation coefficient is higher for runs with explicit cumulus convection and 4 km resolution with the Yonsei PBL scheme and Thomson microphysics with aerosol climatology. In addition to the influence of the thermodynamic characteristics of the atmosphere, orographic forcing on the development of a strong mesosystem is of great importance for the intensification of convective cells and the production of large amounts of precipitation.