Hail frequency, distribution and intensity in Northern Greece

Hail numerical and physical parameters are examined for an assessment of frequency, spatial and temporal distribution and intensity of hailfalls in Central Macedonia periphery, Northern Greece. Data from weather stations of the Hellenic National Meteorological Service (HNMS) indicated a mean yearly point frequency varying between 1 and 2 hail days for Central Macedonia. Crop insurance data from the Hellenic National Agricultural Insurance Organization (ELGA) showed a mean regional frequency of 22.3 hail days for the total cultivated area of Central Macedonia, about 6,500 km2, for the warm season, from April to September. Hailpad data representing almost one third of the total cultivated area of Central Macedonia, indicated a regional average of 8 hail days and 45 hailpads recording hail for the warm season. Spatial analysis over the hailpad area revealed a large variability of hail occurrence, with local maxima at the higher altitude and close to mountain barrier areas and a decreasing frequency over areas closer to the sea. The size distribution of a sample of 22,000 hailstones measured by the hailpads, showed a great majority, of 85.7%, having diameters up to 11 mm. An inter-comparison of hail impact energies according to crop damaging potential indicated Central Macedonia hailfalls as the less intense compared to those of areas of Northern America. Application of the revised TORRO hail intensity scale extending to classes from H0 to H10, permitted a classification of Central Macedonia hailfalls appropriate for comparisons and correspondence between areas and countries about the severity and damaging of hailfalls.