Tornadoes, severe hail, and their environments in Turkey

This thesis investigates the tornadoes, severe hail, and their environmental features in Turkey. Climatologies of tornadoes and severe hail are prepared using various data sources, from official records to newspaper and internet reports, after a rigorous quality control check. The first part presents the first and most comprehensive climatology of tornadoes in Turkey to date. Tornado reports in Turkey historically have been sporadic and difficult to obtain, but reporting has improved in recent years for a number of reasons. Nonmesocyclonic tornadoes (waterspouts) are relatively common in the fall and winter along the Turkish coastlines, especially the southern and western coastlines of the Mediterranean and Aegean Seas, respectively. In fact, the southern coastline from Antalya to Anamur is likely among the most tornado-prone regions of Europe. Tornadoes in interior Turkey are less common, or at least reported less often. However, Turkey's strongest (and deadliest, despite a relatively low-population density) tornadoes have occurred here, most often in late spring, and are associated with supercells. The second part focuses on the severe hail occurrences in Turkey. Investigating the spatial and temporal distribution of severe hail is a prerequisite for understanding and ultimately predicting the environmental conditions that are favorable for severe hail. Turkey's severe hail climatology reveals that all parts of the country are vulnerable to severe hail (larger than or equal to 1.5 cm), and it can occur in any season of the year. The largest hailstones exceed 5 cm in diameter and 480 g in mass. Severe hail in Turkey is most likely in May and June, when severe hail is most likely in the interior of the country, especially in the east. Severe hail is least likely in the winter, though when it occurs in winter, it is most likely along the southern and western coasts. The afternoon and early evening hours are the most favorable time of the day for severe hail. The long-term variations in Turkish severe hail events (e.g., the 1960s maximum and early 2000s minimum) are also discussed. Thermodynamics of severe convective storms in Turkey are similar to relatively stronger than those in Europe, but considerably weaker than those in the US. This can partially be attributed to the latitude, and surrounding warmer seas. For deep layer shear, the situation is similar. However, low level shear appear to be lower. Complex topography of Turkey, being not represented in coarse reanalysis data might have contributed to this, effecting also the SRH values. LCLs are much lower than US environments, and similar to European ones, as expected. Composite parameters can be useful for discriminating severe weather. EHI and especially SCP are found to be useful in discriminating supercell and very large hail environments, as well as mesocyclonic tornado events from other storm categories. However, STP is not found to be a good discriminator for tornado forecasting.