Status:Ongoing analysis Material Status: Finalised Material from: Ivan
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Discussed in the following Daily reports: |
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A severe thunderstorm was initiated over the Balkan mountain range (Stara planina in Bulgarian) in north-western Bulgaria. It moved to the east-northeast and developed quickly to a supercell badly affecting the town of Byala Slatina and Pleven, one of the biggest cities in northern Bulgaria in the afternoon hours on 15 May 2018. The storm caused all possible types of convective hazards: strong winds, large hail, heavy rain and accompanying flash flooding. It inflicted a lot of damage on properties, cars and infrastructure. Strong winds uprooted trees and caused power outages. In the municipalities of Byala Slatina and Pleven has been declared a state of emergency.
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ATDnet lightning flash density (left) and ESWD reports (right).
ATDnet flashes - animation.
2. Description of the event
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The radar imagery reveals a hook echo which is a sign of the mesocyclone associated with the supercell.
Radar imagery from the Hail Suppression Agency in Bulgaria.
Radar animation reveals that the storm was very long-lived. It formed at around 14 local time (11 UTC) and could be tracked by this radar station till about 19:00 local time (16 UTC), about 5 hours in total.
Radar animation of the storm development. Data are from the radar station Bardarski Geran provided by the the Hail Suppression Agency in Bulgaria. All the times are in local Eastern European summer time (UTC + 3 hours).
3. Predictability
3.1 Data assimilation
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These new parameters are derived from hourly model output and they will be tested in replacing current CAPE and CAPE-shear in the EFI product. An example that compares these new model outputs to the instantaneous CAPE and CAPE-shear for this case of severe convection are shown below.
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Probability of maximum CAPE greater than 1000 J/kg at T+114h (left) and T+18h (right).
Maximum CAPE and maximum CAPE-shear parameters have been used to compute the EFI/SOT for this case. Below, the operational EFI (left) and the EFI with the new parameters (right) is presented.
EFI/SOT for CAPE-shear: operational (left) and with new maximum CAPE-shear parameter (right). The navy triangle denotes the city of Pleven.
EFI/SOT for CAPE: operational (left) and with new maximum CAPE parameter (right). The navy triangle denotes the city of Pleven.
3.4 Monthly forecasts
3.5 Comparison with other centres
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4. Experience from general performance/other cases
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5. Good and bad aspects of the forecasts for the event
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