Storm Forecast
Valid: Tue 04 Aug 2020 06:00 to Wed 05 Aug 2020 06:00 UTC
Issued: Mon 03 Aug 2020 20:02
Forecaster: PUCIK
A level 2 was issued across the eastern Adriatics and adjacent areas mainly for excessive rainfall, large to very large hail, severe wind gusts and to the lesser extent tornadoes.
A level 1 was issued across Serbia, Hungary and southern Slovakia mainly for excessive rainfall and to the lesser degree for large hail.
A level 1 was issued across northern Tunisia and Italy mainly for large hail, excessive rainfall and tothe lesser degree for severe wind gusts.
... SYNOPSIS ...
Scattered to widespread convective storms are forecast in association with a deep mid to upper tropospheric cyclone centered over northwestern Italy, which will shift southeastwards during the day. Associated synoptic-scale lift is also forecast to translate east during the day, ovespreading much of the Adriatic Sea and western Balkans by Wednesday evening. Closer to the ground, a wavy frontal boundary will stretch from eastern Poland through western Slovakia into Hungary, Croatia and northern Italy. Lift from warm air advection regime along the front will be confined to northern Adriatics, southern Austria, western Hungary and southern Slovakia.
... DISCUSSION ...
... Eastern Adriatic Sea / Western Balkans ...
It is quite likely that storms will be already ongoing over parts of the highlighted area in the morning hours, particularly over the northern half of the Adriatics and near the stalled frontal boundary. By early afternoon, combination of synoptic-scale lift, lapse-rates of around 6.5 K/km and abundant lower tropospheric moisture will yield MLCAPE values in between of 1000 to 3000 J/kg over the Adriatic Sea, increasing towards south and decreasing inland. Ahead of the low, strong mid-tropospheric flow will yield 0-6 km bulk shear values over 20 m/s and 0-3 km over 15 m/s in a belt from southeastern Slovenia towards the southern Adriatics. Here, well-organised storms, including supercells are possible with a large variety of severe weather threats. Over northern part of the Level 2, excessive rain will be the dominant threat, while large hail and wind gust threat will increase towards the higher CAPE regime in southern half of the Level 2. Storms will spread along the coastline towards the south during the day and will potentially reach northwestern Greece by Wednesday 06 UTC.
... Central Italy to northern Africa ...
Central parts of Italy, as well as parts of northern Africa will be mostly outside of the favourable synoptic-scale lift. Thus, convective coverage will be lower compared to the Adriatic Sea. Nevertheless, in a belt from northern Africa through Sicily into Central Italy, moderate to strong 0-6 km bulk shear, combined with substantial CAPE near the coastlines will yield an elevated risk of severe storms.
... Hungary, southern Slovakia, Serbia ...
Degree of vertical wind shear and thus also the probability of severe storms will be lower compared to the Level 2 area. Some storms may exist over the northwestern part as the first frontal wave ejects to the north in the morning hours. With southerly flow advecting steeper lapse rates towards north, a plume of 500 - 1500 J/kg of MLCAPE will develop by the afternoon hours. Development of convective storms will depend also on the evolution over the Adriatic Sea. Nevertheless, NWP models generally agree on increasing storm coverage in the late afternoon to evening hours. Storms will generally spread towards east and north. Dominant threat will be excessive rainfall, but isolated large hail will be possible too, particularly over southwestern Hungary / northwestern Serbia, where 0-6 km bulk shear will be in between of 15 and 20 m/s.
