Severe storms: A level 2 issued for Eastern Europe
Valid: Tue 02 Jul 2019 06:00 to Wed 03 Jul 2019 06:00 UTC
Issued: Mon 01 Jul 2019 21:32
A level 2 was issued for parts of Slovakia, Hungary, Romania, Ukraine, Moldova and Russia for severe wind gusts, large hail and excessive precipitation.
A level 1 was issued for S France, Switzerland, S Germany, Liechtenstein, N Italy, Austria, Slovenia, Croatia, W Hungary, and Bosnia and Herzegovina for large hail, severe wind gusts and excessive precipitation.
The intrusion of a polar maritime air mass in Europe results in an elongated frontal boundary extending from France to Russia. The warm and moist air mass in central and eastern parts of the continent is pushed quite violently south-southeast. At the warm sector ahead of the front, we expect numerous thunderstorms which will locally become severe. In the cold sector of the front, some lower-topped thunderstorms are expected in NE Europe and Scandinavia. Local storms are also forecast in the Iberian Peninsula and Algeria, and some of them will be capable of producing large hail and severe wind gusts but their spatial coverage does not justify issuing a threat-level area.
Slovakia, Hungary, Romania, Ukraine, Moldova and Russia
On the aforementioned boundary in eastern Europe, the weakly capped, rich in moisture and warm air mass will provide the necessary ingredients for deep moist convection. Steep mid-level lapse rates aloft create fat CAPE profiles in the NWP outputs (1000-1800 J/kg), overlapping locally with more than 15 m/s DLS. Comparable bulk-shear-0-3km speeds suggest that some of the storms will be able to evolve into supercells producing large hail and severe wind gusts. Straight forecast hodographs show the potential of convective line developments with an elevated risk of severe wind gusts, especially in Ukraine. PWAT values in an excess of 30 mm show the potential of slow-moving storms and clusters to produce excessive precipitation.
Finally, rather high LCLs and straight forecast hodographs limit tornadogenesis threat, apart from W Russia, where late in the afternoon low-level shear increases with veering winds and LCLs drop.
S France, Switzerland, S Germany, Liechtenstein, N Italy, Austria, Slovenia, Croatia, W Hungary, and Bosnia and Herzegovina
The remnants of the last week's extreme heat wave can still be found in France and Central Europe. Warm air masses with a high content of moisture will be lifted by a low-level convergence zone and diurnal heating. Very steep mid-level lapse rates create locally more than 2000 J/kg MLCAPE in the GFS solution, with the IFS and ICON-EU providing comparable values of CAPE. The CAPE-shear overlap is not very strong, compared to eastern Europe, but storms will take advantage of about 10 m/s DLS (locally reaching 15 m/s) to organize in small clusters able to produce large hail and severe wind gusts. High values of PWAT suggest that slow-moving clusters may produce excessive precipitation inside the level-1 area.