Storm Forecast
Valid: Tue 13 Aug 2019 06:00 to Wed 14 Aug 2019 06:00 UTC
Issued: Mon 12 Aug 2019 20:53
Forecaster: DAFIS

A level 2 was issued for N Italy, Slovenia, Croatia, Bosnia and Herzegovina, Hungary, Slovakia, Ukraine, Belarus and parts of Russia for large hail, severe wind gusts, excessive rainfall and tornadoes.

A level 1 surrounds the level-2 area and additionally covers S Poland, and it was issued for large hail, severe wind gusts and excessive rainfall.

A level 1 was issued for Finland and Estonia mainly for large hail and severe convective wind gusts.

A level 1 was issued for SE Spain and Algeria for large hail and severe wind gusts.

A level 1 was issued of parts of N Germany, the Netherlands and NE Belgium for large hail and severe convective wind gusts.

SYNOPSIS

A deep trough is crossing Central Europe and a strong baroclinic zone has formed over a large part of Central and Eastern Europe. Ahead of this trough, a plume of moist and warm air masses extends from Italy towards Russia, where we expect severe thunderstorms on Tue 13/08 and the early morning of Wed 14/08. In the cold sector of the trough, near the core of the cold mid-level air mass, some thunderstorms may also pose a threat near the coasts of the North Sea. Finally, another interesting spot will be the western parts of the Mediterranean, where locally enhanced thermodynamic ingredients will result in a few strong thunderstorms.

DISCUSSION

.... N Italy, Slovenia, Croatia, Bosnia and Herzegovina, Hungary, Slovakia, Ukraine, Belarus and parts of Russia .....

Under the weakening, yet very strong, jet stream, unstable air masses with a few hundred to 2.000 J/kg MLCAPE will overlap with steep lapse rates. First, the active elevated thunderstorms over Poland, Ukraine and Belarus will continue propagating NE-E with a limited threat for local flash floods until the early morning of Tue 13/08. Later, diurnally driven storms are expected along the boundary from Italy towards, Hungary, Ukraine and Belarus. Some of these storms will form into a strongly sheared environment with veering winds and supercells are well possible. Steep lapse rates and 15-20 m/s 0-6km DLS guarantee large hail and severe wind gusts in the areas denoted with the level-2 area.
The tornado threat is maximized near the borders of Ukraine, Belarus and Russia, where strongly low-level veering wind profiles, low LCLs and strong 0-1km shear will create a very favorable environment for tornadogenesis. The threat will be limited during the night in Russia as the thunderstorms will be mostly elevated, but the flash flood threat will still be very high.
During the night, as the approaching trough from the west will enhance the synoptic lift over NE Italy, Slovenia, Croatia, Bosnia-Herzegovina, and Hungary, a second round of strong storms is expected according to several NWP model outputs. These storms will be able to produce large amounts of precipitation, tornadoes/waterspouts near the coasts and locally large hail mostly to the southern parts of the level-2 area.

.... Finland and Estonia ....

An embedded short-wave trough is expected to cross the Baltic States and SE Scandinavia providing lift to unstable air masses. Different NWP model outputs about the true available convective potential energy limits the predictability. In the worst scenario, MLCAPE may reach values up to 1.000 J/kg and DLS/0-3km shear 10-12 m/s. Some of the storms may produce hail which can reach up to the large hail threshold, or severe wind gusts may cause damage. For this reason, a level-1 area has been issued.

.... SE Spain and Algeria ....

Strongly capped air masses near the coasts will limit convective initiation, but this will not be the case in the mountainous areas of Spain and Algeria. This area will be placed at the leading edge of the long-wave trough and storm initiation should begin around noon. Storms will be able to produce large hail and severe wind gusts given 1.000 - 2.000 J/kg MLCAPE (with high NCAPE) and 15-25 m/s DLS. Storms will weaken and stop in the late afternoon of Tue 13/08.

.... N Germany, the Netherlands and NE Belgium ....

The cold air masses near the core of the trough will be enhanced with moisture over the North Sea and combined with steep mid-level lapse rates will result in a few hundreds of CAPE. Large hail is low but still possible, as well as local convective wind gusts.