Storm Forecast
Valid: Sun 28 Jul 2019 06:00 to Mon 29 Jul 2019 06:00 UTC
Issued: Sat 27 Jul 2019 19:45
Forecaster: PUCIK
A level 2 was issued across parts of Central Italy mainly for excessive rainfall, large to very large hail and damaging wind gusts.
A level 2 was issued across N Adriatic mainly for excessive rainfall and to the lesser degree for large hail and tornadoes.
A level 2 was issued from S Croatia towards Montenegro for excessive rainfall, large to very large hail, damaging wind gusts and tornadoes.
A level 1 was issued across N Italy, Slovenia, Hungary, Austria, Czech Republic and Slovakia mainly for excessive rainfall and to the lesser degree for large hail and severe wind gusts.
A level 1 was issued for Serbia and SW Romania mainly for severe wind gusts, excessive rainfall and to the lesser degree for large hail.
A level 1 was issued for Denmark mainly for excessive rainfall.
A level 1 was issued for S Scandinavia mainly for large hail, severe wind gusts and excessive rainfall.
SYNOPSIS
At mid to upper troposphere, a short-wave trough will quickly move from Corsica across the Adriatic Sea towards Serbia, transforming into a separate low and filling out in the process. At the same time, a cut-off low will move from N Germany through Denmark to the Northen Sea and is forecast to merge with a rapidly deepening low over the Atlantic, centered S of Ireland as of Monday 06 UTC.
Closer to surface, a wavy frontal boundary will remain over BENELUX and its cold part is forecast to surge across S Germany in the evening hours and across parts of the Mediterranean Sea towards Italy. Abundant lower tropospheric moisture is found east of the frontal zone, from Italy to Germany and Denmark. Isolated to widespread thunderstorm activity is forecast across large portions of S Scandinavia, Central and S-Central Europe during the day with enhanced chances of severe weather.
DISCUSSION
... Italy to Balkans ...
Widespread thunderstorm activity is forecast across the region, particularly over the western coastlines of the Tyrrhenian and the Adriatic Sea. As of Sunday 06 UTC, widespread DMC will already be ongoing over parts of the areas, namely Central Italy and the northern Adriatic. This activity may already be severe. During the day, as the short-wave moves eastward, convective coverage will decrease over Central and N Italy and increase over the parts of Adriatic Sea as the storms spread S along the Adriatic coastline.
Across the N Adriatic, main threat will be excessive rainfall given weaker vertical wind shear and slower storm motion. Organisation of convection will increase towards S and well organised multi to supercells are forecast over Central Italy and from S Croatia towards Montenegro. Here, large to very large hail and severe wind gusts will also be possible besides excessive rainfall, given the overlap of CAPE and 0-6 km bulk shear exceeding 20 m/s. From S Dalmatia towards Montengero, NWP also simulates strongly curved hodographs with SRH exceeding 300 m2/s2 in the 0-3 km layer and LCLs below 1000 m. Tornadoes, even strong ones, may accompany supercellular convection over this area. It is likely that a large convective system will eventually form and progress across S Bosnia, Montenegro into Serbia and SW Romania, in conjunction with the passage of the short-wave trough in the overnight hours.
... N Italy into Czech Republic and Slovakia ...
Scattered to widespread thunderstorms are forecast over this area in the environment of moderate CAPE, low LCLs, high RH throughout the troposphere and relatively slow storm motions. Storms will be organised into multicell clusters, given DLS around 10 m/s with predominant threat of excessive rainfall. Large hail and wet downbursts are not ruled out with stronger cells.
... Denmark into S Norway ...
As the cut-off low approaches the area, mid-tropospheric lapse rates are forecast to increase to 6.5 K/km, yielding MLCAPE of 500 to 1000 J/kg. Over Denmark, DLS around 10 m/s will yield multicell storms with threat of excessive rainfall. Over S Norway and Sweden, NWP simulates long, linear hodographs with bulk shear both in the 0-6 and 0-3 km layer approaching or slightly exceeding 20 m/s. Thus, splitting supercells and well organised convective lines are anticipated. While initiation is more questionable over S Sweden, widespread storms are simulated over S Norway and Lvl 2 was considered for combined threat of large hail and severe wind gusts. Decided to stay with lvl 1 due to the skinny CAPE profiles decreasing large hail risk and moist boundary layer limiting the severe wind gust risk to some degree.
