Storm Forecast
Valid: Wed 19 Jun 2019 06:00 to Thu 20 Jun 2019 06:00 UTC
Issued: Wed 19 Jun 2019 06:28
Forecaster: PUCIK
A level 1 was issued for parts of France, W Germany, E Belgium, E Netherlands, Denmark and SW Sweden mainly for large hail, severe wind gusts and to the lesser extent excessive precipitation.
A level 1 was issued for N Sweden, Central Finland and N Russia mainly for large hail and severe wind gusts.
A level 1 was issued across parts of Central and SE Europe mainly for excessive rainfall and large hail.
A level 1 was issued across Turkey and the Caucasus area mainly for excessive rainfall and large hail.
SYNOPSIS
Main macrosynoptic features are a large cyclonic vortex centered N of the British Isles and two ridges, one across the Central Mediterranean and the other over Ukraine and Belarus. In between of the ridges and the cyclonic vortex, a broad moderately strong SW-ly to W-ly flow has established over W and N parts of Europe. Two short-wave troughs are embedded in SW-ly flow, one will cross from France towards BENELUX during the day and the other will approach France by late evening hours. Another smaller scale low is currently residing over SW Turkey.
Closer to the surface, a frontal zone runs from NW Spain through France into the Northern Sea and Denmark. During the day, a cold front is forecast to cross France, BENELUX towards W Germany, while a warm front will lift NE-wards across S Sweden. Scattered to widespread DMC is forecast along the frontal boundary. Further DMC activity is expected in environment of weak flow, but abundant lower tropospheric moisture over parts of Central, Southeastern Europe and Turkey.
DISCUSSION
... France towards S Sweden ...
As of 06 UTC, elevated thunderstorms have formed over Belgium, N France and the English Channel on the edge of the advancing EML that was well sampled by 00 UTC Trappes sounding. At the same time, a large shield of clouds, remnant from the overnight convection over S France, is advected from France further NE-wards. It is possible that the elevated thunderstorms, as well as the cloud shield will affect surface heating in the following hours across BENELUX. Surface observations reveal dewpoints mostly between 12 to 16 deg C over the area, which is consistent with the latest model output.
By the afternoon, it is forecast that 1000 to 2000 J/kg of MLCAPE will develop over much of the region thanks to the steep lapse rates exceeding 7 K/km. DLS will be mostly between 10 and 15 m/s, favouring multicellular type of convection. Towards the evening, DLS will increase and transient supercells may occur, particularly over Denmark, where curved hodographs with around 150 m2/s2 of SRH in the 0-3 km layer are simulated. Current thinking is that scattered DMC will develop along the front and over Massif Central and move NE-wards. Towards the evening and night, an MCS may form over BENELUX, NW Germany and/or Denmark, as storms cluster together and move towards S Sweden.
Forecast soundings reveal steep lapse rates and high LCLs with well mixed and deep boundary layer, so that severe wind gusts may accompany stronger storms, particularly if an MCS will form in late afternoon or evening hours. Abundant CAPE in the hail growth zone will also allow for large hail and this threat will be most pronounced with transient supercells. Excessive rainfall may accompany the storms in the late evening or night, as LCLs decrease and storms cluster in bigger systems.
... N Sweden, Central Finland, N Russia ...
Along the diffuse frontal boundary, NWP agrees on the initiation of storms in the environment of modest lower tropospheric moisture and mid-tropospheric lapse rates of around 6.5 K/km. This combination will allow for MLCAPE values of 500 to 1000 J/kg. With strong mid-tropospheric flow aloft, long and straight hodographs are simulated, with DLS between 20 and 25 m/s. Thus, splitting supercells are forecast, bearing the threat of large hail and severe wind gusts. With 0-3 km shear reaching 15 m/s and as cells cluster as they move towards Russia, one or two linear segments may develop, enhancing the severe wind gust threat in the later parts of the forecast period.
... Central to South-Eastern Europe ...
Surface observations reveal very moist airmass, with the highest readings over Hungary, where dewpoints of up to 20 deg C can be found. As surface heating progresses, the whole area will be under moderate to high CAPE, locally exceeding 2000 J/kg, but at the same time DLS will be generally below 10 m/s, suggesting strong, but mostly short-lived updrafts. An exception will be NE Italy, where DLS over 10 m/s may favor some well organised multicells and even transient supercells. With slow storm motion and abundant moisture, the primary threat will be excessive precipitation, followed by large hail.
... Turkey and Caucasus region ...
Very similar pattern is also forecast for this region. Abundant CAPE, but very weak shear and slow storm motions will favour disorganised convection, which may locally produce heavy rainfall and large hail.
