Please note that this forecast is by ESTOFEX.




Storm Forecast
Valid: Sat 25 Jun 2016 06:00 to Sun 26 Jun 2016 06:00 UTC
Issued: Fri 24 Jun 2016 23:44
Forecaster: TASZAREK
A level 2 was issued for E Germany, SE Denmark, W Poland, W Czech Republic and NW Austria mainly for excessive precipitation, severe wind gusts, large hail, and in lesser extent for tornadoes.

A level 2 was issued for N Italy, Slovenia, NW Croatia and S Austria mainly for excessive precipitation, severe wind gusts and large hail.

A level 1 and 2 was issued for S Greece mainly for excessive precipitation, severe wind gusts, large hail and in lesser extent for tornadoes.

A level 1 was issued for parts of the CNTRL, S and SE Europe mainly for excessive precipitation, severe wind gusts and large hail.

A level 1 was issued for CNTRL Finland and W Russia mainly for large hail, severe wind gusts, excessive precipitation and in lesser extent for tornadoes.

SYNOPSIS

A tropical airmass sector continues to crowd into CNTRL and N Europe on the eastern flank of the approaching long-wave trough and a cold front. An axis of the aforementioned trough extends from British Isles up to N France. A weakening low without well-pronounced frontal sections is located over Greece. A high overbuilds over E Ukraine and W Russia. Jet streak areas are located within cyclonically curved trough over W Germany, North Sea and British Isles, and over S Finland and W Russia. Severe thunderstorms are mainly expected within the weakly sheared but highly unstable tropical airmass over CNTRL, S and SE Europe. Thanks to very moist vertical profile the main threat is associated with excessive precipitation and local flash flooding. Severe wind gusts within downbursts and large hail will be also possible due to a considerable instability and high delta theta-e values. Thunderstorms will be electrically highly active.

DISCUSSION

...CNTRL and S Europe...

An impressive southerly advected boundary layer's moisture up to 13-15 g/kg with diurnal heating and lapse rates exceeding 7 or even 7.5 K/km will develop a CAPE up to 1500-2500 J/kg with a local peak values up to 3500-4000 J/g. Since the main jet will be located further west, thunderstorm will remain in the weakly sheared environment of DLS mostly around 10 m/s, and increasing to 15 m/s in NW Germany. Thanks to weak airflow and considerable instability, a pulse thunderstorms will develop in the afternoon hours, and within very slow motion will be clustering into multicells in the training mode. Due to locally enhanced SRH, a few supercells capable of producing large hail are not ruled out. Along with high PW values (40-45 mm) the main threat will fall on the excessive precipitation that locally may exceed 60-80mm causing a flash flooding. Considerable high delta theta-e values indicate also an elevated threat for strong downburst and microburst phenomena capable of producing wind gusts exceeding 100-120 km/h. A meso-low will develop over W Czech Republic and move northwardly along W Poland. A level 2 over W Poland, E Germany and W Czech Republic denote areas where mesoscale NWP models are the most consistent in CI and large precipitation and where meso-low will pass. Although DLS will be low, a locally enhanced LLS and 0-1km SRH over Czech Republic and S Poland cannot rule out a brief tornado in the evening hours. NWP models do not all agree in a CI signal over N Italy and Slovenia, but due to very high instability (2500-3500 J/kg) and a possibility of extremely severe weather resulting from strong flash flooding or very large hail, a level 2 was issued.

...S Greece...

Within an northeastwardly moving trough from CNTRL Mediterranean, a severe thunderstorms in the highly sheared environment will be capable of producing a severe wind gusts and large hail. Due to orographic lift, some thunderstorms may remain stationary and especially in the mountainous areas may produce a flash flooding. Current NWP runs indicate an impressive accumulated stratiform and convective precipitation locally up to 100-150mm. Due to DLS exceeding 20 m/s and a local enhancement of LLS up to 10 m/s along with favourable wind profile (0-1km SRH ~ 100-200 m2/s2), a tornado event cannot be ruled out.

... W Russia and S Finland ...

North from the building high over E Ukraine and W Russia, along the quasi-stationary frontal boundary between tropical and polar airmass (stretching from S Finland to NW Russia), a thunderstorms in the high shear (DLS ~ 25 m/s) and low CAPE (~ 300-500 J/kg) environment, will be capable of producing severe wind gusts. In the warm sector where instability will be considerably higher (1000-2000 J/kg CAPE) but shear will drop to 10 m/s DLS, similar as in CNTRL Europe, convective cells will have a potential of producing an excessive precipitation, large hail, and severe wind gusts thanks to high delta theta-e values. Locally enhanced LLS in the late afteroon hours cannot rule out a tornado event.