Storm Forecast
Valid: Thu 09 Jul 2015 06:00 to Fri 10 Jul 2015 06:00 UTC
Issued: Thu 09 Jul 2015 05:12
Forecaster: GATZEN

A level 1 was issued for western Russia, the central Ukraine, and central Romania mainly for large hail and severe wind gusts and to e lesser extend excessive precipitation.

A level 1 was issued for central and southern Italy and for the western Balkans mainly for large hail and severe wind gusts and to a lesser extend excessive precipitation.

SYNOPSIS

A Scandinavian trough will slowly move into the Baltic Sea today. A strong mid-level jet curves around this trough from the British Isles to the Alps and northern Balkans and further into western Russia. Two intense short-wave troughs are embeded in this trough, crossing Germany, Poland, and the Baltic States, whereas ridging takes place over western Europe in the wake of the trough. Cool and rather dry low-level air affects northern Europe today, and given weak lapse rates, chance of thunderstorms is pretty low.

Furthern south, a cold front has moved into the south-west Mediterranean, central Balkans, and western Russia. Over northern Italy, warm and moist air has remained due to cyclogenesis south of the Alps. Bora winds have set in across the Adriatic Sea that will replace the moist air from the north-east during the next hours.

Main focus of convective activity will be the moist air mass remaining across central and southern Italy as well as the cold front that moves east across the Ukraine and western Russia. Storms are also expected across the central and southern Balkans and Black Sea region.

DISCUSSION

Italy and western Balkans

Latest LIRE sounding indicates rich low-level moisture overlapping with an elevated mixed layer (CAPE 2000 J/kg). A broad convergence zone will persist today near the centre of the Italian low pressure system that will be superimposed by the sea breeze. Additionally, weak DCVA is expected due to an approaching trough from the north-west. Especially in the noon and afternoon hours, initiation is expected across Italy and over parts of the western Balkans.

Weak flow at mid-levels will limit storm organization, but 0-3 km vertical wind shear can exceed 10 m/s due to easterly low-level winds in the northern parts of the region with deep moist convection. Multicells are possible, along with isolated supercells. Main convective mode will be weakly-organized clusters of storms. The overall threat is lower compared to Wednesday, but some large hail reports and severe wind reports are expected. Additionally, excessive rain cannot be ruled out locally.

Central Romania into central Ukraine and western Russia

A cold front will move east across the region. Prefrontal air mass indicates steep low-level lapse rates and limited moisture, but diurnal heating is expected to allow for CAPE. Best moisture and CAPE are expected across Russia, where GFS indicates values up to more than 1000 J/kg. At mid-levels, a lifting trough passes by to the north-west.

Current thinking is that a prefrontal line of thunderstorms will form in the noon and afternoon hours. Vertical wind shear will increase to the north due to a strong southerly low-level jet, allowing for well-developed multicells across Russia. Additionally, isolated storms ahead of the line may become supercells. Large hail and severe wind gusts are forecast today. Excessive precipitation in not ruled out, especially in the southern parts of the level 1 due to slower storm movement.

Poland

Showers and thunderstorms are expected in the deep polar air mass of the mid/level trough. Weak vertical wind shear will limit storm organization. A few severe wind gusts are not ruled out.