Storm Forecast
Valid: Wed 18 May 2022 09:00 to Thu 19 May 2022 06:00 UTC
Issued: Wed 18 May 2022 09:32
Forecaster: GATZEN

A level 1 was issued across western Ireland for severe wind gusts.

A level 1 was issued across northern Iran and Azerbaijan for large hail and wind gusts.

A level 1 was issued across western and northern France, the Channel region for large hail and severe wind gusts.

A level 1 was issued across SE England for severe wind gusts and heavy rain.

SYNOPSIS

A well-developed Atlantic trough progresses slowly towards Europe. Amplified ridging across western Europe and downstream development across eastern Europe result in an increasingly meridional flow. Warm air advection intensifies over western Europe, and dry polar air spreads rapidly towards south-eastern Europe.

DISCUSSION

Western Ireland

A strongly-forced situation is going on across the east Atlantic, with a tropopause fold moving across Ireland today. Satellite images indicate a narrow cold-frontal rain band that will cross Ireland today. In a high-shear, low-CAPE environment, thunderstorms are most likely in the western parts where the equilibrium level temperature is expected to be lowest. Farther east, cloud tops are forecast to be lower due to a mid-level inversion. Main severe threat is severe wind gusts with bowing segments along the cold-frontal rain band.

Northern Iran and Azerbaijan

Ahead of the deepening soiuth-east European troiugh, a mid-level short-wave trough passes the area in a strong mid-level flow. Diurnal heating of a moist air mass will result in some CAPE with weak CIN across the high terrain, and scattered showers and thunderstorms are forecast. Despite weak CAPE, moderate vertical wind shear can support some multicells capable of producing large hail. Additionally, severe wind gusts are expected since low-levels are well-mixed and some bowing lines are possible with stronger storms.

Western and northern France towards the Channel and SE England

Ahead of the approaching long-wave trough, warm air advection has set in, and a plume of elevated steep lapse rates has reached southern Iberia. Today, string low-level heating will cause rapidly improving lapse rates over Spain that spread into France as well. At low levels, moisture increases over France and the Channel region, resulting in MLCAPE in the order of 1000 J/kg.

Convection initiation is questionable over most places due to weak lift. Best potential exists along the nose of the warm air that affects the Channel region in the late afternoon and evening. Storms form in moderate to strong deep layer vertical wind shear with increasing south-westerly mid-level flow, and multicells and supercells are forecast, capable of producing large hail and severe gusts.

Due to strong 0-3 km shear and strong lift, storms are forecast to organize into an MCS that travels east along the warm front, capable of producing severe wind gusts and heavy rain. This activity can also affect SE England during the night. While the storms turn elevated, they move farther into the North Sea until the morning.

Along the southern flank of the cluster, scattered storms will form across France along the outflow boundary. CAPE-shear overlap seems to be sufficient for some stronger multicells, and severe wind gusts and large hail are still possible during the night.