Storm Forecast
Valid: Thu 17 Feb 2022 06:00 to Fri 18 Feb 2022 06:00 UTC
Issued: Wed 16 Feb 2022 23:06
Forecaster: GATZEN

A level 2 was issued across southern Poland, north-eastern Czech Republic, northern Slovakia, and western Ukraine for severe wind gusts and to a lesser extent tornadoes.

A level 1 was issued across south-eastern Germany, northern Austria, northern Hungary, northern Romania, northern Modolva, and western Ukraine for wind gusts.

A level 1 was issued for Ireland, Wales, and western England for wind gusts.

SYNOPSIS

Strongly-forced synoptic situation continues on Thursday with an amplifying trough across Central Europe and strongly rising geopotential to its west in response to downstream development. A well-developed mid-level vorticity-maximum and tropopause fold crosses Poland towards the Ukraine and Black Sea. It affects a rather moist low-level air mass that can become unstable ahead of a cold front.

To the west, strong ridging takes place downstream of an intense north-Atlantic trough. Explosive cyclogenesis is expected to affect the British Isles on Friday morning.

Finally, the central Mediterranean cut-off trough is further digging south reaching northern Libya and Egypt where it will be associated with thunderstorms.

DISCUSSION

Strongly-forced synoptic situation continues on Thursday with an amplifying trough across Central Europe and strongly rising geopotential to its west in response to downstream development. A well-developed mid-level vorticity-maximum and tropopause fold crosses Poland towards the Ukraine and Black Sea. It affects a rather moist low-level air mass that can become unstable ahead of a cold front. To the west, strong ridging takes place downstream of an intense north-Atlantic trough. Explosive cyclogenesis is expected to affect the British Isles on Friday morning. Finally, the central Mediterranean cut-off trough is further digging south reaching northern Libya and Egypt where it will be associated with thunderstorms.

Ongoing high-shear, low-CAPE event is forecast on Thursday morning, with a line echo wave pattern travelling across southern Poland and northern Czech Republic and Slovakia. Due to initially rather rich low-level moisture, with mixing ratios in around 5 g/kg, and steepening lapse rates ahead of the cold front and close to the PV intrusion, marginal MLCAPE is forecast. This instability overlaps with 20 to 25 m/s low-level bulk shear and high storm-relative helicity.

Main threat is ongoing wind gust potential, in particular along bowing segments of the convective line. However, especially initially, a tornado threat exists where cloud bases are low and mesocyclones can develop.

On its way east, the PV intrusion will move into an area with decreasing low-level moisture. Potential for thunderstorms will therefore decrease due to weaker MLCAPE. However, current thinking is that the strongly-forced event is still accompanied by convective storms. While low-level vertical wind shear decreases, severe potential will also slowly diminish, with severe wind gusts the main threat until the afternoon, when instability across Belarus and Ukraine is expected to become zero.

Farther to the west and north, a few additional storms are forecast across SE Germany and N Poland. In the wake of the cold front, still strong vertical wind shear exists, but without strong low-level convergence, showers and thunderstorms will be rather weak and contribution to the wind gust threat is considerably lower compared to the frontal thunderstorms to the east.

British Isles

Model data suggests explosive cyclogenesis and an intense mid-level PV intrusion moving into the British Isles. Strong lift of a moist air mass will result in some steeper lapse rates and marginal CAPE is forecast.

Within the frontal rain band of the occlusion, isolated elevated thunderstorms are forecast. Along the occlusion and cold front, some surface-based storms are expected. Latest models indicate that the PV intrusion will be rather low, and storms will be low-topped. Therefore, lightning is a little bit uncertain at this time. However, if storms will form, they will enhance the wind gust threat that is already very high.