Storm Forecast
Valid: Wed 16 Feb 2022 07:00 to Thu 17 Feb 2022 06:00 UTC
Issued: Wed 16 Feb 2022 07:26
Forecaster: PUCIK / TUSCHY

A level 3 was issued for N Germany and W Poland mainly for extremely severe wind gusts and tornadoes.

A level 2 was issued in a belt from N Ireland through the central UK towards the Netherlands, N Germany, and Poland for widespread severe wind gusts and tornadoes.

A level 1 was issued for W Greece mainly for heavy rain and waterspout risk.

SYNOPSIS

NAO+ features a strong ridge building into SW Europe with anomalous low heights between S Greenland to Norway. A tightening thermal gradient in between evolves and causes a strong mid/upper jet configuration with speed anomalies in the Q90 range for the 79-00 CFSR climatology (200 hPa u wind). This jet crosses the UK and pushes into Central Europe during the night.

Left exit region of the seasonably strong jet-streak results in pressure falls over S Norway and a gradually consolidating surface low is forecast to exit Scotland, cross the North Sea and S Norway before entering the Baltic Sea during the end of the forecast. IFS-ENS MSLP forecasts cluster around 965 hPa with a few members down to 960 hPa (similar to GFS/GEFS). A cold front will cross the whole region in the evening to overnight hours.


A cut-off low slowly moves across the Ionian Sea towards the SE. A diffuse low-level vortex accompanies this event, which pushes an occluded front towards Greece.


DISCUSSION

... UK through BENELUX towards Poland ...

A long-lived convective windstorm is expected to cross the region between Wednesday evening and Thursday morning.

Ahead of the cold front, abundant low-level moisture with mixing ratios exceeding 7g/kg will be available. Combined with strong forcing and steepening mid-tropospheric lapse rates, marginal CAPE will develop along the cold front with MLCAPE values between 100 and 200 J/kg. Kinematics along this front will be impressive as the 1 km AGL flow reaches 35 - 40 m/s, yielding 0-1 km bulk shear values of 20 - 25 m/s. As low-level lapse rates steepen with mixing ahead of the front, effective downward transport of momentum is forecast. Numerous convection-allowing models simulate the development of one or more convective lines that will progress SE across the area. Widespread convectively enhanced severe to extremely severe gusts will occur along these lines. The threat will pick up in the 15 - 18 UTC timeframe over the UK, between 21 - 00 UTC over BENELUX and W Germany, and towards 06 UTC over central Poland.

Besides the wind threat, an isolated tornado risk will be present along the convective line, especially if line-echo wave pattern develops. ICON D2 simulates a number of enhanced vorticity tracks, suggestive of areas of rotation within the convective line. The tornado threat will be augmented by the presence of rather large SRH (> 300 m2/s2 in the 0-1 km layer) ahead of the cold front, low LCLs, and steep low-level lapse rates. A strong tornado can not be ruled out given large magnitudes of low-level shear.

... W-Greece ...

A slow-moving MCS will propagate SE along the coast with heavy rain being the main risk. An isolated tornado event along the coast is possible with somewhat better thermodynamics and low-level shear.