22-01-2025 21:10 | Estofex | m.b.t. 23-01-2025 t/m 24-01-2025
Storm Forecast
Valid: Thu 23 Jan 2025 06:00 to Fri 24 Jan 2025 06:00 UTC
Issued: Wed 22 Jan 2025 21:10
Forecaster: TUSCHY
A level 2 was issued for S UK mainly for severe wind gusts with a few tornado events possible. A strong event cannot be ruled out.
A level 1 surrounds the level 2 area with a similar risk but lower probabilities.
SYNOPSIS
The flow pattern over W Europe turns more zonal during this forecast in response to substantial geopotential height decrease over the NE Atlantic.
This drop in thickness is accompanied by an impressive 200 kt zonal jet along its southern fringe, which points towards NW Europe. A rapidly approaching surface low from the SW (probably in form of a diabatic Rossby wave) crosses this jet to the north. Its attendant moisture rich cross-isentropic WCB ascent and attendant strong irrotational wind response cause a splitting upper jet with a resultant coupled jet configuration (combined with extreme upper divergence). A 24h MSLP drop in the latitude corrected 2 bergeron range is forecast and this depression approaches Ireland during the end of the forecast from the SW. It reveals an impressive warm seclusion structure and we would not be surprised to see a mixed cold jet (potential sting jet) event evolving offshore with NWP guidance offering gusts up to 200 km/h. Convective-wise there seems to be no substantial risk of activity despite some isolated CI along the leading edge of the NE ward wrapping dry slot. Forecast soundings don't support electrified convection. Anyhow, severe to extreme gusts are possible, but limited confidence in CI precludes any level issuance. Slantwise convection along the tip of the cold jet remains offshore until 06Z without lightning activity.
One part of the splitting upper jet dives into a lead impulse, which results in a sharp trough passage over parts of UK. This event becomes the main player for DMC activity.
DISCUSSION
... S UK ...
An active cold front passage is forecast during the daytime hours, placed beneath the left exit of an intense mid/upper jet (e.g. up to 45 m/s at 700 hPa). The accompanied upper trough is filled with IPV rich air, so combined with strong QG lift we expect modest instability build-up in an extreme shear environment. Forecast hodographs are rather straight, but offer abundant LL shear with lots of LL streamwise vorticity, so rotating updrafts are possible, including a risk of a few tornados and severe gusts. Given rapid translation of thunderstorms, any tornado could be long-tracked and even a strong event cannot be ruled out. The main tornado risk seems to evolve along and S of a Bristol-London line, where the highest BL moisture resides in a low LCL environment. Limited LL CAPE could confine the overall risk more to the coastal areas (up to 200 J/kg), but not much modification is needed for some better LLCAPE build-up further N.
Convection my race E towards the coastal areas of W Belgium/SW Netherlands with an ongoing severe gust risk.
Tornado/hoosverschijnsel(en) | Verwachtingen/waarschuwingen | Wind/storm (-schade)
