Storm Forecast
Valid: Tue 16 Jan 2018 06:00 to Wed 17 Jan 2018 06:00 UTC
Issued: Mon 15 Jan 2018 20:10
Forecaster: DAFIS

A level 1 was issued for parts of Ireland, UK, France, Benelux and Germany mainly for severe convective wind gusts.

A level 1 was issued for Croatia mainly for severe wind gusts and tornadoes.

DISCUSSION

A large low-pressure system with its core over Iceland in combination with the Azores High create a vigorous wind field in NW-W and Central Europe. A negatively tilted trough over the North Sea brings polar maritime air masses over continental Europe, with a strong jet configuration at the W-SW side of the trough, with a noteworthy jet streak of 80 m/s wind speed at 500 hPa (as forecast for Tuesday evening SW from Ireland). In the eastern parts of the continent, a cut-off low over Ukraine is gradually pushed north by the approaching trough from the west and the high-pressure system in Russia. Rather steep lapse rates in the Aegean Sea result in some hundreds of CAPE, where non-severe thunderstorms are expected.

This jet configuration in NW Europe brings 25-30 m/s of non-convective winds at 850 hPa according to GFS over France, Benelux and Germany where limited convective phenomena are expected but they will able to produce severe or damaging convective wind gusts at the surface. Apart from the wind gusts, which will continue to be the main threat also on Wednesday, locally large amounts of graupel are expected in the aforementioned countries. In the early morning of Wednesday, storms in N Adriatic Sea may become severe as the leading edge of the approaching trough brings high values of PVA, along with cold mid-levels which create steep lapse rates with 300 J/kg CAPE or more. Overlapping strong DLS and LLS may enhance convection near the coasts of Croatia, where a level 1 has been issued for severe wind gusts and tornadoes. Excessive precipitation will also be a threat in mountainous areas but later in the morning of Wednesday.