Storm Forecast
Valid: Sun 15 Dec 2013 06:00 to Mon 16 Dec 2013 06:00 UTC
Issued: Sun 15 Dec 2013 02:15
Forecaster: VAN DER VELDE

No threat levels were issued (see text).

SYNOPSIS

A deep depression moves northeastward between the Shetland islands and Iceland. The European mainland (except Scandinavia) is under the influence of a high pressure system.

The strong pressure gradients create gale conditions for northern parts of the British Isles during the morning and early afternoon. The Atlantic cold front turns into an occlusion and should reach Scotland in the early afternoon. The chances for well developed convection at this front are low, with little to no CAPE forecast and a low (warm) EL. Non-convective wind gusts can reach over 100 km/h (27 m/s). Deep convection will be probable behind the cold front in the cold air mass, which only has mixing ratios below 4 g/kg, limiting electrfication. Cell motion will be 30-35 m/s and may produce similar speed gusts at the surface (northwest of Scotland). The Shetland islands lie at the edge of the curled occlusion around 15Z and may experience a sting jet with wind gusts at the ground of over 33 m/s.

Another feature of interest is a mid level frontal boundary in the surface level warm sector with elevated instability of up to 200 J/kg MUCAPE between the Azores and southern England. GFS computes significant convective precipitation signals. EL is colder than -20°C and there is a sort of "atmospheric river" of moist air (8-10 g/kg) rapidly advected to the English south coast with rain sums locally exceeding 15 mm.