Storm Forecast
Valid: Wed 30 Dec 2015 06:00 to Thu 31 Dec 2015 06:00 UTC
Issued: Wed 30 Dec 2015 02:51
Forecaster: TASZAREK

A level 1 was issued for British Isles mainly for the excessive precipitation and severe wind gusts.

SYNOPSIS and DISCUSSION

An extensive high centered over Poland and Baltic Countries influence weather pattern over most of the NE and E Europe, and blocks the zonal flow. A large geopotential wave moves eastward from the Atlantic and within a well pronounced trought's warm section and a cold front it enters British Isles, France and the North Sea. A secondary trough at the peak of the wave will form during a forecast period over British Isles. A powerful jet stream (with wind speeds up to 85 m/s) encircles a longwave. Between a mentioned high and a jet streak, a tongue of a warm polar air mass stretches from W Mediterranean up to Svalbard. A poorly marked mid-level cold drop with an advection of PVU moves over C Mediterranean and provides locally over marine areas a conditions for an isolated weak thunderstorms. Convection capable of producing severe weather is although possible over British Isles, where an excessive precipitation due to a superimposing large-scale and a convective precipitation together with a parallel flow along the frontal boundary is expected. A passing cold front that will be accompanied by a very dynamic airflow may locally be capable of producing a convective severe wind gust. However, due to a marginal or almost absent thermodynamic instability the convective enhancement of a pressure-gradient wind gusts is questionable. In the cold sector, a significantly steepening lapse rates and CAPE over marine areas up to 200-400 J/kg with equilibrium levels in the graupel zone will contribute to the increased potential for the lightning occurrence.