Storm Forecast
Valid: Thu 26 Dec 2019 06:00 to Fri 27 Dec 2019 06:00 UTC
Issued: Thu 26 Dec 2019 01:23
Forecaster: GATZEN

SYNOPSIS

Dry air masses have spread into most of Europe, limiting the potential of thunderstorms. A deep trough is placed across eastern Europe. A vorticity lobe rotates around its southern edge and affects the east Mediterranean where some low-level moisture is present. Increasing lapse rates will result in some weak CAPE here. Upstream, the west-European ridge is overrun by another vorticity maximum that moves eastward into France and reaches Italy late in the period. While lapse rates will also increase in this area, pretty weak moisture is expected.

DISCUSSION

East Mediterranean

A tropopause fault is located across the Mediterranean, with several waves moving along the mid-level front. Some low-level stretching is expected to result in steepening lapse rates that overlap with higher moisture over the southern Adriatic and also the east Mediterranean. Latest model data indicate that CAPE will especially develop near the base of the trough, where vertical wind shear is weak. Main severe threat is that of waterspouts close to the shores. Convective activity will spread east during the period.

The Channel region

The passage of a mid-level front in the noon will result in steep low-level lapse rates, overlapping with some low-level moisture. Although the equilibrium level temperature is only expected to be around -10°C, some thunderstorms are not ruled out. Given strong vertical wind shear and curved low-level hodographs, storm organization is expected, and severe wind gusts and a tornado are not ruled out. Overall threat is too limited to issue a level 1 though, since CAPE is only marginal.