Storm Forecast
Valid: Mon 28 Dec 2015 06:00 to Tue 29 Dec 2015 06:00 UTC
Issued: Sun 27 Dec 2015 18:20
Forecaster: VAN DER VELDE

A level 1 was issued for W Ireland, Portugal and W Spain mainly for tornado chances.

SYNOPSIS

Between European high pressure and Atlantic low pressure, a southerly flow of relatively warm air is present from Spain to Iceland. An Atlantic cold front is arriving to the same region. There are two regions of interest. Warm surface air is advected from subtropical regions into Portugal and SW Spain ahead of the cold front, increasing the SBCAPE to 200-500 J/kg. In combination with 10-20 m/s 0-1 km shear and 0-3 km SREH enhanced over 150 m²/s², convection with an isolated tornado is possible, if the fragile CAPE materializes.
The low west of Ireland is the second focus, when its occlusion touches the west coast of Ireland between 19-23Z (GFS-12Z timing) and moves off to the north. 35 m/s deep layer shear and over 12 m/s 0-1 km would pass over western Ireland with steep mid level lapse rates overlapping the surface occlusion wrapped around the low. A band of high SREH is aligned with the occlusion. A field of 25 m/s mean low level winds surrounds the low. There is some chance of a tornado or convective severe wind gust.