Storm Forecast
Valid: Thu 02 Feb 2017 06:00 to Fri 03 Feb 2017 06:00 UTC
Issued: Wed 01 Feb 2017 23:24
Forecaster: GATZEN

A level 1 was issued for northwestern Spain mainly for severe wind gusts.

SYNOPSIS / DISCUSSION

Broad low geopotential across the North Atlantic and ridging over Europe are associated with a well-developed delta of the mid-level jet over south-western Europe. Explosive cyclogenesis is expected in this area on Thursday, with a first storm turning northward to the west of Ireland with a possible sting jet event at its southern flank. A second storm evolves upstream along a frontal wave and moves rapidly into the Bay of Biscay on Friday morning. Both storms are associated with dangerous non-convective winds that are not further addressed in this outlook.

Deep moist convection is expected to form near the mid-level trough axis associated with the first storm. Isolated showers and thunderstorms are forecast especially across the Bay of Biscay during the day, spreading east. As moisture and low-level convergence are weak behind the surface cold front, storms are not expected to become severe. Severe wind gusts are well possible, mainly due to the large pressure gradient and not as a consequence of convective storms.

The second storm that follows during the night hours indicates some better chances for organized convection. At its southern flank, rich low-level moisture is overspread by the upper-level front. A deep stratospheric intrusion and associated low-level stretching is expected to result in steep low-level lapse rates that overlap with the warm conveyor belt. Weak CAPE and strong lift along the cold front could support a convective line. High winds due to mesovortices are forecast with this line of storms that could enter north-western Spain on Friday morning, however, latest models indicate that moisture decrease will result in weakening CAPE at that time, so that main activity would stay offshore.