Storm Forecast
Valid: Mon 02 Jan 2012 06:00 to Tue 03 Jan 2012 06:00 UTC
Issued: Sun 01 Jan 2012 18:38
Forecaster: DAHL

A level 1 was issued across Ireland mainly for severe convective straight-line winds.

SYNOPSIS

The progressive pattern continues with an upper trough crossing the western and central parts of Europe on Monday. The southern tip of this trough will be stripped off as the system crosses the Alps, yielding a small cut-off low over the NW Mediterranean by early Tuesday morning. Ahead of this developing upper low, SFC cyclogenesis will occur, which will be a focus for convective development on Monday.
A subsequent short-wave trough and an attendant compact and deepening SFC low will affect the western British Isles late in the period.

DISCUSSION

... NW Mediterranean ...

Weak CAPE is expected to develop in the warm-sector air mass over the NW Mediterranean ahead of the developing upper cut-off low in the second half of the forecast period. GFS 12Z indicates rather patchy deep-layer shear, whose maxima are rather decorrelated with the regions where CAPE is expected. This suggests that the overall severe threat is rather low.

... Ireland ...

A rather marginal situation in terms of deep convection will exist along the cold front of the compact Atlantic system reaching the western British Isles late in the period. Although no deep instability is advertised by either GFS or HIRLAM, strong mesoscale forcing for ascent along the cold front may support a narrow/shallow line of forced convection. Given wind velocities of 35 m/s at 850 hPa, the outflow of this convection may be accompanied by severe wind gusts.
The updrafts of this convection may be too weak and shallow to produce an appreciable amount of lightning.