Storm Forecast
Valid: Sat 25 Oct 2008 06:00 to Sun 26 Oct 2008 06:00 UTC
Issued: Fri 24 Oct 2008 16:03
Forecaster: DAHL

SYNOPSIS

An intense and large, deep-layer low-pressure complex is covering much of N Atlantic, resulting in a vigorous W/SWly mid-/upper-level flow over the British Isles, the northern Norh Sea, and Scandinavia. A strong jet streak imbedded in this flow regime will cross the British Isels on Saturday, and attendant to its left-exit region, an intense peripheral SFC low will travel across the N British Isles and the northern North Sea into the central Norwegian Sea by Sunday 06Z. Elsewhere, weak upper lows persists over the southern Balkan States as well as over the N Maghreb States.

... DISCUSSION ...

... N British Isles ... S Norwegian Sea ...

GFS predicts appreciable ICAPE in the plume of warm/moist air mass underneath the left-exit region of the jet streak where strong mesoscale ascent is anticipated. EL temperatures of about -30°C reflect the simulated shallow nature of the convection, which may be sufficiently deep however, to augment the strong/severe large-scale gradient flow. Convection should be of linear nature, but isolated tornadoes do seem to be possible, especially where breaks in the line occur. Lightning activity may be somewhat scarce with this system, but a thunderstorm area seems to be marginally warranted.

In the wake of the frontal system, weakly electrified cellular polar-air convection should advect into the Norwegian Sea late on Saturday. Main threat should again be a local enhancement of the wind gusts.

... W Mediterranean ...

Weak thermodynamic fields as well as weak shear profiles should limit the severe threat over the W Mediterranean, though some 15 m/s of 0-6 km bulk shear are simulated south of Sicily. An isolated marginally severe wind/hail event cannot be discounted over this region, but the overall severe potential is too low for a threat area.