Storm Forecast
Valid: Fri 04 Mar 2011 06:00 to Sat 05 Mar 2011 06:00 UTC
Issued: Thu 03 Mar 2011 21:05
Forecaster: SCHLENCZEK

A level 1 was issued for parts of Norway and W Sweden mainly for severe wind gusts and a possible tornado.

SYNOPSIS

One feature of interest on Friday is an upper cut-off low centered over Iberia. Relatively cold air overspreads large portions of SW and central Europe and therefore instability is rather marginal. GFS shows around 100 - 200 J/kg CAPE over the central and western Mediterranean and also over Iberia and S France in a weakly sheared environment.

Strong pressure gradients are observed over the northern parts of Scandinavia, caused by a broad upper high over western / central Europe and a 975 hPa low pressure system over the Barents Sea. Some instability is forecast to be created in the wake of the cold front which should have passed W Norway and Sweden around 06 UTC on Friday. Strong low level winds are present in the trough region, reaching 20 - 25 m/s at 850 hPa.

DISCUSSION

...Iberia, W Mediterranean, C Mediterranean...

Most of the convection will evolve in a weakly sheared environment except for storms which will develop near Sicily. Deep layer shear in order of 15 - 25 m/s in this region may allow a few organized multicells and / or short-lived supercells which are capable of producing isolated severe wind gusts. As strong capping is predicted for this region, no threat level is issued.

...C Norway, NW Sweden...

Some narrow bands of strong linear forcing are predicted near the Norwegian coastline which could aid to initiate a narrow convective line. The strong LL winds may lead to non-convective gusts in order of 20 - 25 m/s in a broad area and may become convectively enhanced. Some gusts may reach more than 34 m/s. Even though the role of convection for straight-line wind damage is still uncertain in this case, a threat level 1 is warranted. SRH is locally enhanced and some embedded mesocyclones may spawn a tornado.