Storm Forecast
Valid: Mon 10 Sep 2018 06:00 to Tue 11 Sep 2018 06:00 UTC
Issued: Sun 09 Sep 2018 23:55
Forecaster: VAN DER VELDE

A level 2 was issued across E coast of Spain and Balearic Islands for large hail, severe wind gusts and extreme rainfall.

A level 2 was issued across N Algeria for large hail and severe wind gusts.

A level 1 was issued for S Sweden for tornado chances.

DISCUSSION

A negatively tilted trough enters Scandinavia. A cold front will move through a region with modest CAPE. Deep layer shear is marginal and low-level shear quite good for elevating tornado chances slightly.

An upper cold pool maintains unstable conditions over the eastern half of the Iberian Peninsula, Balearic Sea and Algeria. The southwesterly jet stream creates a lot of wind shear (>20 m/s 0-6 km) with the easterly low-level winds. CAPE is in the 1000-2500 J/kg range over sea and a shortwave trough will likely erode the CIN and a mesoscale convective system may be triggered over the Balearic Sea. Cells may easily bring severe wind gusts thanks to the low-mid level humidity contrast enhancing downdraft buoyancy (delta-Theta-E over 20K). Large or very large hail may be produced. Over eastern Spain, weak storm motion can cause local flash floods.
Over Algeria, GFS creates convergence patterns suggesting MCS development. Chances of large hail and severe gusts are likely.

The region from Turkey to Estonia also deals with unstable airmasses. An upper cold pool over S Ukraine pulls northwestward a moisture plume. However, vertical wind shear is weak. Waterspouts may occur over the Black Sea (except western parts where the winds are strong).

Most CAPE over the central and eastern Mediterranean Sea seems capped or lacks vertical motion to trigger convection.