Storm Forecast
Valid: Thu 30 Jul 2015 06:00 to Fri 31 Jul 2015 06:00 UTC
Issued: Wed 29 Jul 2015 22:50
Forecaster: GATZEN

A level 1 was issued for the central Mediterranean mainly for large hail and to a lesser extend severe wind gusts, excessive rain, and tornadoes.

A level 1 was issued for eastern Spain mainly for very large hail and to a lesser extend excessive rain, severe wind gusts, and tornadoes.

SYNOPSIS

A long-wave trough affects northern Europe. A strong mid-level flow extends from France north-eastward into eastern Europe. A short-wave trough and associated jet streak travels from the west Mediterranean to the Adriatic. Upstream, another trough moves into Iberia late in the period. Below the jet stream, an intense frontal zone extends from the west Mediterranean towards the Black Sea region.

DISCUSSION

Central Mediterranean

The passing short-wave trough will be associated with some QG forcing. With south-westerly winds, an elevated mixed layer will spread into the central Mediterranean where it overlaps with rich moisture. During the day, the sea breeze will advect this moisture inland, where diurnal heating will result in weak convective inhibition. Convergence zones will assist in initiation.

Storms are most likely along and east of a surface pressure trough that extends into Corsica and Sardinia. Given strong deep layer vertical wind shear, multicells and supercells are not ruled out, capable of producing large hail and severe wind gusts. Locally, excessive rain is possible. Tornadoes are also not ruled out as 0-3 km vertical wind shear is around 15 m/s. Storms are expected to spread into the Adriatic later on.

Eastern Spain

In the wake of the Mediterranean short-wave trough, a weak ridge affects eastern Spain. Easterly surface winds will advect Mediterranean moist air onshore, where it overlaps with steeper lapse rates due to diurnal heating. Upslope flow and convergence may assist initiation of some storms during the day. With westerly winds aloft, strong 0-3 km vertical wind shear is forecast, supporting well-organized storms. Supercells may produce very large hail. Severe wind gusts and excessive rain are not ruled out. Tornadoes seem to be most likely in the northern portions of the level 1 region. A level 2 was not issued due to the expected isolated nature of severe storms.