Storm Forecast
Valid: Thu 09 Aug 2012 06:00 to Fri 10 Aug 2012 06:00 UTC
Issued: Wed 08 Aug 2012 21:38
Forecaster: GATZEN

A level 1 was issued for northern Italy mainly for large hail.

A level 1 was issued for northern Spain mainly for large hail.

SYNOPSIS

A Scandinavian long-wave trough affects most of Europe. Dry and rather cool air masses spread southward into the Mediterranean. High geopotential across the Mediterranean ridges into Iberia and the British Isles.

DISCUSSION

Alps and surroundings

In the wake of the Scandinavian trough, a trough axis moves eastward across Germany and the Alps. At the anticyclonically-sheared flank of the mid-level jet, some QG forcing is expected. At lower levels, a tongue of moist air currently across the Benelux countries will spread south-eastward into the Alpine region. Additionally, moist low-level air is situated to the south of the Alps.

Over the southern Alpine region, rich low-level moisture and steep mid-level lapse rates will result in CAPE exceeding 1500 J/kg at most places. Weak CIN is forecast and storms are likely to develop. Easterly surface winds are expected to enable favorably veering profiles locally, although the large-scale SRH is only marginal (0-3 km values below 100 m²/s²). Diurnally driven storms may organize and supercells are not ruled out capable of producing large hail and excessive precipitation.

To the north of the Alps, in the cool and rather well-mixed air mass, diurnal heating is forecast to lead to CAPE during the day. Upslopw flow and low-level convergence are expected to support deep moist convection. Vertical wind shear is not strong, and severe convection is not likely. An isolated large hail event is not ruled out.

Central Baltic Sea

Near the trough center, a well-mixed and moist air mass is located across the Baltic Sea. Weak vertical wind shear and rather strong low-level buoyancy may favor waterspouts especially in association with the land-sea circulations near the coasts.

Southern Balkans to northern Turkey and Romania

Numerous storms are forecast along a frontal boundary over this region. The weak flow will limit vertical wind shear, and organized storms are not forecast. Convection will merge into clusters. However, large CAPE and high moisture are present, and a few excessive precipitation events are not ruled out. Additionally, pulse storms may result in large hail as well.

Northern Spain/southern France

Storms that may form over the mountains have a high chance to organize given large hodographs in the region due to strong warm air advection. However, the capping inversion in the warm air may suppress initiation. Current thinking is that storms will not develop. However, every storm that forms has the potential of producing very large hail.