Storm Forecast
Valid: Thu 09 Jul 2009 06:00 to Fri 10 Jul 2009 06:00 UTC
Issued: Thu 09 Jul 2009 06:11
Forecaster: SCHLENCZEK
A level 1 was issued for NE Spain mainly for large hail and severe gusts.
A level 1 was issued for NE Algeria / N Tunisia mainly for large hail and severe gusts.
A level 1 was issued for a belt from N Italy and the Balkan peninsula to NE Greece mainly for large hail and tornadoes.
A level 1 was issued for W Denmark / N North Sea mainly for spouts.
SYNOPSIS
On the eastern flank of an upper low centered over the Baltic sea, a 990 hPa surface low will move northward towards northern Sweden. In the first half of the forecast period, a well-defined cold front that stretches from Central Ukraine via W Russia towards S Finland will travel northeastward while weakening. This will reduce instability on the warm side of the front which limits the chance of severe thunderstorms.
Another surface low on the western flank of the upper trough moves towards northwestern Germany. Cold upper air overspreads the North Sea and parts of Germany and the Netherlands, leading to showers and thunderstorms.
From N Portugal via NE Spain and Sardinia to Italy, there is a frontal boundary which should become a focus for convective activity. A westerly 35 m/s jet streak at 300 hPa overspreads large portions of southern Europe with its left exit region initially located over NE Greece. There is a well-defined EML and more than 1 kJ/kg MLCAPE in southern Italy but a strong capping inversion will likely preclude initiation of storms.
DISCUSSION
...NE / E Spain...
In the vicinity of the upper jet streak, about 1 - 2 kJ/kg MLCAPE should be available over the eastern portions of Spain. Deep layer shear in order of 15 - 20 m/s as well as SRH3 around 150 - 200 mē / sē are present and any storm that initiates in this environment is likely to become supercellular and may pose a threat of large hail and severe gusts.
...NE Algeria, N Tunisia...
Moderate instability (1,5 - 2 kJ/kg MLCAPE) and 20 - 25 m/s deep layer shear should be in place and some small embedded upper vort-maxima may provide enough lift for initiation. Most storms should become well-organized multicells and high-based supercells which will likely produce large to very large hail and severe gusts.
...N Italy and region from N Balkans to NE Greece...
Ahead of a surface low over the Adriatic Sea, hot and moist air with 1 - 2 kJ/kg MLCAPE is present. Deep layer shear will reach values up to 20 m/s which is sufficient for organized multicells and a few supercells. Locally enhanced LLS and rich BL moisture may lead to a slightly enhanced tornado threat, but the main threat should be large hail. Later in the period, the focus of thunderstorm activity will shift southeastward from N Italy towards NE Greece.
...Baltic States, Belarus...
In the wake of the cold front, diurnally driven showers and thunderstorms will evolve in an environment with some hundred J/kg CAPE and almost no vertical shear. There may be local flooding due to heavy rainfall but overall threat is too marginal for a level 1. As CAPE vanishes after sunset, thunderstorm activity will come to an end.
...North Sea region, W Denmark...
Some hundred J/kg of CAPE will be created during the day and scattered showers / thunderstorms will evolve. Especially over the northern North Sea, waterspouts should be possible. Storms will be diurnally driven with peak activity in the afternoon hours.
