Storm Forecast
Valid: Sun 08 May 2011 06:00 to Mon 09 May 2011 06:00 UTC
Issued: Sun 08 May 2011 04:54
Forecaster: SCHLENCZEK
A level 1 was issued for NE Algeria and N Tunisia mainly for large hail and severe wind gusts.
SYNOPSIS
There are two upper level features on the map which will likely be associated with deep convection on Sunday: A strong upper low west of Ireland moves slowly eastwards and the jet stream on the southern / eastern edge points towards England and Scotland. Some deep convection is expected near the cold front and in the vicinity of the upper cold core.
The second feature is a tiny upper low over the Balearic Islands with its upper level jet affecting N Algeria and Tunisia. Instability is quite low but a good overlap with strong deep layer shear is very likely.
Some diurnally driven convection may develop over the rest of western / central / eastern Europe, but severe weather is not expected. Another large upper low over eastern Europe does not seem to contribute much to the convection.
DISCUSSION
...British Isles...
An upper level vort-max is forecast to move across the British Isles from SSW to NNE during the late morning / early afternoon. In its vicinity, some few hundred J/kg CAPE should be available. 0-6 km shear is in order of 30 - 35 m/s, around 15 m/s shear in the lowest 3 km, but no significant LL shear and 0-3 km SRH are forecast. As mixed layer LCL heights tend to increase around the afternoon, there will be a threat of isolated severe wind gusts. Compared to the day before, severe weather seems to be much less likely and no threat level is issued despite the chance of isolated severe wind gusts and / or an isolated tornado.
...N Algeria / Tunisia...
The southern tip of the upper low will reach NE Algeria / N Tunisia during the late morning hours. Locally 150 - 250 mē/sē SRH3 and 15 - 20 m/s 0-3 km shear are in place with some low-end instability and the combination of strong shear in the mid levels and enhanced SRH suggests that supercells should be the most likely convective mode. Despite the strong capping, initiation should be likely as strong DCVA is forecast. Due to the fact that most of the storms will be rather elevated, isolated large hail and isolated severe wind gusts should be the main threat. Shear and forcing will likely decrease during the evening and the large hail / wind threat will diminish.
