Valid: Tue 13 Nov 2012 06:00 to Wed 14 Nov 2012 06:00 UTC
Issued: Mon 12 Nov 2012 20:24
A level 1 was issued for parts of SSW Mediterranean, N Algeria and N Tunisia mainly for excessive convective rainfalls, large hail, severe winds and tornadoes.
A trough with history of flooding events across parts of the Mediterranean in the last days weakens and its cut off transformation on the south is finally complete. An intense upper low then rotating over northern Algeria and serves as a focus for another day of convective activity. A surface frontal zone lies in SSW Mediterranean sea.
... parts of SSW Mediterranean, N Algeria and N Tunisia ...
An intense rainfall threat over central Italy finally dimishes and should end within the morning hours of this forecast. Active day remains around the upper low which wobbles over northern Algeria throughout much of the forecast period. A strong mid-level jet rounds the core of the low and provides moderate to strongly sheared environment along the frontal zone extending from the SFC centre low south of Malorca and curving SE-wards towards N Tunisia. Strong SE-erly WAA maintaining unstable airmass within the frontal zone. With cold midlevels over still very warm (positive SST) waters of Mediterranean, moderate to strong MLCAPE in excess of 1500-2000 J/kg should be available. Expect rounds of organized storms acting as multicells and supercells, including possible clusters. Bringing heavy rain and large hail threat, while strong wind field and shear supports tornado threat as well. Excessive rainfalls and flash floods possible within coastal areas of NW Algeria where combination of convective precipitation and orographic features simulate high accumulations.
Activity gradually diminishes overnight to Wednesday when slowly shifting SE-wards. Maintaining a high-end level 1 due to threat mainly over open waters, while upgrade to level 2 remains possible for WSW parts if needed.
Elsewhere, no severe threat expected.