Storm Forecast
Valid: Mon 19 Dec 2016 06:00 to Tue 20 Dec 2016 06:00 UTC
Issued: Mon 19 Dec 2016 05:55
Forecaster: VAN DER VELDE

A level 2 was issued for the Balearic Islands, Sardinia and S Corsica mainly for excessive convective precipitation.

A level 1 was issued for the western Mediteranean basin mainly for excessive convective precipitation, waterspouts/tornadoes and severe convective wind gusts.

SYNOPSIS / DISCUSSION

Pressure in a low over the Alboran Sea is predicted to fall during the day while the system migrates into the western Mediterranean basin near the Balearic Islands. This causes steep pressure gradients with high winds over Sardinia, Corsica and the northern half of the western Mediterranean. 500 hPa temperatures under -25C over 2m temperatures of greater than 16C cause great instability, with moisture adding up to 300-700 J/kg MLCAPE and cold ELs within the 50% thunder area. Moist low level air converges in a band circling the same region, with upslope moisture advection most pronounced across eastern Spain (Alicante-Valencia), NW Algeria, south/east sides of Sardinia and Corsica, and the eastern Provence. Here the chances of onshore advection of convection are highest, with excessive rainfall as possible outcome. Balearic Islands will get this conveyor belt mainly at night, while cell motion slows down to below 3 m/s. Vorticity in this zone mainly over the Balearic Sea can spin up as waterspouts under convective updrafts. Vertical shear is strong east and north of the low with 250-600 m2/s2 of SREH in the lowest 3 km, so it may be possible that mesocyclones form in some storms over Sardinia, Sicily and perhaps Corsica with chances of tornadoes and large hail in addition to severe wind gusts.