Storm Forecast
Valid: Mon 21 Nov 2011 06:00 to Tue 22 Nov 2011 06:00 UTC
Issued: Mon 21 Nov 2011 05:29
Forecaster: VAN DER VELDE

A level 1 was issued for eastern Spain and Balearic islands mainly for excessive convective precipitation.

A level 1 was issued for Sardinia and Sicily mainly for severe convective wind gusts, large hail and possibly a tornado.


SYNOPSIS

A low pressure area has now installed itself in the western Mediterranean with increased amounts of CAPE. The mid level potential vorticity maximum which entered Africa will start digging into the southern Mediterranean during the afternoon and develop a cold/dry front subsequently moving over Sardinia and Sicily. The Balearic islands will be near the almost stationary occlusion with where models trigger quite a lot of precipitation.

DISCUSSION

...eastern Spain...

The region south of Valencia will see most orographic moisture lifting as the low level wind direction turns from easterly to more northerly directions. As has already been the case during the night, persistent storms should continue there for some more hours and cause locally excessive rain sums. Storm motion should remain very weak.

...Sardinia and Sicily...

GFS and HiRLAM disagree on the areal distribution of vertical wind shear and helicity, but are quite in agreement on the amount of CAPE (800-1500 J/kg). While shear is around 15 m/s over a deep layer, SREH can reach 300 m2/s2, most sure over Sicily. Both models agree on a band of >22 m/s mean winds between 1-3 km AGL over Sardinia. A linear convective system with severe wind gusts is a likely scenario. Embedded supercells could also create large hail and perhaps a tornado

Waterspouts are likely to be observed here and there over a large section of the western Mediterranean.