Storm Forecast
Valid: Sat 22 Oct 2016 06:00 to Sun 23 Oct 2016 06:00 UTC
Issued: Fri 21 Oct 2016 23:10
Forecaster: TASZAREK

A level 1 was issued for Balearic Islands and part of W Mediterranean mainly for large hail, severe wind gusts and in lesser extent for excessive precipitation.

A level 1 was issued for W Greece mainly for excessive precipitation and severe wind gusts.

SYNOPSIS and DISCUSSION

A broad cold-core low with stable airmass is placed over CNTRL Europe and inhibits convective activity over most of the W, N, CNTRL and E Europe. Thanks to latitudinal thermal gradient, a western flow dominates over Mediterranean basin. Thunderstorm possibilities in this area are enhanced due to moist boundary layer (10-13 g/kg MIXR), locally increased vertical lapse rates (> 7 K/km) and passing shortwave troughts. In such setup, thermodynamic instability develops both in western and eastern Mediterranean up to 1500-2000 J/kg. Although southern part of this airmass is strongly capped under warm low-levels, northern edges near Balaric Islands and Greece areas provide chances for DMC.

At the beginning of the forecast period, ongoing elevated convection from the previous day will remain active in the aforementioned areas. Although multicell clusters will be weakening over W Greece, they will maintain a potential of producing severe wind gusts and excessive precipitation (given 30mm PW, slow motion of the cells and orographic lift factor). Later during the day, convection should develop over Aegean Sea, but severe weather potential will be limited due to rather small CAPE and only moderate to small shear.

Within the support of shortwave and PVA lobes, a few thunderstorm clusters may develop over W Mediterranean. In the environments of ~ 1500-2000 J/kg CAPE and 15-25 m/s DLS, convection may quickly cluster into line with the potential of producing severe wind gusts. Thanks to 200-300 m2/s2 SRH, a few isolated/embedded supercells capable of producing large hail are also possible. Excessive precipitation potential is partly limited due to increased motion of the convection, but given PW exceeding 30mm, it cannot be ruled out. However, because severe thunderstorm threat befalls in this region mostly on the water surface areas, flash flooding threat is not involved.

While convection will fade over Aegean Sea in the late afternoon hours, it should remain active over W Mediterranean until nighttime. Thunderstorms in the end of the forecast period are also possible over W Portugal, where a cold front from W will approach.