Storm Forecast
Valid: Sun 19 Apr 2015 06:00 to Mon 20 Apr 2015 06:00 UTC
Issued: Sun 19 Apr 2015 02:17
Forecaster: TASZAREK

A level 1 was issued for Finland mainly for severe wind gusts and tornadoes

A level 1 was issued for NE Spain, Balearic Islands, Sardinia and Sicilia mainly for large hail, severe wind gusts and excessive precipitation

SYNOPSIS

Europe stays under the influence of extensive high (1035 hPa) over the Norwegian Sea with ridge stretching to Balkan Peninsula (1025 hPa) that inhibit convection in most of the NW and central Europe. This high together with trough over W Russia provides also the intrusion of cold and dry air masses to much of the central and SE Europe, creating marginal thermodynamic instability in E parts of Europe. Warmer and more humid air covers SW Europe and the Mediterranean Sea with its surroundings. Two jest streaks are present in the forecast period, the first one separating Norwegian Sea's high and Russia's trough stretches from Svalbard to the Baltic countries, while the second one extends latitudinally from Spain to Greece. Within these two jet streaks and the presence of thermodynamic instability, severe convective storms may occur.

DISCUSSION

...Finland...

In the core of the mid and low level jet with DLS reaching 50 m/s NWP models forecast that marginal thermodynamic instability up to 150 J/kg together with favorable QG-lift associated with the passage of the short wave may occur. Although free convective layer is expected to be shallow, impressive air flow up to 3km (0-3km shear ~ 25 m/s) with directional wind shear measured by 0-3km SRH over 300 m2/s2, may organize convection into linear feature and/or supercells that may be capable of producing severe wind gusts. High LLS (~ 15 m/s) and 0-1km SRH (~100 m2/s2) create also the small risk for the tornado occurrence. The highest threat for severe weather occurrence is forecast between 1200 and 1800 UTC in central and S parts of Finland.

... NE Spain, Balearic Islands, Sardinia and Sicilia ...

Weakening cut-off that passed through Spain provide steep lapse rates that especially in the morning hours of the forecast period will overlap with moist boundary layer (~ 10 g/kg) in SE Spain and Balearic Islands where the severe weather threat is expected to be the highest. Resulting CAPE of almost 1000 J/kg will coincide with DLS up to 25 m/s and 0-3km SRH 250 m2/s2. Supercells that may occur in a such environment may be capable of locally producing severe wind gusts and large hail up to 3-4cm. Precipitable water exceeding 25mm and rich boundary layer's moisture poses also the risk for excessive precipitation phenomena. In the afternoon hours thunderstorms should weaken and move over Sardinia. In the evening and during the night, convection is likely to occur over Tyrrhenian Sea, but its activity is expected no to be very high.