Storm Forecast
Valid: Wed 04 Apr 2007 06:00 to Thu 05 Apr 2007 06:00 UTC
Issued: Tue 03 Apr 2007 21:02
Forecaster: GATZEN

SYNOPSIS

South-east of amplified high pressure over north-eastern Atlantic, a broad upper-level trough is located over most of Europe, with an axis from Baltic States to northern Balkans, central Mediterranean and Iberian Peninsula. While cold and stable air mass spreads southeastward at the eastern flank of the high, Mediterranean regions are dominated by warmer air mass that is characterized by relatively steep lapse rates and some boundary layer moisture. This region will be the focus of expected convective development. Given weak vertical wind shear and forcing, most thunderstorms will be not organized. Two short-wave troughs embedded in the westerly flow at the southern edge of this trough are expected to lead to slightly better thermodynamic profiles, where chance for organize convection is enhanced compared to surrounding areas. Another region of interest is south-eastern Europe, where steep mid-level lapse rates have formed. Although boundary-layer moisture is weak, instability will likely develop during the period, as upper trough axis moves eastward and will likely produce some lift, and chance for showers and thunderstorms is expected to increase gradually.

DISCUSSION

South-western Mediterranean as well as southern Adriatic

Both regions will be affected by weak short-wave troughs embedded in the westerly flow. Weak to moderately strong jet streaks/vort-maxima travel eastward at the eastern flank of both short-wave troughs, providing some QG forcing. Affected air mass will likely destabilize due to some boundary-layer moisture indicated by latest ascends as well as relatively steep lapse rates, that may improve due to mid-level height falls. Showers and thunderstorms that are expected over a rather widespread region will likely concentrate in this regions. Given some vertical wind shear reaching 20 m/s 0-6 km shear, some thunderstorms may organize into multicells. There is also a potential for supercells as low-level winds shift to the south due to deepening surface pressure underneath the trough axis. Most significant severe thread is expected to be some large hail, while strong wind gusts and an isolated tornado is not ruled out. Thunderstorms will likely merge into clusters during the period and may go on through the night hours, while severe potential is forecast to weaken.

South-eastern Europe

Although low-level moisture is weak, a few showers and thunderstorms are not ruled out as upper level trough migrates eastward providing some forcing. Steep mid-level lapse rates and expected high cloud-base as well as locally inverted-V profiles (dependent on diurnal heating) may increase the potential of strong wind gusts. By now, we do not expect severe wind gusts given weak winds as well as weak forcing.