Storm Forecast
Valid: Thu 26 Mar 2009 06:00 to Fri 27 Mar 2009 06:00 UTC
Issued: Wed 25 Mar 2009 18:52
Forecaster: GATZEN

SYNOPSIS

Wavy north-westerly frontal jet affects western, central, and south-eastern Europe west of a long-wave trough over the eastern portions of Europe. A weak ridge is situated over south-western Europe. A strong upper jet streak now situated across western central Europe is expected to travel south-eastward at the southern flank of a sharp short-wave trough. It will likely be associated with strong DCVA from the Adriatic region to the Aegean region during the period.

DISCUSSION

Adriatic region

Numerous thunderstorms have formed across western central Europe on Wednesday in the range of the sharp upper short-wave trough that will travel further south-eastwards during the next hours. On Thursday morning, the trough axis will be located over northern Italy. The affected air mass is characterized by steep lapse rates and dry low levels as indicated by latest soundings. However, some more substantial low-level moisture can be found to the west of Italy, and models suggest that this air mass will advect into parts of the Adriatic Sea. Given strong forcing, mid-levels are expected to cool significantly, and latest GFS indicates rather deep instability and cold equilibrium temperatures. Limiting factor is poor low-level moisture. Showers and thunderstorms may form. Strong deep layer vertical wind shear is present just at the cyclonic flank of the aforementioned jet streak, where thunderstorms may organize into small bowing lines or mesocyclones. Although the chance seems to be low, a tornado is not completely ruled out with this convection that will spread south-eastward during the period.

Aegean to southern Turkey

Situation on Thursday seems to be comparable to the Adriatic region. Air mass over the Aegean and south of Turkey is rather cold with steep lapse rates and some low-level moisture. As the upper trough axis approaches in the evening hours, upper height falls will likely lead to deeper instability. Strong forcing is expected and showers and thunderstorms are forecast. Best potential for severe thunderstorms is expected near the cyclonic flank of the upper jet streak, where deep layer vertical wind shear is strong. With stronger cells, a tornado cannot be ruled out completely. Additionally, rather strong low-level winds may favor a few severe wind gusts along bowing segments.