Storm Forecast
Valid: Wed 11 Jul 2007 12:00 to Thu 12 Jul 2007 06:00 UTC
Issued: Wed 11 Jul 2007 13:23
Forecaster: GATZEN

SYNOPSIS

A cut-off low is present over Europe. Axis of cold mid-level air mass is situated from southern Scandinavia to Poland und farther to northern Adriatic on Wednesday. A strong mid-level jet is present a the periphery of this trough, moving across western, and central Mediterranean, central Balkans, Romania, western Ukraine, Belarus, eastern Poland, and Baltic region. At lower levels, associated cold front will move eastward into western Russia, eastern Belarus, central Ukraine, and southern Balkans. Remaining warm air mass is expected over the Adriatic Sea. Instability is likely especially in the range of the cold front, where low-level moisture is best, as well as underneath the trough axis, where steep lapse rates are forecast.

DISCUSSION

Bulgaria, Romania into southern Ukraine

Well-developed frontal boundary is present over central Romania. East of the boundary, warm air mass is still remaining over eastern Romania. This air mass is characterized by steep lapse rates as indicated by latest soundings. Low-level moisture has recovered especially near the Black Sea over eastern Bulgaria, but dewpoints around 15°C are also present in the range of a convergence zone over central Romania. During the next hours, strong upper jet streak is expected to move across western Romania, and right entry region will affect central and eastern Romania, where QG forcing is likely. Given that a weak surface low pressure system has developed over Bulgaria, leading to easterly winds across eastern Romania, expect that thunderstorms will go on/initiate along the convergence zone. Strong vertical wind shear is forecast given strong southerly mid-level winds, and thunderstorms will likely organize. Expect that supercells will form with a potential of producing large or very large hail. However, most significant severe threat will likely be severe wind gusts, when convection moves eastward into Moldova and Ukraine, where well-mixed air mass and dry low-levels are present. Expect that a couple of strong downburst windgusts are possible during the next hours. Limiting factor is rather weak instability due to dry low-levels. But given actual thunderstorms, current scenario seems to be quite likely. Thunderstorms will likely weaken in the evening hours given weakening forcing, and instability.

Southern Scandinavia into Adriatic

Underneath the trough axis, chance for waterspouts will remain high locally given weak vertical wind shear and rather high low-level buoyancy especially over relatively warm sea surface.