Storm Forecast
Valid: Tue 29 Aug 2006 06:00 to Wed 30 Aug 2006 06:00 UTC
Issued: Tue 29 Aug 2006 09:32
Forecaster: VAN DER VELDE

SYNOPSIS

A deep upper longwave trough is situated over northern and central Europe. Shorter waves under the strong jetstream swinging around the upper low affect the eastern Ukraine, northern Italy/Adriatic and the eastern Poland/western Belarus/Ukraine area.

DISCUSSION

...eastern Ukraine, southern Russia...

A very dynamic situation with a shortwave upper trough/surface low plowing northeastward into locally >2000 J/kg MLCAPE (00Z Tuapse sounding) under strong vertically sheared conditions (>20-25 m/s DLS, >15 m/s LLS, 0-3 km SREH 200-400 m2/s2) is capable of producing a very severe weather episode. Supercells with chance of very large hail, tornadoes and (very) severe gusts are probable, but the most coverage will be of bowing MCS storms doing widespread damage by severe straightline winds.

...central Europe...

With modest instability, a strong jet nearby to the south, and strong low-level flow, we should anticipate a few tornadic events and marginally large hail, given 0-1 km shear greater than 10 m/s that could yield short-lived mesocyclones in storms.

...northern Adriatic Sea area...

Positioned under a very strong jetstream, an intensifying wave in the very baroclinic frontal zone with some CAPE forecast by the GFS model, mainly over the warm sea ... the strong shear conditions (deep-layer shear 30-40 m/s!) are certainly adequate for supercell storms producing large hail, severe winds and a couple of tornadoes, helped by low LCL heights, moderate to strong low-level shear and very steep temperature lapse rates over the northern Adriatic Sea, especially during the night hours when the wave moves through.

...North Sea and Baltic Sea coasta...

With colder air advecting over relatively warm water surfaces, GFS indicates that surface to 500m AGL lapse rates become very strong again, to superadiabatic values of >15 degrees. Expect waterspouts to occur especially where low-level winds are relatively weak and low level buoyancy strong, e.g. near the surface trough over Denmark. Beware of convection occurring at lines of convergent 10m winds, sources of vertical vorticity to be stretched.