Storm Forecast
Valid: Tue 26 Aug 2008 11:00 to Wed 27 Aug 2008 06:00 UTC
Issued: Tue 26 Aug 2008 12:10
Forecaster: VAN DER VELDE

SYNOPSIS

A west-east oriented ridge over France to Romania keeps most of central and western Europe stable. A thermal low pressure area with thunderstorms lies over Spain, similar conditions over parts of Turkey and the southern Balkan. An upper cut-off low is situated over Italy. An active low affects western Russia with windy conditions. Through a zone from Ireland to Denmark, marginal elevated instability is forecast, which however should be shallow (low MU-ELs) and thunder is likely to remain very limited.

DISCUSSION

...W Russia...

Indications of MU-EL and uncapped source layer depth suggest development of convection, despite poor MLCAPE. The area is in a region of high LL and DL shear (both around 15 m/s, depending on exact position) and 250-400 m2/s2 SREH3 is present. In addition forecast LCL heights are close to the ground. This picture may support linear systems with near-severe gusts and isolated possibly embedded supercells with an additional threat of tornadoes.

...Greece, Macedonia, W Bulgaria...

Strong convergence and synoptic scale lift are forecast through this region, which should see around 1000 J/kg MLCAPE or 2 MJ/m2 column-integrated CAPE (ICAPE). DL shear of 10-15 m/s support multicell cycling. Large hail can occur in several locations, as well as an isolated flash flood.

...Spain...

A situation fairly similar to Greece in quantities of CAPE and shear, here there is less shear in upper levels and more in lower levels, GFS projecting good 1-4 km shear and 0-3 km SREH 100-200 m2/s2 along the NW-SE mountain ridge. Higher LCL (2500m) and drier mid levels support locally severe downburst winds, and large hail is supported by the energy (also 0-3 km LLCAPE) and kinematics. Storms are most likely to initiate over the higher terrain bordering the supply of 12 g/kg 0-1 km absolute humidity from the Mediterranean Sea in the level 1 area.