Storm Forecast
Valid: Mon 29 Aug 2011 06:00 to Tue 30 Aug 2011 06:00 UTC
Issued: Mon 29 Aug 2011 05:55
Forecaster: VAN DER VELDE
A level 1 was issued for northern Russia mainly for tornadoes.
A level 1 was issued for southern Scandinavia mainly for tornadoes.
A level 1 was issued for Belarus and part of Ukraine mainly for large hail.
A level 1 was issued for southern Spain mainly for large hail.
SYNOPSIS
A large low filled with a cool unstable airmass moves slowly eastward over Scandinavia. Warm air advection from the south increases conditional instability over Spain and the western Mediterranean Sea.
DISCUSSION
...northern Russia...
A large area of 0-1 km shear greater than 10 m/s overlaps a region with several hundred J/kg MLCAPE ahead of a cold front. LCL heights will be low. Supercells with tornadoes are possible. Large hail and isolated severe gusts may also occur.
...southern Scandinavia...
Near the center of the surface low pressure area over southern Norway, low-level winds are rather weak resulting in very slow storm motion. A jet is present at higher altitudes. Vorticity may spin up in the form of waterspouts. Spouts are also possible over the rest of the thunder area. Over Denmark, low-level shear and helicity are actually good for tornadogenesis. Strong gusts can also occur there.
...Belarus...
15 m/s deep layer shear will be present and can organize multicells producing isolated marginally large hail. The shear vector is parallel to the narrow zone of not very large CAPE , which favors linear over discrete convection. CAPE is even almost disappearing in GFS, so the level 1 is likely a marginal one.
...southeastern Spain...
100-200 mē/sē SREH, 15-20 m/s 0-6 km shear vectors and 1000-2000 J/kg MLCAPE with LCLs above 2000m and steep lapse rates are favorable for large hail formation. Forcing is provided by a passing PV maximum, which may allow the storms to persist into the night and drift towards the Balearic islands.
