Storm Forecast
Valid: Sat 25 Jun 2011 06:00 to Sun 26 Jun 2011 06:00 UTC
Issued: Sat 25 Jun 2011 04:59
Forecaster: VAN DER VELDE
A level 1 was issued for eastern Romania, southern Moldova, eastern Bulgaria, southern Ukraine and western Black Sea mainly for excessive convective precipitation and large hail.
A level 1 was issued for central Finland and northern Sweden for land- and waterspout type tornadoes.
SYNOPSIS
A large upper trough is situated over eastern Europe. A cold front stretches from northern Greece into Ukraine and western Russia. The airmasses are unstable on both sides of the front.
The strongest lifting takes place at the forward side of the mid/upper level potential vorticity lobe over eastern Romania but appears to trail the unstable zone on the warm side of the front. Also over western Ukraine and Belarus QG lift is significant, as well as around a surface low over Finland.
The cold air mass thundershowers in the area from Romania to Poland can sometimes be accompanied by 1-2 cm size hail.
The jet rounds the upper trough and in some places runs over the unstable airmasses on both sides of the front, providing an environment of moderate vertical windshear. But CAPE in these areas is pretty weak and LCLs are low, reducing hail chances.
DISCUSSION
...parts of Romania, Moldova, Bulgaria, Ukraine, Black Sea...
Some 1000 J/kg MLCAPE could develop over Bulgaria. Moderate vertical shear (15 m/s 0-6 km and some 200 mē/sē SREH 0-3 km) is predicted over and parallel to the front. This adds some potential of supercell storms or organized clusters producing large hail. Larger seems the chance of excessive precipitation as storms move parallel to the front, in a large precipitable water and saturated environment. GFS also simulates large convective precipitation signals.
...Finland and N Sweden...
A profile as sampled by the 00Z Sundsvall sounding (very moist, weak winds and with CAPE in low levels) is favorable for spout occurrence. Over Finland, low level vorticity is enhanced in convergence zones in and around the low pressure center, and similar profiles can be expected locally. The slow storm motion of just a few m/s may cause brief local flash floods.
