Storm Forecast
Valid: Mon 09 Aug 2010 06:00 to Tue 10 Aug 2010 06:00 UTC
Issued: Sun 08 Aug 2010 20:59
Forecaster: DAHL
A level 2 was issued for the central Belarus and extreme NW Russia for large hail, damaging wind gusts, excessive convective rainfall, and tornadoes.
A level 1 surrounding the level 2 was issued for the western Ukraine, Belarus, eastern Finland, and extreme northwestern Russia, mainly for large hail, damaging winds, excessive convective rainfall, and tornadoes.
A level 1 was issued for Poland and E Germany for excessive convective rainfall.
A level 1 was issued for N Spain mainly for large hail and damaging wind gusts.
SYNOPSIS
A broad large-scale upper trough is located over the central parts of Europe, with a rather complex upper-flow structure in its interior. Several upper-low centers are present over E Germany and the Baltic Sea region. These features will lift east-/northeastwards during the period, affecting the eastern parts of Europe. Another, rather intense Atlantic upper low will reach the British Isles late on Monday. The S and E periphery of the large-scale trough will stretch from northern Iberia across the northern Mediterranean, and then curving northwards towards eastern Scandinavia/western Russia. S and E of this upper frontal zone, warm and unstable air is present with quiescent synoptic SFC conditions.
DISCUSSION
... W Ukraine ... Belarus ... NW Russia ...
No soundings are available from the critical air mass over eastern Europe on Sunday, so that the thermodynamic profiles
are unknown -- other than the fact that rather ample CAPE is available. The soundings east of the area of interest feature deep/dry CBLs, but it seems that this air mass will not be involved in Monday's convective scenario.
The DLS should be weaker compared to Sunday, though 15 to 20 m/s should still be available. Higher values 20 m/s are expected over the Belarus, E Finland, and NW Russia. In addition, patches of LLS maxima in excess of 10 m/s are simulated over this region late in the day. This suggests that in a strip from the western Ukraine towards NW Russia, well-organized multicells and especially in the northern regions, supercells, will be possible. These will be capable of damaging winds, and large hail. Locally excessive convective precip may occur. A tornado threat exists especially over the extreme NW corner of Russia late in the period.
... N Spain ...
The one sounding available from N Spain on Sunday does not suggest strong instability owing to the shallow nature of the moisture. However, it seems likely that locally deeper moisture is made available by convergence tied to orography or other mesoscale boundary-layer features. This setup should also be present on Monday.
Shear profiles should be adequate for well-organized multicells and supercells, capable of large hail and damaging winds. Local flooding may also occur given briefly intense rain rates. A lack of low-level shear should limit the tornado threat, though a brief spin-up cannot be ruled out if outflow/orography-enhanced lobes of enhanced LLS are encountered. However, the overall tornado threat seems to be rather low.
... N Italy ...
15-20 m/s DLS along with some CAPE are simulated over northern Italy, but it seems that only very isolated convection will develop per model guidance. The storms that do form may briefly produce marginally severe wind gusts/hail, but the overall probabilities are too low for a LVL1 threat.
... Poland ... E Germany ...
Widespread showers and thunderstorms should form over Poland and estern Germany in nearly uncapped and rather moist air. This activity will likely result in excessive convective precip. In addition a few funnel clouds and maybe a brief non-mesocyclonic tornado or two could occur. The LVL1 is issued for the precipitation threat.
