Storm Forecast
Valid: Fri 10 Jul 2009 06:00 to Sat 11 Jul 2009 06:00 UTC
Issued: Thu 09 Jul 2009 16:51
Forecaster: TUSCHY
A level 1 was issued for parts of Italy and the N-Balkans mainly for large hail and severe wind gusts.
A level 1 was issued for parts of Romania, Bulgaria, N-Greece and Macedonia mainly for large hail and severe wind gusts.
A level 1 was issued for parts of W-Russia mainly for large hail and severe wind gusts.
A level 1 was issued for parts of NW-Germany and the Netherlands mainly for severe wind gusts.
A level 1 was issued for parts of Finland and parts of extreme W-Russia mainly for large hail.
A level 1 was issued for N-Tunisia mainly for large hail.
SYNOPSIS
A large, cyclonic vortex over Norway and Sweden is the steering mechanism for most parts of Europe. Various short waves, embedded in this flow, cause regional enhanced thunderstorm chances over SE/E and NE-Europe. The weather is hot and stable over the Iberian Peninsula.
DISCUSSION
... Italy and the N-Balkans ...
A warm and moist boundary layer is present as upper trough axis approaches from the NW during the day. Scattered thunderstorms are forecast in an environment with modest shear (10-20m/s), which increases towards the Alps. Large hail and severe wind gusts are the main risk. During the night hours, activity onshore decreases whereas offshore activity is on the increase, given cooler airmass atop of the warm Adriatic Sea. LL CAPE is on the increase and next to strong wind gusts an isolated tornado risk can't be ruled out, mainly along the coastal areas.
.. Romania, Bulgaria, N-Greece and Macedonia ...
Despite weak vorticity maxima and convergence zones, no real forcing mechanism is seen. Scattered, mainly diurnal driven thunderstorms are forecast, which could locally produce large hail and severe wind gusts, given abundant instability and 10-15m/s DLS. The maximum of thunderstorm activity is during the day but isolated storms will persist well into the night/morning hours.
... NW-Germany and the Netherlands ...
A sharp trough crosses the highlighted area during the morning hours from the NW. Strong shear at lowest 3km could produce a few severe wind gusts in conjunction with convective elements but this precipitation field looks more stratiform in nature. After the passage of the trough axis, abundant subsidence ought to keep convection limited and weak, so despite strong shear signals at lowest 1-3km, no severe risk is forecast.
... Highlighted region over W-Russia ...
Along a slowly eastward moving cold front, weak cyclogenesis is forecast. Prefrontal airmass features roughly 1000 J/kg MLCAPE with 15m/s DLS so large hail and severe wind gusts are possible. A more serious tornado threat could evolve dependent on the exact strength of the depression but we want to see more constant model runs for this depression in respect of path and strength, before including higher tornado probabilities. For now, we introduced low tornado probabilities mainly over the northern level-1 region.
An update/upgrade due to the tornado risk may be issued later-on.
.. N-Tunisia ...
Forcing is the main issue due to the overall weak nature of short waves, which cross the region from the west. Isolated thunderstorms are forecast, which produce large or even very large hail events, given magnitude of DLS (25m/s) and roughly 1000 J/kg MLCAPE. An upgrade may be issued if more widespread initiation is likely.
... N-CNTRL Finland and east ...
A sharpening moisture gradient zone is the focus for mainly daytime driven thunderstorms. MLCAPE up to 800J/kg and 15m/s DLS are adequate of an isolated large hail and strong wind gust risk. Hence a marginal level-1 was issued. The risk rapidly decreases after sunset.
... The Balearic Islands (until noon)...
At least isolated thunderstorms are possible during the passage of a broad thermal trough at mid-levels. There is no clear forcing mechanism so initiation ought to be isolated at best. Shear and instability are more than adequate for large hail/severe wind gusts but very isolated nature of storms and uncertainty of initiation preclude thunderstorm probabilities and any level area.
