Storm Forecast
Valid: Fri 22 Jul 2011 06:00 to Sat 23 Jul 2011 06:00 UTC
Issued: Thu 21 Jul 2011 21:16
Forecaster: TUSCHY
A level 1 was issued for E-Spain mainly for a few large hail events.
A level 1 was issued for parts of Slovenia, Croatia and Hungary mainly for a few large hail events.
A level 1 covers most parts of E-CNTRL and NE-Europe mainly for large hail, isolated severe wind gust events, a few tornadoes and locally excessive rainfall.
SYNOPSIS
A quasi-stationary upper low over central Europe and a strengthening surface depression over Poland result in the advection of a warm and moist air mass well to the north, covering all of E/NE-Europe. A zonal flow covers the Mediterranean with hot conditions present from S-Italy, Greece all the way to the far E-Mediterranean, whereas CAA continues over W/NW-Europe.
DISCUSSION
... Parts of Spain and the W-Mediterranean ...
Flattening upper-level wave comes in from the NW during the daytime hours, resulting in some modest QG forcing. Overall zonal streamline pattern causes warm tropospheric temperatur profiles and hence strong capping throughout the forecast period. Sporadic to isolated thunderstorm initiation is expected, mainly bound to areas, where either QG forcing or mesoscale assistance (coastal convergence zones) will be present. Thunderstorm coverage will be probably more scattered over E-Spain. Due to the proximity of the strong mid/upper jet, 0-6 km shear will be enhanced with up to 20 m/s. A few large hail and strong wind gust events are likely. Coverage probably matches our level 1 criterion over E-Spain, whereas areas further east may only see very isolated initiation.
... N-Italy and N-Balkans ...
Weak lee depression just south of the Alps assists in ongoing moisture advection beneath cool mid-levels. Widespread 500 - 800 J/kg MLCAPE are forecast next to 20 m/s DLS. A few large hail and strong wind gust events are expected. Only parts of this area will be highlighted with a level 1, where best CAPE/shear overalp is forecast. Onshore thunderstorm coverage gradually decreases after sunset, but increases offshore/along the coast of the NE Adriatic Sea. Locally heavy rain and strong wind gusts are forecast.
... E/NE Europe ...
An extensive LL depression evolves over Poland and moves slowly towards the N. Ahead of this feature, a warm and moist air mass advects far to the north. With this fetch of unstable air, widespread thunderstorms are expected. DLS of 10-15, locally up to 20 m/s is supportive for multicells, a few well organized ones well possible. Due to weak capping and the overall favorable upper streamline pattern, widespread thunderstorm development occurs with a rapid clustering trend. A few large hail and strong wind gust events occur next to locally heavy rainfall.
Also due to ongoing deepening of the surface depression, LL wind field remains quite strong (15-20 m/s at 850 hPa). Augmented directonal shear (100-250 m^2/s^2 SRH-1) and LCLs below 1000 m overlap. The result is an enhanced tornado risk, probably maximized from far W-Russia, Latvia/Estonia to S-Sweden.
Also, dependant on the exact position of the LL depression, an augmented excessive rainfall risk may materialize over S-Sweden/N-Denmark with favorable influx of moist air and a strengthening deformation zone during the night hours. We therefore expanded the level 1 further to the west, to include this risk.
... Parts of France and Germany ...
Weak shear and 200-500 J/kg MLCAPE assist in weakly organized and daytime driven thunderstorms. Marginal hail and wind gusts accompany that actvitiy. Storms decrease after sunset.
