Storm Forecast
Valid: Thu 10 Apr 2014 06:00 to Fri 11 Apr 2014 06:00 UTC
Issued: Wed 09 Apr 2014 21:15
Forecaster: GATZEN

A level 1 was issued for northern Iberia mainly for large hail.

A level 1 was issued for western Turkey mainly for excessive rain.

SYNOPSIS

Low geopotential is present across eastern Europe. An embedded trough cuts off over Central Europe and digs into the Balkans. Low-level moisture is limited at first, but increases underneath the base of the cut off. Additionally, steep lapse rates are expected below the troughs centre. Thunderstorms are forecast from Poland to Hungary and surroundings during the day. In the night hours, some new storms may form further south as the cut-off approaches there. Overall risk of severe storms is weak due to weak CAPE and rather weak vertical wind shear. Best potential is expected across the western Balkans where shear is about 15 m/s in the lowest 3 km. Multicells seem to be the dominant mode and large hail is not completely ruled out.

DISCUSSION

Iberian Peninsula

High geopotential across western Europe will weaken due to Atlantic troughs moving eastward. An Atlantic trough will affect the Iberian Peninsula through-out the period. With southerly winds, low-level warm air advection is expected across the northern portions, where QG forcing is expected ahead of a short-wave trough as well. Latest soundings indicate a well-developed elevated mixed layer, whereas low-level moisture is rather poor.

Diurnally driven thunderstorms are forecast that may become severe given 15-20 m/s deep layer vertical wind shear. Main severe threat will be large hail, but severe wind gusts are also not ruled out. Storms will weaken after sunset.

Western Turkey

Ahead of the approaching cut-off low, a short-wave trough will move across western Turkey in the morning hours. The affected air mass is characterized by rich moisture over the Aegean Sea as well as steep lapse rates indicated by latest GFSA model. With upslope flow and QG forcing, thunderstorm initiation is quite likely. In the afternoon and evening hours, a jet streak travels around the base of the Aegean trough and leads to strong DCVA over western Turkey. Thunderstorms will likely go on and may become more organized due to increasing vertical wind shear. Latest models indicate a deep layer shear of 20 m/s and multicells and supercells are not ruled out. Some hail reports are not ruled out, and a tornado may be possible as well. Main focus will be strong rain, though, and upslope flow may cause some excessive rain along the western coasts of Turkey.