Storm Forecast
Valid: Sun 12 Jul 2009 06:00 to Mon 13 Jul 2009 06:00 UTC
Issued: Sun 12 Jul 2009 06:02
Forecaster: SCHLENCZEK
A level 1 was issued for NW Turkey mainly for large hail and severe gusts.
A level 1 was issued for the Black Sea region, E Romania, Ukraine, E Belarus and W Russia mainly for severe gusts and excessive rainfall.
A level 1 was issued for W Germany mainly for tornadoes and large hail.
SYNOPSIS
An intense low pressure system over Ireland is forecast to travel westward while the upper trough axis tilts from W-E to SW-NE. Over the central Mediterranean, geopotential heights rise and a building upper ridge will induce a strong SWerly flow from the Iberian Peninsula towards Germany. In the following days, very hot and moist air should be advected into W-central Europe and one or more significant severe thunderstorm events are expected to occur. On Sunday, the advection process just starts and there is almost no CAPE within the airmass over Spain. The warm front of an associated frontal wave will enter E France and W Germany in the afternoon.
Over Romania, a small upper trough moves eastward into the Black Sea region while weakening. Ahead of the trough, hot and moist air is advected northward into parts of Romania and S Ukraine. The associated frontal boundary stretches from Greece towards W Belarus and E Estonia with thunderstorms forecast east of the front.
DISCUSSION
...NW Turkey, W Black Sea, E Romania, central Ukraine, E Belarus, W Russia...
About 1,5 - 2 kJ/kg MLCAPE should become available over NW Turkey and the Black Sea region during the day. The left exit of a southerly 35 m/s upper jet streak points at S Ukraine and will translate northward during the period. Deep layer shear should reach values up to 25 m/s in the region with the most unstable airmass which should be enough for a MCS and maybe a few supercells. Over W Turkey, most storms should stay discrete and produce large hail and perhaps severe wind gusts.
Further north, the hail threat should decrease where formation of a front-parallel MCS in the vicinity of an upper vort-max is more likely and severe gusts as well as excessive rainfall will be the main threat.
In the extreme northern parts of this area, there is less instability forecast but deep layer shear is pretty strong (20 m/s). A cluster or MCS over Belarus and W Russia may produce torrential rainfall as well as severe gusts.
...W Germany...
As the warm front enters W Germany during the day, LL moisture advection as well as insolation will lead to a few hundred J/kg CAPE. An upper vort-max will enter the region near Cologne in the afternoon and should provide enough lift for initiation. The question is whether instability will be sufficient or not because deep layer shear will reach values up to 25 m/s and there should be 150 - 250 mē/sē SRH3. If convection develops, discrete storms will probably become supercellular and will pose a threat of tornadoes as forecast LCL heights are very low and there are more than 10 m/s LLS and enhanced SRH1 over large portions of western Germany. A few large hail reports are not discounted either. In the evening hours, instability will diminish as the warm front moves eastward which reduces the threat of severe weather.
