Storm Forecast
Valid: Sun 13 Jul 2014 06:00 to Mon 14 Jul 2014 06:00 UTC
Issued: Sun 13 Jul 2014 06:21
Forecaster: VAN DER VELDE

A level 1 was issued for parts of Estonia, Latvia, Belarus, Ukraine and Russia mainly for isolated large hail.

A level 1 was issued for parts of Germany and Czech Republic mainly for large hail.

SYNOPSIS

A low pressure system is centered near Denmark. Its cold front reaches from southern Sweden eastward to Belarus and Ukraine, a warm front stretches northeastward over Finland.
A second system has followed immediately in its wake with a warm from the Shetland islands to Austria and a cold front over the United Kingdom, pushing through France, backed by a shortwave trough in mid levels. Another shortwave is moving from Italy over the Adriatic Sea to the southwestern Balkan. MLCAPE values over western and central Europe remain modest, mostly under 600 J/kg, as result of generally weak lapse rates.

DISCUSSION

...parts of Estonia, Latvia, Belarus, Ukraine and Russia...

A moderate 1000-1500 J/kg of MLCAPE is forecast in this prefrontal band along Belarus and Ukraine. There is only some 7-10 m/s 0-6 km shear and weak lift, but along with medium LCL heights updrafts of mainly multicells can be strong enough to produce locally large hail. The deep layer shear increases to over 15 m/s in the northwest section (Latvia and Estonia) where CAPE decreases, some marginal supercells may form and release large hail there as well. Problem could be the linear triggering by the cold front/PV intrusion there and low LCLs.

...eastern Germany, Czechia, western Poland...

This region should see steeper mid level lapse rates and higher cloud bases than the rest of western/central Europe while also GFS model hodographs look large enough but not very circular, which can help formation of some brief rotating updrafts in cells. 0-6 km shear is forecast to reach over 15 m/s but SREH remains low. The storms will likely produce some local large hail, especially when terrain can help create helicity.

...France...

The cold front and shortwave trough should easily trigger many thunderstorms, which form under some 10-15 m/s 0-6 km shear but not much helicity. However, 0-1 km shear is raised over 10 m/s which could benefit tornadogenesis, but by lack of deeper layer shear magnitude it does not seem to be important enough for a level 1.

...southeastern UK, Netherlands...

Storms will move rather slowly and some local elevated precipitation sums may arise. Also, the absence of flow and vertical shear is beneficial for development of spout-type tornadoes, but 00Z soundings looked quite stable with dry layers in the low to mid levels, so no level 1 area was issued at this point.