Storm Forecast
Valid: Tue 15 May 2012 06:00 to Wed 16 May 2012 06:00 UTC
Issued: Mon 14 May 2012 22:32
Forecaster: TUSCHY

A level 1 was issued for NE Greece, SE Bulgaria and W-Turkey mainly for an isolated tornado event, large hail and strong wind gusts.

A level 1 was issued for the aforementioned areas, all of Bulgaria and parts of Romania mainly for isolated heavy rainfall.

SYNOPSIS

Complex streamline pattern in place over Europe with intense cyclonic vortex situated over N-Europe. Numerous upper lows round that main vortex and affect S/E parts of Europe. Transient ridging builds in over the Iberian Peninsula with dry and hot conditions during the forecast period.

DISCUSSION

... N-Aegean Sea, Bulgaria, Romania, Moldova, Ukraine and parts of extreme W-Russia ...

A cyclonic vortex over the Aegean Sea lifts to the north with peak intensity during the morning hours and with a gradual weakening trend thereafter. Models agree well in path and timing of that feature, so expect the low to cross Bulgaria until sunset and with a loosely organized circulation present over Romania during the night hours. Strongest shear remains displaced to the south over W-Turkey with 0-6 km shear up to 20 m/s, decreasing to 10 m/s or less further to the north. MLCAPE forecast is quite messy with best CAPE/shear overlap forecast over far NE Greece, W-Turkey and SE Bulgaria until 15Z. Well organized multicells/isolated supercells are possible with isolated large hail and strong to severe wind gusts. With distinct cyclonic flow pattern in place, enhanced LL shear exists over those areas with lowered LCLs, so an isolated tornado event can't be ruled out. Also over W-Bulgaria and parts of Romania, adequate moisture and slow moving storms pose an heavy rainfall risk. The overall coverage and intensity of storms decreases after 15Z.

To the north of that vortex (here: Moldova northwards), deep SE-erly flow regime sets-up with the NW-ward advection of slightly better mixed mid-level air mass atop modest BL moisture. Isolated to scattered storms are forecast with peak activity during the afternoon and evening hours. An isolated large hail event is possible but marginal shear/CAPE preclude an enhanced severe risk. Also, initiation is questionable with weak forcing present, so no level area was introduced. 15-% thunderstorm area was expanded far to the NW due to a few elevated storms during the night.

...Ireland, UK, Benelux, NE-France and Germany ...

A well structured upper trough enters the highlighted area from the NW with 500 hPa temperature dropping to less than -30 °C atop marginal BL moisture. Hence, a strong diurnal convection cycle is expected with weak shear and SBCAPE up to 500 J/kg. Marginal hail and strong wind gusts accompany stronger storms with peak activity over Benelux, UK and far W-Germany. Would not be surprised to receive an isolated tornado report in the 50-% thunderstorm area with augmented LL CAPE build-up and weak background shear.

Another focus for some severe will be the eastward sliding cold front, which intensifies over C-Germany due to some prefrontal heating. Placed beneath a 15 m/s mid level jet, shear is sufficiently enhanced for an isolated better organized multicell event over C/E-Germany. Isolated large hail and strong wind gusts accompany those storms. The activity is too limited in strength and coverage for a level 1. Thunderstorms gradually decay after sunset.