Storm Forecast
Valid: Sun 21 Sep 2008 06:00 to Mon 22 Sep 2008 06:00 UTC
Issued: Sat 20 Sep 2008 22:55
Forecaster: SCHLENCZEK

SYNOPSIS

Blocking high persists over NE Europe and cool and stable conditions continue over eastern-central Europe. The main features for deep moist convection in Europe are two upper cut off lows over the Mediterranean region. A plume of high Theta-E from Morocco / Algeria is advected into eastern Iberia where a small 30 m/s upper jet streak will shift northeastward.

DISCUSSION

...S Iberia...

WAA at lower levels and diurnal heating will create some hundred J/kg of CAPE during the afternoon. GFS puts most of the instability both ahead of the upper trough and below the upper cold core whereas the latter is characterized by weak vertical shear. Between 15 and 30 m/s deep layer shear and locally augmented SRH3 will be in place in a small region near the upper jet streak between northern Morocco and the Balearic Islands. During the afternoon, a small upper vort max will overspread the region and some organized multicells / possibly a few supercells with large hail / damaging gusts may form. Some storms may persist for some hours over the same region which may lead to local flash floods.

Some spatial uncertainties with the low level moisture remain. An upgrade will follow if CIN is relatively small and LL moisture at least as high as forecast by GFS 12 UTC.

...Black Sea...

In the vicinity of an upper cut off low centered over N Romania / SW Ukraine, diurnal heating will create a few hundred J/kg of CAPE. Showers and thunderstorms are forecast for a relatively broad area. LCL heights will stay quite low and very steep LL lapse rates combined with weak LL winds suggest that an isolated funnel / waterspout is not ruled out. Overall threat should be too low for any threat level.