Storm Forecast
Valid: Tue 14 Aug 2012 06:00 to Wed 15 Aug 2012 06:00 UTC
Issued: Mon 13 Aug 2012 23:20
Forecaster: KOROSEC
A level 1 was issued for NW Iberia towards NW France/SW UK mainly for large hail, damaging winds, excessive rainfalls and tornadoes.
A level 1 was issued for Ukraine and surrounding areas mainly for excessive rainfall threat.
SYNOPSIS
An omega blocking pattern persists over Europe with two upper lows on its western and eastern flank. A small but intense upper low wobbles over central Ukraine while a larger upper low is located over eastern Atlantic sea. Its axis moves towards NW Iberia and W Europe on Tuesday where a deep cyclone with a sharp surface cold front takes place.
DISCUSSION
... NW Iberia into parts of W Europe ...
A well-defined DCVA will be a focus for convective activity on the western flank on the blocking area. A sharp trough is pushed from Atlantic towards NW Iberia where strong mid-level jet rounds its base and creating favorable strong shear for organized storms. 20-30 m/s of deep layer shear will result in the afternoon/overnight hours. Marginal instability will become available along the front, so expect severe storms to take place posing threat for large hail, intense rain and damaging winds. A tornado or two is also possible given the strongly enhanced LL shear/helicity just ahead of the cold frontal boundary. This threat seem maximized towards the evening hours before activity spread northwards towards UK overnight. Extreme NW France towards SW UK were also included into the level 1 area given the some threat for especially severe winds, excessive rainfalls and possibly a tornado as both SREH and LL shear remain high overnight.
... Ukraine and surroundings...
A quite impressive SFC low rotates over central Ukraine and only slowly fills out during the forecast period. Storm modes will be quite slow, while PWAT is very high and at least some hundreds J/kg of instability will be available. This points to a intense rainfall and flash floods threat locally which warrants a a marginal threat level 1. Activity should diminish later in the evening when instability vanishes.
Elsewhere, only daytime driven mostly pulsating convective activity is expected, mainly confined to local complex topography.
