Storm Forecast
Valid: Wed 06 Aug 2014 06:00 to Thu 07 Aug 2014 06:00 UTC
Issued: Wed 06 Aug 2014 08:21
Forecaster: PUCIK

A level 1 was issued for Central Sweden mainly for severe wind gusts and to the lesser degree for large hail.

A level 1 was issued for Baltic States, eastern Poland, Hungary mainly for excessive precipitation.

A level 1 was issued for Balkans mainly for excessive precipitation, large hail and to the lesser degree for severe wind gusts.

SYNOPSIS

Not much of a change is expected to occur regarding the synoptic-scale pattern when compared to the previous days. Lower geopotentials will persist over much of western, central and southeastern Europe. Enhanced 700 - 300 hPa southeasterly flow between the low over the Atlantic and a ridge over northwestern Russia. Most of the DMC over Europe is expected to form along a weak boundary with convergent low-level flow running from Sweden through the Baltic States towards Balkans.

DISCUSSION

... Central Sweden towards Norway ...

Sundsvall 00 UTC sounding features steep lapse rates between 900 and 600 hPa level along with enhanced southeasterly flow at mid-levels as was featured by model output and strongly capped 1000 J/kg of CAPE. As surface heating erodes the cap towards the afternoon, scattered DMC is expected to form. With mostly unidirectional wind shear and bulk shear of 10 to 15 m/s in the 0-3 km layer, linear multicellular systems will be possible, posing the risk of severe wind gusts. Steep lapse rates also point to the enhanced threat of large hail, especially in case that some rotating updrafts manage to develop.

... Baltic States through Poland towards Balkans ...

Yet another day with very weak steering flow and low-level convergent flow will likely result in more storms posing the risk of excessive precipitation. Perhaps the greatest threat will exist over the Balkans, where the highest degree of low-level moisture is present. Widespread DMC is expected, mostly chaotic in nature, but may organize into large systems along the local convergence zones. Stronger cells may be capable of large hail or downbursts, especially over the southern part of Lvl 1 (Bulgaria, Greece, the Aegeans), where steeper lapse rates will be present.

... Northeastern Spain ...

Both GFS and ECMWF simulate some spotty initiation over the region, along the surface convergence of the sea-breeze boundary. Moderate CAPE values are simulated along the narrow strip of the coast, with DLS values approaching 15 m/s towards the afternoon. If storms manage to develop, which is questionable, they may attain supercellular nature with the risks of large hail and severe wind gusts. A potential Lvl 1 is issued for the region.