Storm Forecast
Valid: Sat 04 Jul 2009 06:00 to Sun 05 Jul 2009 06:00 UTC
Issued: Fri 03 Jul 2009 20:22
Forecaster: GROENEMEIJER

A level 1 was issued for N and E Spain, mainly for large hail and severe winds.

A level 1 was issued for parts of Germany, Czechia, and the Alps, mainly for excessive rainfall.

A level 1 was issued for central parts of the Balkan peninsula, mainly for excessive rainfall.

SYNOPSIS

Saturday at 0600 UTCsignificant features on the mid- and upper-level height maps are i) a large low over the northern Russian Plains, ii) a weak ridge curving from the Norwegian sea over northern germany to the western Mediterranean, and iii) a slowly eastward travelling low centered over Ireland. Additionally, a zonal jet streak west of Portugal translates eastward and traverses the Iberian Peninsula during the forecast period. Over central parts of Europe

DISCUSSION

N and E Spain...

On approach of the mid-/upper- jet streak, forcing for upward vertical motion is should overspread the Iberian peninsula from the west. Rather high amounts of (ML)CAPE, on the order of 1500 J/kg, should be available across the NE parts of Spain. Storms are expected to develop in the early afternoon across the Pyrenees and later further south across eastern Spain. Within the deep-layer wind shear being in the 15-20 m/s range, sustained updraught rotation is probable with some of the high-based storms. Some will likely produce large hail. A deep, dry boundary layer should favour strong evaporational cooling downdraughts, so that a couple of severe downbursts are possible, too. Storm activity should gradually diminish after sunset.

Germany, Czechia, Alps...

Ahead of a very subtle mid-level trough, widespread storms will likely develop in a similar fashion as on Friday, albeit further to the east. Around 1000 J/kg MLCAPE is expected to be available in most areas in combination with very weak shear. Some larger clusters will likely develop, which can produce a couple of flash flood events. A few marginally severe hail events are also possible. During the evening storm activity should diminish.

Balkans...

Across the southern Pannonian Plain around 13 g/kg of moisture should be present, and ample MLCAPE in excess of 1000 J/kg in places. In an environment of weak vertical wind shear, scattered to widpread storms are expected with a threat of flash floods caused by excessive rainfall. A few marginal large hail events are also possible.