Storm Forecast
Valid: Tue 05 Jul 2016 06:00 to Wed 06 Jul 2016 06:00 UTC
Issued: Mon 04 Jul 2016 21:47
Forecaster: DAFIS

A level 2 was issued for S Germany and N Austria mainly for excessive rain, severe wind gusts and large hail.

A level 2 was issued for Spain mainly for severe wind gusts and large hail.

A level 1 was issued for a large part of Central Europe mainly for excessive rain severe wind gusts, large hail and to a lesser extent tornadoes.

A level 1 was issued for Spain and N Portugal mainly for severe wind gusts and large hail.

SYNOPSIS

A negative tilted shortwave trough over the British Isles is travelling SE and enters continental parts of Central Europe during Tuesday, associated with a cold front on the surface. Rather low geopotentials in North parts of Mediterranean basin result in weak instability and we expect numerous pulsating storms but with a low confidence for severe weather events to due to weak shear and the absence of a wave advection. A vigorous low pressure system is found near the surface in NW Russia with its frontal waves producing convective rainfall and severe wind gusts. The cold front that resulted in numerous severe events the previous days is moving outside our domain to the east, but the occluded front that is about to form, will feed numerous storms in Finland and NE Sweden.

DISCUSSION

..... Central Europe .....

Prefrontal air mass over Germany and West Poland is characterized by rich moisture in the lower troposphere with 950 hPa dewpoints around 16°C and surface Tds in excess of 18°C. Upper-level forcing will be quite weak, but we expect widespread initiation along the slowly eastward moving cold front, which crosses the highlighted areas during the forecast from west to east. Shear is strong over E-Germany and W-Poland but decreases to 10-15 m/s 0-6 km DLS in the afternoon, but not in the central parts of level 1, where we have placed a level 2 threat. A good overlap of DLS, 0-3km shear and 1000-1500 J/kg CAPE is forecast for this area after 12z. Despite weak forcing, the possibility of rapid thunderstorm clustering increases the threat for excessive rainfall and in addition, steep lapse rates indicate a threat for large hail and strong downdrafts. Finally, in a case of a linear storm mode over Poland, there is a probability of tornadogenesis as LLS increases under moderate DLS and CAPE, after 15z.

.... Spain and Portugal .....

WAA over Spain brings air masses with very steep lapse rates, where weak to moderate instability will coexist with 15-20 m/s DLS and 10-15 m/s 0-3km shear. Capping seems to be weak, mostly near the shores and storms may be numerous, leading to unfavorable interactions, a few multicells are likely, capable of large hail and damaging winds given the high cloud bases.

Several other areas of the continent will experience DMC, but no level was issued, as good thermodynamics may be too marginal.