Mesoscale Discussion
Valid: Wed 30 Jul 2014 12:00 to Wed 30 Jul 2014 18:00 UTC
Issued: Wed 30 Jul 2014 12:09
Forecaster: BEYER

A surface low has formed with its center over northwestern Poland / northeastern Germany (1006 hPa). It separates drier airmasses to the east of its center (Td: 13°C) from humid airmasses showing dewpoints around 20°C. This difference is also visible in the current satellite image with almost no clouds over northern Poland.

In addition a strongly convergent flow can be derived from surface winds vectors. Thus strong lift can be expected that helps to develop thunderstorms in an airmass with mixing ratios of 12/13 g/kg. CAPE values of around 1000 J/kg can be expected with the experience of last days when a similar airmass was present.

Some thunderstorms have already formed that show hourly radar precipitation amounts of locally up to 50 mm. A further development of thunderstorms is expected in the highlighted area. Having in mind that ppw values are about 35 to 40 mm excessive precipitation events are possible. Also Corfidi vectors point to this risk since they show quite slow thunderstorm movement as well as the possibility for training storms. Rain amounts of 50 to even more than 100 mm are possible within a few hours.

Besides the most prominent rain threat marginal hail as well as locally severe wind gusts (when an effective cold-pool manages to develop) are possible.