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Convective Outlooks hilft unsere
valid from: 13.08.2015, 12:30 UTC
to: 14.08.2015, 06 UTC
issued : 13.08.2015, 12:30 UTC
Forecaster: Armin K., Sebastian B.
A Severe Threat 2 has been issued for S France mainly for large hail, isolated severe wind gusts und to a lesser extend for tornadoes.
A Severe Threat 1 has been issued for N France, Be-Ne-Lux and W Germany mainly for excessive precipitation including flash floodings, small to medium size hail and to a lesser extend for strong wind gusts and tornadoes.
Ahead of a long-wave trough sfc cyclogenisis takes place over northern France in response to day time heating and slight QG forcing. With the maximum theta e values, a tight convergence travels from France to Germany whereas the original cold front remains rather ill defined over wrn France with a weak theta e-gradient.
An active MCS has formed along a upr short wave over S France. With ML CAPE around 1500 J/kg and enhanced 0-6 km DLS of 20 m/s well organized tail-end storms currently affect the region north of Avignon . These storms may include supercells capable of producing large hail and isolated severe wind gusts. Later on, after airmass recovery with a well defined EML, a second wave of severe tsms will influence soutehrn France with a total severe potential around 12 %. Thus we intruduced a Severe Threat 2 for that area.
…Northern France, Be-Ne-Lux, Western Germany…
To the North of the forecast area there are similar CAPE values (1000-1500 J/kg) but a less kinematic environment with DLS of 10-15 m/s. DMC that initiates at the aforementioned convergence will thus be of pulse storm-nature, but also a few multicells are possible. According to High res model data an organization into a broken line is likely. Due to backward and sideward storm builds, training effects with heavy rainfall and flash floodings are forecast. Also a few hail events (1-3 cm in diameter) will occur. As ll flow strengthens in the evening and SRH strengthens in the evening a tornado event cannot be ruled out especially if storms remain sfc based for a longer time.
Later on the storms will get a more westerly propagation component and effect wrn German during the night hours. With no insolation the severe potential will gradually weaken.
Model consistency, additional remarks
Except for the exact position of the convergence and the location of CI, the situation is simulated consistently.