Geoscience Reference
In-Depth Information
4.2 The 7 September 2010 “Cevenol” event
24 January 2009 - 0600 UTC - 1.5 km AMSL
100km
Fig. 6. Comparison between ALADIN operational (blue) and radar-derived winds (red) at
1500 AMSL on 24 January at 6 UTC. Black circles show area where the 2 analyses
significantly differ.
4.2.1 Overview
During the fall season, the southeastern region of France is often affected by intense flash-
flooding episodes ensuing from the formation of quasi-stationary mesoscale
convectivesystems along the south-eastern flank of the Massif Central Mountains (Cevennes
region). These systems can generate considerable amount of precipitation in relatively short
periods of time. A well-known example of such systems is the so called “Gard case”
(
Delrieu et al. 2005) during which ~ 800 mm of rain fell down in less than 24 hours over the
French Gard department, resulting in many fatalities and total damage amount of about 1.2
billion US dollars. Observing and understanding the dynamical and to some extent
microphysical processes at play during these high impact weather events is critical to
develop effective flood warnings systems and to improve their forecast. In the following we
present examples of radar analyses produced during a heavy precipitation event that
