Geoscience Reference
In-Depth Information
occurred in the Nimes area on 7 September 2010. Although this storm did not generate
major damage, it locally produced rainfall accumulation in excess of 300 mm in just a few
hours.
The 500 hPa analysis at 12 UTC, 7 September 2010 is shown in Fig. 7. Note that at this time
convection over the Gard department has already started and was already well established.
The upper level analysis indicates the presence of an
upper-level cold low centered over the
British Islands with an associated trough extending
southward toward the Iberian
Peninsula. This synoptic pattern generates a mid-to-upper level southwesterly flow over
France and a low-level southerly flow over the Mediterranean Sea veering slightly south-
easterly near the French coast.
The corresponding Deutscher Wetterdienst (DWD) low-level analysis (Fig. 8b) shows a
surface low centered over Ireland and a main front extending meridionally through central
France ahead of the trough which attained France on the 6 September (Fig. 8a). A secondary
front can also be noticed a few hundred kilometers west of the main front, over the Atlantic
Ocean. The latter is associated with a low-pressure anomaly located slightly north of the
Spanish coast. In the following hours (Fig. 8c-d), this front and its associated surface low
propagated rapidly eastwards to ultimately catch up with the leading front. The low
surface pressure anomaly reached Western France by 18 UTC (Fig. 8c) and rapidly extended
over a large part of the country (Fig. 8d).
Fig. 7. Operational analysis of geopotential height at 500 hPa valid on 7 Sept 2010 at 12 UTC.
