We’ve been talking about this for several days: the current week at the end of September is very happy. Despite the moderately cold nights, good sunlight allows the days to be very mild. This period of good weather will continue until Friday or Saturday before the next day is expected to get worse. A sevens episode is envisioned between Sunday and Monday, which is a priority of normal intensity, however under observation. This situation was considered in our previous articles, but the models deviated considerably.
Today GFS and CEP seem to have found a relative agreement in the coming situation. But before we go into the details, let’s remember the difference between “a Covens episode” and a “Mediterranean episode” like every autumn. When the Cowenas episode affects Cowanes, the Mediterranean episode worries … the Mediterranean arc! While this may make sense, the media use the term Cévennes episode for an event that happened in Perpignan or Nice.
Synchronously, The Mediterranean episodes have the same conditions as the formation of the Sevens episode. Hot and humid air is brought in by the sea breeze. At the same time, there is cold air at high altitudes. Air mass supports convection and the formation of lightning, especially on planes and beaches (see diagram above right). Another difference related to the Mediterranean episode, The sailor has less power than the Sevens episode. Caven does not carry clouds to Covans. Stops flow in the interior to form a low-level cohesiveness. Thus, the storm develops at the level of this fusion. Some examples of Mediterranean episodes are: October 3, 1988, in Nimes, September 6, 8, 2005, Montpellier and Nile, June 15, 2010, Cannes October 3, 2015.
For the Sevens episode, see the diagram at the top left: First, we notice a strong sea breeze. Lots of moisture. This wind carries the clouds to Covens, where they suffocate. This soft air is forced to rise by encountering reliefs, so one can talk about orthographic compulsion. At the same time, the cold air at altitude creates a strong thermal difference. Therefore, Storm rain is developing in Covens and may continue as long as the situation prevents it. We have to wait for the change of wind to stop the wet supply from the Mediterranean. Finally, the Cévennes episodes remain Phenomena specific to our region. The hurricane devastation affecting Montpellier, Noms or Perpignan cannot be considered Covens episodes, but Mediterranean episodes.
But what to expect this weekend? Here is a comparison between GFS and CEP:
Unlike yesterday, Greenland and the United Kingdom both agree today about temporarily establishing a major low pressure area near the Atlantic. A low pressure area (low pressure area) is expected to slide into the Bisque Bay and northern Spain on Sunday. Against this background, a very dynamic southerly flow will be established temporarily (with very strong sea winds) favorable to the diverse rainfall in the region. Russellon and Western Languedoc will be exposed again by rain.
On the other hand, the closest it gets to the east of Languedoc, especially the Sevens, it gets the most rain, with an unusual occurrence, the models simulate a maximum of 175/200 mm in relief (C ‘is normal, with little impact at this time of year). The interior of the guard and the East Harold should experience good rain, albeit temporarily, but again with normal collection. Hence the importance of remembering that a Sevens episode does not mean that a disaster will occur (fortunately it is not systematic).
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