A new DANA, known in meteorological terms as Isolated High Level Depression, has crossed Spain since Tuesday, causing intense rains and generating a maximum alert scenario in several regions.
In places like Malaga and the southern coast of Tarragona, authorities have issued red notices, while the storm has spread torrential rains along the Mediterranean and much of Andalusia. This phenomenon, however, is about to transform into an isolated cold storm (BFA), lor which represents a significant change in its behavior and scope.
The evolution of the system
As the pocket of cold air approaches the Atlantic, it is expected that, towards Thursday, this system will begin to develop fronts associated with a low pressure system on the surface, thus losing its DANA structure and becoming an isolated cold storm.
This transformation will stop the phenomenon from being an erratic atmospheric event located in the high levels of the atmosphere, acquiring a higher level of predictability and affecting both height and surface.
Unlike DANA, characterized by its unpredictability and random movement, an isolated cold storm behaves like a conventional storm, although detached from the general atmospheric circulation. This change is of particular importance for weather forecasting, as it will reduce uncertainty and allow areas of precipitation to be better anticipated. However, instability is expected to remain over some regions of Spain, prolonging the rains until the end of the week..
During the early hours of Thursday, rain will persist in some areas of the east and south of the country, although they will tend to decrease as the day progresses. For the afternoon, it is anticipated that the heaviest rainfall will be concentrated in the southwest, affecting provinces such as Huelva, Cádiz, Seville and areas of Extremadura. In other areas, rain will generally be weaker, with possible episodes of sporadic rain in the south, east and center of the peninsula.
As the days go by, the isolated cold storm is expected to move towards the southwest, which will lead to a notable improvement in weather conditions for much of the country. For the weekend, the outlook points to greater stability, allowing a respite after the intense days of rain that have affected various areas of the peninsula.
DANA vs. cold storm
DANA arise when a portion of cold air in the middle and upper layers is isolated from the general atmospheric circulation, which causes its erratic behavior and its tendency to trigger intense rain if the right conditions occur. In contrast, the isolated cold storm is a complete low pressure system that affects from the surface to the upper layers and, although it can arise from a DANA, this is not always the case.
The origin of an isolated cold storm can be due to several factors, one of the most common being the disconnection of a storm from the polar jet or the formation of a new storm associated with a pocket of cold air at altitude. In these cases, the development of sufficient convection allows the appearance of a low pressure core on the surface, which distinguishes it from DANA, which are phenomena typical of higher levels without direct influence on the surface pressure.
Continuous surveillance
This atmospheric phenomenon that is evolving over Spain is a reminder of the power of nature and the importance of constant meteorological monitoring.
With alerts still active and stability on the horizon, this change from DANA to an isolated cold storm highlights the need for understanding weather systems to anticipate and respond to their effects on the ground.
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