After several weeks with temperatures well above average and a sunny environment, rain is set to return to the country within a few days, in the form of a cold front.
Forecasts by Alfredo Graça, geographer and editor-in-chief of Meteored Portugal, indicate rainy and unstable weather from Friday, October 13th.
The cold front will pass through during part of Friday 13th and Saturday 14th, distributing rain unevenly between the various regions, concentrating mainly further north of the country. However, the meteorological instability will not stop there, on Sunday 15th, the arrival of an atmospheric river is expected.
What is an atmospheric river?
The phenomenon that will intensify the rain in mainland Portugal within a few days is known as an atmospheric river. An atmospheric river is a long, narrow, transitional strip in which horizontal transport of water vapour occurs. This water vapor is supplied by tropical and/or extratropical moisture sources. The atmospheric rivers that affect mainland Portugal originate in the Atlantic and are responsible for carrying temperate and very humid subtropical air. The precipitation resulting from this is usually abundant.
Among the possible effects of the atmospheric river, there is rain that could be locally heavy, a sharp drop in maximum temperatures and wind that will blow moderate to strong.
On the way to reaching mainland Portugal on Sunday, the depression with the atmospheric river, will cross a very hot sea surface, which will contribute to the stimulation of water vapour that will serve as “fuel” for the intensification of the rain. The possibility of the rain being accompanied by thunderstorms cannot be excluded.
