September begins with dry weather dominating much of Portugal, but predictions from the European ECMWF model, cited by Meteored Portugal, point to the return of rain in the coming days. Atmospheric circulation should undergo changes over the next ten days, with two periods of greater instability forecast.
The first change is expected on Friday, September 4, and Saturday, September 5. An upper-level disturbance could approach the Iberian Peninsula, accompanied by the entry of colder air at mid-levels of the atmosphere, favoring the development of showers in the North and Central regions. The forecast accumulations are not significant, with about 1.9 millimeters in Aveiro, 1.8 millimeters in Guarda and 1.5 millimeters in Bragança, while in the South precipitation should be reduced or nonexistent.
After this episode, weather should stabilize between Sunday, September 6, and Tuesday, September 8, with a new reinforcement of the ridge over the Iberian Peninsula temporarily pushing the instability away.
From Wednesday, September 9, an Atlantic disturbance could approach the mainland territory, possibly bringing a front with precipitation between late Wednesday and early Thursday, September 10. Minho and Douro Litoral appear as the most exposed regions, although there is still uncertainty regarding the trajectory and intensity of the front. For the week between September 7 and 14, the ECMWF forecasts less precipitation than would be usual for this time of year, especially in the North.
