Autumn began this Sunday at 12:44 and the weather is following the new season. It arrived with clouds and showers and from Tuesday it will offer us a huge atmospheric river, which will bring intense and persistent rains, especially in the North and Center of the continent.
This is a tropical air mass, coming directly from the Caribbean, which crosses the entire Atlantic, with a very high water vapour content. It moves together with the anticyclone located south of the Azores and with a depression in the North Atlantic. To visualise this: the winds of the anticyclone rotate clockwise, those of the storm or depression exactly the opposite, so this mass of water gains speed and more humidity as it passes between them.
A humid air mass associated with a cyclonic system that will pass north of the continental PT will leave a lot of rain in the mountains of the north and center, with 100 to 200 mm possible between the 24th and the 26th. Windy and muggy weather is also expected. :/ /t.co/5B94BwGW4q pic.twitter.com/KNDrF1wN3c
– Best weather (@bestweather_) September 22, 2024
???? An atmospheric river is expected to reach mainland Portugal next week. It will bring #rain abundant ????️ to several regions.
????????? High risk of flooding, landslides and runoff, especially after fires ????.
????️ More information: https://t.co/IXmI6xH5xD pic.twitter.com/Ve3qjsuj9Y
—Meteored | Tempo.pt (@MeteoredPT) September 20, 2024
When it reaches the continent, and although temperatures will remain high but now cooler, all this humidity will turn into rain, which will be heavy especially on the coast and in the mountainous regions of the North and Center.
The IPMA has already issued a statement and is expected to put districts on alert on Tuesday. “Persistent rain is expected from the 24th in the North and Central regions, and will sometimes be intense on the 25th and 26th, especially on the northern coast of Cabo Mondego and mountainous areas,” it explained. For the South region, rainfall will generally be light, although unlikely in the interior of the Lower Alentejo and in the east of the Algarve, and may be temporarily moderate during the morning of Thursday, when this atmospheric river finishes passing.
And the models insist on the “atmospheric river” for next week… There will be a direct connection between Portugal and the Caribbean, tropical humidity will arrive here and discharge heavily in the Northern Region, especially in Minho. pic.twitter.com/pd0uYEkj5G
— Márcio Santos – Meteorology and Environment (@MeteoTrasMontPT) September 21, 2024
The IPMA points out that the accumulated precipitation values during the three days of passage of this humid tropical air mass could reach between 100 and 200 millimetres in Miño, Duero Litoral and in the mountains of the districts of Viseu, Aveiro and Coimbra, and between 50 and 100 millimetres in the rest of the coast north of Cabo Mondego. Most of the precipitation will occur between Wednesday and Thursday morning.
This air mass also brings wind. It will increase in intensity between Wednesday afternoon and Thursday morning, especially in the North and Central regions. It will be a warm wind, characteristic of these air masses coming from tropical areas.
The National Emergency and Civil Protection Authority (ANEPC) had already advised on Friday that preventive measures be taken in areas affected by fires due to the rains, which could cause landslides. According to ANEPC, the areas affected by the rural fires are left without vegetation cover and are more exposed and vulnerable to rainfall.
Once the rains have passed, autumn seems to be here to stay and it is possible, according to current models, that temperatures will drop another two or three degrees, especially at night. It will be the first arrival of a cold air mass this year. And maybe now you can try on your first knitted sweaters. Especially at night. But, and there is always a but, everything is temporary, there will always be the summer of S. Martinho shortly after to compensate.
???? TEMPERATURES WILL DROP AT THE END OF THE WEEK
Following heavy rains in the northern and central-northern coastal regions, the first polar air worthy of the name will arrive in mainland Portugal in the middle of this week, bringing temperatures below the average for the period. pic.twitter.com/Uv9gTZejq2— Márcio Santos – Meteorology and Environment (@MeteoTrasMontPT) September 22, 2024
Source: Observadora
