Autumn is officially here: what kind of weather awaits us?
It is usually the rainiest season of the year in many regions.
BarcelonaAfter another sweltering summer, this Monday, September 22nd, astronomical autumn officially arrives, although the meteorological season began on September 1st. It will begin at 8:19 p.m., according to the National Astronomical Observatory, and that's when the equinox occurs. The new season will last almost 90 days, until December 21st, when winter arrives.
It's usually the rainiest season of the year in many regions, especially on the coast and pre-coastline. This is because the sea warms up after summer, fueling rain and storms with the more frequent arrival of low pressure areas and cold air pockets.
We're coming off a summer that has ended with strong storms and downpours in several areas of the country. All this after the abundant rains of spring finally put an end to the historic drought of recent years. The reservoirs in the inland basins end the summer with a spectacular 74% of reserves, nothing compared to the 28% just a year ago. Therefore, if autumn behaves well, we could arrive in winter with excellent figures. But what do the forecasts say?
Autumn with erratic rainfall
According to various long-range weather models, rainfall could be erratic this fall depending on the region of the country. The usual rainfall for this time of year could fall along the coast, while inland and in the Pyrenees could see below-average rainfall. The maps indicate that October could be the wettest month, while November could be the driest of the entire season.
Therefore, according to these maps, the most significant rainfall episodes would affect the coastal area. This could be an indication of the arrival of pockets of cold air that, upon colliding with warmer-than-normal sea water, would cause rain and downpours on the coast and pre-coastline.
In any case, these long-term forecasts should be taken with a grain of salt, as they only indicate seasonal trends. We'll have to take stock in December to see if the predictions have finally come true.
Above-average temperatures
As for temperatures, all the models are in line. It looks like we'll once again have a few months with slightly higher than usual values, following the trend of recent years. Forecasts indicate that temperatures for the whole of autumn could be around one degree above average.
This doesn't mean we won't have cold spells with the first winter breezes in November or early December. But overall, the weather is expected to be milder than normal. For now, after the showers and storms that will arrive starting this Sunday, we'll be affected by a cold air mass of polar origin. Therefore, on Monday night we'll enter autumn with a clear cooldown, and during the first days of the new season we'll have temperatures below average. A radical change of atmosphere after days of summer heat.
Difference between equinox and equilux
The equinox occurs twice a year: when we officially enter autumn and spring. At that precise moment, the two hemispheres are balanced and are not tilted, causing the Sun to strike perpendicular to the equator. Therefore, during the equinox, in theory, there should be exactly 12 hours of day and 12 hours of night. But that's not the case.
This is because the Sun is not a point in the sky, but a disk. Its rising and setting are considered to occur when the center of the solar disk appears at sunrise or sets behind the horizon at sunset. This is how the equinox is calculated. But the problem is that it doesn't take into account that when the center of the Sun is below the horizon, there are solar rays illuminating us for a few minutes. In addition, the refraction of the Earth's atmosphere causes the Sun's rays to deflect, meaning we can still see a portion of the star even before it has risen or set.
Therefore, these two factors cause that, in reality, there are a few more minutes of sunlight that make the night and day not last exactly the same. To correct this discrepancy, the term equilux, which indicates the exact date on which there are as many hours of sunlight as darkness. In Catalonia,equilux It takes place a few days after the autumn equinox and a few days before the spring equinox. In this case, it will be September 25th.