Atlantic low west of Portugal, named by Portugal's IPMA on 17 January 2025. Its front reached the Canary Islands with heavy seas, thunderstorms with hail, wind and intense rainfall; its effects were felt most strongly in Spain between Monday the 20th and Wednesday the 22nd, with widespread rain across the mainland and the Canaries, snow at high levels, flooding and hail.
Cortes de carreteras en Tenerife y Gran Canaria, inundaciones locales en zonas bajas del sur peninsular.
Garoé was named by the Portuguese IPMA in January 2025 and sat west of Portugal, so what reached the Canaries was not its centre but its front. That is worth saying plainly, because the data say it: measured on Gran Canaria, this episode was not exceptional in any of the three variables. What it did bring was thunder and hail, small-scale phenomena that a reanalysis with a 28-kilometre cell cannot see. It is a good reminder that “does not stand out in the series” and “nothing happened” are different things.
The figures that follow are not estimates and have not been copied from any bulletin: they were computed on ERA5, the European Centre’s reanalysis, at a point representative of the area affected — Gran Canaria — and compared with the 31 complete years of the series. What matters is not the number but the rank.
| Variable | During the episode | Rank in the series |
|---|---|---|
| Minimum pressure | 1,012.8 hPa | falls in the most extreme 5 % of the series of the 271,752 hours measured |
| Maximum 10 m wind | 21 km/h | does not particularly stand out in the series of the 271,752 hours |
| Rainfall over 3 days | 6.2 mm | does not particularly stand out in the series of the 11,321 3-day windows |
| Minimum temperature | 13.2 °C | falls in the most extreme 5 % of the series of the 271,752 hours |
At this particular point, none of the four variables falls in the most extreme 1 % of the series. That does not mean nothing happened: it means what happened was on a smaller scale than the model cell, or that it unloaded somewhere else. To place the rainfall: the wettest 3-day episode recorded at Gran Canaria in the whole series was 82.1 mm, on 24 September 2022.
ERA5 works with cells of about 28 kilometres and smoothed terrain. It describes the air mass well and allows one storm to be compared with another on the same yardstick, which is precisely what cannot be done with station records that have changed site. What it does not see is the detail: a storm that unloads over one particular ravine is averaged across a cell of 800 square kilometres, and that is why its totals are always lower than those of a well-sited rain gauge. For the official figures of an episode, AEMET is the authority.
Data: ERA5 · Copernicus Climate Data Store, CC-BY licence. Sources and methodology →
