Meteocat Says Strong El Niño Already Affects Catalonia’s Weather
Meteocat says a very strong El Niño is already having an impact, but its effects on Catalonia's rain, cold and drought remain uncertain.
The Servei Meteorològic de Catalunya (Meteocat, the Catalan weather service) has warned that a very strong El Niño, which it calls the Superniño, is arriving, while stressing that its effects on Catalonia are highly uncertain. Toni Barrera, a climate change specialist at Meteocat, told the media the phenomenon “és molt fort i ja ens està impactant” (it is very strong and is already affecting us), according to go.eln.cat.
Meteocat points to two atmospheric signals that show El Niño’s remote effects, known as teleconnections, are already active.
What are the two signals Meteocat is watching?
The first is an atmospheric river that reached the Iberian Peninsula this week. Meteocat says it is very probably the result of a subtropical jet stream strengthened by the Superniño. That jet is a current of westerly winds high in the troposphere, at 10-16 km altitude, around 25-35° latitude. El Niño can intensify it and shift it south, which favors the transport of atmospheric rivers across the North Atlantic.
An atmospheric river is a band in the atmosphere that carries large amounts of water vapor from tropical or subtropical areas toward higher latitudes. It can bring heavy rain.
The second signal is a weakening of the polar vortex, the large circulation of winds around the polar regions that normally keeps very cold air near the poles. El Niño can spread atmospheric waves that weaken or break it, which can cause intense cold in Europe or North America some weeks later. Meteocat says it could break on Nov. 24, which would be the earliest it has happened.
Which recent storms does Meteocat blame on it?
Meteocat says it is very confident that storm Charles was a consequence of the Superniño. Charles was a subtropical storm produced by the atmospheric river, and it mainly hit the Atlantic side of the peninsula, with red warnings in Àvila and Càceres. The service leaves open the possibility that storm Bruna was also linked, pending more study.
It does not attribute the dana Adam of October to El Niño. A dana is a cut-off low, a pocket of cold air high in the atmosphere that can cause heavy rain.
Is a cold wave coming?
A weakened polar vortex does not necessarily bring a cold wave to Europe, Meteocat insisted, because too many variables are involved. For Catalonia, Barrera called a cold wave caused by a polar vortex break unlikely. The phenomenon mainly affects areas closer to the pole, and Catalonia is nearer the temperate zone.
What about rain and drought?
Barrera raised the possibility of more rain, but only in the western half of Catalonia and on the southern slopes of the Pyrenees, mainly between December and January.
On drought, he said there is no clear link between El Niño and drought in Catalonia. Meteocat does warn of a very serious drought in the short term in Les Nogueres and the Segre Mitjà, but says the available information does not tie it to El Niño. The service adds that the situation could improve soon thanks to the rain it mentioned.
What does this mean for Catalonia?
Meteocat says El Niño’s effects in the region are quite uncertain because the western Mediterranean has high climate variability, which makes it hard to isolate a clear signal. Global warming adds to this, since it has raised temperatures and increased both the frequency and the intensity of some extreme events. In the scientists’ words, “no es pot atribuir automàticament qualsevol anomalia meteorològica dels pròxims mesos” to the phenomenon (no weather anomaly in the coming months can automatically be blamed on it).
The one effect Meteocat describes as clear is on temperature. El Niño will raise the average temperature, and each year is expected to be warmer than the last. Readers should follow official Meteocat warnings and local authorities for any weather alerts.
Source: go.eln.cat
