Barcelona residents could face periods of intense rain and strong winds this autumn if low-pressure systems cross an exceptionally warm Mediterranean, according to a report published by Metrópoli Abierta on Saturday 26 September.

The report says sea-surface temperatures off the Barcelona coast recorded a summer anomaly of up to 7°C above average. It says that extra heat could supply moisture to weather systems over the sea, increasing the potential for torrential, localised rain when humid air meets coastal mountain ranges.

Forecast depends on several atmospheric factors

Metrópoli Abierta describes the expected climate pattern as a “Super Niño”, an exceptionally strong El Niño phase of the El Niño-Southern Oscillation, a natural Pacific Ocean and atmosphere cycle that can affect weather patterns worldwide.

According to the report, the pattern could alter the high-altitude jet stream and allow troughs, elongated areas of lower atmospheric pressure, to move further south towards the Iberian Peninsula. It stresses that this is conditional on other atmospheric factors, rather than an automatic result of El Niño alone.

  • Sea temperatures off Barcelona were reportedly up to 7°C above average during summer.
  • The report expects the risk of rapidly deepening low-pressure systems near the Catalan coast to increase towards October.
  • It says autumn conditions could be at either extreme, with very dry weather or episodes of very heavy rain.

Possible Mediterranean cyclones

The report also raises the possibility of medicanes, Mediterranean cyclones that can develop a warm core and display some features associated with tropical hurricanes. Such systems can bring severe winds and torrential rain to limited areas, but the report does not state that one will form off Barcelona.

It says medium-range forecast maps point to a higher probability of explosive cyclogenesis, a rapid fall in atmospheric pressure that can strengthen a low-pressure system, near the Catalan coast in October. Residents should follow official weather warnings if severe-weather alerts are issued.

Reported by metropoliabierta.elespanol.com, Metrópoli Abierta - Urban Life.