Few weather phenomena cause as much concern in Spain as the DANA (Depresión Aislada en Niveles Altos — an upper-level isolated depression). Every autumn, news broadcasts fill with images of overflowing rivers, flooded streets and dramatic rescues along the Mediterranean coast. Understanding what a DANA is, why it happens and how to prepare can make the difference between safety and danger.

What is a DANA?

DANA stands for Depresión Aislada en Niveles Altos (upper-level isolated low). It is a pool of cold air in the upper troposphere (between 5000 and 9000 metres) that detaches from the main flow of the polar jet stream. Once isolated, this cold pool drifts slowly and erratically, making its exact trajectory difficult to predict.

When this very cold upper-level air mass sits above warm Mediterranean waters (which can exceed 25 °C in autumn), an extreme vertical temperature contrast develops. The atmosphere becomes highly unstable: warm, moist surface air rises violently, building cumulonimbus towers that can reach 12-15 km and produce torrential rainfall.

DANA vs. gota fría: are they the same?

Technically, they are not synonyms, although they are used interchangeably in everyday language:

  • DANA: a technical term describing the upper-level atmospheric structure (the isolated cold pool). A DANA does not always produce torrential rain — it may pass unnoticed if there is not enough surface moisture.
  • Gota fría (cold drop): an older, popular term referring to the outcome — the torrential rain and flooding. Not every DANA produces a "gota fría" and occasionally torrential rain can occur without a clear upper-level DANA.

AEMET recommends using the term DANA as it is meteorologically more precise.

When do they occur?

DANAs can form at any time of year, but their most devastating effects are concentrated between September and November, when:

  • The Mediterranean is at its warmest (sea surface temperatures of 24-27 °C after summer), providing enormous water vapour.
  • The polar jet begins to dip to lower latitudes as the summer anticyclone weakens.
  • The orography of the eastern Spanish coast (mountain ranges close to the sea) amplifies the ascent of moist air.

Highest-risk areas

The Spanish Mediterranean coast is one of the most exposed zones in Europe to DANA-related torrential rain:

  • Valencia region: especially the Safor, Marina Alta, Ribera and l'Horta areas. The city of Valencia and its metropolitan area are highly vulnerable due to converging ravines and dry riverbeds.
  • Murcia region: the Campo de Cartagena, Mar Menor and Vega Baja del Segura suffer recurrent flooding.
  • Alicante: the Vega Baja and southern districts hold some of Spain's rainfall records.
  • Catalonia: the Maresme, Garraf and Ebro river districts.
  • Balearic Islands: Mallorca, especially the Llevant area and Serra de Tramuntana.
  • Almería and Granada coast: dry riverbeds that activate suddenly.

Rainfall records

  • Oliva (Valencia), November 1987: 817 mm in 24 hours, Spain's record.
  • Jávea (Alicante), September 1957: 871 mm in 48 hours.
  • Sant Llorenç des Cardassar (Mallorca), October 2018: a flash flood that claimed 13 lives.
  • Pilar de la Horadada (Alicante), September 2019: over 500 mm that flooded extensive areas.

How to prepare and protect yourself

  • Check weather warnings daily during autumn. Orange and red warnings indicate significant risk.
  • Avoid driving through ravines, dry riverbeds and flood-prone areas when a warning is active.
  • Never cross a flooded ford: 15 cm of moving water can knock a person down and 30 cm can sweep away a vehicle.
  • If caught on the road: reduce speed, turn on your lights, avoid low-lying roads and seek higher ground if water levels rise.
  • Prepare an emergency kit in risk areas: torch, water, portable charger, documents and medication.
  • Follow instructions from Civil Protection and the 112 emergency services.

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