Met Office Quantitative Volcanic Ash Charts

Quantitative Volcanic Ash Charts (QVA) are produced in accordance with ICAO Annex 3 requirements and are provided as well as the London Volcanic Ash Advisory graphics (VAG) and advisories (VAA). The lowest QVA threshold (0.2 mg/m³) matches to the areas depicted in the VAA and VAG. Both expected ash concentration and probabilistic forecast information is provided in the chart viewer blow for eruptions occurring in the London VAAC Area of responsibility.

Charts will only be available during an eruption or when tests and exercises are carried out.

Information on interpreting the QVA information.

Expected Ash Concentration

This is the ash concentration expected for 5000ft thick layers of the atmosphere.

Flight level

Timesteps

In addition to the ICAO QVA defined products we also provide lower resolution concentration charts for thicker atmospheric layers out to 5 days for additional awareness purposes. These align with the pre-QVA concentration charts.

Note: these charts will be retired in late 2026 or 2027.

Flight level

Timesteps

Probabilistic Ash Concentration

This is the probability of exceeding four different concentration thresholds (0.2, 2.0, 5.0 and 10.0 mg/m³) at 5000 ft thick layers of the atmosphere.

Low 0.2g/m³ Medium 2.0g/m³ High 5.0g/m³ Very high 10g/m³

Flight level

Timesteps

Operators should refer to national NOTAMs for official guidance on any restrictions / actions regarding flight in affected airspace, and the official boundaries applicable to such restrictions/actions.
Airlines operating in UK airspace should review the document "Guidance Regarding flight Operations in the Vicinity of Volcanic Ash", issued by the CAA, found on the CAA website.