Chemical Meteorology (CHEMET) service

The Met Office’s CHEMET service is used to predict the likely dispersion track of a chemical or aerosol release in the atmosphere.

In the event of an incident involving a large fire or release of hazardous chemicals into the atmosphere, local Fire and Police services can contact the Met Office Environment Monitoring and Response Centre (EMARC) for support. Typical scenarios could be a recycling plant fire, chemical spillage or release, a fire at an industrial plant or oil depot, or a road traffic accident in which a hazardous substance has either escaped or ignited. EMARC produces meteorological guidance and a plume prediction with its chemical meteorology (CHEMET) service, used for advising where the hazardous aerosol is likely to affect on a local OS map. For larger release events, such as the Buncefield Oil Depot fire, more-sophisticated plume modelling techniques are utilised.

What does the CHEMET service provide?

Telephone advice is available on demand to give a simple short-range prediction of the anticipated behaviour of the plume. Within 20 minutes, the formal forecast and plume map will be sent by email. The CHEMET will also be made available to view on Hazard Manager.

CHEMET consists of three elements:

• A forecast
• A map showing the plume below 100 metres
• Telephone consultation with the forecaster

When a CHEMET is requested, the Met Office meteorologist will need some information from the requesting agency about the incident, and will then use this information, combined with meteorological observations and forecasts of weather and atmospheric conditions, to run a computer model simulation that will predict the dispersion pattern of the chemical.

How do I request a CHEMET?

If you are an emergency responder or public agency, to request a CHEMET telephone the Met Office EMARC on (01392) 447947 and please identify yourself and the nature of the incident. A CHEMET may also be requested by emailing the information requested in the request guidance to emarc@metoffice.gov.uk, but a subsequent telephone call should always be made to ensure the request has been received by the Met Office.

Buncefield Oil Depot fire case study

On Sunday, 11 December 2005, a little after 6 a.m., there was a major explosion at the Buncefield Oil Depot in Hemel Hempstead, Hertfordshire, resulting in the largest peacetime fire in Europe to date.

The fire burned for four days before it was extinguished.

Several government departments and agencies asked the Met Office to provide guidance on the smoke plume — including Defra, the Cabinet Office, various emergency services and the Health Protection Agency. Information on the transport and dispersion of the plume provided by the Met Office assisted with decisions on potential evacuation areas and safe approaches for fire crews and played a vital part in getting people to safe locations.

Met Office actions

• We used sophisticated dispersion models (NAME), together with our weather forecasting model to predict the spread of the smoke.

• We used the dedicated Facility for Airborne Atmospheric Measurement (FAAM) research aircraft to take gas and aerosol measurements from within the plume.

• Our atmospheric dispersion modellers, based in Exeter, used information gathered to further refine the forecasts and verify our results.

• Forecasters and support was also available 24 hours a day through our Environmental Monitoring and Response Centre (EMARC).

As a result of the services from the Met Office the emergency services gained:

• clear guidance on how the smoke would move, spread and disperse;

• identification of the areas at risk from grounding of the smoke plume;

• indications on what the plume contained.

CHEMET can also be produced for incidents where an impactful release may occur but has not yet happened (speculative) for use in planning purposes, e.g. damage to a pipeline or systems failure at an industrial plant.

Further details can be found in the CHEMET user guide on Hazard Manager.

For more information about our services for Government, please contact our Contact us.