Weather situation on 21 December 2006

Weather

A large area of high pressure became slow moving for several days over central, southern and south-eastern England. This allowed widespread and persistent, locally freezing fog to form across much of this area, which in some locations persisted for three to five days.

In many places, visibility was reduced to below 100 metres and in some cases to below 30 metres. Transport hubs, including the major London airports in the South East were particularly badly affected.

Had this weather type been a one-day event it may well have been a yellow event. However the longevity of the fog, once established, means this would have been an amber event.

Impacts

An Aircraft in the fog

• Fog caused problems on the roads, with one man killed in a crash on the A20, leading to delays for motorists heading for channel ports.
• Police appealed to motorists to slow down and keep their distance as they continued to clear wreckage from a series of accidents on major roads.
• Rail operators were braced for the busiest day of the year as air passengers piled on to packed long-distance trains - many having given up on air travel from south-east England.
• Up to 70,000 people suffered delays or cancellations at airports across the south-east as airlines axed almost two thirds of their flights on some days.

Warning Assessment

Based on the new warning system the following assessments would have been made:

• Likelihood -medium
• Impact - high

This would have resulted in an amber warning for fog: