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Frequently asked questions - NSWWS improvements

The National Severe Weather Warning Service (NSWWS) is produced by the Met Office as a part of our commitment to the Public Weather Service (as defined in the Civil Contingencies Act 2004). The warnings are required for two purposes:

1. To enable civil emergency authorities and the Ministry of Defence to trigger plans to protect the public from impacts,
   in advance of an event, and help them recover from any impacts after the event
2. To alert the public to take action prior to the event

They are being made following consultation with the public and those with the responsibility for protecting the public. Issues with the previous warnings included:

1. Too many
2. More focus needed on extreme weather than severe weather

Distinction between severe weather and extreme weather events Routine Severe Weather Advisory on Met Office website Enhanced web display showing a “traffic light” type alert system

Severe weather events are not unusual and are experienced on a number of occasions throughout the year, but more commonly winter months. They will impact on individual areas, but often not significantly. Extreme weather events are unusual and only happen around three or four times per year. They have a significant impact on infrastructure and may lead to casualties.

This is a web-based service. Advisory messages are a combination of a traffic light alert system, highlighting the areas most at risk from impacts, and a written commentary - indicating the likelihood of occurrence, the weather elements forecast and the areas where impacts are expected. The advisory will also highlight whether it is a severe or extreme event.

There are four colours which indicate varying levels of risk of impacts and a comment on actions to take at each level.

1. GREEN – No severe weather is expected.
2. YELLOW - 'Be aware' which means you should remain alert and ensure you access the latest weather forecast.
3. AMBER - 'Be prepared' which means you should remain vigilant and ensure you access the latest weather forecast.
   Take precautions where possible.
4. RED - 'Take action' which means you should remain extra vigilant and ensure you access the latest weather forecast.
   Follow orders and any advice given by authorities under all circumstances and be prepared for
   extraordinary measures.

We used colour-blindness simulators to test for the common forms of colour deficiency. The colours chosen are a compromise to cover normal sight and common forms of colour blindness. The information depicted by the maps is a summary of the warnings in force, the full guidance will always be available in text along side the map.

The maps below show an original sample map and a deutranope and protanope simulation produced by Vischeck:

There are no changes to the way Flash Warnings are issued, but these will be reflected in the traffic light alert.

Early Warnings will be indicated in the traffic light alert. Plus the likelihood of widespread disruption will only indicated areas with a risk above 60%.

• Fewer warnings
• Earlier indication (up to 5 days ahead) of severe and extreme weather events
• Severe and extreme weather events would be highlighted in advance during normal working hours at all times
• Differentiation between severe and extreme events
• Emergency planners should better be able to forward plan and increase (or decrease) mitigation actions through time
   as an event nears.