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The new National Severe Weather Warning Service

Icons used to represent different hazards

Help understanding the warnings

This section introduces the basic concepts of the warnings service, including:

timescales;
types of warnings;
weather types;
warning levels;
colour of warnings;
Chief Forecaster’s assessment;
web presentation;
useful information.

Timescales

Warnings are issued out to five days ahead for the UK.

Types of warnings

There are two types of warning:

warnings — issued up to 24 hours ahead;
alerts — issued more than 24 hours ahead.

Weather types

Warnings are issued for:

rain;
snow;
wind;
fog;
ice.

Warning level

Warnings are based on a combination of:

likelihood – How likely the event is to occur;
impact – The potential impact the expected conditions may have.

Colour of warnings

A combination of likelihood and impact is measured against a matrix to give each warning a colour:

red;
amber;
yellow.

An example of the matrix used to define the warning colour is shown below. In this case, an event with a high likelihood and medium impact would result in an amber warning.

Matrix shows how as likelihood an impact increase, so does the level of warning.

The matrix information showing how a warning was assigned its colour will be available for all warnings via the ‘View Warning Assessment’ option. However, you don’t need to view this level of detail if you don’t want to. You can simply use the following guidance for each colour:

Green implies no severe weather, yellow implies be aware, orange implies be prepared, red implies take action

Chief Forecaster’s assessment

The Chief Forecaster’s Assessment explains why the warning has been given the colour it has, as well as indicating where any uncertainties lie.

Presentation of warnings on our website

The screenshots below show how the warnings are displayed on our website. Alternatively a video walk-through of this guide page is available.

Screenshot of the UK NSWWS view

Screenshot of expanded warning overview box

UK view

The UK warnings page provides an overall summary of warnings issued for the UK.

Summary

A quick visual summary indicates the types of warnings in force for the UK over the next five days. This is displayed on all pages of the Met Office website as a simple notification of warnings.

Map

A map displays warnings and alerts which have been issued. Areas where warnings are in force are indicated by the colour shading. The shading shows the colour of the warning (e.g. red, amber or yellow) and the icon indicates the warning type (e.g. rain, snow). Links above the map will jump to a specific day in the forecast period.

Warnings Overview

The Warnings Overview box shows simple thumbnail maps coloured when warnings or alerts are in force for the next five days. Clicking on an overview map will jump to a specific day in the forecast period.

Regions

The Regions box shows a summary table detailing which regions have warnings in force for the selected day. The icon type and colour indicates the colour and weather type of the warning. Clicking on a row will take you to more detailed information for that region. Links above the region box will jump to a specific day in the forecast period.

Icons

Hovering over an icon gives you basic information about the warning including its start and end dates and times.

Key to colours

A key to the warning colours indicating the action to be taken for each colour. Find out more about warning colours.

Key to hazards

A key to the warnings icons.

Useful links

Useful links providing further information and guidance.

Warning assessment

If required, you can choose to view additional information about a particular warning by expanding the Warning Assessment and selecting a warning.

Chief Forecaster’s Assessment

The Chief Forecaster’s Assessment explains why a warning has been given a particular colour, as well as indicating where any uncertainties lie.

Weather Impact Matrix

The Weather Impact Matrix shows how the colour of the warning was decided based on the likelihood and potential impacts. Find out more about the weather impact matrix and colours.

Screenshot of regional warnings page

Regional view

The regional warnings pages provide the details of warnings for that region.

Map

A map is used to display warnings and alerts. Areas where warnings are in force are indicated by the colour shading. The shading shows the colour of the warning (e.g. red, amber or yellow) and the icon indicates the warning type (e.g. rain, snow). Links above the map will jump to a specific day in the forecast period.

Warnings overview

The Warnings Overview box shows simple thumbnail maps coloured when warnings or alerts are in force for the next five days. Clicking on an overview map will jump to a specific day in the forecast period.