Reading an alert

Severity

Every event gets a severity score from 0 to 100. Each category has its own rules for the score, written out in the code rather than learned. A magnitude, a warning level or a storm category each map onto the same scale, so a flood warning and an earthquake can be compared at a glance.

The map's severity filter uses the same scale.

Act-worthy

An event is act-worthy when it carries a protective action for people in the area: shelter, evacuate, get out of the heat. Being severe is not enough.

Weather warnings: act-worthy when the issuing agency rates them Extreme, or Severe when the hazard is observed or likely and imminent or expected.
Earthquakes: a score of 65 or more, or magnitude 5 or more shallower than 50 km.
Tsunamis: a warning or an advisory.
Hurricanes: category 2 or stronger, or a category 1 hurricane or a tropical storm when the forecast puts its centre over land within 48 hours. A forecast counts only when it predicts category 2 or stronger and a landfall.

An AMBER alert is urgent, but it is not act-worthy, because it asks you to watch rather than to protect yourself. EHW keeps "how urgent" and "what to do" as separate questions.

Plain-language warnings

Official warning codes are hard to read. US National Weather Service event types and MeteoAlarm awareness levels come from small fixed lists. EHW maps each code to one plain sentence and one line of what to do. An event's detail panel shows this above the official text, and the official text stays, labelled as official.

A code EHW does not recognise gets no plain reading. EHW would rather show nothing than guess.

Badges

An event's detail panel can carry a badge saying where the event came from:

NEWS REPORT: the event was detected in news coverage, not published by an official agency.
NEWS CORROBORATED: several independent news reports of the same conflict event agree.

An event with neither badge came straight from the agency that published it.

News coverage

An event's panel lists news articles about it, each with its outlet and when it was published. An article is attached only when all of these hold:

it belongs to a group of reports that EHW has already placed in the event's country
it names the event's kind of hazard, such as an earthquake or a flood
it was published after the event began, and within the last 48 hours
when the country has more than one current event of the same kind, it also names this event's place

A place name alone is never enough, because the same town appears in quake reports, storm reports and election results. When nothing qualifies, the panel says there is no recent coverage rather than showing something close.

Below the articles, the panel can offer the region's live news channel when it is on air. That is a general news channel for the region. It is not coverage of the event, and the panel says so.

Repeated alerts

Agencies often issue the same warning many times, for neighbouring areas or as updates. A cluster groups these into one row, so one storm does not bury everything else.

The red banner appears only for an event that matters beyond its own area:

nuclear, tsunami, armed conflict or biological events
any event scoring 85 or more
hurricanes scoring 70 or more, and volcanic events scoring 80 or more

Market moves and routine local weather warnings never take the banner. When two events qualify, one that has escalated in the last 24 hours wins over a larger one that has not changed.