How It Works

How AlertWatch World turns official alerts into one global view

AlertWatch World brings weather-alert information from multiple official sources into one map and dashboard.

Different countries and warning services publish alerts in different formats. AlertWatch collects available records, converts selected information into a common structure, checks the resulting publication, and presents it through a consistent interface.

AlertWatch World does not issue weather warnings and does not independently confirm weather conditions on the ground. The original issuing authority remains the authoritative source for its warnings and instructions.

1. AlertWatch collects information from official sources

The Weather service currently uses four main source groups:

• the U.S. National Weather Service (NWS);
• Environment and Climate Change Canada (ECCC) land alerts;
• Environment and Climate Change Canada Marine warnings; and
• international warning information available through the World Meteorological Organization’s Severe Weather Information Centre (WMO/SWIC).

The default Worldwide view combines the direct U.S. and Canadian sources with available international WMO/SWIC warning records.

AlertWatch’s automated systems retrieve and prepare this information before it reaches the public website.

2. Different source formats are converted into a common structure

Weather-warning systems are not standardized in every respect.

One source may provide a severity category, detailed geographic polygons, issue and expiry times, instructions, or structured event information.

Another source may provide some of those fields differently or not provide an equivalent field at all.

AlertWatch converts the available information into a common record format that can include:

• alert name;
• severity;
• country or area;
• timestamps;
• location or geometry;
• description;
• instructions; and
• issuing source.

AlertWatch does not invent missing information simply to make every record look the same.

3. AlertWatch applies source-specific rules

AlertWatch uses the common display levels:

Extreme · Severe · Moderate · Minor · Unknown

The way a record reaches one of those categories depends on the source.

Canadian Marine warnings currently appear with Unknown severity because AlertWatch does not have a sufficiently comparable source severity value for those records.

Unknown does not mean harmless or low risk. It means a comparable severity value is not available or defensible for AlertWatch’s common scale.

Similar source-specific rules are used for marine warnings, waterspout classification, timestamps, geographic areas, and warning lifecycle information.

Visitors who want the exact technical rules can read Methodology.

4. Geographic information is prepared for the map

Depending on the source, AlertWatch may display:

• an official alert polygon;
• an official warning or forecast zone;
• multiple source geometries combined for one record; or
• a point marker when point information is supplied.

These areas help users understand where an alert applies, but they should not be interpreted as exact boundaries of the weather hazard itself.

A storm or hazard can affect only part of a displayed area, extend outside it, or change after the dataset was published.

5. Records are checked before publication

Before updated alert data is published, AlertWatch performs automated validation intended to identify structural problems or obviously incomplete publications.

These checks help reduce the chance that a failed or incomplete source update replaces usable data.

They do not independently determine whether a warning is meteorologically correct or whether the hazard is occurring on the ground.

That responsibility remains with the issuing authority.

6. AlertWatch may retain last-good information during a source failure

Official data services and network connections can occasionally fail.

Where the system has a safe fallback, AlertWatch can preserve previously validated information rather than replacing it with an incomplete publication.

For example, if part of the WMO update fails, the previous complete Worldwide publication can remain available with its original timestamp.

Canadian Marine processing also has last-good behaviour in certain failure situations.

This is why the publication freshness indicator matters.

Retained information is not presented as though it were newly downloaded.

7. Freshness tells you when AlertWatch’s publication was generated

The Weather dashboard displays the age of the selected AlertWatch publication.

The freshness indicator describes when the AlertWatch dataset was generated.

It does not mean that every warning inside the dataset was issued at that time.

AlertWatch currently begins indicating aging data after two hours and identifies the publication as stale after three hours.

A fresh dataset may legitimately contain an older warning that is still listed by its source.

A stale dataset means AlertWatch has not successfully replaced that publication recently enough. It does not, by itself, tell you whether individual hazards have ended.

8. Similar alerts may be grouped for readability

Large weather events can generate many separate warning records.

AlertWatch may group similar records in parts of the dashboard—such as Major Alerts—to reduce repetitive presentation.

Grouping does not necessarily mean that the underlying warnings have been merged into a single official alert.

The original records and geographic areas can remain distinct.

9. Filters change what you see, not the underlying publication

Visitors can explore the Weather dashboard using filters such as severity, hazard type, Marine, and Waterspout.

Filters change the records shown in the interface. They do not rewrite the source information.

The Global Alert Activity chart is different: it represents the record count from successful Worldwide publications and remains independent of the current dashboard filters and dataset mode.

10. Alert counts need context

Two countries experiencing similar weather can have very different alert counts.

That can happen because warning systems differ in:

• geographic area size;
• how many warnings are issued for one event;
• language;
• update practices;
• marine-warning structures;
• lifecycle handling; and
• data availability.

AlertWatch country totals represent published alert records, not a measure of how dangerous the weather is.

A higher alert count does not necessarily mean greater risk.

A lower count does not necessarily mean greater safety.

11. “Worldwide” does not mean complete global coverage

AlertWatch’s Worldwide view combines the international sources currently available to the project.

It does not guarantee that every warning from every country or marine area will appear.

Coverage can vary because some authorities do not participate in the feeds AlertWatch uses, warning formats differ, geographic information can be incomplete, feeds can be delayed or unavailable, or AlertWatch may withhold a record when it cannot be represented reliably.

The absence of a displayed alert does not prove that an area is safe or that AlertWatch World has complete coverage.

12. Some international records have lifecycle limitations

International warning feeds do not all handle expiry, cancellation, and lifecycle information in exactly the same way.

AlertWatch currently does not apply one universal expiry rule to every WMO/SWIC record.

As a result, some records in the Worldwide publication can have older or unavailable expiry information.

For that reason, AlertWatch treats the dashboard as a view of published or currently listed alert records, rather than claiming that every displayed record has been independently verified as an ongoing hazard.

13. The map is for awareness, not emergency decision-making by itself

AlertWatch World is designed to make official weather-alert information easier to discover and understand.

It is not:

• an emergency service;
• a weather-warning authority;
• a replacement for local emergency information;
• a guarantee of complete coverage; or
• independent confirmation that a hazard is occurring.

For decisions involving safety, evacuation, travel, marine activity, or severe-weather preparation, follow the instructions of the applicable official authority.

Want more detail?

For detailed rules concerning severity, marine handling, waterspout classification, geometry, timestamps, grouping, fallback procedures, freshness, history, and record counts, see Methodology.

For provider and provenance information, see Sources.