Alert updates and cancellations

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When an alert changes, issue a new alert that refers to the previous alert, instead of changing or removing the existing alert from your feed. After an appropriate amount of time (e.g. 24-48 hours), remove cancelled, updated, or expired alerts from your feed.

<msgType> Update or Cancel must include at least one <references> element. As specified in the CAP standard, any alert message that updates a previous alert should use <msgType>Update</msgType> and set <references>code</references> to all previous related messages that haven't reached their <expires> date. The update or cancellation must apply to a non-expired alert.

There are three ways to cancel events, in order of preference:

  1. Set an <expires> datetime for each event, with the message description setting the expectation that this alert will end on its own.
  2. Issue a new <alert> with <msgType>Update</msgType>, <responseType>"All Clear"</responseType>, and <expires> a short time in the future.
  3. Issue a new <alert> with <msgType>Cancel</msgType>.

Example update

<alert xmlns="urn:oasis:names:tc:emergency:cap:1.2">
  <identifier>PAAQ-4-mg5a94</identifier>
  <sender>wcatwc@noaa.gov</sender>
  <sent>2013-01-05T10:58:23-00:00</sent>
  <status>Actual</status>
  <msgType>Update</msgType>
  <source>WCATWC</source>
  <scope>Public</scope>
  <code>IPAWSv1.0</code>
  <references>wcatwc@noaa.gov,PAAQ-1-mg5a94,2013-01-05T09:01:16-00:00 wcatwc@noaa.gov,PAAQ-2-mg5a94,2013-01-05T09:30:16-00:00 wcatwc@noaa.gov,PAAQ-3-mg5a94,2013-01-05T10:17:31-00:00</references>
  <incidents>mg5a94</incidents>
  <info>
    <category>Geo</category>
    <event>Tsunami Cancellation</event>
    <responseType>None</responseType>
    <urgency>Past</urgency>
    <severity>Unknown</severity>
    <certainty>Unlikely</certainty>
    <onset>2013-01-05T10:58:23-00:00</onset>
    <expires>2013-01-05T10:58:23-00:00</expires>
    <senderName>NWS West Coast/Alaska Tsunami Warning Center Palmer AK</senderName>
    <headline>The tsunami Warning is canceled for the coastal areas of British Columbia and Alaska from the north tip of Vancouver Island, British Columbia to Cape Fairweather, Alaska (80 miles SE of Yakutat).</headline>
    <description>The tsunami Warning is canceled for the coastal areas of British Columbia and Alaska from the north tip of Vancouver Island, British Columbia to Cape Fairweather, Alaska (80 miles SE of Yakutat). - Event details: Preliminary magnitude 7.5 (Mw) earthquake / Lat: 55.300, Lon: -134.900 at 2013-01-05T08:58:20Z Tsunami cancellations indicate the end of the damaging tsunami threat.  A cancellation is issued after an evaluation of sea level data confirms that a destructive tsunami will not impact the alerted region, or after tsunami levels have subsided to non-damaging levels. </description>
    <instruction>Recommended Actions:   Do not re-occupy hazard zones until local emergency officials indicate it is safe to do so. This will be the last West Coast/Alaska Tsunami Warning Center message issued for this event.  Refer to the internet site ntwc.arh.noaa.gov for more information. </instruction>
    <web>http://ntwc.arh.noaa.gov/events/PAAQ/2013/01/05/mg5a94/4/WEAK51/WEAK51.txt</web>
    <parameter>
      <valueName>EventLocationName</valueName>
      <value>95 miles NW of Dixon Entrance, Alaska</value>
    </parameter>
    <parameter>
      <valueName>EventPreliminaryMagnitude</valueName>
      <value>7.5</value>
    </parameter>
    <parameter>
      <valueName>EventPreliminaryMagnitudeType</valueName>
      <value>Mw</value>
    </parameter>
    <parameter>
      <valueName>EventOriginTime</valueName>
      <value>2013-01-05T08:58:20-00:00</value>
    </parameter>
    <parameter>
      <valueName>EventDepth</valueName>
      <value>5 kilometers</value>
    </parameter>
    <parameter>
      <valueName>EventLatLon</valueName>
      <value>55.300,-134.900 0.000</value>
    </parameter>
    <parameter>
      <valueName>VTEC</valueName>
      <value>/O.CAN.PAAQ.TS.W.0001.000000T0000Z-000000T0000Z/</value>
    </parameter>
    <parameter>
      <valueName>NWSUGC</valueName>
      <value>BCZ220-210-922-912-921-911-110-AKZ026&gt;029-023-024-019&gt;022-025-051258-</value>
    </parameter>
    <parameter>
      <valueName>ProductDefinition</valueName>
      <value>Tsunami cancellations indicate the end of the damaging tsunami threat.  A cancellation is issued after an evaluation of sea level data confirms that a destructive tsunami will not impact the alerted region, or after tsunami levels have subsided to non-damaging levels. </value>
    </parameter>
    <parameter>
      <valueName>WEAK51</valueName>
      <value>Public Tsunami Warnings, Watches, and Advisories for AK, BC, and US West Coast</value>
    </parameter>
    <parameter>
      <valueName>EAS-ORG</valueName>
      <value>WXR</value>
    </parameter>
    <resource>
      <resourceDesc>Event Data as a JSON document</resourceDesc>
      <mimeType>application/json</mimeType>
      <uri>http://ntwc.arh.noaa.gov/events/PAAQ/2013/01/05/mg5a94/4/WEAK51/PAAQ.json</uri>
    </resource>
    <area>
      <areaDesc>95 miles NW of Dixon Entrance, Alaska</areaDesc>
      <circle>55.3,-134.9 0.0</circle>
    </area>
  </info>
<Signature xmlns="http://www.w3.org/2000/09/xmldsig#">
  ...
</Signature>
</alert>