Event changes or expiration

When an alert changes, issue a new alert that refers to the previous alert. Don't change or remove the existing alert from your feed. After an appropriate amount of time like 24-48 hours, remove canceled, updated, or expired alerts from your feed.

Handle event changes or expiration in the following way:

An UPDATE or CANCEL <msgType> must include at least one <references> element.
There are three ways to cancel events, in order of preference:
1. Set an <expires> dateTime value for each event. In the message description, set the expectation for this alert to end on its own.
2. Issue a new <alert> message that contains <msgType> UPDATE, <responseType> "All Clear", and <expires> a short time in the future.
3. Issue a new <alert> message with <msgType> CANCEL. In the <references> element, refer to the original alert to cancel.

Examples

<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: Don't 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 won't 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>