Public Information Statement
Issued by NWS National HQ

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NOUS41 KWBC 231920

Service Change Notice 17-35
National Weather Service Headquarters Washington DC
1050 AM EDT Thu Mar 24 2017

TO:  Subscribers:
  -NOAA Weather Wire Service
  -Emergency Managers Weather Information Network
  Other NWS Partners and NWS Employees

FROM:  Ben Kyger
  Director, NCEP Central Operations (NCO)

SUBJECT:  Changes to Access, Planned Termination of Common
  Alerting Protocol (CAP) version 1.1, and Operational
  Implementation of CAP 1.2 Effective April 30, 2017

Effective April 30, 2017, NWS will transition Watch/ Warnings/
Advisories (WWA)in Common Alerting Protocol (CAP) version 1.2
format to operational status. NWS will also provide details
regarding dissemination channels and the termination of CAP
version 1.1.

The most recent notification of a planned NWS transition to
format Watch/Warning/Advisory (WWA) messages  using eXtensible
Markup Language (XML)-based Common Alerting Protocol (CAP)
version 1.2 (v1.2) and planned termination of CAP version 1.1
(v1.1) messages was provided in a Public Information Statement
on Nov 21, 2016. This notification solicited comments on a
proposal to make these service changes in early 2017.

After reviewing and assessing all comments received, considering
changing technologies, and aiming to enhance our user support,
NWS now will implement several operational changes. There will
be significant changes in how partners retrieve digital NWS
alerts in CAP format. Important details on these operational
changes follow.

Operational Implementation of CAP v1.2 and changes to access:
After considering the multiple formal and informal notifications
with significant lead times to the weather enterprise on NWS
considerations to transition to CAP v1.2, and after careful
consideration of the feedback we received, the NWS is
operationally implementing the formatting of WWA messages using
XML-based CAP v1.2 effective March 31, 2017. This designation
means NWS alerts in CAP 1.2 format can be considered the
equivalent of WWA issued in traditional alphanumeric formats.
CAP v1.2 messages will be provided through multiple
dissemination channels, including the web (using JavaScript
Object Notation (JSON)-based Application Programming Interface
(API) endpoints), http and ftp file listings, and NOAAPORT
satellite broadcast. Details follow in Sections 1-4 below.

1)    Provision of CAP v1.2 on the web: For an interim period
through at least September 1, 2017, NWS CAP v1.2 content,
recently located at

for the comment period, has moved to

Partners and users consuming CAP v1.2 from NWS web pages should
pay particular attention to this Uniform Resource Locator (URL)
interim change. Partners should also note the "New Search"
option from the Alerts homepage. This new section offers options
to build custom searches by Weather Forecast Office, Event Type,
Urgency, Severity and Certainty. Users can also search the past
7 days of (inactive) CAP messages.

2) The method for retrieving CAP content has changed. Users
should examine the new CAP v1.2 documentation at

The documentation describes the method to access CAP v1.2 and
Atomic Syndication Format (ATOM) via the web. This method now
includes an option to retrieve active alert indexes in CAP XML
or JSON-LD (Linked Data) formats via toggling the http "accept"
header. Linked Data is a way to create a network of standards-
based machine interpretable data across different documents and
Websites. Linked Data facilitates interoperability by allowing
an application to start at one piece of linked data and follow
supplied links to other pieces of linked data that are hosted on
different sites across the web. The NWS alerts JSON-LD
application is designed to allow partner websites to consume NWS
data and allow dynamic access to other alerts or prior, related

3) Planned Termination of CAP v1.1: To smooth the NWS
operational transition from CAP v1.1 to CAP v1.2 and to provide
users with extensive lead time for permanent service changes,
the NWS will continue providing CAP v1.1 at

until at least September 1, 2017. The NWS will continue
providing CAP v1.2 at the interim URL of

until at least September 1, 2017. On or after September 1, 2017,
the NWS will permanently provide CAP v1.2 at

NWS will permanently cease production of CAP v1.1 in any form or
on any NWS website. A future SCN will specify the exact
effective date of these changes.

4) Provision of CAP v1.2 using http and ftp file listings
CAP v1.2 is available in raw CAP/XML format using the http and
ftp protocols at

on the NWS Integrated Dissemination Program (IDP) file servers.
These file listing provide a traditional directory listing of
all CAP alerts issued for the past 7 days as well as directory
lists (ls-l and ls-lt) for CAP consumers wishing to frequently
check for any new CAP messages in the directory and accustomed
to access NWS via the IDP file servers.

5) Providing CAP v1.2 via NOAAPORT CAP v1.2 through NOAAPORT
satellite broadcast under the WMO Heading XOaa5i KWBC, where aa
corresponds to US, AK, CA, GM, HW, or ZS, and i is equal to 0
(zero) to 9.

As a reflection of continued improvements to NWS service
delivery, NWS CAP v1.2 messages may periodically undergo minor
changes or the addition of CAP elements or parameters. Since CAP
is XML-based, the addition of elements or parameters should not
impact the ability of NWS partners and users to properly parse
the CAP messages; however, partners and users are encouraged to
monitor the up-to-date documentation pages referenced in
Section 1 for all changes or updates to the CAP v1.2 elements
and parameters that could impact use of NWS CAP or provide
additional value.

We continue to solicit your questions and suggestions,
particularly as they relate to our provision of CAP v1.2

For any technical issues regarding access and connectivity,
please contact:

 NWS IDP Operations Center
 (301) 713-0902

For other non-operational technical questions, please contact:

 Robert Bunge
 (301) 427-9608

For questions about meteorological or hydrologic content within
CAP messages, please contact:

 Mike Gerber
 (301) 427-9118

National Service Change Notices are online at: is the U.S. government's official web portal to all federal, state and local government web resources and services.