NOUS41 KWBC 231920



Service Change Notice 17-34

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 version 1.1, and Operational

          Implementation of Common Alerting Protocol Version 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 April 30, 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: