IPAWS_on_44

An experimental feed of public emergency alerts from the U.S. "Integrated Public Alert and Warning System" (IPAWS) operated by the Federal Emergency Management Agency (FEMA), relayed to licensed radio amateurs via 44net, plus a Maidenhead grid-square lookup service for setting up local alert filters. MQTT service reachable at 44.27.128.55, from 44net (AMPRNet) addresses only; connections from any other address are refused.

What Is IPAWS?

IPAWS is the national master feed of public warning messages from local, state, and federal agencies. It includes weather warnings, earthquake notices, missing persons alerts, and local emergency alerts of all kinds. IPAWS is the primary source for wireless cellphone alerts and the Emergency Alert System on radio and television. This feed delivers alerts authenticated by FEMA within seconds of their issuance.

Client program

ipawsClient outputs the alerts for a grid square as they arrive, using the two services below. Builds for Linux, macOS and Windows: latest release (v0.3.0) (source and full instructions at github.com/artbotterell/ipaws44client).

ipawsClient CM87vh        # alerts for CM87vh, as JSON
ipawsClient CM87vh raw    # the same, as the original CAP XML
ipawsClient               # all alerts nationwide in JSON format

It matches alerts to the square by county, by the alert's polygon or circle, and by NWS forecast zone. From v0.2.0 it also supports NWS Partial County Alerting: in the 20 large or oddly shaped counties that NWS divides into partitions, an alert naming only some partitions is passed only for squares in those partitions.

Alert feed (MQTT)

Broker 44.27.128.55:1883, anonymous, read-only, 44net addresses only: subscribe to ipaws/#; publishing is not permitted.

Topic	Payload
`ipaws/cap/raw`	Each CAP 1.2 alert exactly as received from IPAWS, XML, including its digital signature.
`ipaws/cap/json`	The same alert as compact JSON, with the XML signature removed.

Messages are published as alerts arrive and are not retained: a subscriber sees alerts received while it is connected.

mosquitto_sub -h 44.27.128.55 -t 'ipaws/cap/json' -v

JSON conventions:

Keys are CAP element names: identifier, msgType, info, areaDesc, and so on.
Elements that CAP allows to repeat are always arrays, even with one entry: code, info, category, responseType, eventCode, parameter, area, polygon, circle, geocode.
eventCode, parameter and geocode entries are {"valueName": ..., "value": ...} objects. Wireless Emergency Alert text appears as the CMAMtext and CMAMlongtext parameters.
Elements absent from the XML are absent from the JSON. Line breaks in text fields are kept as \n. <resource> elements are not yet included.

Grid-square lookup (HTTP)

GET https://ipaws.kd6o.ampr.org/v1/squares/{code}

code is a 4- or 6-character Maidenhead square, such as CM87 or CM87vh. Plain http://44.27.128.55/v1/squares/{code} also works. Like the MQTT service, the lookup answers 44net (AMPRNet) addresses only; other addresses get 403. This page itself is public.

{"centroid":{"lat":37.3125,"lon":-122.2083},"fips":["06081","06085"],"same_partial":[],"square":"CM87vh","ugc":["CAC081","CAC085","CAZ512"]}

Field	Meaning
`centroid`	Center of the square, rounded to four decimal places (about 11 m).
`fips`	5-digit FIPS codes of every US county that intersects the square: counties it overlaps or touches, the county it lies inside, and counties lying wholly inside it. Sorted; empty over open water or outside the US. CAP alerts carry the same county as a 6-digit SAME geocode, `"0"` followed by the FIPS code (`06085` → `006085`).
`same_partial`	6-digit SAME codes of every NWS partial-county partition that intersects the square, by the same rule, sorted (`408005`, Western Arapahoe County, CO). Only a few large or oddly shaped counties are partitioned, so this is usually empty. Alerts for such a county may name partitions (first digit 1–9) instead of the whole county.
`square`	The code as requested.
`ugc`	NWS UGC codes for the square, sorted: the zone code (`CAZ512`) of every public forecast zone that intersects it, by the same rule as `fips`, plus the county-form code (`CAC085`) of each county in `fips`. Match an alert's `UGC` geocodes against this list.

A malformed code returns 400 with {"error":"invalid maidenhead code","code":...}; any other path returns 404. County boundaries are from the US Census Bureau's 2025 cartographic boundary file (1:500,000); forecast zones and partial-county partitions are from the NWS public zone and NWR partial-county files dated 2026-04-16.

Disclaimer

This is a voluntary experimental service for the Amateur Radio community. No warranty of accuracy, completeness, or reliability is offered. Should not be relied upon for critical or life-safety applications.