Definition
A continuous broadcast of summarized hazardous weather information transmitted over selected VOR navigation frequencies. The broadcast contains the latest AIRMETs, SIGMETs, Convective SIGMETs, Center Weather Advisories, urgent PIREPs, and severe weather forecast alerts that affect the area within roughly 150 nautical miles of the broadcasting station. Note: HIWAS was discontinued in 2020 by the FAA, but the term still appears in legacy charts, older training material, and reference handbooks.
Plain English
A non-stop weather warning broadcast that pilots could tune in on a navigation radio to hear about dangerous weather in their area without having to call anyone or change frequencies.
Context Anchor
Seen in FAA weather-source discussions, especially in older training material, when describing ways pilots could receive weather hazard updates while already in flight.
Derivation
“Hazardous” means dangerous, “in-flight” means during flight, and “advisory service” means an information service that gives warnings or notices. The full name describes exactly what HIWAS was meant to do: provide weather hazard information to pilots while they were flying.
Why Pilots Care
It gives pilots immediate access to critical weather warnings without needing to request updates or change frequencies.
Intuition Check
Do not read “advisory” as casual or optional information. In this context, an advisory is a warning about weather that can affect the safety of the flight.
Example Sentence 1
The older textbook described how a pilot could tune the VOR audio to receive HIWAS broadcasts when thunderstorms were forecast along the route.
Example Sentence 2
HIWAS alerted the crew to developing thunderstorms along the planned route.