Aethopia
Hong Kong weather, wind and storms, on iPhone, Android and the web.
Today: live weather readings, rain bands, sun and Moon 
Map: global particle wind, a ten-day timeline, press any point to read it 
Storms: distance, heading, closest approach and the No. 8 chance
Six things it does
Today at a glance
Current conditions, the nine-day forecast, hourly detail, UV, air quality, sun and Moon.
Storm alerts
A notification when the tropical cyclone signal changes, including advance notices, a storm comes within 500 km, or a new storm is named; No. 8 and above at once, the rest held overnight.
No. 8 signal chance
Our own estimate in three-hour steps, clearly marked as not an official forecast.
Particle wind field
A ten-day wind field on a sphere; press and hold to read temperature, pressure and gusts.
Aviation
VHHH runway components, METAR and TAF decoded, both ends of a flight and its distance from any storm.
Past storms
Mangkhut, Hato and others replayed against the station readings of the day.
Widgets
Questions
When does a notification arrive?
Three cases: the tropical cyclone signal is raised, lowered or cancelled (No. 1, 3, 8, 9 or 10); the nearest storm comes within 500 km of Hong Kong; a new storm in the western North Pacific or South China Sea is named by an agency. Anything involving No. 8 or above goes out at once; other alerts are held between 23:00 and 07:00 and sent at 07:00. You can also turn on the optional daily morning tip in Settings (off by default), sent at 06:00 HKT and exempt from the 23:00 to 07:00 quiet hours. If you are more than 50 km from Hong Kong, you can also turn on the optional morning tip abroad (off by default), sent at 06:00 local time with the local forecast.
How is my location used?
Only after you tap Allow location or turn it on in Settings; it is read once each time the app opens or returns to the foreground and is never tracked continuously. Within 50 km of Hong Kong the location is not kept and the app shows Hong Kong; beyond 50 km the coordinates travel with each request to draw the Here page, and the server neither logs nor stores them. See the privacy policy.
Where does the data come from?
Public weather, aviation and air-quality data; the No. 8 chance and the particle wind field are our own computation. See Sources and limits for each source and its licence.