Is WeatherKit wind direction backwards?

Question

It seems like the direction of the wind is reported in the direction it's heading vs the direction it's coming from.

Most of the time in other weather products, wind is reported in the direction it's coming from. eg. A west wind is coming from the west (heading east) and would have a bearing of 90.0 ° (coming from the west)

Am I correct in thinking that the below reported wind is actually a "West wind"?

WeatherKit.Wind(compassDirection: East, direction: 90.0 °, speed: 7.09 km/h, gust: Optional(18.18 km/h))

WeatherKit

810

Posted by

acorscadden

Reply

Add a Comment

Answer 1

Yes - what's reported is a "west wind." But the wind bearing is east.

The wind direction is the compass heading from which the wind is blowing (so, 90.0 °, or West), but the wind bearing is the direction in which the wind is moving, so East. Put a weather vane in a west wind and it will point east.

In short, compassDirection = windBearing.

That's my understanding.

Posted by

sarkonovich

Thanks! Yea, I think you're right sarkonovich, that makes sense.

—
acorscadden
Put a weather vane in a west wind and it will point east. - not it won't, because the pointer on a weather vane is on the narrow end. Normally the tail of the vane has a big wind-catching surface. Do an image search if you don't believe me!
—
endecotp
I believe you! But, I think that wind bearing is still the direction the wind moving, right?

—
sarkonovich

Add a Comment

Answer 2

Yes - what's reported is a "west wind." But the wind bearing is east.

The wind direction is the compass heading from which the wind is blowing (so, 90.0 °, or West), but the wind bearing is the direction in which the wind is moving, so East. Put a weather vane in a west wind and it will point east.

In short, compassDirection = windBearing.

That's my understanding.

Posted by

sarkonovich

Thanks! Yea, I think you're right sarkonovich, that makes sense.

—
acorscadden
Put a weather vane in a west wind and it will point east. - not it won't, because the pointer on a weather vane is on the narrow end. Normally the tail of the vane has a big wind-catching surface. Do an image search if you don't believe me!
—
endecotp
I believe you! But, I think that wind bearing is still the direction the wind moving, right?

—
sarkonovich

Add a Comment

Answer 3

Actually according to the documentation both direction and compassDirection should refer to the direction the wind is coming from. Respectively,

Direction the wind is coming from in degrees, with true north at 0 and progressing clockwise from north.

...and:

General indicator of wind direction, often referred to as “due north”, “due south”, etc. Refers to the direction the wind is coming from, for instance, a north wind blows from north to south.

In the example Wind object:

WeatherKit.Wind(compassDirection: East, direction: 90.0 °, speed: 7.09 km/h, gust: Optional(18.18 km/h))

It’s indicating “wind out of the east” (as a simplified weather report may phrase it), specifically from compass direction 90º, which is due east.

A wind blowing from due west would be blowing from a direction of 270º.

Posted by

Scott

Hmmm, now I'm even more confused. We almost never get East winds at the point I'm looking at. We get west winds quite a bit and WeatherKit is forecasting them as East winds.

Either WeatherKit is returning the reciprocal bearing or their forecasts are wrong.

—
acorscadden

Add a Comment

Answer 4

I think the wind API should be interpreted as documented, and you’re just seeing bad data as mentioned in your other post.

In simple testing here, I get perfect agreement between the iOS 16 Weather app and WeatherKit for various test locations (including Penticton, BC), but disagreement between those and the iOS 15 Weather app. In particular the wind direction there is roughly backwards between the two.

Posted by

Scott

Add a Comment

Is WeatherKit wind direction backwards?

Accepted Reply

Replies