beta.wx.photoephemeris.com has one more new feature: cloud observability indicators.
You can enable/disable this as shown. When enabled, a series of concentric geodesic circles are displayed. Each circle corresponds to the limit of visibility of a cloud the given height above the ground, assuming otherwise perfect conditions.
For example, a cloud at height 4,000m (13,000 ft) above the ground could in theory be seen on the horizon at a distance of ~210km (~132 miles).
The calculations are based on seeing a ~0.25° ‘slice’ of cloud on the horizon. That allows for low contrast and also matches up with the average semi-diameter of the Sun and Moon, given a handy mental reference point.
What’s the point of this? Well, in the screenshot above, I’m showing the high cloud layer. That covers clouds that are more than ~7000m above the ground. Using the cloud observability indicators, you can quickly assess whether or not clouds are likely close enough to be seen from your location, or to obstruct a rising or setting Sun/Moon.
They also serve as a handy distance scale making it much easier to assess the visibility forecast. For example, today we have fairly poor visibility - the green suggests visibility of only around 15km - you can immediately see that that is pretty limited and that you’re not going to be seeing any distant clouds today!
Be sure to hover your mouse over each ring - you’ll see a tooltip such as this:
Let me know what you think!